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FRONT COVER PICfURE: Local maize germplasm collection of Rwanda grown

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MAIZE IMPROVEMENT, PRODUCTION

AND PROTECTION IN EASTERN

AND SOUTHERN AFRICA

Edited by

Brhane Gebrekidan

Proceedings of the Third Eastern and

Southern Africa Regional Maize Workshop

Nairobi and Kitale, Kenya, September 18-22, 1989

Sponsored by: The Government of Kenya and CIM MYT


TABLE OF CONTENTS

INTRODUCTORY ADDRESS

Address by the Minister for Research, Science

and Technology, at the Opening of the Regional

Maize Conference for Eastern and Southern

Africa.

Hon. George K. Muhoho. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Introduction and Background to the Third

Regional Maize Workshop of Eastern and Southern

Africa.

Brhane Gebrekidan. . . . . . . . . . . . . . . . • • . . . . . • . . . . . . . . . . 5

MAIZE IMPROVEMENT

A comprehensive Breeding System for Developing

Improved Maize Hybrids.

S.A. Eberhart. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Breeding Strategies to Overcome Constraints and

Increase Maize Productivity in Sub-Saharan Africa.

A.O. Diallo, G.O. Edmeades, c.Y. Tang, J.A. Deutsch

and M. Bjarnason. . . . . . . . . . . . . . . • . . . . . . . . . . . . • . . . . . . 36

Progress in Maize Improvement at CIMMYTs

Zimbabwe Maize Research Station

R. Wedderburn, K. Short and H. Pham. . . . . . . . . . . . . . . . . . . . 63

The CIMMYT Headquarters Highland Maize Program

J.E. Lothrop. . . . • . . . . • . . . . • . • . . • . . • . . . • . . . . . . . . . . . . 75

Effect of Selection for Yield on Major Agronomic

Traits in the Variety Cross 'Kitale Synthetic II x

Ecuador 573' Over Nine Cycles of Reciprocal

Recurrent Selection.

JAW. Ochieng, D.K. Muthoka and R.E. Kamidi. . . . . . . . . . . . . . 95

Path Coefficient Analysis for Grain Yield and

Maturity Traits in MaiZe (Zea mays L.).

O.M. Odongo, A.P. Tyagi and G.P. Pokhariyal. • • • . . . . . . . . . • . . 115

Pedigree Selection: A New Dimension in Kenya's

Applied Maize Improvement Programme.

J-J. Chumo, JAW. Ochieng, K. Njoroge and

WA Compton.... .•..•...•.... ..••.•• •• . .. ..•. . .• .•. 119


ii

Maize Improvement in the Southern Highlands

of Tanzania.

W.Y.F. Marandu, N.G. Lyimo, A.E.M. Temu

and D. Kabungo. . . . . . . . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . 123

Evaluation of Elite Composite Maize Varieties

for Their Relative Affinity.

Benti Tolessa, Kebede Mulatu, Legese Wolde

Gezahegne Bogale and Assefa Meta. . . . . • . . . . . • . . . . . . . . . . . 137

Progress in Maize (Zea Mays L.) Population

Improvement for the Eastern Highlands of Ethiopia.

Dejene Makonnen. . . . . . . . . • • • . • • • • • • • • • . • . . . . . . . . . . . . 145

The Role and Contribution of CIMMYT/IITA to

Maize Research in Uganda.

Denis T. Kyetere and George Biginva. . • • . . . . . . . . . . . . . . . . . . • 155

The Performance of Introduced Maize Hybrids

at Kawanda Research Station.

Elizabeth Byanjeru Rubaihayo. . • . • . • • . . • • . . • • . • • . • . . . . • . 158

Overview of the Burundi Maize Breeding Program

Emmanuel Rufyikiri. . . . . . . • . . . . . . • . . . . . . . . . . . . . . . . . . . 164

Maize Breeding in Somalia

Anab Farah Saidi. . . . . . . . • . . . • . . . • . . . . . . . . . . . . . . . . . . . 170

Yield Stability of Different Types of Maize Varieties

D. Ristanovic and C. Mungoma ~ • • • . . • . • • . • . . . . . . 172

Breeding Flint Maize Hybrids (Hard Endosperm

Grain) in Malawi in Response to Smallholder

Processing Needs.

W.G. Nhlane. . . . . • . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . • 182

The Performance of CIMMYT Maize Germplasm and

Their Contribution to Varietal Development in

Mauritius.

N. Govinden, K. Rummun and M. Rughoo. . . . . . . . . . . . . . . . . . . 188

The Maize Mega-Environments of Eastern and Southern

Africa and Germplasm Development.

Brhane Gebrekidan and Bantayehu Gelaw. . . . . . . . . . . . . . . . . . 197


iii

NUUZE PATHOLOGY AND ENTOMOLOGY

Effects of Delayed Harvest and Host Genotype on

the Incidence of Ear Rots in Western Kenya.

T.E. Ochor, CJ. Kedera and JAW. Ochieng. . . . . . . . . . . . . . . . . 212

The Status of Maize Streak Disease in Kenya

J.G.M. NJuguna, J.M. Theuri and J.M. Ininda. . . . . . . . . . . . . . . . 218

Effect and Application Methods of Insecticides

on Maize Streak Virus in Zimbabwe.

C. Mguni. . . . . . . • • . . . . . . . • . . . . . • . . • . . . . . . . . . . . . . . . . 224

The Status of Maize Diseases in Malawi

Patricia Ngwira. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230

Maize Stalk Borer Research in Ethiopia

Assefa Gebre-Amlak. . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . 239

Insecticidal Control in Stored Maize Insects

with Special Reference to Maize Weevil

Sitophilus zeamais Motsch at Awassa, Ethiopia.

Adhanom Negasi. • . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . . . . 253

MAIZE SEED PRODUCTION

Seed Maize Production, Certification and

Testing in Kenya.

Francis M. Ndambuki and Charles M. Ndegwa. . . . . . . . . . . . . . . 257

Maize Seed Production and Utilization in Tanzania.

AJ. Moshi and S.N. Nnko. . . . . . . . . . . • . . . . . . . • . . . . . . . . . . 268

Maize Seed Production in Ethiopia

AJemseged Aregai. . . • . . • . . • • • . . . . . • . . . . . . . • . . . . . . . . . . 274

Zimbabwe Hybrid Maize Seed Industry: Emphasis

on Cob-Rots and Isolation.

MJ. Caulfield and E.K. Havazvidi. . . . . • . . . . . . . . . • . . . . . . . . 282

Maize Seed Production in Zambia Trends and Problems.

P.N. Thole. • . . . . • . • • . . . . . • • . . . . . . • • • . . . . . . • • . . . . . . . 293

An Integrated Approach to Maize Seed Production

and Supply in Malawi.

P.N.H. Zulu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303


iv

MAIZE AGRONOMY

Striga Control Methods

Robert E. Eplee. . . . . • • . . . • . • • • • . . • • • • • • • • . • • • • . . • • • • • 314

Towards Appropriate Agronomic Recommendations

for Small-holder Maize Production in the

Highlands of Western Kenya.

N.M. Mwania, M.C. ShiluH and M.K. Kamidi. • . • • . . • . • . . . . • •• 321

Studies on Intercropping of Maize with Beans

H.O. Bhuong, H.M. Wakonya and O.M. Odongo. . . • . . . . • • . . . . • 338

Effect of Continuous Use of Sulphate ofAmmonia

Fertilizer on Soil Acidity and Grain Yield of Maize

A.E. Temu. • . • • • • • • • . • • • • • • • • • • • • • . . • • . . • • . • . . . . • . • • 346

Effect of Method of Placement of Urea Fertilizer

on Grain Yield of Maize.

A.E. Temu. • . . . . • • • . . • . . • • . • . • • . . • • . • • • • • . . • . . • . • • • • 353

Crop Weed Competition Studies in Maize at Asossa

Dawit Mulugetta, AseCa TeCeri and Mosisa Worko. . . • . . . . • . . • .. 361

Recent Developments in Maize Agronomic Research

in Zambia 1987-89.

M.S. Reddy, B.K. Phiri, K.S. Gill and M. Gumbo. . • • . • . . . • . . . •• 370

Performance of Maize Varieties Under High and

Low Input Conditions at Two Locations in Southern

Mozambique.

A. Bueno, MJ.M.B. Pereira and D. Marioti. • • . . • • . . . . • . . . • • .. 397

Evaluation of Maize Varieties in Diffferent

Row Spacings and Plant Densities in Northern

Mozambique.

A. Bueno, D. Marioti and MJ.M. Pereira. • • . • • • . • . • . . . . • . • . . 410

Status of Maize Research in Madagascar

L. Rondro-Harisoa, R. RamiJison, B. Clerget. • . . . . • • . • • • . . • . •. 423

MAIZE ON-FARM RESEARCH/ECONOMICS

On-Farm Economic and Agronomic Evaluation of

Selected NP Fertilizer Rates on Maize Around

Balm Western Ethiopia.

Legesse Dadi and Gemechu Gedeno. . . .• ....•....•........ 428


v

Socio-Economic Constraints to Maize Production

in Ethiopia.

Legesse Dadi, Wilfred Mwangi and Steven Franzel. . • . • . . . . . . . • 436

Policy Issues in Maize Production Marketing

and Consumption in Uganda.

Samuel Zziwa and Manuel Venegas. • • • . . • . . • . . • . . . . . . . . . . . 450

The Farming Systems in the Lava Region of Rwanda:

Crop Rotations and Combinations.

O. Castanie and C. Karangwa. • • . • . • • . . • . . • • . . . . . . • • . . . .. 459

Response of Maize to Nitrogen and Phosphorus

Application on Small-Scale Farms in Zimbabwe.

D. Hikwa, D.F. Mataruka and M. Natarajan. . . . . . . . • . . • . . . . . 467

Recent Maize Workshop by the Adaptive Research

Programme in Malawi.

C.C. Moyo, C.S.M. Chanika, W.C.C. Mughogho

and R.L. TInsely. • • . . . • . • • • • . . . . . • . • • • • . . . . . . . . . . • . . . 477

On-Farm Research on Maize Production Technologies

for Smallholder Farmers in Southern Africa:

Current Achievements and Future Prospects.

Allan C. Low and Stephen R. Waddington. • • • . . • . • . . . . . . . . . • 491

WORKSHOP PROGRAM. . . • . . • • . . . • . . . . . . . . . . . . . . . . • . • . . 513

LIST OF PARTICIPANTS. . . . . • • . . . . . . • • • • • . . . . . . . . . . • . • . . 522


vi

ACKNOWLEDGEMENTS

I would like to thank the following gratefully:

The Government of Kenya for co-sponsoring and hosting the workshop.

Kenya Agricultural Research Institute (KARl) for assistance in local

arrangements and administrative support.

National Agricultural Research Center, KARl, Kitale for preparing and

hosting the station tour.

Kenya Seed Company for tour of their facilities and hosting a luncheon.

CIMMYT for co-sponsoring and funding the entire workshop.

R.P. Cantrell and R.L. Paliwal, CIMMYT Maize Program director and

associate director, respectively, for their encouragement and support.

A.F.E. Palmer for reviewin~ the agronomy and on-farm research sections of

the workshop papers, assistmg in the workshop organization and

implementation, and providing the cover picture.

Bantayehu Gelaw for initiating these series of regional maize workshops and

for coordinating papers and participation from Southern Africa.

J.K. Ransom for his assistance in printing the papers.

Rosalind Ngoima, CIMMYT secretary, for her skilled contribution in typing

and printing the papers, and handling all workshop correspondence and

logistics support.

H.G. Awich, office manager, for his administrative assistance in arranging

and handling hotel, transport, and financial matters.

The Pan-Afric Hotel Management for providing accommodation and

conference facilities.

Brhane Gebrekidan

Workshop Organizer


ADDRESS BY THE MINISTER FOR RESEARCH, SCIENCE AND

TECHNOLOGY, HON. GEORGE K. MUHOHO, EGH, MP, AT THE OPENING

OF THE REGIONAL MAIZE CONFERENCE FOR EASTERN AND SOUTHERN

AFRICA HELD AT PANAFRIC HOTEL, NAIROBI

FROM 18-22, SEPTEMBER 1989

The Chairman of the Conference,

Conference Organizers,

Participating Research Scientists,

Ladies and Gentlemen,

On behalf of the Government of the Republic of Kenya, I welcome you most

heartily to our country. I hope that your journey to Nairobi was comfortable and

that you have now rested and settled for the task ahead of you for the next few days.

The conference you are starting today is a very important one, as it deals with the

most important food crop in our region, namely maize, that plays a very important

role in Africa's food system.

Mr Chairman, let me briefly review the situation prevailing in Africa during

the last three decades. It is on record that many countries in Africa have recorded

dismal performances in Agricultural Economics sector in general, and the food subsector

in particular. The continent has moved from being self sufficient and net

exporter of food products to one of experiencing recurrent food crisis. Some

countries have experienced massive famines and a number are now dependent on

food aid.

In Africa, the annual growth rates of per capita food production declined by

0.7 per cent in the 1960s, and the decline reached 1.25 per cent in the 1980s. Africa

is spending colossal amounts of foreign exchange earnings on food imports, thus

constraining the continent's ability to import capital goods and services for further

development.

Mr Chainnan, the scenario I am citing affects a large population. The

population in Sub-Sahara Africa is estimated at 460 million and is growing at 3 per

cent per annum compared to 2.7 per cent in the sixties. Approximately 30 per cent

of the African population is undernourished. It is estimated that three out of five

children die before the age of five, primarily due to hunger and hunger related

diseases.

.. There are many factors that have contributed to the {'oor performance of

food production in Africa. First and foremost, there is too little irrigated land in

Africa, with most African countries irrigating less than 5 per cent of the arable land.

Without irrigation we cannot control that most important determinant production

factor, soil moisture. It is therefore not surprising that the green revolution has not

had as much impact as occurred in the irrigated agricultural lands of Asia and Latin

America. We all appreciate that high costs have reduced the expansion of

irri~ation. It would appear that Afnca has no option but to invest in irrigated

agnculture if the continent is to open up the vast arid and semi-arid areas for food

production to meet the nutritional requirements of approximately one billion people

10 the year 2010.

The second set of factors are of a policy nature. Farmers require incentives

to produce marketable surpluses. Distorted policies of low producer I.'rices and low

consumer prices for the politically articulate urban population is a diSIncentive to

farmers. African Governments must provide support services such as agricultural

research, extension services, efficient farm input supply systems, agricultural credit

and market outlets for farmers' produce. It is essential that African countries invest


2

more in the development of agriculture which currently averages 10 per cent. The

Organization of African Unity calls for African governments to allocate 20-25 per

cent of public spending to agriculture.

Finally, Mr Chairman, we cannot fail to recognize that external factors

exacerbate Africa's ability to feed itself. Africa frequently experiences natural

disasters such as the severe Sahelian drought of the 1970s and the recent drought in

Eastern and Southern Africa that devastated crops, decimated large herds of

livestock and ~islocated human populations. Occasional floods occur and migratory

pests such as locusts and army worms are an ever present threat.

The final aspect of external factor is the foreign debt. African Governments

are overburdened by excessive external debts estimated to be in excess of US$200

billion. This astronomical external indebtedness has really constrained Africa's

ability to develop its agriculture. The debt servicing ratio rose from 9 per cent in

1980 to 30 per cent in a period of 2 years and is still rising. Some countries have

reached a ratio of 60 per cent. The situation is aggravated by very poor terms of

trade of African exports. The prices of non-oil products exported by Sub-Sahara

Africa declined by 35 per cent between 1980 and 1987. Mr Chairman that is the

reason why African heads of state and Government are constantly calling on

industrialized countries to cancel the debts.

Ladies and gentlemen, I have presented the above scenario to indicate the

constraints under which you are operating and the challenges before you as research

scientists. But all hope is not lost. The Food and Agriculture Or~anization (FAO)

of the United Nations has shown that collectively, African countnes have at the

moment the potential to feed 780 million people (the projected population in the

year 2(00):

1.5 times at low level of technology

6 times at an intermediate level of technology

17 times at a high level of technology

It is for you, research scientists, to enhance the required level of production

technology. The political will to support your efforts has been expressed by heads of

state and Government through the Lagos Plan of Action for the period 1980-2000;

Africa's priority programme for economic recovery 1986-2000; and the United

Nations programme of Action for Africa's economic recovery and development

adopted in 1986.

Mr Chairman, maize is the most important food grain in our region and plays

an important role in the economic and nutritional needs of our people. Allow me to

illustrate its importance, taking Kenya as example:

(1) Out of the 3.2 million hectares under major crops in Kenya, maize

occupies some 1.2 million, or 38 per cent of the total and therefore

ranks highest in land utilization.

(2) With a total annual production of 2.5 million metric tonnes, maize

contributes approximately 75 per cent of total cereal consumption, 44

per cent of total energy needs and 32 per cent of total protein

requirements in Kenya.

(3) The total value of eroduction, based on producer prices, is estimated

at some Kshs.3.7 bIllion shillings annually, and ranks highest in value

among croes. The much talked coffee takes second position valued at

Kshs. 2.1 bIllion annually.

(4) Maize production also contributes significantly to employment. Some

860 million manhours are spent on maize production annually, which

is equivalent to 700 manhours per hectare per year.


(5) The gross production per hectare per year, which averages Shs.3000 is,

however, low compared to crops such as coffee, tea, Irish potatoes,

rice and pyrethrum. This low figure is attributed to the low average

maize yields.

Mr Chairman. the above facts demonstrate that maize is probably the most

important agricultural commodity in Kenya and I believe the same applies to other

countries in the region. In a nutshell, it is the most important source of both income

and subsistence for the rural population, and any positive changes in the level and

efficiency of its output would inevitably have a major impact on overall national

development.

There is potential for increasing the output of the crop immediately if certain

actions are undertaken. Allow me to once agaIn cite the example of Kenya. The

average farmer in Kenya who grows hybrid maize eroduces about 2 tonnes of grain

per hectare. A good farmer produces 5 tonnes whlle a very good farmer attains a

level of 9 tonnes per hectare. Research station yields of 11 tonnes per hectare are

common and it is biologically possible to produce 20 tonnes of maize grain per

hectare

Ȧ simple calculation indicates that the average farmer has a yield 40 per cent

of that of a good farmer, 22 per cent 9f the yield produced by the best farmer, 18 per

cent of research station yield, and 10 per cent of the biological limit. The above

story demonstrates that production technology is not a constraint to doubling of

maize production in Kenya.

Plant breeders have therefore done their job well. We now require a more

intensified extension effort, focussed on good crop husbandry, reduction of losses

during storage, and other incentives to motivate the farmer. I cannot overemphasize

the role of good agronomy in increasing maize production.

Mr Chairman, I note that the conference a~enda is quite comprehensive and

covers most aspects of maize improvement includIng plant breeding, agronomy, soil

fertility, plant pathology and entomology, on farm research and economics. The

inclusion of country reports will familiarize participants with the state of the crop in

the neighbouring countries.

With your indulgence I wish to share with you a few thou~hts on issues which

I feel have not been adequately addressed by the research scientIsts in the region:

(1) As I stated earlier, Mr Chairman, there is a large gap between what

the farmer gets and what is feasible with available technology. I also

postulated that intensified extension focussed on agronomy and

supported by favourable policy instruments could bridge the gap.

These latter aspects indicate the need for the national agricultural

research systems in general, and the maize research efforts in

particular, to seriously consider incorporating policy research

activities as part of the overall research efforts. Government

ministers and planners in head offices would welcome information on

the best policy 0rtions available to us to enhance production and

improve the weI being of our farmers. What I am alluding to, Mr

Chairman, is that biological research is not sufficient in itself.

Technology generated must be put into place through appropriate

policy instruments.

(2) The second worrying factor is the a~ravatedsituation of disease

outbreaks that has caused serious yIeld losses in recent years within

the region. During this year maize streak virus was very prevalent,

especially in the central Kenya highlands were infection was in excess

of 60 per cent. The resistance that had been incorporated in the

earlier hybrids and breeding populations seems to have broken down.

The spread of the maize streak virus appears to pose a great threat to

3


4

Kenya's continued production of maize. Coupled with your efforts to

re-incorporate resistance, you might wish to investigate whether the

changing farming system of continuously growing of maize season

after season is exacerbating the disease situation. Other diseases that

are occurring with frequency are rusts and blights.

(3) Mr Chairman, the third issue relates to new tools that have become

available to agricultural research scientists, particularly biotechnology,

I believe an erroneous impression has been created that

biotechnology is a replacement for plant breeding, creating the

impression that a scientist workin~ III a biotechnology laboratory will

come up with a wonder maize vanety containing all the desired

attributes. This attitude is misleading especially to our new graduates.

I implore you senior scientists to give gmdance that the correct

balance must be struck between the traditional plant breeding

strongly rooted on observations and judBements based in the field. I

am a strong supporter of training scientISts in our region in the new

horizons of science, but it is my belief that the new tools are

complementary to the traditional sciences I am still to be convinced

that a scientist who is highly specialized in biotechnology, but who has

never been to the maize nursery in the field, will single-handedly

produce that wonder cultivar.

In conclusion, Mr Chairman, let me pay tribute to all of you ~athered here

today. Special welcome to Dr Ron Cantrell, the Director of the MaiZe Programme

and his team who have travelled all the way from Mexico to participate at this

conference. I also recognize the presence of Dr Steve Eberhart who contributed so

much to Kenya's maize improvement programme in 1960s together with others not

present here such as Dr Larry Darrah, the late Dr Festus Ogada and Dr Eliud

Omolo, whose breeding methodologies still form the basis of my country's maize

improvement programmes.

It is now my pleasant duty to declare the Third Regional Maize Workshop of

Eastern and Southern Africa officially open.

Hon. G.K. Muhoho, EGH, MP

Minister for Research, Science & Technology

Nairobi

18thSeptember 1989


5

INTRODUCfION AND BACKGROUND TO THE THIRD REGIONAL

MAIZE WORKSHOP OF EASTERN AND SOUTHERN AFRICA

Brhane Gebrekidan 1

In the eastern and southern Africa region as a whole maize is the most

important crop. It is a staple food in most of the countries of the region. Regional

maize workshops of this type are important to forge closer links among the national

programs of the region.

The main purpose of this regional workshop, as similar ones in the past, is to

bring together again maize researchers of eastern and southern Africa to share

experiences and exchange results, discuss maize related regional technical problems

and potential solutions, and strengthen regional cooperation.

This workshop follows the first and the second regional maize workshops

held in Lusaka and Harare in 1985 and 1987, respectively. Both the Lusaka and the

Harare workshops were attended by about 100 participants each and the

proceedings have been published by CIMMYT and distributed to all the national

maize researchers and other interested parties. The delegates of the Lusaka

workshop passed a resolution stating that such regional maize meetings be held

every two years with the venue and host rotating among the countries of the region.

In that recommendation, CIMMYT was requested to take the lead in organizing

and sponsoring the workshop. This workshop is, therefore, a continuation of that

series which started in Lusaka in 1985 and hopefully will continue for many years to

come.

In this workshop, we expect the number of participants to be similar to the

last two. Invitations have been sent to the national maize programs of the region,

selected seed companies, regional and international organizations

interested on the maize crop. We have received positive responses from many of

them as is evidenced by the record attendance in this workshop.

Although this workshop is jointly organized by CIMMYT and Kenya

~eultural Research Institute (KARl) we have received excellent cooperation

from the Kenya Seed Company (KSC) in the planning stage of the field trip part of

the workshop. Funding and sponsoring of the workshop has been provided by

CIMMYT whose special interest is evidenced by the presence of the Director of the

Maize Program, Dr R.P. Cantrell, throughout the workshop and the Director

General of CIMMYT, Dr D.L. Winkelmann, for the last day and the closing

ceremonies of the workshop. In addition, all CIMMYT staff in the eastern and

southern Africa region involved in maize are present in this meeting.

At this time, I would like to briefly comment on the background and

organization of the workshop and what you should expect during the week. We

have just completed the official opening ceremonies of the workshop. From now

1. CIMMYT, P.O. Box 25171, Nairobi, Kenya


6

until the end of the workshop on September 22 we have about 50 papers planned to

be presented and discussed.

Last November a committee consisting of the CIMMYT maize staff in

Nairobi and Harare met and agreed on the major issues related to this workshop. It

was agreed in that meeting that the papers to be presented in the workshop by

maize researchers of the region should be based, as much as possible, on completed

experiments and concrete data in the broad areas of breeding, crop management,

seed production, crop protection and economics. It was further agreed that

prominent scientists outside the region be invited as guest speakers to address the

participants on topics important to the region. Generalized country papers not

supported by experimental or survey data were indicated to receive low priority.

Glancing at the program and the abstracts of the papers submitted, I trust you will

agree with me that we have had excellent responses from maize researchers in the

region as well as the guest speakers on the special topics. In national programs

where specific topic papers have not been possible, the presentations of general

papers ensure the participation in the workshop of the relatively smaller national

programs of our region.

This is the beginning of plenary Session 2 which deals with introductory

issues and lead papers presentations. We have two prominent guest scientists, Drs

S.A Eberhart and R.E. Eplee, who have been invited to present lead papers on

Maize Breeding and Striga Control, respectively. Both topics are relevant for our

region and I am sure we will all gain from the papers and discussions of Drs

Eberhart and Eplee. The three papers to be presented by CIMMYT Mexico and

CIMMYT Harare staff are intended to highlight some of CIMMYT's activities at

our headquarters as well as the CIMMYT Mid-altitude Maize Research Station in

Harare.

Session 3 with 10 papers focusing on Breeding and Session 4 dealing with the

broad issues of Agronomy/On-Farm Research/Economics in 12 papers will be held

concurrently this afternoon. Group 1 will attend Session 3 and Group 2 will attend

Session 4. Choose the topic that is of most interest to you and join the appropriate

group.

, Sessions 5 to 8 will all be plenary and held in this hall. Session 5 with seven

papers will concentrate on maize plant pathology and entomology and Session 6 will

focus on the seed industry and maize seed production in the region. The six papers

on seed production from the six leading maize producing countries of the region

should provide a good picture of the maize seed industry situation in the region and

also serve as a good basis for discussion.

Sessions 7 and 8 will be held on the last day of the workshop after we return

from the field trip to Kitale. Session 1 groups together all general papers and

overall country status reports. The main reason for including this session is to paint

a more complete picture of the maize situation in the region. National programs

which are unable to present papers based on completed experiments have

opportunity to present the status of maize research in their respective countries in


Session 7. Session 8 is intended to provide a base for discussing and strengthening

regional cooperation on germplasm development and movement as well as regional

training on crop management research. The concepts of focusing on megaenvironments

in gerrnplasm development and devolving crop management research

training to the region are consistent with CIMMYTs Strategic Plan. The two

papers in this session should stimulate discussions on these concepts.

As shown in the program, Wednesday 20th September and Thursday 21st

September are scheduled for field trips to Kitale which as you know is famous for

both good maize research and production. In that field trip, we look forward to

seeing the facilities of a lead research station and an outstanding seed company and

discussing the activities with the respective staffs of the National Agricultural

Research Center, Kitale and the Kenya Seed Company as well as observing well

grown maize fields of farmers.

In the paper presentations, chairmen and rapporteurs are assigned for a

group of related papers. It is suggested that papers be presented without

interrupting discussions following the schedules shown on the program and

discussions will be held at the end of presentations of a given group of papers.

Please write down your questions or comments on paper and bring them up during

the allocated discussion period. The chairmen will of course monitor the

discussions and the rapporteurs are responsible for documenting them.

At this time, on behalf of aU those involved in and contributing to the

organization of this workshop I would like to take this opportunity to express my

appreciation to the Government of Kenya for hosting this workshop. As usual, the

financial and moral support we have generously received from CIMMYT was

indispensable for the organization and success of this workshop. We are, therefore,

grateful to the directors of the CIMMYT maize program for their usual

encouragement and support.

Finally, on behalf of CIMMYT I would like to say welcome to all ofyou and

please eQjoy your workshop week.

Thank you for your attention.

7


B

ABSTRACf

A COMPREHENSIVE BREEDING SYSTEM FOR

DEVEWPING IMPROVED MAIZE HYBRIDS

SA Eberhart 1

Further increases in maize production in Africa can be achieved from

improved hybrid and open-pollinated varieties developed with a

comprehensive breeding system that includes: 1) selecting the best

gennplasm available for compositing into appropriate seed parent and

pollen parent breeding populations; 2) using reciprocal recurrent selection-­

inbred tester with multi-stage selection for important agronomic traits to

cyclically develop improved disease resistant, insect resistant, stresstolerant,

and high yielding breeding populations that respond to improved

cultural practiCes; and 3) developing superior hybrids (or the advanced

generation of the population cross) from these improved breeding

populations for commercial use. Increases in maize production will be much

greater from effective population improvement programs in fewer

populations than from ineffective programs in many populations.

Because fanners seek both risk avoidance and high yields in the

hybrid and open-pollinated varieties they select to grow, resistance to

diseases and insects, resistance to root and stalk lodging, and tolerance of

drought and other stresses is critical. Use ofhigh plant densities in all field

plantings is critical to select for greater stress tolerance and reduced

lodging. Fanners also have strong preferences for grain color and texture.

Multi- stage selection is the key to the simultaneous improvement ofthe

essential agronomic traits.

With the greater yield advantage of hybrids over open- pollinated

varieties, hybrids can be expected to be the commercial product whenever

conditions pennit the production and sale of high quality hybrid seed. The

comprehensive breeding system not only provides superior methodologies to

develop hybrids, but it provides the advanced generation of the populationcross

as a superior open-pollinated variety until hybrids become feasible.

Significant increases in maize production require improved

agronomic practices in addition to the improved hybrids. Timely date of

planting, optimum planting rate, good weed control, and rotation with a

legume crop are important factors in maize yields that can be obtained with

no cash expenditure. Application of modest levels of fertilizers is needed for

further yield increases which will require a cash input. Although hybrid seed

requires a cash purchase each year, it can be used as a lever to get the

fanner to adopt the total package.

The perfonnance advantage ofhybrids will be realized by the fanner

only when high quality hybrid seed is available to him. Seed companies in

Ethiopia, Kenya, Malawi, Nigeria, Zambia, and Zimbabwe have provided

this high quality seed to their customers at very modest prices.

Because maize (Zea mays L.) is not an indigenous crop in Africa, many

introductions have been made. Recent acquisitions by maize breeders, including

CIMMYT populations, represent a wide range of genetic diversity. This germplasm

1. Director, U~DA-ARS National Seed Storage Laboratory,

Fort Collins, Colorado 80523, USA.


9

has been evaluated in most countries and the best material has been selected for

further improvement. Subsequent progress depends on breeding objectives

and methodolosies.

Further mcreases in maize production in Africa can be

achieved with improved hybrid and open-pollinated varieties

developed with a comprehensive breeding system (Eberhart et aI., 1967) by: 1)

selecting the best germplasm available; 2) using an effective breeding system to

develop disease resistant, stress- tolerant, and high yielding source breeding

populations that respond to improved cultural praCtices; and 3) developing superior

hybrid and/or open-pollinated varieties from the improved breeding

populations for the commercial products. Kenya has been extremely successful with

hybrids developed with this program, whereas Zambia, Zimbabwe, South Africa,

Egypt, and Nigeria have developed hybrids with traditional pedigree breeding

methodologies.

The comprehensive breeding system requires the development of two diverse

breeding populations that maximize the population-cross performance. This

provides greater flexibility because the commercial.{>roduct can be: either 1) single,

three-way, double- cross, or top-cross hybrids involvmg inbred lines derived from

successive cycles of reciprocal recurrent selection; or in a few situations 2) the

advanced generation of the population cross that can be used as an elite openpollinated

variety until hybnds can be developed and produced.

DEVEWPING ELITE SOURCE BREEDING POPULATIONS

Envirorurtental factors within the two ecological zones in eastern and

southern Africa require slightly different source materials. These ecological zones

are the medium altitude and high altitude zones.

Recommendations are sometimes made that each micro-environment within

each ecological zone will require hybrids or open-pollinated varieties developed

specifically for that micro-environment, but extensive trials in Africa (Eberhart et

al.,1973; Darrah, 1976; and Darrah and Mukuru, 1978) and experiences of maize

seed companies fail to confirm these suppositions when appropriate germplasm is

used with appropriate breeding objectives. Genotype-by- environmental

interactions can be dramatically reduced by developing breeding populations and

hybrids with higher levels of disease and insect resistance, higher levels of tolerance

to stresses such as low soil pH (aluminum toxicity), low soil moisture, low nutrient

availability, and good resistance to root and stalk lodging (Kim et al., 1985;

Fajemisin et aI., 1985). Such cultivars will have a very broad area of adaptation

within their ecological zone.

, The correct maturity for length of growing seasons that are limited by the

rainfall distribution is very important. Eberhart et al. (1973), Darrah (1976), and

Darrah and Mukuru (1978) have demonstrated a large differential response to

varying altitudes (Table 1). Presumably the response to night temperatures is a

major factor although diseases may be involved unless the cultivars have a higher

level of resistance. Northern corn leaf blight (Helminthosporium turcicum) and

common rust (Puccinia sorghi) often limit yields at higher elevations whereas

southern corn leaf blight (Helminthosporium maydis) and southern rust (Puccinia

polysora) are serious diseases at lower elevations throughout Africa. Note that the

cultivars developed from medium altitude germplasm failed to respond in the high

altitude environments, whereas the high altitude cultivars were extremely high

yielding at high elevations and at least equal to the medium altitude cultlvars in the

medium elevations. In addition to the leaf blights and rusts, F~·emiSin et al. (1985)

included maize streak virus, Curvularia leaf spot, maize mottle chlorotic stunt, and

downy mildew in their list of significant maize diseases. They ist Fusarium,

Diplodia, Botryodiplodia, Rhizotonia, and Macrophomina as causal organisms for


10

Table 1. Observed yields with altitude lbA) and environmental (hI) responses lor sdeaed entries in

the 1976-77 Eastern African Maize Variety Trial.a

Hybrid

Observed Yields

LowMedium High

(O-.09km) (O.9-1.6km) (1.6-2.2km)

----------qJha----------------

Environmenlal Responses

Mean bA hI

-l/ba qjha/km qfhafI

-------------------------------------------------------------

High elevation varieties

H611C 36.1 48.4 73.8 58.3 U.5 .95

H611(R)C5 43.7 51.5 90.8 68.1 22.6 1.07

EAH6304 47.9 61.6 983 -'6.4 25.9 1.00

Mean 42.6 53.8 87.6 67.6 20.3 1.01

Medium elevation varieties

H632 42.0 48.7 57.2 51.7 -11.6 1.20

SR52 50.3 50.0 56.2 52.7 -20.8 1.35

KwCAxKwCB 47.1 44.5 46.6 45.7 -18.0 A.OO

ZCA x ZCZ 44.1 38.9 40.8 40.3 -17.9 .97

(MlxC)xETO 41.4 35.5 26.1 32.0 -26.4 .74

Mean 45.0 43.5 45.4 44.5 -18.9 1.05

aFrom Darrah and Mukuru (1978).


11

stalk and ear rots in Africa. Important insect pests of maize were listed as the stem

borers (Sesamia calamistis, Sesamia butanephega, BLisfeola fusca, Chilo partelus,

Chilo orichalcociliela, Eldana saccharina); underground insects and nematodes

(Buphonella murina, HeterofTYchus licas, and Dereodus recticollis); and army worms

(Spodoptera exempta).

The parasItic weed, Striga hennon/mea, often causes serious losses.

Fajemisin et a1..(1985) and Kim et a!. (1985) reported differential responses to striga

among maize hybrids.

Simultaneous selection for many desirable traits will result in very little gain

from selection for any trait. Hence, a key challenge for the breeder is to select a

limited number of the most important traits that will lead to yield improvement and

risk avoidance for the farmer.

Allan (1971) demonstrated that hybrid seed and fertilizer must be

accompanied by improved husbandry, including timely planting and weed control

(see FIg. 1; Eberhart and Spra~e, 1973). With the total package, Kenya farmers

had tbe potential to increase Yields from 2 to 8 tons/ha, and most farmers succeeded

in at least doubling their yields. The increased production resulted in a significant

profit above inputs. Hybrids have been used on over 50% of the maize acreage in

Kenya for the past decade.

The heterotic pattern is a key factor in selecting germplasm for the breeding

populations in order to maximize the population- cross performance. If breeders in

all countries would use a common supenor heterosis pattern, the exchange of elite

inbreds among breeding programs over time would result in improved commercial

hybrids and would permit more effective population improvement with minimum

nsk of the loss of genetic variability from genetic drift v.'ith small effective

population sizes.

WeHhausen (1978) re-em'phasized the excellent population-cross

performance from T~eno and its related Caribbean and USA dents with Cuban

Flint and Coastal Tropical Flint. Several tropical breeding proWams have utilized

the Tuxpeno (dent) / Caribbean Flint heterosis pattern, includmg Brazil, Colombia

and Peru (Paterinani, 1985). The Brazitian dent population (ESALQ-VD-2) is

mainly Tuxpeflo germplasm and the flint one (ESALQ-VF-1) is mostly Caribbean

Flint. Recent experimental trials with improved CIMMYT populations continue to

show hi~h population-cross yields from this pattern (Vassal et aI., In Preparation).

EvaluatIons of populations formed by mixing these germplasm types within each

population, however, demonstrated good population per se performance, but

mediocre population-cross performance with almost no heterosis (Vassal et al., In

Preparation).

, Wellhausen (1978) recommended: "Instead of the formation of 12

populations, in which raCial complexes and hybrid patterns are disregarded, it seems

to me that tropical maize breeders might better focus their main cooperative efforts

on the development of two broad-based, high yielding, widely adapted, fertilizerresponsive,

more nutritive, biologically efficient popUlations., as follo....'S: (a) a dent

composite consisting of the combination of Tuxpeflo and related dents, such as the

Cuban, West Indies, and U.S.A dents, and their precursors, and (b) a flint

composite, consisting mainly of the Cuban, Coastal Tropical and Cateto flints and

their precursors." Goodman (1972, 1978) used morphological and geographic data

to show a close relation of the Tuxpeiio, Vandeo, and Celaya races.

In Kenya, a large amount of heterosis was obtained with two very narrow

base populations, a Tuxpefio-derived Kitale Station Maize and a high altitude flint

collection (No. 573) from Ecuador (Darrah et al., 1978 and Darrah, 1986). The

population-cross yield of two elite broad base populations, KCB x KCE, was only

86% of the population-cross )ield of the very narrow base populations, Kitale

II(Rll)C1 x Ec573(R12)C1 (Eberhart et al., 1973).


12

LOCAL

PRACTICES

q/ha

48.9 q/ha

($113.0S/ha)

80.6 q/ha

($208.87/ha)

RECOMMENDED

PRACTICES

Fig-. 1. :\J:li7.e improvement in Kenya throngh improycd hus­

/);\IH\ ry and [lit· lise of h vlnid seed and fen i IiJ:er. 1ncrcase


In the United States and central Europe, the Stiff Stalk Synthetic (dent) I

Lancaster (semi-flint) heterotic pattern has been very successful. Kim et al. (In

Press) and others have demonstrated that introgressIOn of Com Belt inbreds into

tropical germplasm can be useful for reducing plant height and increasing responses

to fertilizer as long as the disease resistance of the tropical germplasm is retamed.

Grain color and texture of the commercial product must be acceptable to the

consumer. However, these traits are highly heritable and can and must be rapidly

changed by selection once the breeding populations are formed. Experience has

shown that selection from mixed yellowjwhite to white ~rain color requires intense

selection because of minor genes and epistatic gene actIOn in some germplasm.

Seed size and shape and performance of seed parent single crosses and

especially seed parent inbred lines is critical to the reliability and cost of hybrid seed

production. Hence, designation of the Tuxpeno--Stiff Stalk breeding populations as

seed parent populations and the Caribbean Flint--Lancaster breeding populations as

pollen parent populations has merit. Selection for important seed parent traits will

then be required in only the seed parent breeding populations.

Several populatIOns and some inbred lines have been developed and released

that are adapted to .environmental conditions in eastern and southern Africa. Some

of these populations are listed in Table 2. The best population-cross performance

can be expected from populations improved by recurrent selection, especially

reciprocal recurrent selection and from the introgression of the best inbred lines

back into these superior populations. Many breeders have already formed elite

breeding populations with high population-cross performance and have impruved

them by recurrent selection. In these cases further introgression should be

extremely limited.

Eberhart et al., (1967) emphasized that the final population cross mean can

be predicted from data obtained in a partial diallel when epistasis is negligible. If

vaneties M to M m are composited mto the seed parent J?opulation (A) and

varieties N 1 to N n are composited into thelollen populatIOn (B), the populationcross

performance (A x B) can be predicte

as follows:

(Ax B) = (limn) (M 1 N-.1 + MJ1'l'2 + ... +MmN n ).

Introgression of Kitale II(Rl )Cn and GSll(R)Cl mto populations such as

Embu I, KwCA, and ZCA and introgression of EC573(Rl2)Cn and GSl2(R)Cl into

Embu II, KwCB, ZCZ, and UCA(F)Cn should have the potential to markedly

increase population-cross performance, not only in yield and stress tolerance, but

also in resistance to H. turcicum and P. sorghi.

Vassal et al. (In Press) report that Pop. 24 (Tuxpeno-Antigua) gave highest

yields with both Suwan 1 (a Caribbean mixed type improved breeding population

from Thailand) and Pop. 36 (Caribbean Composite) in a CIMMYT regional varietycross

diallel evaluation. Development of a white version of Suwan l-SR to

introgress into southern and eastern African pollen-parent populations may merit

high priority to more fully utilize the Tuxpeno/Caribbean Flint heterosis pattern.

IMPROVEMENT OF THE ELITE BREEDING POPULATIONS

Population improvement is the foundation of a maize breeding program

seeking to maximize long-term genetic gain per year.

Additionally, both short-term and mid-term goals can be achieved. Much

greater improvement of maize production can be achieved from hybrid and openpollinated

varieties developed with effective population improvement programs in

fewer populations than from ineffective programs in many populations.

Maximizing the rate of improvement of the population cross is vital because

this determines the rate of improvement of the denved hybrids and the advanced

generation of the population cross when this is used as the commercial product (Fig.

2). Choosing the appropriate recurrent selection method is critical. Reciprocal

13


14

Table 2. Improved white maize breeding populations for hybrid development

Seed Parent

Tuxpeiio

Kenya Flat White

Stiff Stalk Syn.

Pollen Parent

Caribbean(Mixed)

Ec573

Lancaster

Country

l.High Altitude (1600-2200 meters)

KCB(R)C3

Kitale II(R11)C10

KCE(R)C3

Ec573(R12)C10

Kenya

Kenya

2. Medium altitude (900-16OOmeters) Medium Maturity

Embu 11

Embul

GS11(R)C1

KwCA

ZCA

Early Maturity

Katumani VII

Embu12

Embu II

GS12(R)C1

GS16(R)C1

KwCB

ZCZ

UCA(F)C6

TZMSR-W

HASR

Pool9a

Katumani VIII

Katumaw-SR

Kenya

Kenya

Kenya/Mexiw

Mexico/CIMMYT

Uganda

Zambia

Tanzania

IITA/CIMMYT

Burundi

CIMMYT

Kenya

IITA/Kenya

3. Yellow Medium Altitude Source Populations

FS8B(R)C4

Diente de Caballo(R)C4

4. Streak Resistant Source Populations

TZPB-SR

Pop. 21-SR

Pop. 43-SR

Pop. 49-SR

FS8A(R)C4

Mayorbela(R)C4

Suwan l(S)Cn .

TZB-SR

TZSR-W-1

Pop. 22-SR

Pop. 29-SR

Florida

PuertoRico

Thailand

lITA/CIMMYT

lITA/CIMMYT

IITA/CIMMYT

lITA/CIMMYT


15

>-

Developmental

time lag . '(\

-\.\0

\).\'0-

?O~

o 1 2 3 4 6 7 8 9 10

Cycles of selection

Fig. 2. Expe~tcd improvement of the breeding populations, the

populEtion cross, and the best single cross with reciprocal

recurrent selection.


16

recurrent selection has been used successfully (Table 3) in several programs to

improve the variety-cross performance and to increase the heterosIs (Eberhart et al.,

1973; Helms et al., 1989; Moll and Hansen, 1984; Darrah et al., 1978; Darrah, 1986;

Homer et at, 1989; Odhiambo and co~ton, 1989). Use of different testers with

BSSS diverged BSSS(R)CI0 and BSI3(S C4 so that their variety-cross yield nearly

equaled their respective yields with BS

I(R)CI0.

The modification of using inbred lines from the r ciprocal population for the

tester, as suggested by Eberhart et al. (1973) and Russell and Eberhart (1975), has

real merit because selection for specific bybrid combinations is initiated in the

population improvement cycle, and gain from selection should benefit from the

mcreased variation among testcrosses. Multiple testers will make this system more

effective and should be used whenever feasible for two reasons: 1) multiple testers

provide a more representative sample of the reci{>rocal population and 2) the

probability of guickly identifying useful commerCIal hybrids is increased. The

experimental lines should be divided into three to five sets with a different elite

inbred line tester for each set (any given experimental line will be crossed to only

one tester). Set 1 would include the early Sz lines (based on the maturity of the

parental SJ. lines) with an early inbred tester from the reciprocal population. Sets

2,3,4,and )would include medium early, medium, medium late, and late Sz lines,

respectively, with a reciprocal tester of the corresponding maturity. This procedure

should counteract the correlation of yield with taIl, late genotypes because selection

for testcross yields the next season will be within each set. Then selected lines from

all sets would be recombined in all possible combinations to form the next cycle of

the population. The testers usually will be inbreds used in commercial bybnd

production. Testers will change WIth cycles of selection as improved inbreds are

developed. Single-cross testers can be u ed, but genetic variation among testcrosses

will be much less than for inbred line testers. The use of the reciprocal

population may be necessary for the first two cycles in a new breeding program until

mbred lines can be developed.

The formula for gam per year for the population cross from reciprocal

recurrent selection (Sprague and Eberhart, 1977) can be used to identify key factors

affecting the rate of improvement. This formula is as follows:

1 2

I) k 7; (1+F) SAl

G •

(

-

Y Y 2 1 2

S 1 7; (l+F) S 1>£1 1 2

::" + m' + 7; (1+F) SAl

1 2

+ (1) It 7; (l+F) SA2 .

Y 2 1 2

s, '4 (1+F) S.u:2 1 2

:,;; + m +7; O+F) S.u

where y=years per cycle, k is the standardized selection differential, F is the

coeffictent 0finbreeding of tbe parental plants of the experipentallines used for the

testcrosses, S e is !:2e pooled experimental error variance, S A is the additive

genetic variance, S AE Is the additive by environmental interaction, r is the number

of replications in e~llof m locations (or environments).

Increasing S A should increase gain, but estimates of additive genetic vari~ce

from very diverse popUlations have not been sbown to be larger than those from F

populations (Hallauer and Miranda, 1981) probably because of the finite number of

experimentaflines that can be evaluated. Very diverse breeding populations often

have higher mean yield per se, but the population-cross mean will be lower (Darrah

et aJ., 1972; Vassal et aI., In Preparation).


17

Table 3. YIELDS (TlHA) FROM RECURRENT SELECTION POPUlATIONS

PEDIGREE PARENT A PARENT B AXB HETEROSIS

From Darrah (1988)

KIlCO X EC573CO 4.70 3.80 6.36 50%

KII(R11)C5 X EC573(R12)C5 4.46 4.13 7.24(14%) 69%

KII(S21)C5 X EC573(S22)C5 4.52 4.44 6.59(4%) 47%

From Smith (1983)

BSSSCO X BSCB1CO 5.97 5.34 7.31 29%

BSSS(R)C7 X BSCB1 (R)C7 6.89 5.61 9.13(25%) 46%

BS13(HT)C7 X BSCB1 (R)C7 6.74 5.61 9.00(23%) 46%

BSSSCO X BSSSCO 5.97 5.97 5.97 0%

BSSS(R)C7 X BS13(HnC7 6.89 6.74 8.53(43%) 25%

From Helms, Hallauer & Smith (1989)

BSSSCO X BSCB1 CO 3.99 5.13

BSSS(R)C10 X BSCB1 (R)C10 5.31 7.30(42%)

BS13(S)C4 X BSCB1 (R)C10 5.32 7.45(45%)

BSSSCO X BSSSCO 3.99 3.99 3.99 0%

BSSS(R)C10 X BS13(S)C4 5.31 5.32 7.32(83%) 38%

-----------------------------------------------------------

() Percent improvement In the population cross

Table 4. Predicted yields of H611(R) at varying plant populations a

Cycle

Plant Population/ha

33,333

44,444

55,555

CO

C1

C2

C3

63.4

65.6

67.8

70.1

56.9

62.7

68.4

74.2

54.3

60.3

66.2

72.2

a Selection at 46,880 plants/ha.

From Allan and Darrah (1978).


18

Increasing the level of inbreeding of the parents is strongly recommended. F

increases from zero for S11ines (where the parental So plants are non-inbred) to 0.5

for ~ lines (where the Sl parental plants are 50% inbred). Although the time for a

cycle of selection is extended from y=2 to Y= 3 years, gain per year will be the same

(assuming only one ~ line will be retained from each selected Sl family) and

testcross evaluations must be made every three years instead of every oiller year

(Sprague and Eberhart, 1977). Furthermore, the Sllines can be screened for

disease resistance and other agronomic traits so that only elite S2 experimental lines

are advanced to the testcross evaluations.

Decreasing the phenotypic variance (the denominator) will increase gain. A

suitable experimental design and good field techniques are extremelyimportant.

Number of plan2S per plot ~as a mini~al effect. The error variance S e can b~

expressed as [(S win) + S ], where S is the plot-to-plot error variance :pd S w is

the within plot error variance. ~wenty to 25 plants per plot will reduce S win to a

negligible factor in relation to S (Eberhart, 1970). When testcrosses vary greatly in

plant height, use of two-row plots reduces the competition bias vs. one-row plots.

With high plant densities, the plot must be long enough to eliminate the border

effect caused by t~e alleys. Narrow alleys are desirable.

Because S AE is usually a signifIcant factor, only two replications per

location (environment) and four or five locations (environments) are recommended

(Fig. 3; Sprague and Eberhart, 1977). Increasing t~ numb~ of locations

(environments) reduces the contribution of both Sand S AE to the phenotypic

variance. Brewbaker (1985) recommends the use orvaried planting dates at a

location to provide different environments.

Increasing the selection intensity is a very important means of increasing gain

(Fig. 4) because gain is proportional to k. Gain with a 5% selection intensity

(k=2.06) is 147% compared to a 20% selection intensity (k= 1.40) and 117%

compared to 10% (k =1.76). Selection intensity can only be increased by: 1)

increasing the number of experimental lines evaluated in testcross trials; or 2) by

decreasing the number of lines selected for recombination to form the next cycle.

The development of only two elite reciprocal populations per breeder (with

testcross yield trials for the seed parent and pollen parent population phased in

successive years) will permit a higher selection intensity for the same resources than

will the use of larger numbers of populations. The number of selected lines that are

recombined effects the effective population size (Rawlings, 1970). Results from

studies at USDA-ARS/Iowa State University (Helms, et aI., 1989) show

conside~able genetic drift when only ten line~ a~e selected and rec~mbinedin closed

populatIOns. When several breeders work WIthm a general heterotIc pattern,

exchange derived inbred lines, and then introgress these acquired lines into their

breeding populations, the effective population size of each population will be greatly

increased. Lines for introgression must be carefully selected to maintain or enhance

the population-cross performance. Experience and theoretical considerations lead

to a recommendation of evaluating testcrosses from 250 to 400 S2 lines in order to

select 16 to 20 S2 lines for recombmation each cycle in order to achieve a selection

intensity of 4 to 8%.

SIMULTANEOUS IMPROVEMENT OF TRAITS WITH MULTI-STAGE

SELECfION

Farmers seek both risk avoidance and high yield in the maize hybrid and

open-pollinated varieties they select to grow. Hence, resistance to disease and

insect pests, tolerance to mOIsture stresses throughout the ~owin$ season,

resistance to root and stalk lodging and tolerance to low soil pH (aluminum toxicity)

are among the important agronomic traits for many African farmers. They also

have strong preferences for grain texture and color which must be included in tbe


19

5.0

..........

cu

..c

..........

rr

4.0

L 3.0

cu

Q)

>.

L

Cl>

2.0 ·0(\5

Q. . Ca't \

C

cu

(!)

1 .0

('e

? \ \

°1 2 3 4

Number of

5 6 7

locations

Fig. 3.

Expected gain from reciprocal recurrent selection

with Jarvis and Indian Chief in N. Carolina with 2

and 5 replications per location.


20

RELATION OF K AND SELECTION INTENSITY

IN BREEDING POPULATIONS

3.0

.....J


21

breeding objectives. Multi-stage selection is the key to this multi-trait improvement

because large numbers of So plants and SI lines can be screened in these two

generations. The rate of gam for any trait is reduced when additional traits are

selected; hence, selection in early cycles of improvement should be limited to yield

and the most important of the other agronoffilC traits. Because correlations among

agronomic traits are usually low (Suwantaradon et al., 1975), selection in the early

stages usually has ne~ligible effect on the variation among (amilies in the last stage

(testcross yield trialS).

A recommended scheme with multi-stage selection is shown in Fi~re 5.

Selection among So plants that are being selfed in season C (mass selectIon) is the

first opportunity to eliminate undesirable material. Because the phenotype of the

individual plant is the selection unit, gain will be expected only for traits with very

hicll heritabilities, including maturity, disease resistance (if a heavy uniform

inlection can be achieved), and ear height. Whenever possible, selections should be

made prior to anthesis to reduce the number of self-pollinations needed. In season

D, SI families will be available as the unit of selection which will provide the

opportunity to select for less heritable traits such as insect resistance, maize streak

VlnlS resistance, resistance to lodging, and tolerance to low soil pH. Adequate seed

will be available for laboratory screening, multiple field plantings and even

replication within screening tests if this IS required to increase the heritability of the

mean rating. ~ lines can be planted in season E in isolation blocks and detasseled

to obtain testcross seed. Sele tion in season F among testcrosses should be based

primarily on yield, but some selection pressure may be required for resistance to

root and stalk lod~ing. As many as 15,000 to 30,000 So plants and 1,500 to 3,000 Sl

lines may be reqUIred for reasonable gain in the agronomic traits.

Tolerance to moisture and heat stress is one of the most difficult traits to

improve. Use of higher plant densities in all field plantings is a critical technique as

this intensifies moisture stress. Plant densities for the S1's in season D should be

eSpecial

g

hi~h because of the reduced plant size due to IDbreedin.g. Allan and

Darrah 97 reported that yields of the H611(R)C3 variety cross (Kitale II(R11)C3

x Ed73 RU C3) were increased at 33, 44, or 55 thousand plants per hectare when

selection was done at 47 thousand plants per hectare (Table 4). When this

reciprocal recurrent selection program was initiated, this plant density in testcross

trials was 57% hi~er than the rate of 30 thousand plants per hectare normally used

by farmers (Ebernart and Sprague, 1973). With the subsequent progress, much

higher densities should be used now. A planting date later than the optimum date

often intensifies the moistur stresses, or at least varies the growth stages at which

the moisture stresses occur in comparison with the optimum planting date.

Selection for a higher level of prolificacy reduces the number of barren

plants under stress. The Kenyan variety-cross hybrid KCB(F)C4 x KCE(F)C4, with

136 ears per 100 plants at 16 high- altitude sites (Darrah 1976), was developed by

selecting the parental populations for increased prolificacy and yield for four cycles.

These populations should be excellent source materials to improve prolificacy in

both medium and high altitude breeding populations.

Many of the improved tropical breeding populations are tall and tend to have

excessive root and stalk lodging, which precludes the farmer fIOffi harvesting the full

yield potential of this germplasm. Because ~lant and ear height are highly heritable,

recurrent selection is very effective in reducmg height. However, yielatends to be

negatively correlated with height. In order to develop the desired lodging resistant

and high yielding hybrids, three aspects are critical: 1) use multi-stage selection in

the reciprocal recurrent selection program so that selection for yield follows

selection for reduced height and resistance to lodging in each cycle, 2) use hilUt

plant densities in all field I;'lantings (use of different plant densIties in each orthe

two replications in yield tnals is strongly recommended), and 3) conduct a parallel


22

Year 1

Season A:

Season B:

Recombine selected S2

Recombine F,.s

lines

Year 2

Season C: Self and mass select among So plants

for highly heritable traits

Season D: Plant 8, progeny rows

S, selection among rows

Self and mass select within rows

Year J

Season E: Produce testcrosses of selected 8 2 lines

with inbred tester

Season F:

Conduct yield trials of testcrosses

Fig. 5. Recommended schedule for reciprocal recurrent

selection--inbred tester


23

traditional pedigree breedin~program involving F2' three-way, and backcross

projects, where a short elite lObred line or commercial hybrid within the basic

heterosis pattern is crossed (and often backcrossed) with the best line from the last

cycle of RRS. Development of improved seed parent single crosses should receive

the highest priority.

With a three-year cycle in the RRS breeding program, the populations

should be staggered so that yield trials are grown for the seed parent {'opulation one

year, the pollen parent population the next year and the pedigree projects the third

year to provide a uniform work load.

DEVEWPING COMMERCIAL HYBRIDS FROM IMPROVED BREEDING

POPULATIONS

The rate of improvement of hybrids will be proportional to the improvement

of the population cross between breeding populations (Fig. 2). Hence, the efficient

development of new hybrids after each cycle of population improvement will be an

important phase of the comprehensive breeding system. Procedures normally used

in the traditional pedigree breeding system can be used to develop superior hybrids

from the improved breeding populations, but greater efficiencies will be obtamed by

use of the Yield evaluation tnals from reciprocal recurrent selection as the early

testing phase for inbred line development.

In the reciprocal recurrent selection--inbred tester phase, M testcross

families will have been evaluated for general combining ability in the seed parent

population and N testcross families in pollen parent population. When the elite m

x n hybrids among inbred lines derived from the selected S2 lines are evaluated in

an AB factorial mating design, selection of the best hybrid will result in a selection

intensity approaching 1/(M x N), rather than 1/(m x n).

Hybrids involving inbred lines of Stiff Stalk Synthetic (BSSS) from the

USDA-ARS/Iowa State University maize breeding program illustrate the potential

value of commercial hybrids developed from improved breeding populations.

Hallauer (1983) points out the importance of B14 and B37 developed from cycle 0,

B73 from cycle 5, and B84 from cycle 7. Hybrids involving B73 have been used

extensively not only in the USA, but also in Italy and Spain, and B73 has been used

as a source material for developing inbreds in many countries. The best cross

between selected S2lines from cycle 5 outyielded the population cross, BSSS(R)C5

x BSCB1(R)C5 by 35% (Russell and Eberhart, 1975). Suwantaradan and Eberhart

(1974) reported that the best derived sinaie cross (S2_x Sz) outyielded the variety

cross, BSK(S)C5 x BSSS(R)C5, by 18%. Recently B9U ana B91 have been

develoeed from cycles 7 and 8 of the BSCBl, respectively.

• Darrah and Penny (1975) extracted inbred lines from the second cycle of

Kitale II (Rll) and Ec573 (R12) and evaluated three-way cross hybrids. When the

lines were advanced to S3's, the best hybrid exceeded the cycle 2 variety cross by

17% (Fig. 6). Darrah ano Makuru (1978) reported high yields of double-cross

hybrids with C3 and C4 lines. The Kenya Seed Company subsequently has

produced double-cross hybrids from later cycle lines of these breeding populations.

Homer et aI. (1989) reported a 30% increase in yield of the population-cross

from four cycles of MS·-inbred Tester, but only a 19% increase from Sz selection

(Fig. 7). Elite inbred lines have been developed from this program..

Kim et al. (In Press) reported the develop.ment of elite hybrids for Nigeria

from inbreds derived from the lZB, lZSR and Pop. 21 improved breeding

populations usjn~ traditional pedigree breeding methodologies for developing the

mbreds and hybnds.

Use of multiple inbred-line testers with reciprocal recurrent selection

increases the effectIveness of developing new inbred lines in comparison with the

reciprocal population as tester. When the testers are commercial or pre-


100

Best TWC (967l

Best 1'1. of rwC(9J5)

- - - - ~ ,-O'I.} J'/.

90

1fi R'I,

191 ·fli-l

11 0',·

80

~ Tm 7+)

:! 70

o

,..

~,

60

-(

o I , , ---------,

'] " f, 8

Co (1 (, (1 C"

Years of selection

Cycles

Fig. 6 -Gain in the H611(R)Cn ynriely uoss versus extraction nod evnlualiun of

thrcc-l\'ay crosses (TWC)

+ Slope of the H61 t(R)Cn line ohlnined from a separate evaluation of proJ::rcss from

selection nnd sClllcd through the common entry 1161I(R)C3

tv

.t=


25

o 2

CYCLE

:3 4

Fig. 7. Least squares estimates ofgain from selection for grain yield

when evaluated as population crosses (FS8A Cn X FS8B Cn).

The R2 value is for fit of both lines in a single model.

From Horner, Magloire, and Morera (1989)


26

commercial inbreds (or single crosses), superior hybrids can be identified in the

reciprocal recurrent selection yield tnals (early testing) and then retested at

advanced levels of inbreeding with the same tester. Three-way (TWC) and doublecross

(DC) hybrid performance can be predicted'from single cross (SC) data and

double cross performance from three-way cross results (Otsuka et al., 1972; Sprague

and Eberhart, 1977).

TWC(AB XC) = (l/Z)[SC(AC)+SC(BC)]

DC(AB x CD) = (1/4)[SC(AC) + SC(AD) + SC(BC) + SC(BD)]

DC(AB x CD) = (l/Z)(TWC(AB x C) + TWC(AB x D)]

Use of S3 and S4 inbred lines m commercial hybrids is strongly

recommended over S6 to SlO lines to restrict the loss of vigor of the inbred lines.

However, cold storage vaults and appropriate inbred line maintenance programs are

needed to prevent genetic drift withm each line when S3 and S4 levels of inbreeding

are used.

Once elite inbreds have been developed from the breeding populations, a

limited amount of pedigree breeding with F Z ' first backcross (BC 1 ) and three-way

(TWC) source materials from these elite inoreds may be useful in achieving shortterm

breeding objectives, especially in seeking disease resistance, stress tolerance,

lodging resistance, and reduced heIght. However, the inbreds to be used as source

materials must be carefully selected. For a cross (A x B), the mean of all derived Fn

lines crossed to a reciprocal tester "G" can be predicted (assuming negligible

epistasis) as follows:

(l/Z)(A x G) + (l/Z)(B x G)

Corresponding formulas can be used for first backcross (A x B)A and threeway

cross (A x B)C ~rojectswith a tester G, respectively, as follows:

(3/4) A x G) + (1/4)(B x G)

(1/4) A x G) + (1/4)(B x G) + (l/Z)(C x G)

'When information on the relative performance of all (A x G), (B x G) and

(C x G) type single-cross hybrids is available for the traits of interest, the choice of

source materials can be made objectively to select a limited number of projects with

an improved probability of success.

Multi-stage selection for the key agronomic traits is essential for pedigree

breeding projects as well as for the population improvement program. BeCause

larger numbers of derived Fo.lines are required for multi-stage selection, only a

limited number of different 1'2, BC 1 , and TWC projects will be feasible.

Significant increases in maize production require improved agronomic

practices in addition to the improved hybrids. Timely date of planting, optimum

plantin~ rate, good weed control, and rotation with a legume crop are important

factor~ m maize yields that can be obtained with no cash expendlture. Application

of modest levels of fertilizers is needed for further yield increases which will require

a cash input. Although hybrid seed requires a cash purchase each year, it can be

used as a lever to get the farmer to adopt the total package.

The performance advantage of hybrids will be realized by the farmer only

when high quality hybrid seed is available to him. Seed companies in Ethiopia,

Kenya, Malawi, Nigeria, Tanzania, Zambia, and Zim~abwe have provided this high

quality seed to their customers at very modest prices.

Z. This paper is a revision of "A Comprehensive Breeding

System for Maize Improvement in Africa" by S.A Eberhart,

S.l


27

REFERENCES

Allan, A Y. 1971. The influence of agronomic factors on maize yields in Western

Kenya with special reference to time of planting. Ph.D. Thesis, Vniv. of East

Africa, Kampala, V ganda.

Allan, A Y, and L. L. Darrah. 1978. Effects of three cycles of reciprocal recurrent

selection on the N and plant population responses of two maize hybrids in

Kenya. Crop Sci. 18:112-114.

Brewbaker, J. L. 1985. The tropical environment for maize cultivation. In A

Brandolini and F. Salamtni (eds.), Breeding Strategies for Maize Production

Improvement in the Tropics. Food and Agric. Org. of V.N. Instituto

Agronomico Per L'oltremare, Firenze.

Darrah, L. L. 1976. Altitude and environmental responses of entries in the 1974-75

eastern African maize variety trial. E. Afr. Agric. For. J. 42(2):153-166.

Darrah, L. L. 1986. Evaluation of population improvement in the Kenya maize

breeding methods study. pp. 160-175. In B. Gelaw (ed.), To Feed Ourselves:

A Proceedings of the Firl>t Eastern, Central, and Southern Africa Regional

Maize Workshop. Lusaka, Zambia. 10-17 Mar., 1985. CIMMYT, Mexico,

D.F.

Darrah, L. L., S. A Eberhart, and L. H. Penny. 1972. A maize breeding methods

study in Kenya. Crop Sci. 12:605-608.

Darrah, L. L., S. A Eberhart, and L. H. Penny. 1978. Six years of maize selection in

"Kitale Synthetic II", "Ecuador 573", and "Kitale Composite A" using methods

of the comprehensive breeding system. Euphytica 27:191-204.

Darrah, L. L., and S. Z. Mukuru. 1978. Altitude and environmental repsonses of

entries in the 1976-77 eastern African maize variety trial. E. Afr. Agric. For.

J.43(4):355-368.

Darrah, L. L., and L. H. Penny. 1975. Inbred line extraction from improved

breeding populations. E. Afr. Agric. For. J. 41(1):18.

Eberhart, S. A 1970. Factors effecting efficiencies of breeding methods. African

Soils 15:655-667.

Eberhart, S. A, S. Debela, and A R. Hallauer. 1973. Recurrent selection in the

BSSS and BSCB1 maize populations and half-sib selection in BSSS. Crop

Sel. 13:451-456.

Eberhart, S. A, M. N. Harrison, and F. Ogada. 1967. A comprehensive breeding

system. Der Zuchter 37:169-174.Eberhart, S. A, L. H. Penny, and M. N.

Har:rison. 1973. Genotype by en~ronment interactions in maize in eastern

Africa. E. Afr. Agr. For. J. 39(1).61-71.

Eberhart, S. A, and G. F. Sprague. 1973. A major cereals project to improve

maize, sorghum, and millet production in Africa. Agron. J. 65:365-373.


28

Fajemisin, J. M., Y. Efron, S. K. Kim, F. H. Khadr, Z. T. Dabrowski, J. Mareck, M.

Bjarnason, V. Parkison, L A Everett and A Diallo. 1985. Population and

varietal development in maize for tropical Africa through resistance breeding

approach. In A Brandolini and F. Salarnini (eds.), Breeding Strategies for

Maize Production Improvement in the Tropics. Food and Agric. Org. of

U.N. Instituto Agronomico Per L'oltremare, Firenze.

Goodman, M. M. 1972. Distance analysis in biology. Syst. Zool. 21:174-186.

Goodman, M. M. 1978. A brief surnm~of the races of maize and current

attempts to infer racial relationships. In D. B. Walden. Maize Breeding and

Genetics. Chapter 10. John Wiley & Sons, New York.

Hallauer, A R 1983. Quantitative analysis of Iowa Stiff Stalk Synthetic. Stadler

Symp. Vol. 15. University of Missouri, Columbia, MO.

Hallauer, A R, and J. B. Miranda, Fo. 1981. Quantitative genetics in maize

breeding. Iowa State Univ. Press., Ames, IA

Helms, T. C, A R Hallauer, and O. S. Smith. 1989. Genetic drift and selection

evaluated from recurrent selection programs in maize. Crop Sci. 29:602-607.

Helms, T. C, A R Hallauer, and O. S. Smith. 1989. Genetic variability estimates

in improved and nonimproved "Iowa Stiff Stalk Synthetic" maize populations.

Crop Sci. 29:959-962.

Horner, E. S., E. Magloire, and J. A Morerea. 1989. Comparison of selection for

S2 progeny vs. testcross performance for population improvement in maize.

Crop Sci. 29:868-874.

Kim, S. K., Y. Efron, J. Fajemisin, and F. H. Khadr. 1985. Evolution and progress

of hybrid maize project at UTA In A Brandolini and F. Salamini (eds.),

Breeding Strategies for Maize Production Improvement in the Tropics. Food

and Agr. Org. of U.N. Instituto Agronomico Per L'oltermare, Firenze.

Kim, S. K., M. H. Lee, Y. Efron, F. Khadr, J. Fajemisin, and J. Mareck. In Press.

Combining abilities for maize inbreds of tropical vs. tropical x temperate

origins. Crop Sci.

Moll, R H., and W. D. Hanson. 1984. Comparisons of effects of intrapopulation vs.

interpopulation selection in maize. Crop Sci. 24:1047-1052.

Odhiambo, M. 0., and W. A Compton. 1989. Five cycles of replicated SI vs.

reciprocal full-sib index selection in maize. Crop Sci. 29:314-319.

Otsuka, Y., S. A Eberhart, and W. A Russell. 1972. Comparisons of prediction

formulas for maize hybrids. Crop Sci. 12:325-331.

Paterniani, E. 1985. State of maize breeding in tropical areas of South America. In

A Brandolini and F. Salamini (eds.), Breeding Strategies for Maize

ProductioQ ~mprovementi? the Trop-ics. Food ClJ,ld Agriculture Organization

of U.N. Instltuto Agronomico Per L oltremare, Frrenze.


29

Rawlings, J. O. 1970. Present status of research on long- and short-term recurrent

selection in finite populations -- choice of population size. Meeting Working

Group Quant. Genet. Sec. 22. Int. Union Forestry Res. Org. 2nd (Raleigh,

NC), pp. 1-15.

Russell, W. A, and S. A Eberhart. 1975. Hybrid performance of selected maize

lines from reciprocal recurrent and testcross selection programs. Crop Sci.

15:1-4.

Sprague, G. F., and S. A Eberhart. 1977. Corn breeding. In G. F. Sprague (ed.),

Corn and Corn Improvement. Chapter 6. American Society of Agronomy,

Madison.

Suwantaradon, K, and S. A Eberhart. 1974. Developing hybrids from two

improved maize populations. Theor. App!. Genet. 44:206-210.

Suwantaradon, K, S. A Eberhart, J. J. Mock, J. C. Owens and W. D. Guthrie.

1975. Index selection for several agronomic traits in the BSSS2 maize

population. Crop Sci. 15:827-833.

Vasal, S. K, D. L Beck. and J. Crossa. In Preparation. Heterosis and combining

ability of CIMMYTs tropical early and intermediate maturity maize

germplasm.

Vasal, S. K, J. Crossa, and D. L Beck. In Preparation. Combining ability study in

diallel crosses of CIMMYT's tropical late yellow maize germplasm.

Wellhausen, E. J. 1978. Recent developments in maize breeding in the tropics. In

D. B. Walden. Maize Breeding and Genetics. Chapter 5. John Wiley &

Sons, New York.

DISCUSSION

Question:

Omolo.

How is introduction of genes from one populations to the other done

for resistance to maize streak virus and stem borer.

Answer:

Eberhart.

Few genes are involved in streak resistance. Hence, a backcross

program can be effective in introgressing maize streak resistance.

For stem borers a parallel program is probably needed to first develop

a good source of stem borer resistance. With no dominance for insect

resistance, Full-sib selection (FS) for insect resistance in both the seed

parent population and a separate FS in the pollen parent are

desirable. Once these good sources of resistance are developed,

introgression by conventional breeding or transfer by biotechnology

may be possible.


30

Comment:

Venegas. At the experimentation level we witness a policy objective of

producin~better varieties with high yields. However, the linkages between

the techrucal and economic aspects are not there. Perhaps, one

recommendation coming out from the workshop is to do more research and

policy analysis on linking technical results, farmer responses and economic

expectations.

Chumo. Could you please elaborate more on multi-stage selection.

Answer:

Eberhart. With multi-stage selection for stability i.e. complete disease

resistance, tolerance to stress, tolerance to insects, correct maturity, the

advanced generation of the variety cross will give higher yields under all

conditions (as will the resulting hybrids) than the local variety. In addition

improved a~onomic practice must be used by the farmer - early planting,

clean weed109 correct plant densities per acre, rotation with legumes (or

intercropping with legumes), and modest use of fertilizer.

Question:

Omolo. What are the merits of using a tester in reciprocal recurrent

selection because in a study where we compared the two breeding methods

Sl and RRS for improvement of yield and quality of protein in two maize

populations KCB and KCE RRS still made faster progress without the use of

testers other than using the populations themselves reciprocally.

Answer:

Eberhart. With recurrent selection, the pollen {Jarent should be improved

using inbred lines from the seed parent populatIOn as testers to insure high

yielding hybrids.

~ selection in the seed parent population will increase the yield of inbred

lines but this is only important when the commercial hybrid will be a single

cross.

Question:

Compton. Standability is a difficult trait to improve and at Nebraska we have

never been able to improve standability by mass selection, it also doesn't

look as effective when done on inbred per se basis. How is this done in

, multiple-stage selection without using an index?

Answer:

Eberhart. Sl pro~eniesgrown at hi~h plant densities (perhaps 2 reps) may

have some potential to identify 10dgIOg susceptible lines. Use of a

penetrometer on Sllines (mean rating) might also be desirable based on

research by Zuber and Darrah.

Question:

Dejene. In the reciprocal recurrent selection procedure you explained, is the

inbred tester related to the population intended for improvement?


31

Answer:

Eberhart. No, the inbred testers (multiple testers) are commercial inbreds

from the reciprocal population.

KII (R11)Cn Sz lines would use 4 Ec573 (RlZ) Cn-Z inbred lines as testers.

Ec 573 (RIZ) Cn SZlines would use 4 different KII (Rll) Cn-2 inbred lines

as testers.

Year 1

Season A:

Season B:

Year 2

Season C:

Season D:

Recombine selected S2 lines

Recombine Fl's

Self and mass select among SO plants

for highly heritable traits

Plant S1 progeny rows

S1 selectIOn among rows

Self and mass select within rows

Year 3

Season E:

Season F:

Produce testcrosses of selected S2 lines

with inbred tester

Conduct yield trials of testcrosses

Fig. 5. Recommended schedule for reciprocal recurrent

selection--inbred tester


32

APPENDIX

Description of Breeding Populations

Diente de Caballo(R)C4. This yellow dent Puerto Rican population was improved

with four cycles of reciprocal recurrent selection (Mayorbela tester) for increased

yield and disease resistance at the USDA-ARS Tropical Research Station,

Mayaguez, Puerto Rico.

Ec 573(RI2)ClO. The Kenya Kitale Station introduced the Ecuador 573 race

collection from CIMMYT. Ten cycles of reciprocal recurrent selection (Kitale

II(Rll)Cn tester) for increased yield and disease resistance (H. turcicum) were

completed. This high altitude population also is highly resistant to Pucirua sorghi.

Embu 11. (H621 X Kat. IV)(F X G)(Kat. VI) advanced generation.

Embu 12. (Comiteco X Kat. III)(Comiteco-selected X Kat. V) advanced

generation.

Embu I. This population was formed from a very wide range of germplasm

including Kenya Flat White germplasm, Muratha, Tuxpefio, and Caribbean Flint

type germplasm.

Embu II. This population was formed from a wide range of germplasm including

Eto and other Caribbean Flint type germplasm, Corniteco, KCE, and Jarvis x Indian

Chief.

FS8A C4. This yellow breeding ~opulation was developed at Gainsville, FL by four

cycles of full-sib selection for resistance to SCLB (H. maydis), followed by four

cycles of reciprocal recurrent selection (inbred tester). Source materials were

estimated to be 41% tropical, 40% Southern USA, and 19% Corn Belt.

FS8B C4. This yellow breeding population was developed at Gainsville, FL by four

cycles of full-sib selection for resistance to SCLB (H. maydis), followed by four

cycles of reciprocal recurrent selection (inbred tester). Source materials were

estimated to be 54% tropical, 32% Southern USA, and 14% Corn Belt.

GS07(R)C2. A broad base population, Corn Belt Kenya I, was developed at Kitale

with germplasm 'obtained from Kenya, USA, France, Central and South America.

The Kenya germplasm included Katumani IV, Katumani Panmix, Embu II and

Kenya Pp coastal. Funk Seeds International improved this yellow dent population

by two cycles of RRS in Minnesota before releasing it as GS07(R)C2 (PI 520761).

GSll(R)C1. This population was formed by Funk Semillas at Guadalajara, Mexico

from Kitale II(Rll)C6 by introgressing 12.5% Stiff Stalk Synthetic (RSSC) and

12.5% Tuxpefio planta baja C7. One cycle of reciprocal recurrent selection (ETO

tester) was completed. Available from the USA National Plant Germplasm System

(PI 520764).

GSI2(R)C1. This population was formed by Funk Semillas at Guadalajara, Mexico

from Ec 573(R12)C6 by introgressing 25% CIMMYT ETO (IPTT32 C2 and Leaf

and Tassel Reduction C6) populations. One cycle of reciprocal recurrent selection


33

(GSll tester) was completed. Available from the USA National Plant Germplasm

System (PI 520765).

GS16(R)Cl. This white semi-flint population was developed from ETO (IP1T32 C2

and Leaf and Tassel Reduction CO) populations at Guadaljara, Mexico and released

by Funk Seeds International (PI 520766).

GS17CO. This yellow dent sythetic was developed in Georgia from (Tuxpeno P.B.

C7 X RSSSC) by Funk Seeds International (PI 520762). GS34(R)C2. This yellow

semi-flint population was formed by crossing Ec 573 (R12)C4 TO BSCBl(R)C7.

BSll(FR)C3 AND BS12(HI)C6 and then backcrossing to the Iowa Synthetics.

After two cycles of RRS in Georgia, this population was released by Funk Seeds

International (PI 520763).

HASR. This white High Altitude Streak Resistant variety was developed by

selection for maize streak resistance in local varieties in Burundi.

Katumani-SR. One of the Katumani populations was converted to streak resistance

in a backcross project for Tanzania by liTA.

Katumani VII. This population was formed from Katumani V; (USA 342 X

Camellia); and a Katumani Panrnix involving Mexican accessions, Katumani II and

Katumani III.

Katumani VIII. This broad base p01?ulation was formed from Katumani VI; French

Flint Composite; (Alaskan ComposIte X Central American High Altitude

population); and Com Belt-Kenya II.

KCB(R)C3. The Kenya Kitale Station developed this population from a wide range

of Kenya Flat White maize strains and elite inbred lines. This was followed by an

introgression of 25% Ecuador 573. Four cycles of full-sib selection for prolificacy

and increased yield and three cycles of recIprocal recurrent selection WIth

KCE(R)Cn as tester have been completed.

KCE(R)C3. The Kenya Kitale Station developed this broad base population from

Kitale II and other improved Kenya Flat White maize varieties, ehte inbred lines

from Kitale II, Ecuador 573, Jala, Comiteco, Chalqueo, Colombian inbred lines,

Costa Rica 76, Costa Rica Comp., and collections from the Oloton, Montaa,

Amagaceo, T~eno, Celaya and Cuzco races. Four cycles of full-sib selection for

prolificacy and mcreased yield and three cycles of reciprocal recurrent selection with

KCB(R)Cn as tester have been completed.

Kitale II(Rll)ClO. The Kenya Kitale Station developed this popUlation from the

Kitale Station strain of Kenya Flat White maize by one cycle of half-sib selection

and ten cycles of reciprocal recurrent selection (Ec573(R12)Cn tester) for increased

yield and disease resistance (H. turcicum and P. sorghi). Kenya Flat White maize

was derived from Kickory King, White Horsetooth, Ladysmith White, Salisbury

White, Champion White Pearl and Iowa Silver Mine, which seem to have been

derived from Tuxpeno source material.

Kawanda Composite A (KwCA). This population was formed by compositing

White Star, Western Queen, Muratha, Askari, ZCA, Embu I, H632, SR52, KCB,

and KCE.


34

Kawanda Composite B (KwCB). This population was formed from Caribbean type

germplasm including Diacol varieties and hybrids, Pioneer, Poey, ICA, Agroceres,

INIA and Honduras hybrids, and Ukiriguru populations.

Mayorbela (R)C4. This yellow Puerto Rican population was improved with four

cycles of reciprocal recurrent selection (Diente de Caballo tester) for increased

YIeld and disease resistance at the USDA-ARS Tropical Agricultural Research

Station, Mayaguez, Puerto Rico.

Pop. 21-SR. IITAjCIMMYT develo{'ed this maize streak resistant population from

CIMMYT Pop. 21 in a backcross project. Pop. 21 included the Tuxpefio race

collections Veracruz 48, Veracruz 143, Veracruz 174, Michoacan 137, Michoacan

166, V-52OC, Colima group I-Mix. 1 and Pool 24 (Tuxpefio germplasm).

Pop. 22-SR. lITAjCIMMYT develo{'ed this maize streak resistant population from

CIMMYT Pop. 22 in a backcross project. The components of Pop. 22 were

Tuxpefio, ETO, Antigua group 2, USA hybrids, Compuesto Centro-Americano, lines

from El Salvador, V-520C, Nicarillo, and Pool 24 (Tuxpefio germplasm).

Pop. 29-SR. lITA/CIMMYT develo{'ed this maize streak resistant population from

CIMMYT Pop. 29 in a backcross proJect. The components of Pop. 29 were

Tuxpefio, Cuban Flints and ETO.

Pop. 43-SR. lITAjCIMMYT developed this maize streak virus resistant, downy

mildew resistant population from CIMMYT Pop. 43 (La Posta) in a backcross

project. Pop. 43 was formed from 16 elite inbred lines from the Tuxpefio race.

Pop. 49-SR. lITA/CIMMYT developed this maize streak resistant population from

CIMMYT Pop. 49 in a back cross project. Pop. 49 originated from mitial selection

of 240 fill-sib families from Tuxpefio Crema-l planta baja cycle 17 (derived from

Pop. 21).

Suwan I-SR. IITAjCIMMYT developed this maize streak resistant population

from Suwan 1 in a backcross project. Suwan is a broad base population developed

by Kasetsart University, Bankok, Thailand. Components are mainly elite Caribbean

varieties but Tuxpefio, Salvadoreo and USA germplasm was also included in the

original £opulation (Thai Compo #1). After three cycles of SI selection, a backcross

project (HC3) was completed to obtain downy mildew resistance with Philippine

DMRI and DMR5 as sources of resistance to develop Suwan 1. Subsequent cycles

of SI selection were completed with emphasis on gram yield and other desirable

characters.

lZB-SR. This broad base population was formed by lITA from Nigerian Comp. B

(Tuxpefio germplasm) and Nigerian Compo A (Caribbean Flint germplasm).

Several cycles of SI selection for increased yield were completed. Streak resistance

was obtaIned in a backcross project by lITAjCIMMYT.

lZMSR-W. This streak virus resistant population was formed by ITTAjCIMMYT

from the cross oflZSR with the best available varieties and hybrids from Eastern,

Southern and Central Africa.

lZPB-SR. lITA/CIMMYT developed this maize streak resistant population from

Tuxpeno Crema-l planta baja cycle 17 in a back cross project with streak resistant

plant from lZ-Yellow.


35

TZSR-W-l. This streak resistant population was developed by IITA Tuxpeno

planta baja was the base population with subsequent introgression of TZB, Pop. 21,

and Pop. 22 x TZSR, and streak resistant plants from TZ-yellow.

UCA(F)C6. Ukiriguru Composite A was formed from Kitale Flat White material,

Tuxpeno, and Caribbean Flint type germplasm, and improved by six cycles of Full

Sib recurrent selection.

ZCA Zambia Composite A was formed from seventeen Zambia inbred lines and

Hickory King.

ZCZ. Zambia Composite Z included Sl selections from a Bajio populatio obtained

from Mexico, Corniteco, and Caribbean Flint type germplasm.


36

BREEDING STRATEGIES TO OVERCOME CONSTRAINTS

AND INCREASE MAIZE PRODUCTIVITY

IN SUB-SAHARAN AFRICA.

A.O. Diallo 1 , G.~ Edmeades 2 , c.y.TJn~,

J.A. Deutsch and M. Bjarnason

1. Introduction

Maize in sub-Saharan Africa is cultivated from 14 0 N to about 26 0 S, from sea

level to 3000 m altitude, in conditions which vary with latitude, altitude and rainfall.

Of the total maize area of 15.3 million ha (CIMMYT estimate), 7.2 million are in

the lowl nd tropics and 8.1 million ha in the subtropical/midaltitude and

highland/transition zones (CIMMYT, 1988b).

Maize is mainly grown under rainfed conditions, both in a sole crop and

mixed cropping systems. It is the staple food in many countries of Eastern and

Southern Africa, such as Kenya, Malawi, Zambia and Zimbabwe. In West and

Central Africa maize is a major component of the diet in Benin, Cameroon, Nigeria,

Togo, Ghana and Zaire. However, average maize yield in these countries is

currently about 1 t/ha, which is only 50% of the average yield of all developing

countries and 18% of the average yield for developed countries (CIMMYT, 1986).

Biotic, abiotic, institutional and socio-economic constraints, and an under-utilization

of improved germplasm are the contributors to low maize yields in sub-Saharan

Africa.

The objectives of this paper are to describe the breeding strategies used by

CIMMYT to reduce the impact of drought stress, low nitrogen availability,

aluminum toxicity, Jiseases and insects In sub-Saharan Africa. Given the

importance of maize in the region as human food and its high potential for feed,

CIMMYT research on quality protein maize (OPM) is also summarized.

This paper fists some special-purpose germplasm carrying tolerances to these yieldreducing

agents or genes for improved protein quality, and which are available to

national programs on request. Where appropriate, we draw on data and experiences

from the IITA/SAFGRAD project (to which a CIMMYT staff member was

seconded from 1984 to 1988).

2. Major Maize Production Environments of sub-Saharan Africa

The FAa classification system of ecological zones in sub-Saharan Africa

(FAa, 1978), based primarily on climatic characterizations, has been expanded by

other workers (Gelaw, 1984; Efron, 1985; Fajemisin, 1986; CIMMYT, 1989) to

include non-quantitative assessments of the major abiotic and biotic

constraints found in each zone. For these descnptions to be truly useful in setting

breeding priorities however, the magnitudes of each constraint must be quantified,

and the zones reclassified on the basis of plant performance, consumer preference

and the dominant cropping systems in WhICh maize is

found. Using such an approach, CIMMYT has recently described eisht major

germplasm classes, or "mega-environments", in sub-Saharan Africa (CIMMYT,

1988b; Diallo et al., 1989). This analysis shows (Table 1) that diseases and insects

are the major biotic and drought impose major limits to maize productivity.

The database on which the classification is based is not yet complete; data on

the effect of low soil fertility, weeds, and high soil acidity for sub-Saharan Africa are

1. CIMMYT Maize Breeder, Bouake, B.P. 2559, Cote D'Ivoire

2. CIMMYT Maize Physiologist and

3. Maize Breeders, EI Batan, Mexico


Table 1, Maize production environments and abiotic and blotlo constraints In sub-Saharan Afrlca.

-------------------------------------------------------------------------------------------

Environments 1 2 3 4 5 6 7 6 Total

-------------------------------------------------------------------------------------------

Ecology LT l LT 1 LT LT ST ST ST HLfTZ Area 'lI:.Area

Maturity EfXE2 I LfXL E I LfXL E/I LfXL

Total area (,000 hal 2028 1610 3527 130 2294 4197 71 1461 15,318 100'"

Constraints ('lI:. environment affected)

Moisture stress' 79 15 4 46 62 0,5 0 0 3490 23

Strlga" 2 2 2 0 0 2 0 1 259 2

(Diseases)

(Insects)

Leaf blight

Rust

H, maydls 56 45 66 0 2 0 0 0 4226 28

E. turclcum 2 0 19 62 32 73 30 100 6090 40

P. sorghl 0 0 0 8 32 65 30 58 4343 28

P. polysora 19 16 71 0 0 8 0 0 3465 23

Maize streak virus 72 84 84 54 80 32 0 7 9136 60

Stalk rot

Ear rot

Borers

Stalk rots (not specified) 12 10 61 0 0 2 0 0 2689 18

Fusarium stalk rot 19 12 7 0 0 0 0 0 830 5

Diplodia stalk rot 0 0 0 0 0 0 0 16 240 2

Ear rots (not specified) 10 16 62 0 68 8 0 36 5068 33

Fusarium kernel/ear rot 11 33 22 46 0 29 0 19 3117 20

Diplodia ear rot 11 33 17 0 0 29 0 36 3107 20

Boren! (not specified) 23 41 76 0 0 21 0 19 4979 33

Chilo stem borer 12 15 4 46 6 19 0 0 1605 10

Busseola s1aJkborer 7 3 3 15 81 57 70 76 5727 37

Sugarcane stalkborer 3 2 7 0 0 0 0 0 345 2

Pink stem borer 6 4 5 46 32 34 0 0 6474 33

Armyworm I 21 0 0 0 0 0 0 375 2

Roolworm/cutworm 2 I 2 8 32 15 tOO 36 2539 17

Storage pests 9 17 8 46 32 20 70 38 2996 20

Termites 12 28 9 0 0 45 0 0 2865 t9

-----------------------------------------------------------------------------------------

1 .

LT = lowland tropical; ST = subtropical; HLfTZ = highland transition zone' 2E = early; XE = extra early; I = intermediate; L = late; XL = extra late

* Areas In which moisture stress is frequently or usually encountered during the crop season.

*. Areas In which biotic constraints have a rating of 2 or above in 0-5 scale where 0 Is no presence and 5 vary severe,

*.. Different insects pests or diseases may be present in the same area, and the percentage total ares affected can exceed 100,

Source: adapted from CIMMYT (t988)

w

-...&


38

largely lacking. Experience suggests that these limits to yield are serious, and they

are therefore being addressed by the CIMMYT Maize Program.

3. Breeding for Abiotic Stress Tolerance.

3.1. Prolificacy and General Stress Tolerance

Several studies have shown that a short anthesis-silking interval (ASI) (Dow

et al., 1984) and increased prolificacy (Motto and Moll, 1983) in maize are positively

associated with an increase in tolerance to a range of stresses which cause reduced

photosynthesis per plant at or near flowering. Increased prolificacy has several

advantages in tropical maize; prolific cultivars may show an improved tolerance to

plant density, and stability of yield across a wide range of densities is often increased

(Prior and Russell, 1975; Bertin et al., 1976). Plant density in monocropped sub­

Saharan maize fields typically varies from ade'l.uate to low (e.g., Akposoe and

Edmeades, 1982), and under reduced competitiOn an ability to develop and fill a

second ear on each plant will increase yields at low plant densities. The capacity to

develop second ears may also guard against the risks associated with poor

germination or the failure of an intercrop.

In 1985 three semi-prolific populations were established at CIMMYT from

elite families with prolific tendenCIes. Two of these populations, SPE and SPL

(Table 2), were white-grained, adapted to the lowland tropics, and early and late

maturing, respectively. The third, SPMAT (Table 2), was subtropical, intermediate

in maturity, and of mixed grain color.

AlIl?opulations have undergone four cycles of recurrent selection in a halfsib

recombmation block, in which each family was grown at a high (106-133,000

plants/ha) and a low (35-53,000 plants/ha) plant density. Selection of the superior

50% of families was based on an index designed to produce high grain yield,

improved standability, increased number of ears per plant at high denSity, high ear

numbers per plant, average upper ear height and a short interval between first and

second ear silking.In SPMAT, a major introgression came from a maize x

Tripsacum cross, itself handled as a separate population for four cycles and

backcrossed several times to lowland tropical maize. Trials to evaluate progress

were conducted in 1988 (Table 3), and showed thatthis rather mild selection

procedure had been successful in increasing prolificacy while maintaining maturity.

A concomitant increase in stalk lodging was observed, but no significant

increases in yield potential or in the optimum density for grain yield resulted from

selection.

Recently the breeding scheme has changed to a recurrent S1 selection

scheme, thus allowing reduced tassel size (Geraldi et al., 1985) and reduced ASI to

be'included in the index. The realized heritability and value of individual traits

related to prolificacy or to tolerance of high plant density are being examined by

bidirectional selection, in which synthetics are formed from the best and worst

fractions of the population for the trait in question. These synthetics and cycle bulks

are available for GIstribution to national programs.

3.2 Drought

Drought tolerance is the ability of one genotype to be more productive than

another under a similar condition of drought (Quizenberry, 1982). Ability to yield

well in dry environments may depend on drought avoidance, drought tolerance, or

both. The type of drought environment in which a crop will be grown determines

the type of tolerance mechanisms required and the corresponding breeding

methodology to be used.


Table 2. General charac1eristics of germplasm tolerant to general stresses, drought and low soil nitrogen being developed by CIMMYT, Mexico

Special

Populatlon

Maturltya

(daya)

Grain

color

Graln b

texture

dlseaa.

realatllncea c

A: General atre.. tolerant

Semi-prolific e!lrly

(SPE)

Semi-prolific late

(SPL)

Semi-prolific midaltitude

tropical

(SPMAT)

B: Drought tolerant

Tuxpe~o sequia C 6

Pool 26 sequia

La Posta sequia

Pool 18 sequia

Pool 16 sequia

Drought tolerant

population (DTP)

C: Low fertlilty tolerant

Across 8328 N

95

115

white

white

F/D

F/D

110 mixed F/D

115 white D

115 yellow F/D

120 white D

90 yellow F/D

95 white D

110 mixed F/D

115 yellow D

Ear rots

Tar spot

Ear rots

Tar spot

Ear rots

Streak

virus

Ear rots

Streak

Ear rots

Ear rots

a Days to harvest in an environment averaging 3f:PC and 21 0 C,

respec1ively, for daily maximum and minimum temperatures

b F = flint; D= dent

c Most CIMMYT materials have good levels of resistance to

most foliar diseases including leaf blights and rusts. Noted

here are resistances which are above average for CIMMYT

germplasm

Source: Olallo at aI., 1989

W


Table 3. Changes in gfaln_~eld and other traits between Cycle 0 ~nd Cycle 3 of four populations unde~~oing half-sib recurrent selection for prolificacy when evaluated at three plant densities,

low (2.7 planta m ) (01), intermediate (5.~.7 planta m 2) (02), and high (10.6-13.3 plants m ) (03), in three environments in Mexico, 1988.

Grain Yield Opte Daysd S2- Lodging EPpa GYSE b

01 Opt e densi~ to SIC Root Stem 01 01

pljm 50PSA

Entry -----tjha----- ---------%--------- tjha

Semi-prolific ..,t~ (SPE)

Co 3.16 4.75 7.58 n.8 48.9 3.4 6.1 1.26 0.30

C 3

3.60 5.18 7.70 79.5 29.3 5.3 9.3 1.55 0.87

Seml-prollflc late (SPL)

Co 4.02 5.47 7.52 86.0 57.0 5.9 3.5 1.22 0.28

C 3

3.99 5.60 7.13 87.9 41.4 4.0 7.9 1.37 0.55

SemI-.,.-oIlf1c mlcHJtttude tl'opIC111 (SPMAT)

Co 3.92 5.25 7.22 81.0 47.2 6.2 9.1 1.31 0.37

C 3

3.96 5.20 6.82 82.6 29.0 8.7 10.6 1.64 0.80

Maize x TrlpHCUm

Co 3.66 5.09 7.81 80.9 35.4 6.0 7.2 1.72 0.82

C 3

3.47 4.99 7.77 80.2 30.2 3.9 6.6 1.60 0.83

Checks

Fum 4.01 5.40 6.98 86.8 66.7 2.9 1.7 1.17 0.19

Suw 3.14 4.72 8.21 78.2 69.1 1.7 5.9 1.14 0.10

AcT 3.44 4.47 6.73 80.6 58.2 6.4 5.6 1.10 0.05

FS 3.74 5.40 9.75 82.5 24.4 1.9 11.6 1.39 0.29

LSO 0.72 0.61 1.93 1.00 22.8 4.0 4.0 0.21 0.32

(P < 0.05) between meana within columns

a Ears par plant

b Grain yield 01880000 ears

c Interval between 50% Bilking of the firat and IMlcond ears at

two sites only

d Dllys to 50% anthetll, recorded at two Iltel only, average

&crou all densities

e Optimum denllty for grain yield and grain yield at optimum

density calculated by method of Duncan (1958)

+ Check entriel are, Alspoctlvely, Fumeaua (1) 8321; Suwan 8331;

Across 7845; and FS854. a Cornbalt hybrid.

."

o


41

Almost all ecologies in which maize is grown in ~!Ub-Saharan Africa are

characterized by unpredictable dry periods of 1-3 weeks duration, whose effects on

the crop are exacerbated by the relatively small amount of crop-available water

commonly found in many African soils. For this reason CIMMYT breeders have

concentrated on selecting for improved grain yields when maize is subjected to

drought occurring during the flowering period (Fischer et aI., 1983) when grain yield

is very sensitive to stress (Shaw, 1983). We have generally depended upon the

presence of drought adaptive alleles at reasonable frequencies in elite germplasm

(Blum, 1988), rather than relying on drought-adaptive genes identified by extensive

screening of unimproved landraces. Experience su~ests that the superior yield

potential of improved types and its residual effects III low-yielding environments, the

excellent awonomic type of these materials and the improved performance resulting

from selectIOn have justified this approach.

3.2.1 Breeding for drought tolerance at CIMMYT

Drought is not confined only to Africa: CIMMYTs analysis of megaenvironments

indicates that 52% of its target areas experience drought occasionally

(yield losses of 10-25%) and 28% experience drought commonly (yield losses of 25­

50%). The area commonly affected by drought is greater for early maturing

germplasm than for other maturity classes (Edmeades et al., 1988).

Selection in Tuxpeiio Sequia - Specific selection for drought tolerance began in the

seventies as a methodological study in the tropical late white dent population,

Tuxpeno Sequia (Table 2). The full-sib recurrent selection scheme involved

growing 250 full-sib families in two replications of 2.5 m single row plots under three

water regimes (well-watered; stress at grainfilling, or intermediate stress; stress at

flowering, and grainfillin~, or severe str~s~) at, Tlalti.zapan (19 0 N, 940 masl) during

the dry WInter season USlllg controlled IrngatlOn (FIscher et aI., 1983; Edmeades et

aI., 1987). Selection of the superior 80 families for recombination was based on an

index designed to increase grain yield under stress, increase stem and leaf

elongation rates under stress, maintain grain yield and days to anthesis under wellwatered

conditions, reduce the ASI under stress, and to delay leaf senescence. Low

canopy temperature (measured with an infrared thermometer) became part of the

index from C4 onwards.

Evaluations of the bulks of CO' C2' C 4 , C6 and C8 were carried out in

Tlaltizapan in 1987-8 in large plots under moisture regimes resembling those under

which the selections were made. Extra yield data were taken from less-stressed

border plants in each plot. Cycle 8 outyielded Co by about 900 kg grain/ha across a

wide range of moisture stresses (Fig. 1), but did not differ significantly from Cfu and

there were no significant stress x cycle of selection interactions for grain yield.]oint

linear regressions of grain yield of each genotype on the mean yield for each

moisture regime were fitted. When these were used to predict yields from Co to C 6

at the 2, 4, 6 and 8 t/ha level, and gains estimated by thIS method were 8%, 4.4%,

3.4% and 2.9% J?er cycle, respectively (Edmeades et aI., 1988).

Analysis llldicated that selection significantly increased number of ears per

plant but did not change other yield components. ASI under moisture stress was

si~nificantly reduced by selection, and was negatively and non-linearly associated

WIth grain yield (Fig. 2).

Days to anthesis remained essentially unchanged by selection, although there

was some indication that foliar senescence had been delayed. Selection resulted in

no significant changes in canopy temperature, total biomass production, capacity to

osmoregulate under drought, or in other measures of plant water status. Subsequent

studies have shown that the reduction in ASI under drought is related to increased

biomass partitioning to the ear prior to flowering, resulting in higher relative growth


42

9

o CO

B

C8


- P21

(OJ

.t=

~

7

- I>-

-

~ 6

c

Qj

5

-0

"0

Qj

':;"

c 2

...

aI


43

rates of ears in later cycles of selection, a reduced ASI and increased ear numbers

per plant.

Cycle bulks and other cultivars are currently under test at 20 locations to

determine if the gains observed at one site in the dry season are also observed in

other environments. Also under examination is the hypothesis that tolerances to

drought and high plant densities are positively associated through reduced ASI

(Dow et al., 1984). It seems probable that some ~ains in drought tolerance in

lowland tropical maize can be obtained by selectlllg for reduced ASI in high density

plantings under rainfed conditions.

Recurrent selection for drought tolerance in other elite populations - Four broadly

adapted elite populations were chosen for improvement to provide national

programs with source drought tolerant germplasm from late white, late yellow, early

white and early yellow populations. Recurrent Slselection commenced in three

populations (La Posta SR, Pool 26, Pool 18) in 1~86. The fourth population, Pool

16 (Table 2), consisted initially of full-sib families derived from the

IITAjSAFGRAD program in West Africa (see Section 3.2.2). CIMMYT, Mexico,

provided another testing location for these families, and the selected fraction was

continued as an independent recurrent S1 selection scheme in 1988. Each selection

cycle requires two years, beginning with the generation of 1000 Sl families in Poza

Rica, an unstressed lowland tropical location. These families are screened under

normal irrigation and drought stress in the severe heat of the Sonoran summer in

N\:V Mexico, and the best 250 are sown in the following cycle under three watet

regimes in the dry winter season at Tlaltizapan. The value of individual traits is

examined by bidirectional selection (Section 3.1). Selection of 50 S1 families for

recombinatiOn is based on an index designed to increase grain yield, ears per plant

and individual kernel weight under stress, maintain yield under well-watered

conditions, increase leaf uprightness, reduce ASI and the size of tassels, delay foliar

senescence and reduce leaf rolling under stress (Bolanos and Edmeades, 1988).

Following recombination in Poza Rica, S1 famihes are made and the cycle repeated.

Selection in these populations is pranned to continue for three cycles, when it

is anticipated that these'populations will be suitable for use as sources of drought

tolerance, probably in crosses with locally adapted germplasm or possibly for direct

release. Synthetics selected on the basis of desirable characters, and cycle bulks are

currently available for distribution and testing by national programs.

The Drought Tolerant Population and Drought Testing Network - In an attempt to

generate a population which has greater genetic variability for improved

performance under drought, 13 cultivars with good performance under drought were

crossed in a diallel, re-evaluated as crosses under drought and well-watered

conditions, and the best crosses selected. These were planted in a half-sib

recombination block in 1987 and used to form the baSIS of the Drought Tolerant

Population (DTP). This population is considered a repository of alleles which are

associated with ~uperior drought tolerance, although ItS disease and insect resistance

are only average at this stage. It is an open-ended population; in each dry season 60

80 new source materials with reputed drought tolerance, contributed from national

programs in South Asia, Southern Africa, the United States, Mexico, Central

America and from CIMMYTs Germplasm Bank, are evaluated under moisture

stress, and the best 3-5 crossed with the latest cycle of the DTP and re-evaluatep as

the cross. Iffound to be superior, crosses are included as female rows in the DTP

half-sib recombination block. At present this material is intermediate in maturity,

subtropical in its adaptation, and of mixed grain type.

The DTP (Table 2) has undergone 4 cycles of recombination, and Sl familie

are now ready for more widespread testing. This will allow cooperators to iaentify


44

the superior fraction of the DTP for recombination, and to select Sllines or groups

of lines for further inbreeding and hybrid formation or to form specifically-adapted

synthetics for crossin$ with adapted germplasm. At the same time it is boped that

cooperators will contmue to contribute drought-tolerant germplasm for evaluation

alongside Germplasm Bank entries and for possible incorporation into the DTP.

3.2.2 Breeding for drought escape and drought resistance in

maize· the IITAjSAFGRAD experience.

In the Semi-Arid Food Grain Research and Development (SAFGRAD)

project, the International Institute of Tropical Agriculture (IITA) has the

responsibility for the maize and cowpea research and training activities. The maize

breeding program, based in Ouagadougou, concentrated its research work on the

development of maize varieties for the Sudan savanna zone of West Africa which

either tolerated or escaped drought. This zone is characterized by a unimodal

rainfall distribution pattern (600-900 mm rainfall) distributed over 3-4 months and

potential evapotranspiration during the rainy season (June-September) of 4·6mm

per day. Year-to-year variability in the start and end of the rams, in total rainfall

and its distribution, and the common but unpredictable occurrence of dry spells of

1-3 weeks length during the rainy season (especially during the last decade) are

important characteristics of this zone. This environment, with low water-holding

capacity by the predominant soil types, demands a close fit between the effective

length of the growin~ season and varietal maturity. Under average rainfall

conditions, early maize cultivars (82-95 days from planting to maturity) are

recommended for the Sudan savanna zone. However, in those years when the rains

start late, or when there is a long dry spell of 2-3 weeks after the start of the rainy

season, the Sudan savanna farmer is better off planting (or replanting) extra-early

maize (i.e., less than 82 days from planting to maturity). This will not, of curse,

eliminate yield losses due to drought stress occurring between planting and harvest,

and therefore it is also important to improve the drought tolerance of these maize

varieties.

Breeding for extra early maize - During the 1984 season, 80 early and extra-early

materials from Colombia CIMMYT, liTA, India and Burkina Faso were grown for

observation and seed increase. Forty-eight of them were selected and evaluated the

next year at three locations in Burkina Faso. Across tbe three locations, two

varieties, Kamandaogo Tollo (local yel10w variety) and Guajira-314 (white

Colombian variety) were selected for their extra-earliness (42-43 days to silk). Later

in 1985, 40 early white varieties were crossed with Guajira-314 and advanced to F 2

ana 58 early yellow varieties were crossed with Kamandaogo Tollo and advanced To

F2' In 1986, the best F 2 white and yellow crosses were evaluated. Sixteen crosses

reached black layer 72·78 days after planting with an average yield of 3.5 t/ha

(IITA/SAFGRAD, 1987). The best yellow crosses were then backcrossed to the

earliest yellow recurrent parent (Kamandaogo Tollo) and the be t white crosses

backcrossed to the earliest white recurrent parent (Guajira-314). During the same

growing season the best yellow backcrosses were crossed in a diallel to develop an

extra-early yellow popUlation, TZEE-Y (Tropical Zea Extra Early Yellow). From

the best white backcrosses, 3 extra eady populations were developed (TZEE-W-l,

TZEE-W-2, TZEE-W-3) in a similar fashion.

In 1986 these fOUf extra-early populations along with 6 local checks were

evaluated at 3 locations in Burkina Faso (Table 4). TZEE-Y reached 50% silking 40

days after planting and yielded 3.3 t/ha.

It was 10 days earlier to silk than TZE-4 and 7 days earlier than Local Raytiri

and Safita-2, yet yields were not significantly different. The three other populations

flowered 4 days later than TZEE-Y and yielded 3 t/ha. Extra-early populations


Table 4. Grain yield


46

were ready for green maize harvest 60 days after planting. These four populations

are significantly earlier than available local varieties, have a broad ~enetIc base, and

have good husk cover. They are somewhat susceptible to stalk lodgmg.

Improvement ofPool 16 for drought tolerance - Pool 16 is well adapted to the

Sudan savanna environment of West Africa, and

in 1982 it was identified as relatively tolerant to drought stress. Recurrent selection,

using full-sib families, was undertaken in cooperation with CIMMYT to improve

this material for drought tolerance, and it was renamed Pool 16 DR. Simple and

tied ridges were used to evaluate maize families for drought tolerance (Dlallo and

Rodriguez, 1987; IITA/SAFGRAD, 1988; UTA, 1988). Family selection was based

on average yield under both simple and tied ridges, percentage ~eld reduction

under stress (simple rid~es vs. tied ridges) and ASI. Families With poor husk cover,

ear rots, or other undes1rable traits were discarded. Two cycles of selection have

been completed and seven experimental varieties developed.

In 1987 the mean yield across moisture stress levels of Safita-2 (a check

variety developed from Pool 16 in 1982) and Pool 16 DR cycles 0, 1, and 2 were

2.69, 2.88, 2.99 and 3.15 t/ha, respectively (Table 5), showing an increase of about

5% per cycle.

The corresponding number of days to 50% silking were 51.7, 50.5, 50.6 and

50.3. The three Po.ol 16 DR cycles of selection out-performed Safita-2 at all

moisture stress levels. Pool 16 DR ~ gave yields that were 28.9%, 15.5%, and

14.4% ~eater than those of Safita-2 under high, medium and slight stress levels,

respectIvely (Table 5).

3.3 Low fertility

Although many elements limit maize yields, either because of toxicity or deficiency,

there is little doubt that nitrogen (N) availability is the major nutritional limitation

to tropical maize production, especially in the lowlands (e.g., Akposoe and

Edmeades, 1982; Twumasi-Afriyie and Edmeades, 1983). Limited information

exists on genetic variability within maize for N uptake, the carbon/N ratio in maize

tissue, or the harvest index for N, though some selection studies have shown

promising responses to selection for performance under low N (e.g., Balko and

Russell, 1980; Muruli and Paulsen, 1981). For these reasons a trial of lowland

tropical elite and landrace cultivars was conducted in 1986 to determine if variability

in these traits existed, to select a population for further selection, and to establish a

protocol for selection for improved performance under low soil N. Two soil N levels

wer


Table 6. Correlation coefficients observed between grain yield

observed 'at low nitrogen (N) and other variables in

an evaluation of 11 varieties and in an evaluation of

full-sib progeny ofAcross 8328 (Lafitte and

Edmeades, 1987)

Correlation coefficient

Trait

varieties

(1986A)

Progeny

(1986B)

Grain yield, high N 0.25 0.46**

Chlorophyll at flowering, low N 0.88** 0.80**

Chlorophyll 3 weeks after 0.88** 0.80**

flowering, . low N

Ear leaf area, low N 0.75** 0.61**

Anthesis-silking interval, low N -0.67* -0.58**

Total plant N, low N a 0.79** 0.74**

Nitrogen harvest index, low N a 0.76** 0.74**

Total biomass, low N a 0.97** 0.78**

Green leaves below ear, 69 DApb - 0.75**

Green leav~ below ear, 82 DApb - 0.74**

*

significant at 0.05 probability level

** Significant at 0.01 probability level

a

b

Measured for a subset (73) of the full-sib families evaluated

Not measured in the variety evaluation; count done under low N

.l=

-.J


48

measured trait, chlorophyll per unit ear leaf area (Lafitte and Edmeades, 1987),

measured with a portable chlorophyll photometer (Hardacre et al., 1984).

This selection index has been used to select superior progeny during three

selection cycles, and to identify superior source germplasm from among landrace

and elite cultivars. A preliminary evaluation of progress for improved grain yield

under reduced N indicated that selection for yield alone under low N gave less

progress than selection for the index of traits listed above. A final evaluation of

progress from recurrent selection is currently underway, and selections from Across

8328 are available for distribution to national programs.

3.4 Breeding for tolerance to aluminum toxicity

Acid soil.s are, in ~en~ral, lo~ in availa;ble phosphorus (P), low in base .

exchange capaCIty and hIgh 10 leachmg capaCIty (Clark, 1982). They may be toXIC to

many crops as they frequently contain excessive amounts of exchangeable

aluminum. The biological and physiological effects of excess aluminum on plants

have been summarized by Foy (1983). Pieri (1985) indicated that acid soils with low

fertility in the humid tropical zones of Africa affect large areas in the coastal zone of

the Benin Gulf, the Adamaoua plateau of Cameroon, the Congo Basin, the high

plateau of Madagascar and the highlands dividing the Congo and Nile Basins. Soil

acidity is thought to be a limiting factor to maize yields in several African countries

(An~ola, Burundi, La Reunion, Swaziland, NigerIa, Tanzania, Guinea, Cameroon),

and IS widespread in South America (Magnavaca, 1982). Increasing soil acidity as a

result of cropping activities, and the corresponding high levels of exchangeable

aluminum that accompany this increase, are becoming important limiting factors to

crop productivity in the semi-arid tropics of Africa (PIeri, 1985). Liming is

recognized as an appropriate practice to correct soil acidity, but the cost of the lime,

the difficulty ofits availability and application, and the incompatibility of deep

liming with zero tillage practIces limit its use by smallholders.

With this in mind, breeding for tolerance to high aluminum and acid soil

conditions is recognized as a cost-effective way t,o exploit acid soils for maize

production. Since 1984 the main objective of CIMMYTs South American Regional

Maize Program located in CIAT Colombia has been to develop superior aluminum

tolerant cultivars (S. Pandey and G. Granados, pers. comm., 1984). This program is

cooperating with countries where acid soils of Latin America occur. Presently the

program is handling seven populations which were developed as follows:

SAo! Population Suwan·La Posta Blanco and SA-2 Population Suwan-La Posta

Amarillo: These two populations are based on white and yellow segregates selected

frotn a cross between Suwan-l and La Posta, combining downy mildew resistance

from Suwan-1 with resistance to foliar and stalk diseases from La Posta. Since 1986

these populations have been under improvement for agronomic traits and acid soil

tolerance.

SA·3 Population CIMMYT Seleccion Tolerancia AIuminio: During 1977 at

Santander Quilachao, 192 materials of various origins were planted in single-row

plots with soil at 45% and 75% aluminum saturation. At harvest 70 open-pollinated

ears were selected. Forty-five materials showed good plant development. During

1978 remnant seed of the 45 materials were planted as females and the 70 openpollinated

ears were planted as males in a half-sib recombination block. In 1981, 14

Cateto collections from Brazil were introgressed and the resulting population was

improved using modified ear-to-row selection scheme under aluminum saturations

of approximately 40% and 75%. This population now has good levels of tolerance to

soil aluminum and satisfactory agronomic characteristics.


SA-4 Tropical yellow population-I; SA-S Tropical yellow population-2; SA-6

Tropical white population-3; SAo' Tropical white population-4: In 1985 seed was

obtained from Al tolerant materials of national programs, as we11 as from stable,

high yieldin~ varieties from CIMMYT useful in non-acid soils of Asia, Africa and

Latin Amenca. In 198636 materials were planted for selfing and seed increase.

Seed from selfed ears (613 yellow and 618 white) was saved. Seed from increases

was used to conduct international aluminum vanety trials (ALUMVARS) in 1987­

88 to see if these materials were directly useful, and to determine their initial

characteristics (S. Pandey, pers. corom., 1988).

In 1987, at CIAT-Cali, the S1 yellow lines were topcrossed to two yellow

heterotic lines from ICA, Colombia, and the S1 white lines topcrossed to two other

heterotic ICA white lines. On the basis of~ ~ performance of the lines in the

topcross formation blocks, topcrosses of 250 lines from each group were harvested

for further evaluation. In the second season of 1987 the 613 yellow and 618 white S1

lines were evaluated under three different conditions:

1) a id soil in four different countries.

2) 21factorial combination of aluminum saturation and available

phosphorus

3) non-acid soil conditions.

The topcrosses were evaluated in a modified lattice, with the two topcrosses

of a line planted side by side. In 1988 they were evaluated at Santander Quilachao

under aCid soil conditions and in 1987 and 1988 at CIAT under non-acid soil

conditions. In 1988 second season, on the basis of the ~ ~ performance of the

lines, as well as heterotic patterns, the four populations were developed. The yellow

populations (SA-4 and SA-5) form a heterotic pair, as do the white populations (SA­

6 and SA-7).

All seven populations are presently under improvement in the CIMMYT's

South American Regional program in CIAT Colombia, and are available to national

pro~ams on request. The breeding scheme includes regional and/or international

testmg to allow mterested national programs to evaluate and select useful cultivars

for their countries.

4. Breeding for Tolerance to Biotic Stresses

4.1 Breeding for d~sease resistance

Maize is attacked by a wide range of fungal, bacterial and viral diseases, each

contributing to the low maize yields of sub-Saharan African farmers, and some with

the potential to reduce yield disastrously (Kim et aI., 1989).

CIMMYT mega-environment data (Table 1) show the widespread incidence

of ear rots (73% area), leaf blights (68% area), streak (60% area) and stalk rots

(25% area). Ear rot is very important because it reduces yield and nutritive value of

infected grain, and may lead to mycotoxin formation, thereby constituting a health

threat to humans and animals. Downy mildew occurs in limited areas, including

Mozambique, Burundi, Rwanda, Zaire, Nigeria and Somalia. Maize stripe virus

(MStpV), though limited in locality, often causes severe damage, sometimes

destroying entire crops (Marchand and Hainzelin, 1986). More localized diseases,

or those of minor importance, include Sugarcane MosaIC Virus (SCMV), Maize

mottle/chlorotic stunt, Maize Dwarf Mosaic Virus (MDMV), Curvularia spp. and

Physoderma spp. (Fajemis.in, 1986).

Maize diseases may be controlled through management practices such as the

use of fungicides, maintenance of soil fertility and crop rotations. However, it is

generally acknowledged that the most cost-effective method of controlling maize

diseases is through the development of resistant germplasm. Breeding for disease

resistant maize cultivars has been, and remains, one of the primary objectives of


50

most breeders in African national and regional programs, as well as at lITA and

CIMMYT.

In CIMMYTs Maize Program in Mexico, selection pressure is continuously

exerted for resistance to leaf blights, rusts, and ear and stalk rots, using reliable

artificial inoculation techniques on pro&enies of populations. Further selection for

these and other diseases is made by natIOnal program cooperators when they

evaluate CIMMYT germplasm in Internation~l Proseny Testing Trials (IPTfs).

Methodology and results have been reported by SmIth and Cordova (1987), Mihm

and Renfro (1987) and de Leon and Pandey (1989). In addition, CIMMYT monitors

important diseases in various earts of the world in an attempt to identify new

sources of resistance and possIble changes in pathogens whIch may lead to a

breakdown in existing sources of resistance. Recently the maize program began

screening for resistance to the tarspot complex (Phyllachora maydis and

Monographella maydis), which could pose a future threat to maize production in

many ecologies (CIMMYT, 1988a).

In order to improve resistance to diseases for which selection cannot be done

efficiently in Mexico, CIMMYT Maize staff, since 1974, have been engaged in

cooperative projects with various research institutes and national programs

(Thailand and Philippines for downy mildew, EI Salvador and Nicaragua for corn

stunt and Tanzania and IITA for streak). Rapid pro~ress has been made in the

improvement of resistance to downy mildew and maIze streak, and resistant

germplasm has been deployed by national programs (lITA, 1987; Soto et aI., 1982;

CIMMYT, 1985; 1988a; Bjarnason, 1986; Fajemisin et aI., 1985, Mihm and Renfro,

1987). Many diseases coexist in the same ecological wne, for example, downy

mildew and streak in Africa. This highlights the need to develop multiple disease

resistant material. Consequently, the CIMMYT West African Maize Program is

currently combining downy mildew resistance with streak resistance.

CIMMYTs station at Harare is concentrating on the tropical mid-altitude

ecology, characterized by the prevalence of E. turcicum, r. ~ and stalk and ear

rots. One of the main deficiencies in the germplasm of this regIOn is the lack of

streak resistance, which can be obtained by recurrent selection or backcross

breeding techniques (Kim et aI., 1989). The station has mass rearing facilities for

Cicadulina leafhopper, the major vector of maize streak virus, and streak resistance

will be incorporated into the majority of this program's germplasm. The CIMMYT

Maize Breeder based at the lITA Savanna Substation in Cote d'Ivoire, using similar

methods, will also incorporate resistance to streak into appropriate germplasm and

make it available to natIOnal programs of the region. lITA, Nigeria, has developed

lines resistant to maize streak virus, maize mottle virus, P. polysora, H maydis, P.

sorghi and E. turcicum.

As a result of cooperation among national programs and regional and

international organizations, germplasm with resistance to the most important maize

diseases prevalent in Africa (streak, downy mildew, H maydis, and E. turcicum) is

now available from CIMMYT aI1d lITA (Table 7). Other sources of resistance to

specific diseases are available elsewhere. For example, Buddenhagen (1985) noted

that downy mildew resistant lines are available from Thailand and Venezuela.

Australia has trop'icallines resistant to P. polysora, E. turcicum, MDMV-A, and

Sphacelotheca relliana. Lines with some tropical adaptation have been developed in

Hawaii with resistance to MMV, P. sorghi and E. turcicum, and lines exist in Kenya

and Zimbabwe with resistance to P. sorghi and E. turcicum.

4.2 Breeding for insect resistance.

Insect pests are among some of the key factors limiting maize yield in sub­

Saharan Africa. According to CIMMYT estimates, 94% of the maize area is


Table 7. Disease resiS1ant germplasm developed by CIMMYT and IITA and useful for sub-Saharan Africa.

Reilitant

to

Name 01

DelCrlption

Germplalm

MSV"

TZSA-Wl

TZSA-Y-l

TZESA-W

TZESA-Y

TZUT-W

TZUT-Y

TZMSA-W

Tropical lowland, late white semi


52

affected by various stem borers, 19% by termites, 20% by storage insects and 17%

by rootworm and cutworm.

The trend toward greater cropping intensity and area expansion, the

tendency of encouraging minimum or conservation tillage practices, and the practice

of leaving all or some crop residues on the soil surface are potential causal factors

for insect build up. Concerns for environmental contamination and long term

effects of pesticide use on human health are rising, and it is almost certain that toxic

chemicals for pest control will not be included in pest mana~ement practices of the

21st century (Mihm and Renfro, 1987). Varietal resistance is recognized as tbe

ideal pest mana~ement strategy for resource-limited farmers. This argument is

stronger for Afnca's small subsistence farmers who use multiple cropping systems

and who have an inadequate knowled~e about pesticides and their safe use.

Breeding for tolerance and reSistance to insects has been a continuing

concern of CIMMYTs Maize Program, whose objective is to develop host plant

resistance (HPR) to the most important maize insects. At first CIMMYT's strategy

was to build resistance to insects in ~eneral-purpose populations using modified

half-sib and full-sib recurrent selectiOn, and to develop experimental varieties

resistant to insects pests (Ortega et aI., 1980; Vasal et aI., 1982; Mihm, 1982; 1983a;

1983b). To meet this need, an insect rearing facility was developed at CIMMYT in

1974. Four insect species are currently being reared: fall armyworm (Spodoptera

[rugiperda) (FAW), sugarcane borer (Diatraea saccharalis) (SCB), southwestern corn

borer (Diatraea grandiosella) (SWCB), and corn earworm (Heliothis zea). The

components necessary for implementing a program of breeding for resistance to

insects, the techniques for efficient mass-rearing and infestation as well as for

selection have been described by Ortega et aI., (1980) and Mihm (1982; 1983a'

1985).

In 1983 CIMMYT attempted to speed up delivery of resistant germplasm to

cooperating national programs by developing experimental varieties from families

showing higher levels of resistance in artificially infested nurseries. The first

varieties formed were included in preliminary evaluation trials durin~ 1985 to assess

their agronomic J?erformance. With this approach, some gains in resistance have

been made both IIIvarieties and at the population level, but they have been small

and progress has been slow because of low gene frequencies and competitive

selection concerns (Mihm et at, 1988).

Recently, along with the development of general-purpose populations,

CIMM 1"s Maize Program embarked on the development of special-purpose

populations, including the development of source germplasm With resistance to

multiple insect species, and the international testing of these sources. The first

pop lation, named Multiple Borer Resistant (MBR), was formed from subtropical

and temperate materials re~ rted to have high or intermediate levels of resistance

to FAW, Ostrinia nubilalis ubner), SWCB, SCB and Chilo partellus (Swinhoe)

(Benson, 1986; Mihm, 198 ; Smith et aI., 1987). Fig. 3 shows operations and

breeding methodology used in developing MB , inbred line extraction and the

formation of experimental varieties and non-conventional hybrids from this material

(for more details see Smith et aI., 1987).

The information provided by cooperators (i.e., advanced programs with mass

insect rearing and screening capabilities) will help CIMMYT scientists select the

best progenies for further improvement of the population. It will also help in the

development of insect resistant experimental varieties useful to cooperators in

national programs that are located in areas where these pest species occur, even

though these scientists may not have the facilities for rearing and artificial

infestation needed to develop their own resistant materials. This new population

will be useful in the mid-altitude tropical environment of sub-Saharan Africa as a


53

Sup of operation

Winter 1984

Summer 1984

Winter 1986

Summer 1986

Winter 1986

Summer 1986

WIn"'r 1~l!7

Summer 1987

Wlnur 11188

Summu1988

I

InLornationallr teat

I

f

I

Screen

Screen fuU-sibe-SWCB, SCB

Full- and haIf-mb recombin~

I

i-

Full-sib recombine

+

fuIl-mba-SWCB, SCB

Full- and half-sib recombine

+

I

Scr.... full- and ha\{-siba-FAW, SWCB, SCB

Self-pollin.aLo in reeiJotant familiu

+

Screen SI progeny-FAW, SWCB, SCB

Full-sib recombine1 CrOM to t..t.en

~

I

~ +

ScreenS2e,

full-sib familie , FAW, SCB, SWCB YIeld enlualion

IFAW-MEX, MS, GAl leaf cliaeue (/\IX! o(Loatcr_.

gelf20-30 beat familiu Ad..ance to 93 (MEXI

... + ...

FonnaUon of

experimental Screen 93.

variety

Ad..ance to S4

InLormate ± 10 moet under infe.tation

reei8tant families

.j, ...

Ad...an.ce e][perimental

vanety to F2; bull<

pollin.aLo UBUllJ moat

Continue line

de...lopment

I

I

Recombinatione hued on

heLorolic patt.me from

Loatcroee r..ulLo; (orm

InMct reatetant gane pooUo

real.Otant plant41 u

mal..

... +

,

RepneraLo ~ 300 Form D....lap .xperimental

n... full-mbol aynthelica "noncon...lUioaal" hybrid.

J, ... +

Inurnalionalteat (Cycle 2) Start new cycle Taat uperimental hybrid.. both

Expenm..,ta1 ....Ti.tyteBt of inbreeding infasted and protec:ted plots'

Fig.3. Flow chart showing operations and breeding methodology used in

developing the Multiple, Borer Resistance (MBR)population, inbred line

extraction, and the formation of experimental varieties and

"nonconventional" hibrids (Mihm at al.. 1988).


54

source of insect resistance, and is currently under improvement for leaf disease

resistance.

To meet the requirements of maize farmers in the lowland tropics, the

entomology program is developing a multiple insect resistant tropical (MIRn

population (Mihm, 1986, Smith et. al., 1987). It is composed of germplasm adapted

to the tropical lowlands, and includes selections resistant to FAW and SCB from

CIMMYT pools and populations, from Antigua collections in the CIMMYT Maize

Germplasm Bank, and from University of Mississippi lines. Crosses to sources of

downy mildew and streak resistance are also included. Table 8 lists materials that

have been selected for insect resistance at CIMMYT that are presently available for

limited testing.

The CIMMYT wide cross program is also working on maize x Tripsacum

crosses, and has identified a Triosacum clone with apparent resistance to SWCB.

Effort is being devoted to incorporating this resistance via an integrated HPR

program at CIMMYT.

Throughout the tropics, maize is often left to dry in the field for sevetal

months prior to harvest, and the unhusked ears are commonly stored without

insecticide treatment. To help these farmers, CIMMYT maize breeders have

placed increased emphasis on improved husk cover in all germplasm (CIMMYT,

1985). The entomology program has begun screening germplasm and improved

varieties for resistance to the maize weevil, Sitophilus zeamais, and the larger grain

borer, Prostephanus truncatus. Significant differences among maize cultivars for

resistance have been found. Some of the more resistant materials identified include

varieties from CIMMYTs improved high yielding germplasm (Mihm and Renfro,

1987).

5. Quality Protein Maize

CIMMYT has developed a wide range of quality protein (QPM) materials

with adaptation to both troJ;>lcal and subtropical regions. These materials carry the

opaque-2 gene in combinatIOn with modifier genes that increase endosperm

hardness, and have levels of the essential amino acids, lysine and tryptophane, 50­

60% higher than in normal maize, where their levels impose a limit on maize

protein quality for monogastric nutrition. The protein in QPM has, therefore, a

significantly higher biological value than that of normal maize.

Until recently the emphasis in the program was on the development of the

broad-based populations with good agronomic characters from which experimental

varieties were extracted for testing and possible release by national programs. Now

the program emphasizes the development of inbred lines for use in hybrid

corpbinations, and for the development of synthetics which can be used as openpollinated

varieties where this is appropriate. CIMMYT plans to develop both

conventional hybrids (three-way and double crosses), and various types of nonconventional

hybrids (at least one parent of non-inbred origin), such as top-cross

hybrids and family hybrids.

OMMYT's OPM program will concentrate on selected target countries

where the national program has shown interest in and commitment to QPM

development, and where this material has high potential for making an impact on

the nutritional value of food and feed. In addition to improving the protein quality

of human diets which are based principally on maize, QPM could prove important

as a component of feed in countries which rely heavily on imports of protein

concentrates for the feed industry. QPM maize varieties and hybrids with good

agronomic performance and adequate disease resistance (e.g., streak) are now

available (Table 9) for more intensive testing in selected target countries.


Tab~. 8. CIMMYT germplasm selec:tlld for Inaeot resistance

.

Mater"l Selection. available Inaect Adaptation Maturity Colorlt8xture

Tuxpello Poza Rica 8321 FAW FAW Tropical Late White dent

Antigua-Veracruz 181 Poza Rica 8424 FAW FAW Tropical Late Vellow dent

Pool 24 Half-sib, full-sib and S1 FAW Tropical Late White dent

families, population bulk

Pool 26 Half-sib, full-sib and Sl FAW Tropical Late Vellowdent

families, population bulk

Pop. 23 S1, S2 lines, exerimental SCB Tropical Interm. Whltef1int

varieties, population bulk

'Antigues' Full-sib, Sl and S2 FAW,SCB,SWCB Tropical Late Vellow F/D

families.

Various x Mp Hybrids Full-sib, S1 and S2 FAW, SCB Trop.fsub-trop. Interm. Mixed

families.

Muttlple Borer Res. Full-sib, S1 and S2 families, ECB, SWCB sub-Trop./Temp. Interm. Mixed

Pop'n (M.B.R.) experimental varieties. SCB, SSB, FAW

Multiple Insect Full-sib and S1 families. FAW, SCB Trop./sub-trop. Int./Late Mixed

Res. Tropical population bulk.

---------------------------------------------------------------------------

FAW = Fall Armyworm, Spodoptera frugiperda

SCB = Sucar Cane Borer, Diatraea aaccharalis

SWCB = Southwes1em Corn Borer, D. grandiosella

ACB = Asian Corn Borer, Ostrinia furnicalis

ECB = European Corn Borer, O. nubilalis

AMSB = African Maize Stalk Borer, BullS80la fusee

PSB = Pink Stem Borers, Seaamia sp.

SSB = Spotted Stem Borer, Chilo partellus

Source: Diallo et aI., 1989

V1

V1


Table 9. Quality Protein Maize (QPM) cultivars developed by CIMMYT

Name of Germplasm

Description

Population 61

Population 62

Population 63

Population 64

Population 65

Population 66

Population 67

Popufation 68

Population 69

Population 70

Pool 15 QPM

Pool 17 QPM

Pool 18 QPM

Pool 23 QPM

Pool 24 QPM

Pool 25 QPM

Pool 26 QPM

Pool 27 QPM

Pool 29 QPM

Pool 31 QPM

Pool 32 QPM

Pool 33 QPM

Pool 34 QPM

Tropical early yellow flint

Tropical late white flint

Tropical late white dent

Tropical late white dent

Tropical late yellow flint

Tropical late yellow dent

subtropical intermediate white flint

subtropical intermediate white dent

subtropical intermediate yellow flint

sUbtropical intermediate yellow dent

Tropical early white flint

Tropical erarly yellow flint

Tropical early yellow dent

Tropical late white flint

Tropical late white dent

Tropical late yellow flint

Tropical late yellow dent

SUbtropical early white flint

SUbtropical early yellow flint

SUbtropical intermediate white flint

Subtropical intermediate white dent

subtropical intermediate yellow flint

subtropical intermediate yellow dent

V1


57

Acknowledgements

The authors gratefully acknowledge the helpful discussions and information

provided by Dr. RP. Cantrell, RL. Paliwal, Dr. l.A. Mihm, Dr. RL. Renfro, Dr.

H.R Lafitte, Dr. l. Bolanos, Dr. S. Pandey, Dr. M. Morris and Mr. R Triomphe.

DISCUSSION

Question:

Paul. My understanding is that Nairobi-based ICIPE has an active program

on "maize stem borer resistance". How closely does CIMMYT collaborate

with ICIPE on this program?

Answer:

CantreIJ. We have been collaborating closely with them in the evaluation of

our MBR progeny trials.

Question:

Makonnen. What are the genetic traits considered other than earliness as

major parameters while making selection for drought tolerance?

Answer:

Cantrell. The major pararneter CIMMYT uses for imrroving material for

drought tolerance is narrowing anthesis silking interva .

Question:

Empig.

In Africa where drought is common would yield be more stable if

varieties were bred for non-barrenness instead of prolificacy? Many

times the second ears cannot develop beyond pollination because of

moisture and yet these ears have already competed in the

development of the first ears.

Does your work show any cultivar by stage of growth interaction in

drought resistance or tolerance?

On borer resistance recurrent selection program where progress is

very low what are the C.V.'s you are getting?

Is it possible to do N use effeciency selection at 20 kg N/ha levels as

most African farmers don't use fertilizers at all.

Answer:

Cantrell.

There is a good indication that prolificacy reduces barrenness and the

presence of the second ear does not induce barreness of first ear.

For the primary factors evaluated in our drought studies, cultivar and

stage of growth interaction have not been widely observed.

The CV's for our MBR progenies trials have been variable depending

on the location.

We at this time do not have sufficient information to be able to make

recommendations for various levels of N for the low N treatment.


58

References

Akposoe, M.K., and G.O. Edmeades. 1982. Third Annual Report of the Ghana

Grains Development Project, 1981. Part 2. Research Results. 9Op. CIDA,

Ottawa.

Balko, L.G., and W.A. Russell. 1980. Effects of rates of nitrogen fertilizer on maize

inbred lines and hybrid progeny. II. Correlations among agronomic traits.

Maydica 25:81-94.

Benson, D.L. 1986. Evaluation of stalk borer resistance mechanisms and the

development of multiple stalk borer resistance in maize, Zea mays L. Ph.D.

Dissertation, Cornell University, Ithaca, N.Y.

Bertin, Ch., A. Panouille, and S. Rautou. 1976. Development of varieties of maize

grain with ear prolificacy for wide ecological adaptation. Ann. Amelior.

Plantes 26:387-418.

Bjarnason, M. 1986. Progress in breedin~ resistance to the maize streak virus

disease. p197-207. In: Gelaw, B. (Ed). To Feed Ourselves. A Proceedings of

the First Eastern, Central and Southern Africa Regional Maize Workshop.

CIMMYT, El Batan, Mexico.

Bolanos, J., and G.O. Edmeades. 1988. The importance of the anthesis-silking

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varietal development in maize for tropical Africa through resistance breeding

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Strategies for Maize Production Improvement in the Tropics. Instituto

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drought resistance in tropical maize. CIMMYT, El Batan, Mexico.


60

Foy, CD. 1983. The physiology of plant adaptation to mineral stress. Iowa State. J.

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selection criteria. Paper presented at the Second Eastern, Central and

Southern African Regional Maize Workshop. March 16-20. Harare,

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the First Eastern, Central and Southern Africa Regional Maize Workshop.

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Mihm, J.A 1983b. Efficient mass rearing and infestation techniques to screen for

host plant resistance to maize stem borers, Diatraea spp. CIMMYT, El

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Applic. 6:369-377.

Mihm, J.A 1986. Multiple insect resistance development at CIMMYT. p20-27. In:

CIMMYT 1985 research highlights. CIMMYT, EI Batan, Mexico.

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using host plant resistance, successes and prospects. Paper eresented at the

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its relationship to ther traits in maize. Maydica 26:63-73.

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Breeding Plants ReSistant to Insects. Wiley and Sons, New York.

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, Less Favorable Environments. Wiley Interscience, New York.

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Reactions to Water and Temperature Stresses in Humid, Temperate

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CIMMYT. Trabajo presentado en la XXXlII Reunion Anual del PCCMCA

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62

Smith, M.E., J.A Mihm, and D.C. Jewell. 1987. Breeding for multiple resistance to

temperate, subtropical, and tropical maize insect pests at CIMMYT. Paper

presented at the International Symposium on Methodologies for Developing

Host Plant Resistance to Maize Insect Pests. CIMMYT. El Batan, Mexico.

March,1987.

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maize populations through improved challenge and selection

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Ottawa.

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improvement and utilization program. CIMMYT, El Batan, Mexico.


63

PROGRESS IN MAIZE IMPROVEMENT AT CIMMYf'S

ZIMBABWE MAIZE RESEARCH STATION

R. Wedderburn, K..Short and H. Pham 1

INTRODUCTION

The Maize Research Station at Harare was established in 1985 to address the need

for a greater array of germplasm to fit the mid-altitude ecologies. CIMMYT defines the

mid-altitude ecology as those areas in the tropics between 900 and 1700 masl. It is

estimated that in Africa alone over 6 million hectares are grown in this environment.

Demand for these materials also exists in Latin America and Asia. Initially it was decided

that the station should be situated in Eastern or Southern Africa. The Harare location was

selected with the cooperation of the government and the University of Zimbabwe. The

choice of this location provided the opportunity to incorporate streak virus resistance, a

characteristic which is essential in many areas where this germplasm is utilized. The

prevalence of COIIUllon rust P. sorghi and northern blight H turcicum also provided the

opportunity to increase resistance to these two important diseases.

In early 1988, work on the station was expanded to include breeding activities and

streak resistance work on lowland tropical germplasm. Materials targeted for the lowland

zones of Africa should ideally have resistance to this disease. The work of the station at

Harare is not only a regional activity but is an extension of CIMMYT's global maize

germplasm development network.

The rese(.lIch programs are using 11 hectares of land at the University Farm outside

Harare, (1500 masl) two yield evaluation sites (Rattray Arnold 1300 masl and Glendale

1200 masl) and a 4 hectare winter nursery at Mzarabani (480 masl). In addition tropical

materials are developed on an additional two hectares at Mzarabani and Chisumbanje (400

masl) in the summer season. There are a total of 720 square meters of greenhouse

facilities for mass rearing Cicadulina leafhoppers, an entomologyjpathology laboratory,

and a seed preparation complex with a 10 degree centigrade seed storage room.

Disease resistance breeding for both the tropical and midaltitude

germplasm is an important component of the research at the Zimbabwe station.

The major disease problems in the tropical germplasm are H. maydis and P. polysora. H

turcicum and P. sorglli resistance are essential for materials in the mid-altitude

environments. High levels ofP.sorghi at the sites used by the mid-altitude program have

facilitated the screening of materials under natural conditions. Artificial turcicum

inoculations are being done with chopped, diseased leaves at several stages early in the

development. It is also essential that germplasm for use in both these environments have

adequate levels of resistance to ear and stalk rots caused by Diplodia and Fusarium spp.

When the laboratory becomes fully operational later this year It will be possible to use

artificial inoculation lechniques for greater precision in screening for resi lance to these

diseases.

Maize streak virus, transmined by leafhoppers of the Cicadulina spp., is an

important disease in most of the maize production environments in Africa. Considerable

emphasis is placed in both the tropical and mid-altitude research programs for

incorporation of resistance to this disease. To date most of the resistant sources utilized for

incorporating resistance into our sermplasm are those obtained from the work of

llTA\CIMMYT at Ibadan, Nigena. This has meant that we have been obliged to use

predominantly tropical germplasm sources in crosses with our mid altitude materials. We

have concentrated on rearing the spp C. mbila, which is the most efficient transmitter of the

1. CIMMYT Maize Program, P.O. Box MP 163, Mount Pleasant,

Harare, Zimbabwe.


64

virus. During the 1988-89 growing season. over 10,000 nursery rows were screened for

resistance to streak at the Harare station. Low temperatures like those experienced in

Harare in winter seriously retards the development of the leafbopper colonies. However,

a heating system for the greenhouses allows maintenance of the colonies at high levels year

round.

Cooperation and interaction with national maize program researchers in the region

has a very high priority. Assistance in the evaluation of maize streak virus resistance bas

been one of the most visible signs of cooperation. During the past season we planted and

infested with virulent Cicadulina 220 lines and hybrids from the Zimbabwe program, 92

from the Zambian national program and 20 from other sources in the region. Preliminary

results show that the Zimbabwe program is making some progress in incorporating streak

resistance into their new hybrids. Additional cooperation and interaction has been

achieved through periodic visits by national program scientists, distribution of numerous

germplasm resources, assisting WIth research programs of students from the University of

Zimbabwe, and through direct visits of CIMMYTs maize specialists to countries in the

region.

LOWLAND TROPICAL GERMPLASM

Breeding Objectives and Strategies

There are about 2 million ha. of lowland tropical maize grown in Eastern and

Southern Africa. The early white flints account for 30% of the maize in these regions. In

other areas of Africa intermediate and late white dents are very important. The main

objective of the program is to develop maize germplasm which addresses specific

constraints in the region. Highest pnority at the moment is placed on the llllprovement of

streak virus resistance. Considerable emphasis is placed on breeding for earliness and

harder grain types. Breeding efforts are also directed at improving agronomic characters,.

yield and yield stability, and levels of resistance to important leaf, stalk, and ear patho~ens.

Development of materials with higher tolerance to soil moisture stress for cultivation m

marginal areas is another area of Importance.

To effectively address these objectives several breeding methodologies are utilized:

1. Conventional backcrossing - for rapidly incorporating streak resistance into

elite materials. The products from this approach are potential sources for

population improvement work.

2. Recurrent selection - in the population improvement program, depending on

research objectives and the stage of population improvement, S1, S2 or full

sib families are evaluated at selected lowland sites for yield performance and

other agronomic characters.

3. Continued screening - selecting and creation of newer germplasm complexes

to feed into the population improvement program.

Streak Conversion Through Backcrossing

Backcrossin~is a proven rapid method for incorporating streak resistance into elite

materials thus proVIding national programs with an intermediate product of known

agronomic value. The technique has provided a wide range of streak resistant sources, with

good agronomic characteristics, which are being used in population improvement

programs.

The program at the CIMMYT Harare Station is a continuation of the joint activity

carried out by CIMMYT and UTA at Thadan from 1980 to 1988. During this period many

elite materials were converted to streak resistance and advanced to the 5th and 6th

backcross stages (Fig.1 & Table 1). During the first cycle of evaluation of these materials

at Harare, observed levels of streak expression were quite severe. Similar germplasm

planted at the Mzarabani lowland evaluation site did not give an equally severe reaction.


65

Viliferous hoppers from the same colony were used in both instances, thus it is unlikely that

the observations were strain related. The cooler temperature at the mid altitude site

appears to enhance disease expression. Additional studies have been initiated to further

clarify the effects of low night temperature on the expression of the disease.

Table 1.

Lowland tropical germplasm previously

converted streak to resistance

Population converted

Streak Donor

Sanguere 8330

Ratray Arnold (1) 8349

Across 8331

Palmira 8425

Gusau 81 TZB

Poza Rica 8321

Suwan 8222

Across 8243

Suwan 1 C9

Across 8328

Tlaltizapan 8244

Across 8362

Across 8466

TZESR-W

PR 7843 SR

TZESR-Y

EV 8422SR

PR 7822 SR

PR 7843 SR

TZSR-W 1

TZSR-W 1

EV 8428 SR

TZSR-Y 1

TZSR-W 1

TZSR-W 1

EVPop40SR

Additional populations in the early stages of backcrossing are listed in Table 2.

Early and intermediate white pools from CIMMYT (Pools 15,18, 19, and 20) and 18 maize

populations with good agronomic characters from Thailand, Tanzania, and the Philippines

are being crossed to streak resistant donors. These will provide a broad germplasm base for

future population improvement work either at the station or by interested national

programs.

The conversion of elite materials identified through the international testing

program or germplasm with special characteristics such as insect, disease or drought

tolerance will continue to be a part of the lowland tropical program.

In the coming season we have agreed to undertake the streak resistant conversion of two

varieties from national programs; Katumani from Kenya and Kito from Tanzania. We

think that it is important that we continue to provide this type of short term assistance to

national breeding programs in the region.

During the past years the conversion program produced many streak resistant

donors with good agronomic performance. At present these are being utilized in the

conversion program and as parent sources for the breeding program. Emphasis is,

however, shifting from the backcrossing program to a more concerted effort with recurrent

selection in streak resistant populations where factors such as yield are given high priority.


66

Table 2.

Lowland tropical germplasm in early

stages of conversion

Material

Streak Donor

Backcross

generation

Ferke (1) 8223 EY 8422 SR BC-1

Los Banos (1) ~(ZAM) BC-2

Pop.31 C6 Sl ESR-Y BC-2

Suwan2 C4 EY 8428 SR BC-2

Poza Rica 8326 EY 8428 SR BC-1

Pop.22 C6 Sl(DMR) EY 8422SR BC-2

Pop.28 C6 Sl (DMR) EY 8428 SR BC-2

Pool 15 (QPM) EY 8540 SR BC-3

Pop 61 (QPM) EY 8540 SR BC-3

Pool 18 (QPM) EY 8540 SR BC-3

Across 8563 EY 8540SR BC-2

Poza Rica 7737 Pop 40 SR BC-2

Population Improvement

Most of the lowland tropical streak work carried out in collaboration with IITA

involved the conversion of elite sources. However, CIMMYT population 43 (La Posta) was

crossed to a streak source and improved through recurrent selection at Ibadan. After 4

cycles of selection the levels of resistance in the population was adequate for the material

to be returned to Mexico to re-enter the international testing program.

Early and intermediate white ~ermp'lasm are the predominant types utilized by

programs in tropical Africa. We are Identifying superior streak resistant germplasm m

these categories. It is hoped that these materials will form the base of new resIstant

populations for the continent. One new population (Suwan l-SR x Compo E1- W) being

formed is already showing high levels of streak resistance and good husk cover

characteristics.

MID-ALTITUDE MAIZE RESEARCH PROGRAM

The CIMMYT mid-altitude maize research station was established in Harare with

the specific goals of broadening the mid-altitude germplasm base and (or the incorporation

of performance limiting characteristics into adapted mid-altitude maizeoackgrounds.

Initial germplasm improvement efforts concentrated on the collection and evaluation of a

wide array of maize germplasm sources. Materials were collected from the CIMMYT

Mexico program, IITA/CIMMYT streak conversion program, elite populations, hybrids

and inbreds from national breeding programs in Eastern and Southern Africa. and U.S.

temperate inbreds and populations. These maize germplasm sources were evaluated in per

se testing as well as in combinations. It was quickly observed that considerable population

heterosis was achieved when some of these matenals were used in combinations. Many of

these new

combinations were found to have specific characteristics which gave performance

enhancements in the mid-altitude environment.

Early observations led to the development of a multi-stage recurrentselection

breeding program. The breeding methodology has been designed to remove specific


67

deficiencies while simultaneously generating improved maize products for distribution to

national program cooperators. Three main products are being developed for


FIG. 1

EARLY GENERATION INBRED DEV.

POPULATION FORMATION

t

PERFORMANCE TESTING

(3 LOG-, 3 REPS/LOC, 100 ENTRIES)

t

S1 RECURRENT SELECTION

(20 POPS - 10 EVALUATED/SEASON)

T

1. COMBINING ABILITY

2. PER SE PERFORMANCE

3. DISEASE EVALUATION

t PRODUCTS

• T FS/HS RECURRENT SELECTION

(6 POPS. FS AND 3 HS)

1. FS FORMED BETWEEN S1'S

2. HS- S1 X TESTER

t

1. NARROW BASE SYNTHETICS

2. BROAD BASE POPULATIONS

3. HETEROTIC DEFINED POPULATIONS

4. S3 TO S5 INBRED BULKS

5. BREEDING METHODOLOGY

0'1 co


69

were implemented. The Rattray Arnold Research Station (1300 masl) and the Glendale

site (1200 masl) were used for yield testing only. High levels ofP. sorghi were noted at all

sites. Again this year low levels ofP. polysora were observed at the Glendale site. H.

turcicum was sporadically present at all three sites but at levels less than required for good

differentiation between materials.

Several tests rep-resenting the stages of the population development program were

used to evaluate 230 dIfferent germplasm complexes. A top cross test for GCA assessment

was planted at two sites. Plant populations were 53,OOO/ha at Harare, 44,OOOjha at Rattray

Arnold, and 40,OOOjha at Glendale.

Results and Discussion

Excellent differentiation for resistance to streak virus was observed in the S1lines

from the 14 populations evaluated. These populations were all in the first cycle of recurrent

selection following the formation and recombination phases. The frequency of S1's having

some level of resistance is less than that observed in S1's from Revolution (Fig. 2).

However, sufficient variability existed to make selections from lines rated excellent to

good for streak resistance. Selected populations such as EV7992/EVPOP43SR displayed a

much higher frequency of resistant segregants (Fig. 3). These results indicate that sufficient

levels o(streak resistance may be incorporated early in the population building process,

while maintaining performance levels. The rapid early incorporation of streak resistance

can perhaps now be followed with a greater emphasis on other equally important

constraints present in the target environments.

Evaluations over several seasons has identified several new populations that are

showing considerable yield improvement over existing streak resistant conversions and

other mid-altitude adapted populations (Table 3). Several of these populations are

competing well with excellent Zimbabwe hybrids such as ZS225 and R201.

It appears that mid-altitude adapted sources and even some tropical materials can

be successfully combined with materials having streak resistance. These complex

populations can then serve as more suitable parental types for further recurrent selection,

sources of narrow based synthetics or for inbred development.

Table 3.

Performance of new populations relative to existing

populations and hybrids •

PEDGREE

YLD/HA

(Ions)

DAYS

SILK

P.

SORGHI

1/

EAR

HGT

(m)

%8T

LODG

%EAR

ROT

ZS225

SR52

R201

POP62/GWEBI{1 } TZMSR-W

~2/EVPOP43-SR

EV7992/R201/ /EMSR

EV7992/EVPOP44-SR

AC8232/NPPXSC//GW[ljTZMSR-W

AC8342/IKENNE{1]8149//PL9A

EV7992

EV8744-SRBC6

POP32·SRBC2Fl

EV8549-SRBC5

8.8

8.6

7.9

8.6

8.1

8.0

7.3

7.7

7.3

7.0

6.5

6.3

5.6

70

n

70

n

78

75

76

75

76

75

75

76

73

2.3

3.0

4.0

2.2

2.8

2.3

2.7

3.5

2.0

2.8

5.2

3.8

4.3

1.3

1.8

1.5

1.6

1.6

1.5

1.5

1.6

1.6

1.4

1.4

1.5

1.2

1

6

4

1

1

3

4

3

5

3

7

2

3

12

5

11

6

5

8

2

7

10

6

10

4

7

• Data from 3 Zimbabwe 1989 locations; 3 reps/loc

# Rating: 1= resistant,9 =susceptible


70

Fi':J. 2

RESISTANCE TO MSV IN S1 LINES FROM

EV7992/EVPOP43SR VS REVOLUTION

50

P

E

R 40 1

C i

E

N

T ,. ,

3°1

,

... \

\ \ ./t:-,

------,-'----''t-\---/'--/-----'\,,\-------- -

\ \

0 /

\,-¥ \.

F 20

T /

0

I

T 10~' _ /

A .I /

L /

0'--==

1 2

"'-.

\

\.

\..- ......

3 4 567

MAIZE STREAK VIRUS RATING

8

9

- 81'S -REVOLUTION --+- S'I'S -7992/43SR

,·RESISTANT; 9·VERY SUSCEPTIBLE

Fig. 3 RESISTANCE TO MSV IN S1 LINES FROM 13

POPS IN REC. SELC VS REVOLUTION

50

P

E

R 40

C

E

N

T 30

0

F 20

T

0

T

A

L

10

o

/

,

I

/

/

/

\

\

\

;' \ ~

, I ~~ -

.I //"" ~-

V / / "- "-"'-...

I


71

Evaluation of newly formed F1 populations is a part of the identification process for

selecting new populations for evaluation at the F2 level. F1 populations need to display a

comparative advantage before they are tested at the F2 level and the subsequent possible

entry into a recurrent selection pro~ram. A number of the new F1 germplasm complexes

are exhibiting excellent yields relatIve to Zimbabwe hybrids such as SR52 and RZ01 (Table

4).However it appears that greater emphasis needs to be placed on identification of

materials with a maturity similar to or earlier than R201.

Table 4.

Performance of best 20 F1 populations relative

to R201 and SR52 *

PEDIGREE

DAYS P.

YLD/HA SILK SORGHI

(tons) #

EAR %ST %EAR

HGT LODG ROT

(m)

Best 20 F1's

SR52

RZ01

Test Mean -100 ent.

9.0

8.4

6.9

7.6

77

79

71

76

2.4

2.3

4.0

2.8

1.7

1.7

1.5

1.6

6 4

3 6

14 14

7 7

* Data from 3 Zimbabwe 1989 locations; 3 reps/loc

# Rating: 1=resistant, 9 =susceptible

The Sl recurrent selection programgenerates a sizable number of early generation

lines which have been selected for one or several traits such as performance, streak

resistance, H turcicum resistance or P.sorghi resistance. These S2 bulks were topcrossed to

provide an estimate of GCA Performance of the best 20 of these relative to the late, high

yielding, yellow Zimbabwe hybrid ZS206; and R201, the early hybrid of preference for

marginal environments, are presented in Table 5 . The testers used were the Zimbabwe

sin~le cross hybrid ZS107 and ZL00601 (early generation name = 100rnsrdent49), a streak

resIstant line. Selected top cross entries do hold potential for further evaluation (Table 6).

Yield and resistance to ear rots appear to be useful traits in the new early generation lines.

Greater emphasis needs to be placed on early lines. The best of those lines identified in the

top cross test have been advanced to the S4 level. The tester ZIOO601 has shown excellent

«ombining ability, harder grain texture and a reduction in ear rots relative to ZS107 (Table

7). It has good streak, P.sorghi and Hturcicum resistance levels.

Table 5. Performance of best 20 top crosses relative to ZS206 and R201*

DAYS P. EAR % ST %EAR

PEDIGREE YLD/HA SILK SORGHI HGT LODG ROT

(tons) # (m)

------------------------------------------------------------

BEST 20 TOPCROSSES 10.0 77 2.6 1.7 2 5

Z206 9.5 77 2.0 1.6 4 11

R201

Test Mean -205 ent.

8.3

8.0

72

77

3.8

3.1

1.6

1.6

6

3

15

8

* Data from 2 Zimbabwe 1989 locations; 2 reps/loc

# Rating: 1=resistant, 9=susceptible


72

Table 6.

Perfonnance of selected topcross entries relative

to Zimbabwe hybrids *

DAYS P. EAR %ST %EAR

PEDIGREE YLD/HA SILK SORGHI HGT LOoo ROT

(tons) 1/ (m)

-----------------------------------------------------------

POPSXPOP49j 6-1-1 X/M1 10.4 79 3.0 1.8 1 5

MSR:131/M2 10.2 78 3.0 1.8 1 1

~J-SELF-4-1-~1X/M2 10.1 76 3.0 1.7 3 3

P42JP35HT{#37/#33J-1-1X/M1 9.9 77 12 1.5 0 6

[EV30SRfTZMSRW)#bF82SR-1-XSR/M2 9.9 75 2.8 1.6 4 7

[EV7l»21/EV44SR)#bF8SR-2-XSR/M1 9.7 82 2.2 1.6 0 7

[EVPOP43-SRBC3)-C1-3-XSR/M2 9.6 75 3.5 1.6 2 7

[P42JP22HT[#26/#27]-1-1X/M1 9.5 75 12 1.5 5 5

ZS206 9.5 77 2.0 1.6 4 11

SC501 9.0 74 3.5 17 3 25

R201 8.3 72 3.8 1.6 6 t5

-~---------------------------------------------------- -----

*Data from 2 Zimbabwe 1989 locations; 2 reps/lac

# Rating: 1= resistant, 9 =susceptible; M1=ZLO0601 and M2=ZS107

Table 7.

Means for testers ZS107 and ZLO0601 in top cross evaluation*

PEDIGREE

YLD/HA

(tons)

DAYS

SILK

P.

SORGHI

"

EAR

HGT

(m)

TEX

1/11

%RT

LODG

%ST

WOO

%EAR

ROT

ZS107

ZI..OO601

8.2

7.8

76

78

3.2

3.1

16

1.6

7

5

14

9

2

4

11

4

* 100 Entries per tester

# Rating: 1= resistant, 9 =susceptible

##,

Rating: 1= flint, 9 =soft dent

New germplasm complexes which can function as source populations for more elite

parental types are being identified. Several very useful sources of resistance to the maize

streak virus have also been identified which have good combining ability and agronomic

characteristics. These have resulted from the joint efforts of the CIMMYT and UTA streak

breeding programs.


73

Table 8.

Pedigree

Excellent sources of resistance to MSV identified

through testing program.

Description

EVPOP3O-SRBCZ

EVPOP43-SRBC3

EVPOP44-SRBC3

EVPOP49-SR

EMSR

TZMSRW

OP sr conversion from CIMMYT Pop 30 lEWF

OP sr conv. from CIMMYT Pop43(La Posta)TLWD

OP sr conversion from CIMMYT Pop 44 SLWD

OP sr conversion from CIMMYT POI? 49 TIWD

IITA mid-alt.intermediate sr populatIOn

UTA mid-alt late white semi-dent sr pop.

A major objective of the CIMMYT mid-altitude research effort has been to

incorporate these sources ofstreak resistance into higher yielding, better adapted

populations for the mid-altitude environment. Several materials are providing the adaption

required plus showing good heterosis when combined with some of the streak resistant

conversions.

Table 9.

Excellent sources of mid-altitude adaptation

with good GCA identified in testing program.

Pedigree

POP 32

POP 42

POP 62

EV7992

Pool9a

NPPXSC

Description

CIMMYT Pop 32 (Eto Blanco) SIWF

CIMMYT Pop 42 (Eto Illinois) SIW semi-dent

Tanzanian late white semi-dent eop

Tanzanian OP var. from Pop 92(UCA and Tuxpeno)

CIMMYT Highland transitIOn late white semi-dent

Zimbabwe late white dent population

Building of source populations has also utilized the considerable adaptation and

yield advantage found in the commercially available Zimbabwe hybrids such as SR52,

R201, ZS225 and ZS206. Sources of U.S. temperate com belt materials are also

incorporated in several of the populations in recurrent selection.

, The information gained over the last several years of CIMMYT's involvement in

breeding maize for the mid-altitude environment indicates:

1. Useful variability and source populations exist for the mid-altitude

environment.

2. These source populations per se do not provide the best yield potential and

other necessary attributes for the constraints present in the region.

3. Elite parental types have been most successfully formed using these source

popu[ations as building blocks to the desired product.

An innovative research agenda is needed to effectively serve the germplasm needs

of the region. The mid-altitude program will continue with the present methodology with

several modifications for the future. Greater emphasis will be placed on the development

of populations which fit heterotic groupings. Identification of the most appropriate testers

for use in discernin~ correct heterotic group placement is crucial to the success of this

effort. Drought reSIstant germplasm development will begin with a Zimbabwe-Mexico


74

shuttle this year using the techniques developed in the physiology pro~ram at CIMMYT.

Initial exploratory work with screening Sllines for N use efficiency Wlll also be initiated

this year.

DISCUSSION

Question:

Empig. How many distinct sources for streak resistance have you identified?

the genes involved allelic? How many are they?

Are

Answer:

Short. The mid-altitude maize program at Harare has been using the improved

backcross/conversion streak resistance sources developed by the CIMMYT/IITA

programs. These initial conversions depended on two basic sources of resistance.

Revolution and another source identified at UTA (IB32) were the major donors

used in the earlier conversions. One or a couple of genes control resistance to tbe

streak virus. Again this appears to be related to the resistance source. Studies have

not been done to my knowledge looking at whether the genes involved are allelic.

Improved streak resistant sources that I have found most useful in population

building are CIMMYTs streak resistant versions of populations 30,43,44 and 49 as

well as IITA's TZMSR-W and EMSR.

REFERENCES:

1. PaliwaJ,R.L 1987. Activities of the CIMMYT Maize program in Eastern and Southern

Africa. Towards Self Sufficiency: Proceedings of the Second Eastern Central and

Southern Africa Regional Workshop. Harare, Zimbabwe p.152-159.

2. Ward, R. 1987. OMMYT/UTA Mid-Altitude Maize Research Station Towards Self

Sufficiency: Proceedings of the Second Eastern Central and Southern Africa

Regional Workshop. Harare, Zimbabwe p.168-177.


75

THE CIMMYf HEADQUARTERS HIGHLAND MAIZE PROGRAM

J.E. Lothrop1

ABSTRACT

The CIMMYf headquarters highland maize program is responsible

for developing improved maize germplasm for the coolest areas where maize

is grown or can be introduced in the developing countries. An estimated 10%

of the maize areas in the developing countries fit the climatic requirements

for highland maize. Highland maizes thrive in areas with mean growing

season temperatures less than 20 0 C, but above 12.S o C. The base

temperature for highland maize growth is estimated to be ~C. Most

highland maizes cannot tolerate extended periods of daily hlgh temperatures

much above 2SOC~ In the tropics, these temperature regimes are found

anywhere from 1200·3800 masl (3900-UOOO ft. above sea level). It is

extremely difficult to predict temperatures at a given altitude in tropical

regions because ofthe dual efTects oflatitude and micro-climatic factors.

Highland maize originated in the highlands of Mexico. There is

evidence for a second and minor center oforigin in the Guatemala

highlands. The Andean highlands is a center of diversity, but it is

hypothesized that bighland maize was introduced there. Highland maizes

have been introduced into some African highland environments, where the

highland transition zone maize Ecuador 573 has proven extremely valuable.

Improved highland maizes are just now being introduced into the Asian

highlands.

The CIMMYT highland maize program developed 14 gene pools with

flint dent, and Ooury endosperm in the early 1970's. Then the focus shifted

to development of morocho and Ooury grain types for the Andean highlands

from 1978-1984. The national programs in the Andean highland zone can

now continue the improvement of their unique morocho and Ooury

germplasm with less direct support from CIMMYf headquarters.

Consequently, the headquarters program now is concentrating on the

development of improved germplasm with hard grain type, which accounts

for about 92% of the estimated demand, according to the CIMMYf megaenvironment

data. Populations have been developed with dramatically

improved plant type, and good early generation inbred lines are already

available from populations adapted to the various highland mega·

environments. This array of highland germplasm is available upon request,

and should prove useful especially in the higher altitude areas ofAfrica and

Asia where no or little maize is presently grown.

Highland Maize' Origin, Spread, and Special Characteristics:

Many experts agree that maize (Zeamays) was derived from teosinte and

espedally the Mexican teosintes (Galinat. 1988; Beadle, 1977; M Clintock. 1977.).

Others hypothesize that maize co-evolved with teosinte (Mangelsdorf, 1974). Most

evidence points to a first domestication in Mexico about 7000 years ago

(Mangelsdorf, 1974; MacNeish, 1985; Goodman, 1988). Wilkes (1979) hypothesized

that maize was domesticated in the central highlands of Mexico from an ancestral

wild highland maize. From this prototypic maize, cold tolerant highland ma.izes

evolved early on in Mexico and perhaps Guatemala. The highland maizes of the

Andean region of South America probably originated in Guatemala (Goodman and

Brown, 1988; McClintock, 1977). Earliest domesticates in the Andean highlands are

1. Breeder, Hi~and Maize Program, CIMMYT, El Batan, Mexico


76

dated to 4000 years ago (Grobman and Bonavia, 1978). By the time the Spanish

conquerors arrived in the 1500's, native Americans had selected and domesticated a

wide variety of highland maize types grown as high as 3000 masl in Mexico, and

3800 masl in the Andean highlands. The main grain types selected were semi-dent,

floury, morocho, popcorn, and sweetcorn.

Europeans collected maize from all elevations and took the seed to Europe

for testing. Highland germplasm, especially Mexican hi~land germplasm, was well

represented in the initial introductions grown in Spain m the late 1490's (Trifunovic

1977). It is p!obable that some of the cold tolerance in the European flints traces

back to highland introductions.

In Africa, the introduction of the highland transition wne maiie Ecuador 573

in 1959 has had a great impact (Gerhart, 1975). The current effort by CIMMYT to

introduce true highland maizes into areas where maize is not now grown, may have

a major impact on improving African farmers' circumstances by increasing the

diversity of suitable crops in zones now predominated by barley, wheat, potatoes,

peas, and broad beans. CIMMYT is also currently in the process of introducing

highland maizes into Asia.

Maize has a much broader range of temperature adaptation than other

important cereals such as wheat, rice, barley, and sorghum. In very warm tropical

lowland regions mean growing season temperatures may exceed 26°C, while in the

coolest highland regions the mean may be as low as 12.5°e. CIMMYT breeds true

highland maizes in Mexico at experiment stations with growing season mean

temperatures of 15.9 0 C (EI Batan) and 13.3 0 C (Toluca). Probably the most

important adaptive mechanism of highland maize to cope with cool temperatures,

especially nights below lOoC, is an efficient enzyme system that allows it to continue

metabolizing at temperatures too low for other maizes. In the very cool Toluca

(13.3°C) environment all non-highland maizes are very yellow and grow very slowly

in the vegetative stage. The ability of highland maize to maintain a high chlorophyll

concentration under very cool temperature regimes has been well documented

(Eagles, 1986; Stamp, 1985). Secondary plant characters such as purple and highly

pubescent stems playa role in helping the plant maintain favorable teml2.eratures in

the face of cool conditions. The Mexican national maize program uses 6 u C as the

base temperature for highland maize when calculating heat units. This is 4 0 C less

than the usual standard of Woe.

It is commonly observed that most highland maize germplasm has deep

purple stem color. Darker stem colors have been shown to increase plant

temperatures in Peru and Canada (Greenblatt, 1968; Chong and Brawn, 1969). We

have tested the value of purple vs. green stems in two highland pools after two

generations of phenOtypIC assortative mating for stem color.

In a 1988 yield test in Toluca (13.3°C), the purple stemmed selections

yielded a significant 19% more grain than the green stemmed selections when

averaged over both pools. In one gene pool, Pool lOA. the yield advantage of the

purple stemmed selection was 36%. Associated with the higher yield of the purple

plants were increased plant height and reduced ear rot. Deep purple stem color is

one of the most important criteria for selection in CIMMYT highland populations

being bred for the coolest environments.

Frost and hail occur unpredictably in many highland environments. Highland

farmers who plant maize in very high valleys are aware of the paradox that there is

greater probability of frost damage in the lowest part of the valley than higher up on

the slopes. No maize can survive prolonged freezmg temperatures. But there is

genetic variability for the ability to survive light frosts. A Sept. 10, 1988 frost of ­

0.8 0 C in Toluca caused no significant damage to local maizes, but completely

burned the leaves of exotic maizes. We made some selections for frost tolerance in

local x exotic crosses. We normally experieoce..three to five hailstorms per growing


77

season at our Batan and Toluca stations. Heavy hail damage at anthesis causes

maximum yield losses. Local hi~land maizes have evolved a leaf architecture that

confers partial resistance to haiT damage. Leaves are thick, leathery, narrow, and

extremely droopy. In an Augu t 21, 1989 hailstorm these plant types preserved some

leaf area, while more erect leaf types were stripped to the midrib.

Defining Highland Maize Mega-Environments

The CIMMYT highland maize program aims to develop imprQved

germplasm for the coolest maize environments in dev~loping countries (Appendix

1). As of July 1988, there are an estimated 6.2 million known hectares of hIghland

maize in the developin$ countries. Most highland hectarage is sown to hard grain

types (93%), followed In importance by floury (4%) and morocho (3%) grain types.

The morocho grain is floury but with a hard outer cap. It is convenient to classify

these cold enVIronments into three mega-environments: 1) tropical highlands 2)

tropical highland transitional zones 3) temperate highlands (FIgure 1).

The tropical hi~hland zone encompasses on estimated 3.3 million ha &54% of

the world total). TropIcal highland maize grows in the latitudinal range 0-30 N. and

S., normally at altitudes from 2000-3600 meters above sea level. Mean growin~

season temperatures vary from 12-17 o C, and night temperatures fall below 10 C

throughout the growing season. Daytime high temperatures rarely exceed 26°C.

This group is unique among all maIzes because of its extreme cold tolerance, and it

is easily separated from the tropical highland transitional group because in the

tropical highlands night temperatures are too cool to allow significant natural

epidemics ofH turcicum (Exserohilum turcicum). The major foliar disease problem

in unadapted materials in the tropical highlands is common rust (P. sorghi). A low

level of resistance to H. turcicum is required, and other diseases such as Cercospora

are important in some areas. Fine stripe virus can be a problem in certain areas

without a pronounced dry season. Ear and stalk rots incited by Fusarium spp. are a

universal problem. Insects are not generally a problem, although the corn earworm

(Heliothis zea) is a serious problem in floury and morocho germplasm in South

America. Drought is the major abiotic stress. Some tolerance to freezing

temperatures and cool nights is necessary, as is partial tolerance to hail damage.

The highland maize germplasm, represepted by land races, developed

through natural and human selection in the highlands of Mexico, Guatemala, and

the Andean zone of South America, actually has a fairly narrow germplasm base

which is deficient in genetic variability for certain traits necessary for a modern,

mechanized agriculture. These include greater resistance to root and stalk lodging,

adaptability to minimum tillage systems, shorter plant and ear heights, and a faster

ate ofgram drying in the field. It will be necessary to continue gradually

introgressing exotic germplasm into tropical highland germplasm without

significantly reducing its outstanding cold tolerance, grain quality, ability to emerge

from deep planting (Mexican highland germplasm), and its partial resistance to hail

damage. At present, almost all of the tropical highland maize in the world is being

grown in Mexico, Guatemala, Lesotho, and the Andean zone. However, there is

great scope for introducing improved tropical hi~hland germplasm to the higher

elevations of eastern and southern Africa, the Himalaya regions, southwest China,

and West Irian-Papua New Guinea.

The tropical highland transitional zones support an estimated 2.3 million ha

of maize (38% of the world highland total). Tropical transitional zone maize grows

in the latitudinal range 0-30 0 N. and S., at altitudes as low as 1200 meters and as

high as 2600 m. Mean growing season temperatures vary from 17·19 0 C, and night

temperatures during the growing season seldom drop much below lS o C. Conditions

are often ideal for the development of the foliar disease H. turcicum and all

germplasm for this zone should possess high levels of polygenic resistance to blight


78

Figure 1.

Mega-environments and Temperature Adaptation of Highland Maize

_

Maximum day temperature

Growing season mean temperature

...;..;.;.;.;....=-__1Minimum night temperature

°C

3O-..--------.-----r-----....---

25 77

20 68

EI Batan,

Mexico

Toluca,

15 59

Mexico

I

Santa Catalina, 10 50

Ecuador

5 41

0 32

-5-'------'------'----...L..------L.----.l--23

Highland tropical

3.3 million ha

300N-300 S latitude

Highland transition zone

2.3 million ha

300N-300 S latitude

Temperate highlands

0.5 million ha

300-420 N + S latitude

Note: Arrows indicate growing season mean temperatures of representative

sites in each mega-environment.


79

as well as some P. sorghi resistance. Efforts will be directed towards reducin~ plant

and ear heights, improving H turcicum resistance, introducing genes for resIStance

to the Phyllachora maydis - Monographella maydis (tar spot) comrlex, streak virus,

and continuing development of Pool 9B, a yellow version of Poo 9a (fonnerly

CIMMYTs only transitional zone material.) Also in the development stage are

early and intermediate maturity transition zone populations.

Important abiotic stresses for this zone include low pH soils, drought stress in

some areas, and occasional hail. Besides the diseases already mentioned, there are

several ear and stalk rots incited by Fusarium and Diplodia spp. Important insect

pests include Chilo and Busseola borers and the corn earworm. Since most of the

hectara~e of the Pool 9a type is located in Africa, it is essential to develop mutually

benefiCIal collaboration with African researchers in this zone. Improved yellow

transitional zone maize is needed for areas such as Guatemala, Colombia, India,

Nepal, China and other Asian countries.

The temperate highland zones in the developing countries represent an

estimated 0.5 million ha (8% of the world higWand total). This type of maize must

be adapted to the fairly long daylengths that occur during the growing season at

latitudes 30-42 0 N. or S. It must also be early, cold tolerant, and possess resistance to

cool season diseases that occur in these high valleys at 1000-2500 m. Mean growing

season temperatures range from 14-20°C., and both P. sorghi and H. tureicum

resistance are required. Some resistance to H maydis may also be necessary during

the hottest part of the summer. Fusarium ear and stalk rots are also important.

Abiotic stresses include heat, cold, hail, drought, and frost. An unusual stress

common in the Asian countries, especially Pakistan, is that initial plant densities are

very high (Ca. 150,000 plts/ha). Before flowering, the maize is thinned to 70,000­

85,000 plts/ha, and the thinnings are fed to livestock. Commonly encountered

insects are the European Corn Borer and the corn earworm. Early results indicate

that germplasm resulting from crosses between tropical highland and early

temperate germplasm is promising for this zone. The hypothesis that some types of

highland maize might be useful as winter maize in sub-tropical zones is also being

tested. Since the temperate highland zone has a relatively low hectarage, the

CIMMYT highland program will maintain work on development of germplasm for

this zone as a relatively low priority.

Evolution of the Highland Maize Program and Breeding Strategies Employed

The method of germplasm improvement undertaken at CIMMYT for each

highland population by the various breeders in charge over the years has varied

greatly, but the aim has always been to develop improved highland germplasm in

response to perceived needs of the developing countries. In the 1970's CIMMYT

developed 14 broad based hi~hland gene pools for the tropical higWand megaenvironment.

These were whIte and yellow; early, intermediate, and late; and flint,

dent and floury grain textures. These gene pools were improved using the CIMMYT

modified half-sib selection method. In 1976 five populations were formed from five

of the 14 pools, and 250 half-sib progenies from each were evaluated in IPTfS

(InternatIOnal Progeny Testing Trials). Some of the resulting experimental varieties

were tested in the 1978 EVf 17 (Experimental Variety Trial).

At this point, the CIMMYT nighland maize program shifted focus. Dr.

Suketoshi Taba was posted to Quito, Ecuador with the task of improving the floury

and morocho (floury with a bard outer cap) Andean maizes grown on about 450,000

ha. At headquarters the work on the five populations was terminate ,and work on

the 14 pools wound down ~radually (after completing 5 cycles of selection in some

pools) as resources were diverted to support the Andean effort Eight Andean gene

pools were developed. They were improved by modified half-sib selection. An effort

was made to use shuttle breeding and grow the early pools in Santa Catalina,


80

Ecuador from October to March and in EI Batan from April to September. This

proved difficult to accomplish, and selection at El Batan was made difficult by the

extreme susceptibility of the Andean floury and morocho germplasm to the corn

earworm (HellO/his zea) and Fusarium ear rots. Selection at El Batan tended to be

counterproductive, since the large chalky grains desired by Andean consumers were

highly susceptible to rot. Still, the shuttle breeding approach did help to improve

broad adaptation, and useful Mexican and other exotic germplasm was introgressed

into local Andean maizes. Especially notable has been the contribution of the

Mexican floury race Cacahuacintle, and to a lesser extent the hard-grained

Chalquenos, used in the Andean zone as forage maizes. An effort was also made to

improve the earworm resistance of the floury maizes. This has proven very difficult,

given the large soft grain !y'pe, a,nd work is still continuing.The Quito, Ecuador

based Andean program ultimately developed 6 populations (3 floury and 3

morocho).The method employed involved international testing of 100 full-sib

progenies, completing one cycle of selection in two years. National programs in the

Andean region made use of the germplasm coming from the CIMMYT-Ecuador

program, and strengthened their own programs. By 1985 the Andean national

programs were strong enough that Dr. Taba could return to CIMMYT

headquarters, while CIMMYT continued to support the Andean highland programs

through its regional program based at Cali, Colombia.

From 1978-1984 the major effort at CIMMYT headquarters had been to

support the Andean program. However, work continued on some hard grain

highland maize germplasm for the more than 4 million hectares of this grain type

grown in Mexico, Central America, and Africa. CIMMYT breeders working in

Africa had noted that the highlands of East Africa were much warmer than the

Mexican and Andean highlands, and required entirely different germplasm. A late

white semi-dent gene pool for these highlands was developed in the early 1980's

(now named Pool 9A). Also, work continued on improving the plant type of tropical

highland maizes by introgressing temperate and subtropical germplasm. From 1985

on the work on hard grain types was Increasingly emphasized. However,

collaborative work on Andean maizes has continued, but on a reduced scale.

The introgression of temperate and subtropical germplasm into CIMMYT

and Mexican highland germplasm speeded up the breeding by permitting a winter

nursery. (It is extremely difficult to grow pure highland maize in the winter at the

CIMMYT Tlaltizapan experiment station, 940 masl, mean winter temperate 21.5 0 C,

because of root lodging, asynchrony, and barrenness). One drawback has been some

loss of cold tolerance necessary for the very coolest highland environments such as

Toluca, Mexico (13.3°C.). The resulting populations perform very well at EI Batan

(15.9°C).

In 1986 the Co full-sibs of four hard grained populations was yield tested in

Mexico. These were early and late, white and yellow. One cycle/year is completed in

these populations, and results have been satisfactory in EI Batan (Figures 2-6). An

early white floury population was also started in 1986, but full-sib selection is taking

2 years/cycle since the Cacahuacintle type germplasm involved cannot yet withstand

the stress of a winter nursery. A yellow version of Pool 9A (Pool 9B) was formed in

1988. White and yellow early {'opulations for the temperate highlands were also

formed in 1986. Full-sib families have been tested internationally. In 1989 a new

early white semi-dent ropulation was initiated. It is targeted for very cold highland

enVIronments, and wil be improved using full-sib selection, 1 year/cycle. Also in

1989 white and yellow intermediate maturity hard grained populations for the

highland transition zone were formed.

All highland populations and gene pools managed at CIMMYT headquarters

are being improved through recurrent selection. Characteristics of this germplasm

are listed in Table 1 and Appendix 2. Usually this involves the testing of full-sib


81

Figure 2.

Grain yields of Population 85 full-sib families at EI Batan.

105 check

Co

mean

75

I

60

>0-

(.)

I

c

Ol

I

::l 45 I

c-

...

Ol

L.I..

30

15

I

I

I

0

105

90

-5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5

C1

>0- 75

(.)

Ol

::l

c-

Ol

...

L.I..

60

45

30

15

0

105

90

-5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5

C2

75

>0-

(.)

iii 60

::l

c-

...

Ol

L.I..

45

30

15

0

-5 -4 -3 -2 -1 0 +1 +2 +3 +4 +5

Standard deviations


82

Figure 3.

Results of Population 85 yield trials at EI Batan

100

90

80

70

60

50

40

30

20

10

Percentage 01 progenies

yielding more than

check means

Co

.........

«/?

C1

Cycles

Pop. )(Jcheck ~ % • 150

140

130

120

110

100

90

80

70

60

50

Figure 4.

Results of Population 1986 ylold trials 01 EI Baton

100

90

80

70

60

50

40

Percentage of progenies

yielding more tllan

check means

t,

.......... ,

P -XI h k V 01 ~W:~

op. c ec 1\ 10 E:i;~

150

140

130

120

110

100

90

Co

C2

Cycles


83

Figure 5.

Results of Population 87 yield trials at EI Batan

100

90

80

70

60

50

40

30

20

10

Percentage of progenies

yielding more than

check means

Pop. Xlcheck X % ~I@]

150

140

130

120

Figure 6.

Results of Population 88 yield trials at EI Batan

100

90

80

70

60

50

40

30

20

10

Percentage of progenies

yielding more than

check means

Co

.....

..

Pop. >ucheck 5(

.;. .

,.;.:-:.:-:-:


TABLE 1

ADAPTATION OF HIGHLAND MAIZES co

~

MATERIALS BASED AT CIMMYT, MEXICO

DAYS TO FLOWER AT

TEMPERATURES APROXlMATE EL BATAN WHEN PLANTED

ADAPTATION RANGE °c ALTITUDINAL AT OPTIMUM DATE EAR ROT P.SORGHI H.TURCICUM

N A M E DlULi' MEAN DAILY HIGH DAILY LOW RANGE MEAN RANGE RESISTANCE RESISTANCE RESISTANCE

Highland Early 12-17 28 >0 - 10 2200-3200 m 82 70-88 Fair Excellent N.A. *

White Floury

"Mexico"

Highland Early 12-17 28 ")0 - 10 2000-3200 m 78 62-85 Good Very Good N.A.

White Semi-dent

Highland Early 12-17 28 "/0 - 10 2000-3200 m 78 62-85 Good Very Good N.A.

Yellow Semi-dent

Highland Late 13-18 28 70 - 12 2000-2600 m 95 88-105 Good Very Good N.A.

White Semi-dent

Highland Late 13-18 28 '70 - 12 2000-2600 m 95 88-105 Good Very Good N.A.

Yellow Semi-den~

Highland Late 17-19 30 15 - 20 1200-2000 m 128 120-135 Good Good Good

White Semi-dent

"Africa"

Transitional 17-19 30 15 - 20 1200-2000 m 128 120-135 Good Good Good

Zone Yellow

Semi-dent

Temperate 13-18 29 "70 - 17 1000-2500 m 78 68-85 Good Very Good Good

Highlands

Pq~u1ation

*N.A. = Not applicable


85

families, but in some cases half-sibs or partially inbred lines are recombined. In all

materials, each ~cle the elite fraction IS selfed to develop inbred lines. The best

partially inbred lines go to the CIMMYT hybrid maize program for further

refinement and evaluation. Currently, the most advanced lines are S4, and S5 seed

will be harvested this autumn. The highland program is doing some pedigree

selection to produce improved inbreds.

In the tropical highlands, 99% of the farmers are still growing openpollinated

varieties. Even in Mexico, 98% of the farmers are still grOWIng openpollinated

"criollo" varieties (CAEVAMEX, 1982), despite the fact that the Mexican

national program has had a hybrid oriented breeding program since 1943.

Therefore, the first priority for this zone is to develop good open-pollinated varieties

or synthetics, and the development of inbred lines is a secondary concern.

Preliminary results show good heterosis for grain yield between Mexican and

CIMMYT material. But perhaps more important are the attributes for improved

resistance to root lodging and better plant type which the CIMMYT lines carry.

There is a usable level of heterosis Within CIMMYT derived lines. But considering

the low J?riority of hybrid work for this zone, it is not warranted at this time to

devote Significant resources for developing heterotic groups within the CIMMYT

populations.

In the highland transition zone, about 50% of the hectarage is planted to

hybrids. Therefore, it is important that CIMMYT investigate combining ability and

develop inbred lines. Currently, some inbreds from Pool 9A are beyond the S4

stage, but a large group of S3 lines will not be ready for top-crossing until 1991. Pool

9A (white) and 9B (yellow) may be divided into heterotic groups based on the

results of the topcross trial. Since most of the highland transition zone maize is

grown in Africa, efforts will be made to coordinate this work with key national

programs. In the process of population improvement and inbreeding, intense

selection pressure has been applied for reduced plant and ear heights and resistance

to P. sorghi and H. turcicum leaf diseases, as well as Fusarium and Diplodia ear rots.

Pool 9A is currently being converted to streak resistance at the CIMMYT Harare,

Zimbabwe station, and, in the future, derived inbreds will carry resistance. In

addition, lines and synthetics of Pools 9A and 9B for the Americas will carry

resistance to the tar spot complex disease.

Pool 9A, Hi~land Transition Zone Late White Semi-dent, has shown good

performance in hignland transition zone environments, especially in Africa. This is

not surprising, since the majority of the germplasm in the pool came from Kitale

Synthetic II, Ecuador 573, and SR52. Other important germplasm sources

represented in Pool 9A include "highland" Tuxpenos from Mexico, Guatemala

highland transition zone varieties, and Montana from Colombia. While selecting for

POI~eniC resistance to H. turcicum and P. sorghi, we have lowered plant and ear

hei ts to the point that Pool 9A is about 40-100 cm shorter than the Kenyan hybrid

H6 . We are also selecting a large percentage of ears with flinty grain. All

pollinated ears are inoculated with Fusarium and Diplodia ear rots. It is quite

resistant to Fusarium, but still lacks sufficient resistance to Diplodia. Pool 9A has

been released as the variety Mugamba-1 in Burundi. Future plans for Pool9A

include the development of early generation inbred lines with good combining

ability, and perhaps a division into two heterotic groups.

In the temperate highland zone, most of the maize grown is open-pollinated

varieties, with the notable exception of sizeable areas in southwest China. Most of

these areas are now growing temperate or temperate-subtropical material. Since the

CIMMYT temperate hi~land populations (white and yellow semi-dents) were

developed by intercrossm~ improved hi~hland germplasm with northern U.S. and

Europeanmaterials, it is lIkely that denved lines win combine well with temperate

lines. In these populations we are currently evaluating full-sibs and Sllines. The


86

CIMMYf lines being developed will carry important attributes such as cold

tolerance, earliness, and resistance to both P. sorghi and H. turcicum. Inbreeding was

not started until 1988, so this autumn we will be harvesting S2 seed. Further work

should be coordinated with the Asian countries in the temperate highland zone.

This is especially true because photoperiod insensitivity is required, a trait for which

we cannot select in th field in these latitudes (19-20 0 N. in Central Mexico).

Genotype x Environmental Interaction in Highland Maize:

Implications ror Breeding

Small changes in elevation, especially at the higher elevations, can cause

large genotype by environment interactions (G x E). Since highland maize grows in

environments that are characterized by temperatures that are very dose to maize's

lower limit, maizes from the coldest regions are unproductive in the warmer

highland environments, and vice versa. CIMMYT mega-environment data show that

there are more maize environments per unit land area in the highlands than in the

lowlands.

A variety adapted to El Batan (lS.90q, when planted in Toluca (13.3°C), a

difference in elevation of 300 en, will have its vegetative period increased by 25-30

days an its grain-filling period increased by about 20 days. Thus only' the earliest

varieties at Batan can fit in the growing season in Toluca, and most likely they will

not have enough cold tolerance to be competitive with the best varieties from the

Toluca valley. Therefore, it is necessary to breed maizes specifically for each

environment. Since true highland maizes grow in areas with mean growing season

temperatures of I2.5-l7°C., it is convenient to breed maizes for extremely cold

enVlfonments, I2.5-I5 0 C at Toluca (13.3 0 q, and for the warmer highland

environments 15-l7°e, at EI Batan (IS.9 0 q. In practice it has proven practical to

breed maizes with broad adaptation within these two agro-ecologies, but not

materials that are adapted to both.

Since highland maize evolved in Mexico and farmer-breeders have practiced

selection in a myriad of valleys over 7000 years, there are local adapted land races

for every valley. This is not true for true highland areas in Africa and Asia. Plant

breeders cannot breed maize for each valley, therefore they must strive for broad

adaptation within agro-ecological zones. Most "criollo" (landrace) varieties are so

fine tuned to the requirements of their particular valley that they fail miserably

when planted in other valleys at lower or higher elevation only a few kilometers

away. However, there are a few "enoUos" and several improved varieties and hybrids

that have reasonably broad adaptation. But in a system of subsistence agriculture

suclt as predominates in the highlands of Mexico, the improved m terials will

certainly be inferior in yield in some valleys, and their food qualities. grain type,

color, and texture may not be up to the local standard in many valleys. This helps to

partly e~lain why even now 98% of the farmers in the central highlands are still

planting 'criollo" varieties, despite the fact that highland maize breeding programs

have been active since 1943, and a parastatal company had been making some

efforts to produce seed of the resulting hybrids and varieties. New varieties have

also been slow to gain acceptance in the Andean zone, partly due to G x E problems

and the subsistence nature of the maize production. Recently, highland IDalZe has

become more of a commercial proposition in certain areas such as the Toluca ­

Atlacomulco region of central Mexico (250,000 ha), and farmers are beginning to

buy seed of improved varieties and hybrids from a local seed company. It is expected

that this trend will accelerate in the future, especially if the Mexican government

decides to discourage maize imports (currently 3-5 million metric tons annually) and

encourage local production.


87

Inbreeding

The ease of inbreeding in highland maize is a function of germplasm and the

degree to which that germplasm has been subjected to previous inbreeding. For

example, the CIMMYT Temperate Highland Population has about 60% temperate

germplasm and 40% improved tro.pical highland germplasm. Both sources are

relatively easy to inbreed in, especlally the temperate material, so it has been fairly

easy so far to derive lines from this population. Likewise, the CIMMYT pOI;>ulations

adapted to the highland transition zone are based largely on Kitale Synthetic II,

Ealador 573, SR52, and Montana maizes from Colombia; all of which have been

previously inbred. Line extraction has not proven to be excessively difficult. The

greatest problems occur when one tries to inbreed directly in tropical highland

germplasm.

In Mexico, a hybrid oriented program for the hi&hlands has been in effect

since 1943. In 1989, almost all of ~he hybrids in productlOn still involve S1lines. The

Mexican highland germplasm has a large genetic load and problems of floral

asx?chrooy. Many good lines will tolerate 50% homozygosity, (S1), but almost none

will tolerate more than 87.5% homozygosity (S3). In contrast to this e~erience, it

bas been a pleasant surprise to find that it is relatively easy to inbreed In

CIMMYT's tropical highland populations. This is certainly due to the presence of

inbreeding tolerant exotic germplasm in these populations. Our inbreeding program

is relatively new; our most advanced lines are 93.75% homozygous (S4). They are

quite vigorous and there is good reason to assume that they can be further inbred to

the S6-S8 generations without significant problems. However, the advanced S4lines

selected at Batan show a marked lack of cold. tolerance in the very cold Toluca

(13.3°C) environment. Newer lines at the S1 stage have better cold tolerance, and

lines specifically selected for the Toluca valley will possess good cold tolerance. It

will be interesting to see to what degree one can combine extreme cold tolerance

and resistance to inbreeding stress.

Root Lodging, Tillering, Ear Proliferation at a Node

Pe0I;>le knowledgeable about Mexican highland maizes know that their

weakest pomt is susceptibility to root lodging. Mexican farmers long ago recognized

this problem, and they routinely "hill-up" highland maize 3 times during the

vegetative stage. Still, hi&h winds which accompany summer showers are responsible

for widespread root lodgmg many seasons, especially when manure or medium to

high levels of N fertilizer are applied. Such fields cannot be machine harvested (a

rare practice in the Mexican hl&hlands) and hand harvest is difficult. Yields may be

greatly reduced when root lodgmg occurs just before to just after anthesis. For

example, last year in the Toluca valley one of the best farmers plarited an improved

variety with good management in 2 large fields. In the unlodged field he harvestd 6

tiha, and in the badly lodged field slightly over 1 t/ha. At CIMMYT, the highland

progr~ selects again~t :oot lodgi,ng. by 1) us.i~g high levels of N fertilizer 2) p~anting

on the ndge and not hIllmg-up 3) usmg denSities of 43,745 and 69,336 pits/ham the

breeding nursery and yield trials, respectively.

Ti1lerin~ is partially dominant to non-tillering under our conditions in our

germplasm. It IS ajolygenic trait, and heritability is low because of large

environmental an G x E effects. Many times crosses between two non-tillered

plants produce families or hybrids that are completely tillered. After four years of

selection against tillering, we have greatly reduced it, but have not eliminated it.

Many visitors have noticed that genotypes tiller in El Batan that they have never

seen tiller elsewhere. The four main factors promoting tillering in El Batan are: 1)

high N levels of 150 kS' N/ha, 2) cool but not cold soil and air temperatures

(Miedema, 1982),3) hlgh solar ra,diation per unit of plant development in the early

vegetative stage and 4) short daylengths. The importance of high N cannot be


88

over-emphasized. Maize just across the highway from CIMMYT has no tillers under

farmers' low N management. When one selects an ear from a non-tillered plant

under low N conditions in the highlands of Mexico, it will invariably tiller profusely

under EI Batan conditions. The good side of this situation is that EI Batan is an

ideal location to select for non-tIllering. In the CIMMYT highland maize program.

we select against tillering in all maize types except some forage maizes.

Ear proliferation at a node is another undesirable characteristic of Mexican

highland germplasm. It seems to be associated with a tendency for tillering. The tiny

ear shoots that arise next to the main ear shoot almost never produce any ~ain, and

represent a waste of photosynthate. We have been selecting agains this traIt. But as

with tillering, heritability is low and progress has been slow.

Drought Stress and Deep Planting

Drought stress is extremely common in the tropical highland me~aenvironment.

An estimated 2.7 million hectares (81%) in this mega-envrronment are

planted to maizes that are nsually or frequently subject to moisture stress. Most of

these areas receive less than 1000 mm of precipitauon. Fortunately,

evapotranspiration is relatively low in cool highland environments. Five hundred

mm of well distributed rainfall is sufficient for a good crop when an early variety is

planted on a soil with moderate water retention characteristics.

The occurence of unpredictable dry spells can seriously reduce maize yields.

This is especially true when the dry period coincides with the period around

anthesis. CIMMYT has amply demonstrated that genotypes with a short anthesis to

silking interval (ASI) can best resist this type of drought In the highland breeding

program. we have identified families which silk three days before they shed pollen in

situations of moderate drought stress and high density (70,000 plts/ha). Most

"criollo" varieties have an ASI of

5-12 days under moderate stress. Another reason why these varieties suffer so much

is that they have very poor root development. Improved CIMMYT populations have

much better root strength and ASI. Both traits were introgressed from temperate

and subtropical materials.

Drought in the seedling and early vegetative stages is so common in the

highlands ofMexico that some partial resistance has been built up in farmer

selections. In Mexico, many farmers plant very deep (10-25 em) to place Seeds in

residual moisture to get the crop started before the arrival of the rains. This allows

them to plant a longer season, more productive variety than would be possible if

they waited for the arrival of the rains. But these varieties must be able to utilize

reSidual moisture for growth for about 40-60 days in normal years. Michoacan 21,

the source of the so-called '1atente" trait, is a cnollo variety from an area where

farmers plant highland maize using residual moisture. The latency effect, which is a

temporary slowing or cessation of plant growth, occurs only in the seedling stage and

is limited in its effectiveness. For example, this year a set of Mexican national

program double cross hybrids including one with all 4 lines from Michoacan 21 were

planted in residual moisture. There was no significant rainfall for 90 days. All

hybrids silked at a plant height of 50 cm or less. Still, the ability to emerge from

deep planting depths is a valuable one in most years. Many Mexican farmers in dry

zones with no residual moisture also plant deep so that plants will only germinate

and emerge after a heavy rain, thus increasing the probability they will survive the

seedling stage until the rainy season begins in earnest.

We found that most non-highland maizes (the Hopi and Navajo maizes

famous for their ability to emerge from deep planting depths are related to semihighland

maizes from northern Mexico) will not reliably emerge when planted much

deeper than 13 em. The ability to em~r8e from deep plantings is due to a capacity

for mesocotyl elongation (CofIins, 1914). At CIMMYT, we have developed, after 3


89

cycles of selection, populations that will reliably emerge when planted 20 cm deep,

and have improved agronomic traits and ASI introgressed into a tropical highland

background. We will shortly be developing inbred lines from these populations.

Conclusion

Highland maizes are unique because of their specific adaptation to cool

environments. The tropical highland maizes were among the first maizes to be

domesticated, and amon$ the last to be improved using modem maize breeding

methods. The challenge IS to improve their plant type and resistance to lod~ng

without reducing their cold and frost tolerance, disease resistance, and partIal

tolerance to hail damage. Other challenges must be addressed in breed10g improved

germplasm for the highland transition zone and temperate highlands. It will be a

challenge to introduce highland maizes into areas where little or no maize is

presently grown in Africa and Asia.

The CIMMYT highland maize program has evolved over the years. The

needs of our clients, the national agricultural research organizations, have also

evolved. With gnod communication between CIMMYT and NARS, the hi&hland

maize program will continue to develop the required germplasm products 10 the

future.

Besides tne development of improved germplasm, the highland coordinator

also has a training and communication function. More than a few of the people

attending this meeting have worked with me in the highland maize fields of central

Mexico. I learn a lot from visitors, and I am sure that I will learn a lot as a visitor

during .this meeting in Nairobi. What I learn should serve to help the CIMMYT

highland maize program evolve in a manner beneficial to the needs of the

researchers working in Africa's highlands.

DISCUSSION

Question:

Saint-Clair. Please give me an idea about the growth cycle of Pool 9A

material in the experimental conditions mentioned in your paper.

Answer:

~throp. Pool. ~A is a late maturity maize dev~loped for the tropical

hIghland transitIOn zone mega-enVIronment (Kitale, Kenya type

environment). It has the same maturity as the Kitale 600 series of hybrids.

Question:

Ochieng. Considering that tillering is a trait one observes before flowering

one would be tempted to think that the trait would be amenable to genetic

manirulation. From your paper, you indicated that such is not the case.

Why.

Answer:

Lothrop. Progress in 'reducing tillering has been disappointing, considering

that the trait is expressed before flowering. The trait is of low heritability,

due to large environmental and genotype x environment inter:tetion effects.

The environmental factors which favor tillering are 1) cool but not cold soil

and air temperatures 2) high N fertilizer levels 3) low plant density 4) short

daylengths.

Question:

Karangwa. Pool 9A has a high yield but it is very late for mat~rity.

doing selection for maturity in Pool 9A?

Are


96

Answer:

Lothrop. Yes, we are developing early and intermediate materials with the

same adoptation and grain type as Pool 9A.

Question:

Bigirwa. You mentioned that Heminthosporium turcicum is not a problem in

highland maize. But other sources do show that the disease thrives well in

humid conditions and not dry conditions. What is your comment?

Answer:

Lothrop. Helminthosponum turcicum is a minor foliar disease problem in the

tropical highland me~a-environmentwhere night temperatures are always

below wOe, and mOisture is often lackin&. In the more humid and warmer

conditions (night temperatures above 10 C) of the tropical highland

transition zone mega-environment, H. turcicum is a major foliar disease

p.roblem. In Uganda, almost all of the maize area is rrud-altitude or tropical

highland transition zone, not tropical highland.

Question:

Saint-Clair. What is the virus disease and the vector insect affecting

Highland maize.

Answer:

Lothrop. I mentioned that Fine Stripe ("Rayado Fino" in Spanish) is an

important disease in some tropical highland environments ill the America.

The vector is Dalbulus maydis.

Question:

Meta. Doesn't purple stem coincide with some nutrient difficiencies? What

is the best time to select for purple stem?

Answer:

Lothrop. Purple stem color is under genetic control. It is not a symptom of a

nutrient deficIency. Purple stemmed plants are easily identified before

flowering. The intensity of the purple stem color depends on genotype and

temperature. Low mean temperature ( < lS°C) favor the expression of

purple stem color.

Question:

Empig. What is the physiological basis of the cold tolerance you are working

on?

Answer:

Lothrop. The ability of hi~hland maize to maintain high chlorophyll

concentrations in cool envIronments is the most important phySIOlogical trait

involved in cold tolerance. Purple stem color is very conunon in most cold

tolerant maize, and has been shown to significantly elevate plant

temperatures when compared to green stem color.


91

References

Beadle, G.W. 1977. Teosinte and the origin of maize, p. 113-128. In David B.

Walden (ed.) Maize Breeding and Genetics. International Maize

Symposium, University of Illinois, Urbana - Champaign, Illinois, U.S.A

Published by John Wiley & Sons, New York.

Chong, c., and R.I. Brawn. 1969. Temperature comparisons of purple and dilute sun

red anthocyanin color types in maize. Can. J. Plant Sci. 49:513-516.

Collins, G.N. 1914. A drought-resisting adaptation in seedlings of Hopi maize.

Journal of Agricultural Research, Dept. of Agriculture, Washington D.C.,

Vol. 1, No. 4:293-301.

Eagles, H.A. 1986. Comparative temperature response of corn belt dent and corn

belt dent x pool 5 maize hybrids. Crop Sci: 26:1009-1012.

Galinat, W.c. 1988. The origin of corn. p. 1-31. In G.F. Sprague and J.W. Dudley

(eds.). Corn and Corn Improvement. Third edition. Agronomy Monograph

18. Madison, Wisconsin, U.S.A.

Gerhart, J. 1975. Notes on the diffusion of hybrid maize in Western Kenya.

Abridged by CIMMYT (International Maize and Wheat Improvement

Center). El Batan, Mexico.

Goodman, M.M. 1988. The history and evolution of maize. CRC Critical Reviews in

Plant Sciences, Volume 7, Issue 3: 197-219.

Goodman, M.M. and W.L. Brown. 1988. Races of corn. In G.F. Sprague and J.W.

Dudley (eds.). Corn and Corn Improvement. Third edition. Agronomy

Monograph 18. Madison, Wisconsin, U.S.A.

Greenblatt, I.M. 1968. A possible selective advantage of plant color at high altitude.

Maize Genet. Coop. Newslett. 42:144-145.

Grobman, A. and D.Bonavia. 1978. Pre-ceramic maize on the north-central coast of

Peru. Nature 276:386-387.

Interdisciplinary Maize Group of CAEVAMEX, 1982. Marco de referencia de la

producclOn de maiz en la mesa central de Mexico (sintesis). Secretaria de

Agricultura y Recursos Hidraulicos. Campo Agricola Experimental "Valle de

Mexico". Chapingo, Mexico.

MacNeish, R.S. 1985. The archeological record on the problem of the domestication

of corn. Maydica 30:171-178.

Mangelsdorf, P.D. 1974. Corn, Its Origin, Evolution and Improvement. Harvard

University Press, Cambridge. 262 pp.

Miedema, P. 1982. The effects of low temperature on Zea mays. Advances in

Agronomy 35:93-128.


92

McClintok, B.. 1977. Significance of chromosome constitutions in tracing the origin

and migration of races of maize in the Americas. p. 159-184. In David B.

Walden (ed.) Maize Breeding and Genetics. International Maize

Symposium, University of Illinois, Urbana - Champaign, Illinois, U.S.A

Published by John Wiley & Sons, New York.

Stamp, P. 1985. Seedling vigour of tropical highland maize at different

temperatures. Z. Acker-und Pflanzenbau 154:1-4.

Trifunovic, V. 1977. Maize production and maize breeding in Europe. p.41-58 In

David B. Walden (ed.). Maize Breeding and Genetics. InternatIOnal Maize

Symposium, University of Illinois, Urbana - Champaign, lllinois, U.S.A

Pubfished by John Wiley & Sons, New York.

Wilkes, H.G. 1979. Mexico and Central America as a centre for the origin of

agriculture and the evolution of maize. Crop Improv. 6:1-18.


93

APPEN!)DC 1

MAJOR HIGHLAND MAIZE

PRODUCING AREAS

REGION COUNTRY HECTARAGE GRAIN TYPE

MEXICO MEXICO 2,890,000 SEMI-DENT (98%)

AND FLOURY (2%)

C. AMERICA GUATEMALA 100,000 SEMI-DENT (100%)

S. AMERICA PERU 151,000 FLOURY (64%)

MOROCHO (27%)

OTHER (9%)

BOLIVIA 140,000 MOROCHO (56%)

FLOURY (32%)

OTHER (12%)

COLOMBIA 123,000 FLOURY (49%)

SEMI-DENT (33%)

MOROCHO (18 )

ECUADOR 58,000 FLOURY (49%)

MOROCHO (26%)

SEMI-DENT (25%)

AFRICA KENYA 520,000 SEMI-DENT (100%)

MALAWI 275,000 SEMI-DENT ( 100%)

TANZANIA 240,000 SEMI-DENT (l00%)

ETHIOPIA 200,000 SEMI-DENT (100%)

MOZ~IQUE 100,000 SEMI-DENT (100 )

BURU I 78,000 SEMI-DENT (100%)

UGANDA 52,000 SEMI-DENT (100%)

CAMEROON 50,000 SEMI-DENT (l00%)

ANGOLA 50,000 SEMI-DENT (l00%)

RWANDA 42,000 SEMI-DENT (100%)

MADAGASCAR 20,000 SEMI-DENT (l00%)

MOROCCO 15,000 SEMI-DENT (l00%)

LESOTHO 10,000 SEMI-DENT (l00%)

ZAIRE 5,000 SEMI-DENT (l00%)

ASIA CHINA 532,000 SEMI-DENT (100%)

INDIA 334,000 SEMI-DENT (l00%)

PAKISTAN 190,000 SEMI-DENT (100%)

EPAL 48,000 SEMI-DENT (100%)

ESTIMATED WORLD TOTAL 6,223,000


94

APPENDIX 2

Designatim

Iql. 89

Desc:riptioo

Highland Early \ohite

F1D.lry ''Ml!xi.=''

fStilrated hectarages of this IlBi.ze type

and regims ....nere p:?tenti.a11y useful.

l4!x.i.= (60,000 hal. IUt:enti.al.ly useful

in other high altit:uJe regicns of sa.rt:h

1ln'eri.ca, Africa, Asia.

n

Iql85

IUJl lOa

Hi.ghl..aOO Early \oa1ite

semi.-dent

~ {2,O6O,OOO hal, I.es:ltl-o (5,000 hal.

Potentially useful in shJrt seascn

hi.ghl.aOO envi.rcnrents in varia.IS regi.cns

of SCuth J\rreri.ca, Africa, Asia.

n

Iql. 86

Po::>l 11a

Highland Early Yellow

5emi.-dent

~ (40,000 hal, I.esotlD (5,000 ha),

Ecuador (2,000 hal. Rltentially useful

in slDrt seascn highland envi..rcnre1ts in

varia.IS regi.cns of Salth l\irerica, Africa,

Asia.

"

lq). 87

IUJl 12a.

z.ea.= (600,000 hal, Kenya (20,000 hal,

Potentially useful at higher elevaticns

in sa.rt:h Arreri.ca, Africa, Asia.

n

lq). 88

Po::>l l3a

Highland Late Yellow

5emi.-dent

Mexi.= (80,000 hal, Qlatarala (50,000 hal

Ecuador (14,500 hal. Rltentially useful

at higher elevat.i.cns in Central l\irerica,

sa.rt:h J\irerica, Africa, Asia.

High1.aOO

Transition zcne

Po::>l 9a

White semi.-dent

IIAfrica"

Transitim zcne Late

Kenya (500,000 hal, Malaw:i. (275,000 hal

Tanzania 1240,000 hal, Ethicpia (200,(XX)

hal,~ (lOO,(XX) hal, B.mmli

(78,000 hal, U:Jarrla (52,000 hal,

CCIrerocn (50,000 hal, ArY;!ola (5O,(XX)

ha), ~= (50,000 hal, NEp3.l (24,000

hal, ~ (21,000 hal, ColaIbia

(20,(XX) hal, G.latarala (20,(XX) hal,

zaire (5,000 hal. Rltentially useful

in other transit.i.cnal zooe areas of

central J\lrerica, Sa.1th J\lrerica, Africa,

Asia.

Transitim zcne

Yellow semi.-dent

Qatarela (30,(XX) hal, Nepal (24,000 ha),

Madagascar (20,000 hal ColaIbia (20,000 hal.

RJtent.ially useful in salle areas as

Transition zcne Late \ohite semi.-dent

"Africa", bJt 1Ibere yellow grain ~

~erreq.

TaIperate Highlarrls

IOOia (334,(XX) hal, Pakistan (l90,(XX)

ha), lot:lrocxD (15,000 hal. IUt:entially

useful in taIperate highlaOOs 30-420 N.

and S. latitmes.


95

EFFECT OF SELECTION FOR YIELD ON MAJOR AGRONOMIC TRAITS

IN THE VARJETY CROSS 'KITALE SYNTHETIC II X ECUADOR 573'

OVER NINE CYCLES OF RECIPROCAL RECURRENT SELECTION

JAW. Ochieng 1 , D.K. Muthoka 1 and RE. Kamidi 1

ABSTRACT

The two maize (Zea mays L.) populations, Kitale Synthetic II and

Ecuador 573, 'cycle x cycle' crosses of which were evaluated, have undergone

nine cycles of reciprocal recurrent selection at 10% selection intensity with

grain yield as the major criterion of selection. A study was conducted in

1985 at five sites in Western Kenya to evaluate the direct and indirect

responses to selection in the variety cross. In the equivalent 'cycle x cycle'

crosses, grain yield increased at a rate of4.54% per cycle (b =3.467) and, by

correlated response, the number ofears per plant increased at 2.4% per

cycle. Similarly, ear height was lowered by 26 cm (-1.2 cm per cycle) and

maturity length (days-to.50% anthesis) by four days in nine cycles (-0.4 day

per cycle). However, plant lodging incidence changed erratically, even

though a decreasing trend (-1.2% of a percent per cycle) was evident; whilst

the incidence of bare-tipped ears increased at a rate of2.8% of a percent per

cycle, presumably due to increase in ear size that tended to outgrow the husk

cover. An equilibrium point was observed at cycle four for grain yield

regressed on all possible types of variety crosses.

There seems to exist opportunity for further genetic improvement in

the variety cross 'Kitale Synthetic II x Ecuador 573' by means of reciprocal

recurrent selection for yield. A selection index involving grain yield, reduced

plant lodging and bare-tip ea.rs seems desirable at this stage of the maize

improvement programme at Kitale.

INTRODUCTION

High grain yield of maize (Zea mays L.) is the primary objective of most

maize breeding programmes. A sustainable breeding pro~ramme should be backed

up by a source of genetically diverse material. Current eVIdence from quantitative

genetics suggests that the greatest present and future need in maize breeding is to

Impose on this variation sound recurrent selection schemes designed to be effective

in relation to the long-range goal of achieving very high frequencies of the most

desirable alleles (Comstock, 1978).

A programme geared to developing high yielding maize hybrids is facilitated

by the use of at least two genetically divergent genepools with high population

means and potential heterotic "kick" in their cross. Reciprocal recurrent selection,

one of the components of a maize breeding methods study initiated in Kenya in

1964 (Darrah et aI., 1972), has proved to be the most effective selection scheme for

improving the yield of maize population crosses, albeit with little or no effect on the

populations per se (Hallauer et al. 1981). Comstock et al. (1949) disGUssed at length

the relative advantages of reciprocal recurrent selection 'versus' selection for

general combining ability per se. They observed that in the event of partial to

complete dominance at some loci and overdominance or pseudo-overdominance

(i.e. epistasis or repulsion-phase linkage mimicking overdominance) at other loci,

reciprocal recurrent selectIOn would be more effective than selection for either

general or specific combining ability. Lately, however, Comstock (1978) bas

contended that overdominance is not of overriding importance in maize grain yield

1. Maize Breeder, Director and Biometrician, respectively National Agricultural

Research Centre, P.O. Box 450 Kitale, Kenya.


96

genetics. Inasmuch as specific combining ability is a function of heterosis, i.e.

heterozygosity superior to homozygosity of the best yield (gene) combinations, that

selection scheme capable of tappmg such a reservoir of allelic combinations as well

as alleles governed by additive and additive x additive epistasis would capitalize on

both modes of gene action.

An initial comparative study on the relative efficiencies of various methods

of selection in two Kenya maize populations and the advanced generation of their

variety cross was reported by Darrah et al. (1978). More recently, Darrah (1986)

has presented further evidence in support of the efficacy of reciprocal recurrent

selection in improving the yield of maize variety cross hybrids at Kitale.

This experiment was conducted to evaluate any further response to

reciprocal recurrent selection in the variety cross 'Kitale Synthetic II x Ecuador 573'

over nine cycles of selection for grain yield, ear height, maturity, plant lodging

incidence and bare-tip ears. Results would indicate whether the variety cross is still

responding to further selection and in which direction for each of the major traits.

MATERIALS AND METHODS

The entries used in this study comprised a factorial combination of nine

cycles of Kitale Synthetic II crossed to each of the nine cycles of Ecuador 573. Seed

of the entries was prepared during the season preceding the year of evaluation.

The two maize populations have been subjected to nine cycles of reciprocal

recurrent selection at 10% selection intensity with grain yield as the major criterion

of selection. Selection for the other agronomic characters has been accomplished

largely indirectly during the maize nursery pollination in the recombination phase,

such as by rejecting late and lodged plants with high ear placement.

The results presented herein represent a study on the performance of

equivalent and non-equivalent cycle x cycle crosses for grain yield, ear height, daysto-50%

anthesis, plant lod~ing and bare-tip ears, along with any trait that shows

correlated response with yleld. Plots consIsted of three rows of nine hills per row

that were over-planted and later thinned down, when the plants were knee-high, to a

maximum of 33 plants per plot. Plant spacing was set at 75 cm between rows and 30

cm between plants within the row. This resulted in a density of 44,444 plants per

hectare at ideal plant stand.

Crop husbandry practices involved applying phosphatic fertilizer

(diammollium phosphate, 18:46:0) at a rate of 80 kg P 2 0 5 per hectare at planting

and side-dressing WIth 100 kg N per hectare as nitrogenous fertilizer (calcium

ammonium nitrate, 26% N) after thinning. The crop was kept weed-free by

applyin~ atrazine (Primagram 40% w:v) as a pre-emergence surface spray at a rate

of five htres£er hectare and protected from stalk borer (Busseola fusca) damage

using DDT (5% dust) mixed with fine sand and applied to the whorl of each plant

after the thinning operation.

The 81 entries were generated from an I8-parent array according to 'Design

II' mating design (cross-classification) (Comstock and Robinson, 1948; Hallauer et

al. 1981). The entries were formed by crossing each of the nine cycles of Rll with

each of the nine cycles of R12, thereby producing RllCi (i = j for equivalent and i

not = j for non-equivalent cycle x cycle crosses). The tnal was grown as a 9 x 9

square triple lattice in three-row elots at five locations in Western Kenya in 1985,

viz. Kitale Grassland, Top Farm (Kitale), Chorlim, Jabali and Japata.

Data were recorded on plants from the entire three-row plots for the

following charcacters: number of days from planting to 50% anthesis, total plant

stand count at harvest, ear heights of 10 random competitive plants, number of

usable ears, number of diseased ears and weight (kilograms) and moisture content

(%) of usable grain. Plot yields were transformed to quintals per hectare (qJha)


97

adjusted to a uniform 12.5% moisture content of the grain. Prolificacy was

computed as [100 x (usable ears) + (diseased ears)/harvest stand] on plot basis.

The results were interpreted according to the scheme outlined by Comstock

and Robinson (1948). Sites were considered as random effects but entries as fixed

in a linear statistical model of the type.: k

X" k = ~ + g' + I· + (g1)" + EIJ

where an~ observatlon X ijk

IS a Hnear function of the general mean ( ), the i th site

or location (1-), genotype x"location interaction (g1)i' and a random error

component d~iik)' Linear regressions of yield, perc~nt prolificacy, ear height and

number of days~to-50%anthesis on cycles of selection, as well as simple correlation

coefficients, were obtained and tested following the procedures described by Steel

and Tome (1980).

RESULTS AND DISCUSSION

Results for equivalent 'cycle x cycle' crosses yield performance are presented

in Table 1. Nine cycles of reciprocal recurrent selection significantly increased the

yield of the variety cross at a Significant rate of 4.54% per cycle. This observation is

10 close agreement with that obtained by Darrah (1986) who reported a rate of 5.5%

per cycle after the fifth cycle of selection. The results are further depicted in Fig. 1

for equivalent and non-equivalent 'cycle x cycle' crosses.

Results for equivalent and non-equivalent 'cycle x cycle' crosses performance

for yield and other agronomic traits are given in Tables 2-7 and depicted in Figs. 2-6

for percent prolificacy, ear height and days-to-50% anthesis. Selection increased

prolificacy by 2.4% per cycle, and lowered ear height by 1.2% per cycle and maturity

length by 0.4% per cycle (four days in nine cycle). Lodgin~ incidence chan~ed

erratically, although a decreasing trend (-4.4%) over the nme cycles was eVident.

However, selection tended to increase the incidence of bare tipped ears, presumably

due to correlated response with increased yield: it is conceivable that larger ears

contributing to higher yield would tend to emerge through the husk ends. It has

been found that when selection is practised for hig!) yield alone, correlated increases

occur in prolificacy, ear height and days-to-flower (Darrah et aI., 1972; Mareck et

aL, 1979; Johnson et al., 1986). Additive genetic effects have been invoked as

governing the inheritance of ear height (Harville et al., 1978) and prolificacy

(Sorrells; 1979). Results from this study do not lend themselves to such inferences.

However, if these findings were found to hold true for the genotype evaluated

herein, as seems likely, it should be feasible to effectively mount further selection

for, not only hi~her yield from increased prolificacy, but also for lower ear

placement. This could be achieved by conducting two sets of reciprocal recurrent

selection on each sub-population of the two breeding stocks (Odhiambo and

Compton, 1979): one set emphasizing on grain yield on standing plants and

prolificacy and the other set capitalizing on reduced ear height, early maturity and

good husk cover, and recombining the two sets at some stage of the selection

process

Ṁean square tests on pertinent traits are shown in Table 8. Highly

significant differences (p = 0.01) were found among entries as well as among

locations for all the traits considered herein. However, there was no 'entry x

location' interaction for any trait, most likely due to the disproponionately large

pooled error variances. The rather lar~e locational differences were probably

accentuated by substantial differences In dates of planting, especially effects OD

grain yield, profificacy, ear height and number of days to 50% anthesis, and the

effects due to wide variation in dates of harvesting on the incidence in plant lodging

and bare-tipped ears (Table 1).


Table 1: Grain yield (qjha al 12.5% moisture oonlenl) of equivalent 'cycle x cycle' croases' grown al five sites in the Rift Valley Province of Kenya in 1985.

Entry Selection Kitale Kitale AD.C. AD.C. AD.C.

No. Cycle Grassland Top Farm Chorlim Jaball Japata Mean

-----------------------------------------------------------------------------------------

1 0 47.9 38.7 74.3 57.8 85.4 56.8

11 1 62.1 51.0 59.7 55.0 85.5 58.7

21 2 61.7 36.9 48.0 48.2 85.8 52.1

31 3 69.3 55.4 74.3 62.1 78.0 67.8

41 4 n.2 61.5 84.5 59.6 62.6 69.1

51 5 99.4 48.8 82.8 74.8 88.1 78.8

61 & 76.7 46.6 88.9 85.7 84.0 72.4

71 7 99.8 59.2 81.8 70.2 88.5 79.9

81 8 87.1 66.2 91.2 66.2 89.6 80.0

Mean (9 entries) 75.7

51.6

76.2

62.2

76.4

68.4

CNerall Mean

LS.D.

COY. %

(0.05)

76.5

20.7

17.0

52.4

18.0

21.5

76.1

16.0

13.1

61.1

13.4

13.8

75.5

15.0

12.4

68.3

7.5

15.4

Dale Planled:

Date Harves1ed:

Nov.7

Apr. 4

Nov 22

Apr 22

Dec 11

~r25

Nov 12

Apr 16

Nov 14

~r17

• Data exlracted from evaluation of 81 entries ~.e. 9 cycles of KSII crossed to each of 9 cycles of Ec. 573) as a '9 x 9' triple lattice.


99

86

YIELD (q/ha)

--------------------"'"-------------------

RllCi X RI2Cj' Y-64.5 10 3.472X·"

82

R11Ci X R12C. Y·63.1 I- t.312X"·

R11C. X R12Cj Y·62.6 #- 1.440X·"

78 -

74

70 -

66

62

58

54

1--t-I--1--1-- 1-1--~I--I--I---I

1 2 3 4 5 6 7

o

CYCLES OF SELECTION

8

Fig. I. Linear regression ()f equivalent and non-equivalent Varietal

Crosses- IKitdle Synthetic II x ECUddor 5731 yields on cycles

of reciprocal recurr~nt selection in the pa,"ent populations.

•••• Slope significantly different from zero at p = 0.00\ .


Table 2:Yield (q/ha) of 81 entries in a factorial cross combination

Cycles: co C1 C2 C3 C4 C5 C6 C7 C8 X R11C

o o

co: 56.8 59.4 58.2 67.4 67.8 70.8 62.1 66.0 67.2 64.0

C1: 63.7 58.7 49.4 63.5 64.4 66.7 69.4 69.6 68.5 63.8

C2: 60.9 57.5 52.1 68.4 60.7 58.1 67.8 71.0 62.5 62.1

C3: 60.6 52.0 68.2 67.8 67.6 70.0 69.1 70.3 70.8 66.3

C4: 67.2 68.9 71.1 68.1 69.1 71.7 73.3 ",?'>.{J 74.3 70.7

C5: 67.4 60.9 64.5 655 73.4 78.8 71.6 711 73.6 70.3

C6: 62.7 67.6 70.8 72.7 72.9 72.4 72.4 n,S 79.4 72.0

C7: 68.9 69.3 68.0 68.9 75.4 81.4 72.1 79.9 72.7 73.0

C8: 67.8 66.6 73.8 76.4 73.3 71.6 74.7 70.0 80.0 72.7

X R12C .: 64.0 62.3 64.0 68.7 69.4 71.3 70.3 72.7 72.1 68.31

CNerall Mean = 68.30 q/ha

LS.D. (0.05) = 7.52 q/ha

C.V. = 15.4%

Table 3: Prolificacy (%) of 81 entries in a Tactorial cross combination

Cycles CO C1 C2 C3 C4 C5 C6 C7 C8 ~11C.

---------------------------------------------------------------------------------------------

CO: 93 95 97 106 104 105 96 98 104 100

C1: 101 96 107 99 105 108 101 96 105 102

C2: 99 99 88 100 102 99 100 112 110 101

C3: 99 90 107 104 101 101 115 102 99 102

C4: 93 105 107 B9 106 105 107 105 98 102

C5: 101 91 96 93 108 112 104 105 100 101

C6: 95 105 105 100 105 104 103 111 106 104

C7: 108 106 104 97 104 108 100 100 103· 104

C6: 103 99 113 107 108 114 112 102 113 108

X R12C .:

99

98 103 99 105 106 104 105 104 103

CNerall Mean

L.S.D. (0.05)

C.V.,%

= 103%

= 13%

= 17.5


Table 4: Ear height (cm) of 81 enlrles in a factorial combination

Cycles: CO Cl C2, C3 C4 C5 C6 c;r C8 ~llC.

---------------------------------------------------------------------------------------------

CO: 251 229 231 227 231 230 230 230 231 Z32

Cl: 245 229 232 229 235 Z36 :!28 231 224 231

C2: 242 241 226 229 230 226 234 226 W 231

C3: 236 233 235 229 227 225 226 W 219 :!28

C4: 236 236 230 228 217 231 214 221 225 226

C5: 244 229 227 Z36 228 231 231 W 226 231

C6: 242 238 234 230 225 222 226 221 227 229

c;r: 234 222 243 231 226 229 218 224 220 227

C8: 243 237 231 239 22,8 231 224 228 225 Z32

~12C:

241 233 232 231 227 226 226 225 224 230

CNerall Mean ~ 230.0 cm

l.S.D. (O.OS) ~ 7.4 cm

C.v. ~ 4.5%

Table 5: Maturity (days) of 81 entries from factorial crosses of the variety cross 'Kitsle Synthetic II x Ecuador 573'

Cycles: CO Cl C2 C3 C4 C5 C6 c;r C8 XR11C.

---------------------------------------------------------------------------------------------

CO: 108 106 lOS 105 107 105 106 106 105 106

Cl: 108 106 106 106 107 106 107 106 lOS 106

C2: 108 108 105 106 106 105 106 106 106 106

C3: 106 106 105 106 106 105 105 106 106 106

C4: 106 107 106 104 10S 106 104 105 lOS lOS

C5: 107 lOS 105 104 104 lOS 104 105 105 105

C6: 107 107 lOS 105 106 103 104 lOS 104 10S

C7: 106 lOS 105 105 lOS 105 10S 106 104 105

C8: 106 107 lOS 107 106 lOS lOS lOS 104 105

~12C.: 107 106 lOS 105 106 105 105 106 lOS 105

CNerall Mean ~ l06days

l.SD. (0.05) ~ 1 Qay

C.V. ~ 1.7%

o


Tabla 6: Plant lodging ("") ol81 entriea ol the variaty c:rou over~.. ol reclprocal recurrent aelectlon

---------------------------------------------------------------------------------------------

Cycles: CO C1 C2 C3 C4 cs C8

C7 C8 ~11C.

---------------------------------------------------------------------------------------------

CO: 40.6 49.3 50.0 31.4 36.7 36.1 39.5 44.3 48.6 42.8

C1: 52.4 41.4 33.4 48.3 41.9 33.5 35.9 35.5 34.3 38.6

C2: 43.2 44.3 41.8 44.1 46.9 51.6 45.3 34.5 34.8 43.6

C3: 40.4 59.6 44.5 34.1 25.8 45.3 49.1 28.1 36.4 40.6

C4: 28.5 39.5 31.8 40.4 31.1 36.9 39.6 48.4 28.2 31.4

cs: 30.3 30.6 31.0 44.3 43.1 42.4 40.1 39.1 36.2 36.3

C6: 39.1 38.8 53.6 42.0 35.2 32.6 46.5 33.2 28.1 38.9

C7: 41.4. 39.5 36.8 43.0 39.4 31.!! 33.1 31.1 26.1 36~

C8: 33.9 25.6 38.1 !S.8 41.9 44.3 43.3 41.6 36.2 31.1

~'2C.: 38.9 41.0 42.2 40.3 38.8 40.4 41.4 31.4 34.1 39.45

--------------------------~------------------------------------------------------------------

(Nerall Mean = 39.5""

LS.D. (0.05) = 16.1""

C.V. % =51.1

Table 7: Bare-tipped eanl ("") of 81 entries from a factorial cr01lll8$ of 'Kitale Synth81lc II x Ecuador 513' cycles.

Cycles: CO C1 C2 C3 C4 C5 C6 C7 C8 ~11C.

-------------------------------------------------_._-----------------------------------------

CO: 13.1 11.4 1.4 8.3 5.4 7.1 6.4 10.8 5.5 8.4

Cl: 14.7 20.2 25.8 6.1 1.4 4.9 8.6 12.2 4.3 11.6

C2: 11.1 10.7 1.1 11.4 5.2 6.8 5.8 4.1 1.4 7.8

C3: 22.3 13.5 16.9 13.1 22.8 13.7 14.5 14.3 15.0 16.3

C4: 21.9 4.3 8.4 9.1 8,4 4.5 8.7 6.1 10.3 9.1

C5: 13.5 8.9 9.3 13.2 16.0 5.0 8.1 7.3 11.1 10.3

C6: 17.8 13.3 13.3 16.7 13,1 9.4 13.6 11.3 14.2 13.6

C7: • 18.3 25.1 16.1 8.4 21.3 9.6 10.6 9.6 9.2 14.4

C8: 21.1 19.0 12.8 12.9 14.9 1.4 5.8 1.8 16.4 13.2

---------------------------------------------------------------------------------------------

~12C 11.2 14.1 13.1 11.2 12.7 7.6 9.1 9.3 10.4 11.6

Overall Mean = 11.6%

LS.D. (0.q5) = 5.1""

C.V."" = 61.0 I

0

'"


lU3

PROLIFICACY ('!II)

114,-------------

112

110

R11C; X R12Cj

R11C; X RI2C.

RI1C. X R12Cj

Y-92" 2.667X"

Y-99" O.808X·

Y-100 .. O.135X"

108

106

104

102

100

98

_..-

_.---~--.-­

Prollflo

.... -- ~--

~~••••~a&••••• •••••• A••••••••••••••••••••

.------

Barren

96

94

92"----------

o 1 234 5 6

CYCLES OF SELECTION

7 8

Fig. 2.

Linear regression of percent prolificacy of Varietal Crosses

(Kitale Synthetic II ~ ~cu3dor 573) on cycles of reciprocal

recurrent selection in the parent populations.

., •• Slope significantly different from zero at p

respectively.

o .65 and 0.0 I ,


104

EAR HEIGHT (em)

236,.---------

234

232

230

------

- ------ - -..- -.-- - --."- -....

228

226

224

222

R11CI x R12Cj

R11el X R12C.

R11C. X R12Cj

Y-236 - 1.95X·"

Y-236 - 1.763X···

Y-231 - O.213X

220 L--. . _

o

1 23456 7 8

CYCLES OF SELECTION

Fig. 3. Linear ,-egression of ear height of Varietal Crosses

IKitale Synthetic II ~ Ecuador 5731 on cycles of reciprocal

recurrent selection in the parental populations.

••• Slope significantly different from zero at p = 0.001 .


105

DAYS TO 50.. ANTHESIS

107rc-----------------------,

106.5

106

105.5

-"

105

......

104.5 R11CI X R12Cj Y-l07 - O;317X-

RllCI X RI2C.

R11C. X R12Cj

Y-l08 - O.182X-

Y-l08 - O'-140X-

~

104

0 1 2 3 4 5 6 7 8

CYCLES OF SELECTION

Fig. 4. Linear regression of days-to-SO% anthesis (maturity> of

Varietal Crosses (Kitale Synthetic II x Ecuador 573> on

cycles of reciprocal recurrent selection in the parental

populatiorls.

• Regre3sion slope significantly different from zero at p 0.05 .


106

LODGED PLANTS ('llI)

43,---------------------------,

42

41

40

39

38

37

36

R11CI X R12CJ

R11CI X R12C.

Rl1C. X R12Cj

Y.-42.8 - D.883X

Y-41.4 - D.482X

Y-42.3 - D.721X"

35 --------------------------

o 1 2 345 6 7 8

CYCLES OF SELECTION

Fig. 5. Lln~ar regression of perrent lodging of varietal Crosses

IKitale Synthetic II x Ecuador 5731 on cycles of. reciprocal

,·ecurrent selection in the parental populatio"";;-s .

•• Stope significantly different from zero at p 0.01 .


'07

BARE-TIP EARS (,*,)

16 -----.-------'------...~--.- ..--- -----... - ... -- ...

14 "

13

12

""", " "

,

--.,

,

-"'--.

","

" ./

',--

./

"

,

./

~" ..... '"

"

'" "

1 1

,

./

,,'

" '"

"

" ,

""

,

15 "'-

"'-"""-

/

10 " " ,

"

-' "

" , "

9 " , ,,

R11CI X R12Cj Y-12.8 - O.233X '--

". "

8 R11CI X R12C. Y-15.2 - O.889Xu

R11C. X R12Cj

Y-9.4 • O.552X

7

0 1 2 3 4 5 6 7 8

CYCLES OF SELECTION

"-

Fig. 6. Linear ~egression of percent bare-tipped ears of V~riet~l

Crosses IKitale Synthetic II K Ecuador 573) on cycles

reciprocal recurrent selection in the parent~l

populations.

•• Slope significantly different from zero at ~ = 0.01 .


Table 8: Mean equal. test for four tratte from a diallel crOSl of nine cycles of 'Kitale Synthetic II x Ecuador 573' grown at five locations In t1he Rift Valley Province of Kenya in 1985

-----------------------------~---------------------------------------------------------

Yield

(q/ha)

Prolificacy

(%)

Ear Height

(em)

Maturity

(days)

Source of Variation oF*

Mun Square•

... ... ... ..

Locations (L) 4 :>.9471.4 10690.5 150603.1 11896.9

...

...

... .. ...

... ... ... ... ... ...

...

....

R11Cx A12d

....

.

.. ...

. ..

Reps within Location 10 230.9 726.1 4884.3 27.4

Croae. 80 4733.2 2358.8 4773.1 95.9

X A12


109

Phenotypic and genotypic correlation coefficients between pairs of traits are

presented in Table 9. The negative association of maturity length with prolificacy

and percent prolificacy with lodging incidence appeared to be masked by

environmental influence. Likewise, the high tendency for tall plants to lodge was

compounded by site effect; hence the lack of significance in phenotypic correlation

between ear hei~ht and plant lodging when, in fact, the genotypic correlation

coefficient was sIgnificant.

Yield was highly positively correlated with prolificacy, both genotypically and

phenotypically. This was in agreement with reports by Morales et at. (1975) and

Darrah et at. (1978). There were negative correlations linking grain yield with ear

placement, maturity length and plant lodging. As expected, taller genotypes were

later in maturity and less prolific. this is due to the fact that late maturing genotypes

tend to utilize most of the assimilates for more foliage at the expense of ~rain fill.

The ability of prolific germplasm to resist barrenness at high plant densitIes or to

increase yield at optimal and sub-optimal densities is well documented (Brown et at.,

1923, Crews et ai., 1965; Duvick, 1974; Prior et al., 1975; Nakaseko et aI., 1978).

There were no correlations between bare-tipped ears and the other traits.

Explanations for this observation are hard to find.

Linear regression coefficients for traits of equivalent and non-equivalent

'9'cle x cycle' crosses are given in Tables lOA and lOB and shown graphically in

FIgs. 1-6. The regression slopes in Figs. 1 and 2 for grain yield and percent

prolificacy, respectively, on cycles of selection were spectacularly similar for the

three "forms" of variety crosses (R11Cj x R 12C' x R12C and R 11C x R 12C·).

Regression slopes for all the three type~of crosses were sigriificantl1different

from zero for yield, prolificacy and maturity. However, for ear hei~ht and percent

bare-tip ears, only the regression slope for RllCj x R12C was sigruficantly different

from zero. The slope for yield regressed on equivalent cycle 'cycle x cycle' crosses

was steeper than those for non-equivalent crosses, with an equIlibrium point

observed at cycle four (Fig. 1), implying inbreeding depression in the latter types of

crosses.

Actual and predicted responses to selection in the variety cross over

successive cycles of selection are ~iven in Tables llA and llB. There seemed to be

a high preponderance of non-additive genetic effect for yield expression, especially

from cycles 0-5. Actual and predicted gains of 20.9 qjha and 25.0 qjha, respectively,

were observed after five Cycles of selection. This was in contrast to the higher actual

gain (11.2 qjha) than predicted gain (7.4 qjha) reported by Darrah (1986) at cycle

5. However, the overall actual and predicted yield gains after nine cycles were close

(21.6 vs 21.3 qjha).

Giesbretch (1959) and Sharma et al (1972) reported that additive and

'additive x additive' type epistasis were involved in controlling the inheritance of

maturity in maize. The results of this experiment (Table lIB) bear testimony to

those findings. However, in this study, the predicated and actual changes in

maturity length were similar in 50% of the occasions and different in the other 50%

of the cases.

CONCLUSIONS

There seems to exist opportunity for further improvement in the variety

cross, 'Kitale Synthetic II x Ecuador 573', by means of reciprocal recurrent selection

for increased grain yield (heterosis) and prolificacy and for reduced ear height and

early maturity. Use of index selection for yield, plant standability and prolificacy in

one set of reciprocal recurrent selection and for earliness, lower ear height and good

husk cover in the other set, and recombining the two sets every so often would,

hopefully, pay dividends in future genetic improvement. So far, selection for early,


Table 10: Unear regrell8lon ooefflcienlll (b) 01 major traitll on (nine) cycles of 88180110n In the variety er088: equlvalen1 and non-.qulvalent 'cycle x cycle' Cf08888.

Trait: Cycle er088 on Cycle

......

b +/- S.E' b

R-Squ8fe Intercept (a)

RllCix Rl2C 3.47 +/. 0.63 0.814 54.5 q/ha

J

RllC xRl2C. l

1.31 +/. 0.20 0.654 63.1 •

--------_:~------~~~:~~~------------~.~----_:~-----~~-------~.~---------~~~------

Yield (qjha) - (CO· C4):

_________________ ~~:~~~~l

Yield (q/ha) . (C4 - ee,:

RllCjXRl2C1 3.38 +/. 1.83 0.533 54.1q/ha

RllC.xRl2C 1.72 +/- 0.59 0.740 62.3'

I •

~~~ :~ ~~ ~:~ ~:~ _

Rll'1 x Rl2C. 2.29 +/- 1.25 0.527 62.3 q/ha

RllC. x Rl2d 0.69 +/. 0.29 0.653 67.0 •

I .

RllC x R12C J

0.65 +/- 0.20 0.778 67.8 •

-------~---------------------------------------------- --------------------------

Prolificacy (%\ • (CO· cal:

RllC j x R12~ 2.67 +/. 0.67 0.696 92%

Rll C. x R~2C 0.81 +/. 0.26 0.588 99%

~

I .

___________________ RllC x R12C. 0.74 +/. 0.18 0.693 100% _

Ear Height (em) • (CO· cal:

Rl1C XR12C ·1.95 I j

+/- 1.05 0.331 236 em

Rl1C j

xR12C -1.76 +/. 0.32 0.812 236'

_________________ ~~:~~~S ~:~ :~ ~:~ ~.~ :~~~ _

Maturity (days) • (CO' cal:

RllC l

xR12C j

.


Table l1A: Actual and predicted responses 10 selectiortfor yield and prolifica.:y oller cycles of selection in the lIariety cross

Change

in

Cycles

0-1:

0-2:

0-3:

0-4:

0-5:

0-6;

0-7;

0-6;

Gain in Yield (q/ha / cycle) Gain in Prolificacy (% / cycle)

Actual Predica1ed Differences Actual Predic1ed Difference

------ ---------- ----------- ------ --------- ----------

1.2 8.8 -7.6 3.0 11.0 -8.0

-5.1 5.2 -10.3 -5.0 9.0 -14.0

10.0 14.6 -4.6 18.0 19.0 -1.0

10.6 17.5 ~.9 14.0 11.0 +3.0

20.9 25.0 -4.1 19.0 20.0 -1.0

13.9 13.6 +0.3 10.0 5.0 +5.0

23.7 20.4 +3.3 17.0 10.0 -2.0

21.6 21.3 +0.3 20.0 20.0 0

Table 11B: Actual and predicted responses to selection for ear height and maturity oller cycles of selection in the lIariety cr088

Change

in

Cycles

0-1:

0-2:

0-3:

0-4:

0-5:

0-6;

0-7:

0-6:

Gain in Ear Height (cm./cycle) Gain in Maturity (days/cycle)

Actual Predicted Difference Actual Predicted Difference

------ --------- ---------- ------ --------- ----------

-27 -34 +7 ·1 ·1 0

-29 -35 +6 ·3 -3 0

-26 -49 +23 -2 -3 +1

-39 -46 +7 -3 -3 0

-19 -34 +15 -2 -4 +2

-23 -32 +9 -3 -3 0

-24 -41 +17 -2 -3 +1

-21 .~ +7 -3 -5 +2

.....

.....


112

high yielding genotypes with acceptable ear placement seems tenable using these

maize populations as attested to by the results presented herein.

ACKNOWLEDGEMENTS

Thanks are due to the entire staff of the breeding section of the National

Agricultural Research Centre-Kitale: support staff, technical assistants and fellow

research officers for their help in growing out and harvesting the experiments. Our

gratitude goes to Professor W.A Compton and Mr T.O. Ochor for proof-reading the

original manuscript and making useful suggestions.

Special acknowledgement is due to the Director of the research centre, Mr

David K Muthoka, for his permission to conduct the trials. Thanks are also due to

our respective families for their forbearance while we planned and executed the

experiments, analyzed the data and wrote this paper. The senior author takes final

responsibility for errors, if any, in the interpretation of results presented herein.

This paper is published with the permission of the Director of Agricultural

Research Institute, to whom gratitude is due.

REFERENCES

Brown, E.B. and H.S. Garrison, 1923. Influence of spacing on productivity in single

ear and prolific types of corn. U.S. Dept. Agric. Dept. Bull. No. 1157.

Washington, D.C. 10 pp.

Comstock, R.E. 1978. Quantitative Genetics in Maize Breeding. pp.191-206. In

David B. Walden (ed.). Maize Breeding and Genetics. John Wiley & Sons.

Inc. New York.

Comstock, R.E. and H.F. Robinson. 1948. The components of genetic variance in

populations of biparental progenies and their use in estimating the average

degree of dominance. Biometrics 4: 254-266.

Comstock, R.E., H.F. Robinson and P.H. Harvey. 1949. A breeding procedure

designed to make maximum use of general and specific combilling ability.

Agron. J. 41:360-367.

Crews, l.W. and AA Fleming. 1965. Effect of stand on performance of a prolific

and a nonprolific double-cross corn (Zea mays L.) hybrid. Agron. J. 57: 329­

331.

-,

Darrah, L.L. 1986. Evaluation of population improvement in the Kenya maize

breeding methods study. pp. 160-175. In B. Gelaw (ed.). To Feed

Ourselves. A proceedings of the First Eastern, Central and Southern Africa

Regional Maize Workshop. Lusaka, Zambia: 1Q.17 March, 1985. CIMMYT,

Mexico, D.F.

Darrah, LL., S.A Eberhart and L.H. Penny. 1972. A maize breeding methods study

in Kenya. Crop Sci. 12: 605-608.

Darrah, LL., S.A Eberhan and L.H. Penny. 1978. Six years of maize selection in

'](jtaJe Synthetic IT', 'Ecuador 573' and 'Kitale Composite A' using methods

of the comprehensive breeding system. Eupbytica 27: 191-204.

Duvick, D.N. 1974. Continuous backcrossing to transfer prolificacy to a single-eared

inbred line of maize. Crop Sci. 14: 69-71.


113

Giesbretch, J. 1959. The inheritance of silking and pollen sheeding in maize. Can.

J. Gen. Cytol. 1 (4): 329-338.

Hallauer, AR. and J.B. Miranda Fo. 1981. Quantitative Genetics Maize Breeding.

Iowa State University Press. Ames, Iowa 500100. pp. 468.

Harville, B.G., L.M. Josephson and H.e. Kincer. 1978. Diallel analysis of ear height

and associated characters in corn. Crop Sci. 18: 273-275.

Johnson, E.e., KS. Fischer, G.O. Edmeades and AF.E. Palmer. 1986. Recurrent

selection for reduced plant height in lowland tropical maize. Crop Sci. 26:

253-260.

Marecl


114

Answer:

Ochieng. In the area of their best adaptation, Makueni composite is

expected to yield 1.5-2 tons/ha, Katumani composite B 2-3 tons/ha, Coast

composite approximately 3-4 tons/ha and Kitale hybrids approximately 8-10

tons/ha. However, the first two named varieties, although low yielding, serve

to meet food (maize) security in the marginal rainfall areas where they are

recommended due to their drought-escaping nature. Similarly for Coast

composite, as it was bred for tolerance to Coastal rust (Puccinia polysora).

Question:

Marandu. Negative response between maturity and grain yield was

observed. Has the same been observed in previous seasons or could this be

due to some limiting factor in the year of testing?

Answer:

Ochieng. Although the data presented are based on one year evaluation, I

would still expect the trend observed because we have been conscio'usly

selecting for early maturity in the nursery recombination phase and for high

grain yield in the selection trials of testcross progenies in the reciprocal

recurrent selection procedure that we have been using. Besides, we have

observed that commercial hybrids derived from inbred lines extracted from

advanced cycle populations tend to be higher yielding and earlier in maturity

than hybrids derived from previous cycles.

Comment:

Compton. The "genetic correlations" he used are not genetic correlations in

the usual sense. Genetic correlation is a Population parameter and would be

calculated from families of a population. The correlation he observed

between yield and maturity was due to selection for these two traits.

Question:

Caulfield. At what stage will you select for tip cover (open tips) in the

future?

Answer:

Ochieng. We intend to initiate vigorous selection against open-tip ears either

(a) in our pedigree breeding scheme or (b) in an Sl-testing scheme -- either

way, as soon as resources (human, financial, etc.) are made available,

depending on the complexity of the actual procedure we deem appropriate to

address the problem.

Comment:

Cantrell. If selection is done at high density one has to be careful because

ears will be small and will be difficult to select against ba~ tips.

Comment:

Lothrop. I studied the inheritance of bare tips in lowland tropical maize in

my l?0st-doctoral research at CIMMYT. The trait was highly heritable on a

faOllly basis (0.85) when Sl families were evaluated in 3 locations. 2

replications per location, plant density of 30,000 plts/ha, Sm rows. 200

Kg/ha. By selecting on a family basis, one can make rapid progress. In the

populations I studied. there was no significant correlation between bare tips

and grain yield.


115

PATH COEFFICIENT ANALYSIS FOR GRAIN YIELD AND

MATURIlY TRAITS IN MAIZE (Zea mays L)

O.M. Odongo 1 , A.P. Tyagi2 and G.P. Pokhariyal 3

ABSTRACf

In the present study most of the preharvesting observations for maize

were recorded and their possible impact on grain yield was analysed by

calculating the correlation coefficients. Path coefficient analysis was

conducted to reveal the direct and indirect effects ofthe maturity traits on

yield. It was found that plant height and number of leaves per plant

influence the grain yield considerably. However J days to silking and

tasseling should also be taken into account to breed an early maturity and

relatively high yielding variety for the two agroecological zones Embu (UM 2 )

and Murinduko (UM 4 ) in Kenya.

INTRODUCflON

Grain yield is a complex character which is influenced by several

interdependent factors. The knowledge of maturity components and their

relationships with grain yield is vital for developing a high yielding and early

maturity variety. The calculation and analysis of correlation coefficients of maturity

components with grain yield provides the basis for selection strategy. However, to

have further insi~ht of the interrelationship amongst the components and their

direct as well as mdirect effect on grain yield, the path coefficient analysis is usually

conducted as suggested by Dewey and Lu (1959). In the present investigation this

technique has been used to find out direct and indirect effects of maturity

components on grain yield in maize. This has provided the information about the

relative importance of maturity components to breed a high yielding and early

maturing variety of maize for marginal areas of Kenya.

MATERIALS AND METHODS

The material for the study consisted of five inbred lines of maize namely:

(i) Embu 203 (ii) Embu 204 (iii) Embu 206

(iv) Embu 107 (v) Embu 108

and three exotic lines, namely:

(i) TX 5855 (ii) Bs 13(la) (iii) N6 (Hayes)

, These eight inbred lines were crossed using diallel matmg design during the

short rains of 1984. Twenty eight single crosses (Fls) thus obtained, along with their

eight parents, were sown in a randomized block deSign with four reflications.

The experiments were conducted during long rains season 0 1985 at two

sites Embu (UM 2 ) and Murinduko (UM 4 ). Each experimental plot contained two

rows of twenty two plants spaced 30cm apart while the distance between two

successive plots was kept 75cm. Ten plants were randomly picked from each plot

and distinctly marked for observations in each of the four replications. Data

recorded on the pre-harvest traits were:-

(i) number of leaves per plant,

1. Western Agricultural Research Station, P.O. Box 169,

Kakamega, Kenya.

2. Department of Crop Science and

3. Department of Mathematics University of Nairobi,

P.O. Box 30197, Nairobi, Kenya


116

(ii) plant height (m),

(Iii) number of days to estimated 50% pollen-shed,

(iv) number of days to estimated 50% silking,

and finally the grain yield (g) per plant after harvest was also recorded. From the

recorded observations the correlation coefficients among yield and maturity

components were calculated for both sites, as described by Gauldon (1952). The

path coefficient analysis was carried out as suggested by Dewey and Lu (1959).

RESULTS AND DISCUSSION

The analysis of the results from Table 1 showed appreciable difference on

the grain yield and the influence of various characters on It at two agroecological

sites Embu (UM2) an~ Murinduko (UM 4 ). En9ugh varia~ility among all the .

genotypes tested, for dIfferent pre-harvestmg tr3Jts and gram YIeld, was also noticed.

Table 1.

Variabilily among parenls and hybrids for yield and malurily componenls

In maize at Embu (Ut.l 2

) and Murinduko (UM 4

)

-----------------------------------------------------------

Characters Sites Grain yield Leaves Plant Daya to 50'!(, Dayalo 50'!(,

per plant per plant height pollenshed Bilking

-----------------------------------------------------------

Treatment means UM 2

133.82 13.84 3.00 68.27 67.86

UM 4

103.71 13.94 2.33 66.50 71.48

C.V. (%) UM 2

9.89 3.32 8.77 2.82 3.10

UM 4

10.87 3.28 7.68 3.34 5.44

S.E. (treatments) UM 2

5.63 0.23 0.13 0.97 1.1)5

UM 4

5.64 0.23 0.09 1.11 1,94

S.E. (Replications) UM 2

2.01 0.08 0.04 0.32 0,35

UM 4

2.01 0.08 0.03 0.37 0,64

LSD 5% UM 2

15.75 0.65 0.37 2.70 2.94

UM 4

15.78 0.64 0.25 3.11 5.44

1% UM 2

20.82 0.85 0.49 3.57 3.89

UM 4

20.86 0.85 0.33 4.10 7.19

0.1% UM 2

26.84 1.10 0.63 4.60 5.01

UM 4

26.89 1.09 0.43 5,28 9.27

-----------------------------------------------------------

The grain yield had significantly strong positive correlation with plant height

at both sites (Table 2). However, the number of leaves per plant has significantly

moderate positive relationship with grain yield only at Embu. Similar findiI:tgs were

reported by Sin~h & Malhotra (1970). The number of leaves per plant showed

significant Sk.~tlve correlation with plant height, days to estimated 50% pollen shed

and 50% s' . g, but the relationships were relatively stronger with the first two at

Embu and with the third at Murinduko. The correlation between days to estimated

50% ilking and 50% pollen-shed was obviously positive and very strong at both

sites. Days to estimated 50% silking showed nonsignificant weak negauve

relationship with grain yield at both sites. Results similar to the present study were

reported by Shehata (1975), Singh & Nigam (1977) and Vianna et aJ (1980).


117

Table 2.

Correlation ooefficlenteamong yield and maturity components in maize

Ilt Embu (UM~ and Murlnduko (UM 4

)

SIte.

LBave. per

..

..

..

plant

UM 2

0.67..

Plant height UM.. 0.44

Dayeto5O% UM 2

0.61 0.24

pollenshed UM 4

0.45 0.08

Plant height Days to 50%

poll.nshed

.. ..

UM 0.42 0.01 0.85

2

Dayeto SO%

.. ..

.. ..

..

sllklng UM 4

0.53 -0.16 0.92

Days to SO%

silking

Grain yield UM 2

O.SO 0.73 0.02 -0.26

per plant UM 4

0.22 0.76 -0.27 -0.27

... SIgnificant at P ; 0.01

The path coefficient analysis (Table 3) revealed that the maturity

components namely, plant hei~t, number of leaves per plant and days to estimated

50% pollen-shed showed positive direct effect on grain yield in that order at Embu.

At Murinduko the highest direct positive effect on yield was due to plant height

followed by days to estimated 50% silking. The. number of leaves per {'Iant and days

to estimated 50% pollen-shed showed negative direct effect on grain YIeld at

Murinduko, while at Embu the days to estimated 50% silkin~ showed highest

negative direct effect on grain y'ield. Some of the contradictIOns obtained by path

coefficient analysis can be attnbuted to different agroecological zones of the

experiments. Embu (UM 7 ) having clay loam and relatively higher average rainfall

in contrast to Murinduko {UM 4 ) having sandy loam and less average rainfall.

Shehata (1975) reported that taller plants having high placement tended to produce

more gram.

Table 3.

Path coefficients (direct effects underlined) of maturity components on

grain yield in maize at Embu (UM 2

) and Murinduko (UM 4

)

Ch81acters

Sltea

Leaves

per plant

Planl

height

Days to SO'll.

pollenshed

Days to 50%

silking

rIP) with

yield

LBaves per plant

P1l\/lt height

0.179

-0.080

0.340

0,226

0.123

-0.113

0.048

-0.076

-0.230

0.881

-0.005

-0.070

•• O.SO

0.22

0.73..

..

0.76

Days to SO'll.

pollenshed

0.163

-0.798

0.122

0.423

-0.466

0.800

0.02

-0.27

Days to SO%

silking

..

SIgnificant at P ; 0.01

0.112

-0.140

0.005

-0.246

0.171

-0.319

-0.26

-0.27


118

Therefore, it appears that the main component of maturity which directly

affected yield at both sItes in the present study was plant height. The study

conducted by Hari Singh et al (1977) concluded that the leaf are index (higher

number of leaves per plant) and plant height were the main components of maturity

that contributed towards the grain yield.

Thus to evolve an early maturing and high yielding variety of maize the plant

height and estimated days to flowering must be given due importance because the

analysis of these two and other preharvest observation could be used to predict the

grain yield.

ACKNOWLEDGEMENT

Kenya Agricultural Research Institute and University of Nairobi are

acknowledged for financial support,and technical guidance, respectively. Director,

Regional Research Centre, Embu is also acknowledged.

REFERENCES

Dewey, D.R and Lu, K.H. (1959): A Correlation and path coefficient analysis of

components of crested wheat-grass seed production: Agron. J., 51: 515-518.

Gouldon, C.H. (1952): Partial and Multiple Correlation. Methods of Statistical

Analysis: Ed.2, PP 144-152. John Wiley and Sons, Inc., New York.

Hari Singh, Rai, B. and Asnani, W.L. (1977): Morphological basis for expression of

gr~ yiel~ in ~rachytic-2 dwarf maize and its normal counterparts. Indian J.

Agnc. SCI., 47. 341-345.

Shehata, AH. (1975): Association among matric attributes in varietal maize

population in relation to their future improvement. Egyptian J. Genet. and

Cytol., 4:66-89.

Singh, K.B. and Malhotra, RS. (1970): Interrelationship between yield and yield

components in mungbean. Indian J. Genet. 30: 244-250.

Singh, S.P. and Nigam, H.K. (1977): Path Coefficient analysis for yield components

in maize (Zea mays L.): Allahabad Farmer; 48: 163-165.

Vianna, RT., Gomes, E., Gama, E.E., Naspolini, F.V. and Marvo, J.R. (1980):

Correlation and path coefficient analysis in inbred lines of maize (Zea mays

L), P.B.A., 52: P 686 (7499).

DISCUSSION

Question:

Gathuri. The characters that were used in path coefficient analysis for yield

components and maturity traits in maize can be a result of envirlmmental

effects which can directly affect yield. Please explain.

Answer:

Odongo. It is true traits such as days to rnid-silk, pollen-shed and piant hei~t

are subject to environmental influence but the number of leaves per plant IS

hardly Influenced by environment.

Question:

Dejene. Did you test the inbred lines introduced from U.S.A before making

crossing?

Answer:

Odongo. The inbred lines introduced from USA were tested before making

crosses with local inbreds but the original seed received was planted for seed

increase and was free from local diseases such as rust and leaf blight, an

indication of adaptation.


119

PEDIGREE SELECfION: A NEW DIMENSION IN KENYA'S

APPLIED MAIZE IMPROVEMENT PROGRAMME

ABSTRACf

JJ. Chumo 1 , JAW. O'chiengl:f- Njoroge l ,

and WA Compton

Applied maize breeding for the purpose of inbred line development

has usually been done by the use of pedigree breeding in narrow based

populations, such as single crosses or backcrosses, involving lines from the

same heterotic background. The procedure involves selling in the

segregating generations of single crosses or backcrosses to recover new or

improved lines that have high means for all or nearly all of the important

traits required for commercial use. The choice oflines to use in the system

is based on line compllmentarity. Evaluation of the cross performance may

be delayed until the lines have been selfed several generations with selection

at each stage based on inbred morphology, or advancement may be based on

cross performance itself.

The advantages of pedigree breeding are: I) possibility of selection for

more than one trait without having to resort to index selection by the careful

choice of parents to create the selection population so that the,lines are

complimentary to each other enhancing the chance ofidentitying that rare

inbred line that has a very high mean for all important agronomic traits, 2)

the rapid rate ofdeveloping such elite inbred lines for the purpose of

commercial utilization, and 3) allows improvement of a line that has a

specific weakness ofteribringing a line nearly good enough for commercial

use up to a usable level.

We propose a rather new obje,ctive for using pedigree breeding. Most

pedigree breeding is done in single crosses of elite inbred lines. We feel that the use

of pedigree breeding will allow us to bring new lines developed from our recurrent

selection programs that are lacking in some

agronomic traits that prevent their commercial exploitation up to the levels needed.

Thus the pedigree breeding will make our program more complete and allow us to

make better use of the gains in population improvement evident in recurrent

selection work.

. In Kenya, there is currently an uq~ent need to step up the pace of developing

high yielding, environmentally stable vaneties of maize that have most desirable

::Igronomic traits required by farmers to produce the maize needed to meet the ever

increasing demand. To date, candidate single crosses within Kitale Syn. II and

Ecuador 573 have been identified and planted in the breeding nursery at the

NARC-Kitale to initiate pedigree selection.

There have been two rather distinct ways of breeding maize that have been

widely used in the United States. One approach is essentially similar to breeding

methodology used for improvement of sel-pollinated crops and is called "pedigree

breeding". The other system widely used in maize, and which has also been the

basis for maize improvement in Kenya, is "recurrent selection".

1. Maize breeders, Kenya Agricultural Research Institute,

P.O. Box 450 Kitale, Kenya.

2. Maize breeder/consultant, MIAC-NARP, Kenya Agricultural

Research Institute P.O. Box 450, Kitale and University

of Nebraska, Lincoln, NE 68583, USA


120

Allard describes pedigree breeding as "A system of breeding in which

individual plants are selected in the segregating generations from a cross on the

basis of their desirability judged individually and on the basis of a pedigree record".

He also defines recurrent selection as "A method of breedin~designed to

concentrate favourable genes scattered among a number of mdividuals by selecting

in each generation among the progeny produced by matings inter se of the selected

individuals (or their selfed progeny) of the previous &eneration". We ,might add that

pedigree selection in maize involves selfing selected mdividuals and is otten used to

recycle elite lines that have known strengths and weaknesses. In our paper we

propose using the system in a new way- to recycle new lines from recurrent selection

programs that have some fault(s) not allowing their use in hybrids.

A few years ago, breeders involved in population breeding thought that

selfing new lines from populations improved by recurrent selection would lead

directly to elite inbred lines that.would reflect the improvement made by recurrent

selection in the source population. In retrospect, that was a bit naive, though in

theory it was true. However, the fact of the matter is that only rarely do new lines

selfed from broad-based populations have sufficiently good qualities in all of the

important traits to warrant being called "elite". Again, in retrospect, this seems

obvious, but at that time some of us thought otherwise. Perhaps this was due to the

fact that we wanted to believe it. Breeders are notorious for self-delusion and,

though much of our knowledge about breeding is inexact, we often, falsely, convince

ourselves that we have good solid theory in our grasp.

Since selfing from broad-based populations may not often lead to elite lines,

how can we make use of the gains made by recurrent selection and translate that

improvement into improved lines and hybrids? One answer is to use pedigree

breeding to recycle these lines to improve those weaknesses that prevent their direct

use. Ordinarily in pedigree breeding one chooses two elite lines, chosen for some

particular purpose the breeder has in mind, then begins selection and selfing in the

F2 generation. Selection from that point on may be based on appearance of the

material per se or on cross performance. Our alternative suggestIOn is to use one

line selfed from an advanced cycle of recurrent selection and the other an elite line

from the same heterotic background having exceptional strength in the trait(s) the

other line is weak in. The line selfed from the recurrent selection population will be

as good as one can possibly ~et and will hopefully not be deficient m too many traits,

so that it is fairly close to bemg commercially usable and its weakness can be

countered with a strength in the elite line.

The general theory applied here is that choice of populations to be used in

breedin~ is based on two parameters, the mean and the ~enetic variance, of each of

several Important traits. In choosing the population, weight given to each parameter

is etermined by the length of time allowed to achieve a breeding objective. At the

two extremes are 1) immediate and 2) no time limit. In the second case, all the

weight would be given to the amount of genetic variation. In case 1, however, heavy

weight is placed on the means of all important traits. When one chooses a mating of

two outstanding inbred lines to create the population in which to sleet, one is

attempting to synthesize a population that has some genetic variation (because

without it we could make no ~rogress at all) but that has a very high mean level for

all or nearly all important traIts. The rationale for choosing a line from an a9vanced

cycle of recurrent selection (where the selection criterion has been mainly yield) to

pair up with an elite Jine i that the yield mean in the cross might be superior to that

of the cross of two elite lines and the weakness introduced by the new line is less

important than the hi~her yield potential. In order for this to work the weakness

must be amenable to Improvement. One would be hard pressed to improve some

difficult traits such as drought resistance by selection in the pedigree system if the


121

parental lines are weak in that regard, so one needs to be careful in choosing the

lines to fit the breeding needs.

An advantage to using pedigree selection with an elite inbred line involved is

that the elite inbred may be one that a seed company has had a lot of experience

with. A new line that resembles that well-known line might be easier to incorporate

into commercial seed production. If this is of over-riding importance (such as when

seed prices are very low and seed cost must be kept to a mirumum) then the

population created could be the segregating generation of a back-cross to the

commercial line rather than the Fl.

We not only are planning the use of the pedigree breeding system for better

utilization of our inbred lines from the recurrent selection work but will also use the

system in the usual way of developing lines from two lines already being used

commercially. We have good lines that we consider to be "elite" and whose

characteristics are well known by our seed producers. Such lines with known

attributes are much more easily incorporated into seed production than completely

new lines. With seed prices as low as ours in Kenya, our seed producers need all the

help they can get to hold down seed production costs so that the new hybrids can be

produced and delivered at a price affordable even by the small-holders.

In summary, the Kenya maize breeding program appears to be making

progress in improving populations with reciprocal recurrent selection. On the other

band, we would like to increase the rate of replacement of inbred lines used in seed

production. After some careful thought, we have concluded that we need to add

pedigree selection to our arsenal. In the U.S.A. many public breeders are working

on recurrent selection doing what is (somewhat curiously) called "germplasm

enhancement". Many seed companies develop inbred lines with most of the

breeding done using pedigree selection. In Kenya we do not have the luxury of

having many breeders from many companies complimenting many breeders in

various!ublic breeding roles. In order for us to have a complete breeding system,

we nee to do both types of work so that the improvement seen in our breeding

nurseries is also reflected in our farmers fields as a result of commercial quality

inbred lines usable in commercial hybrid production. To be sure, genetic

information obtained from our work is just as valuable as it would be from any

source, but Kenya is primarily engaged in a struggle to maintain the ability to feed

her people and any investment in research must have a rather quick payoff in terms

of this applied goal. Thus our breeding objective dictates a conservative approach

which seems to be pushing us toward quick new elite lines that may best be

developed by a pedigree breeding system added on to our old work involving mainly

recurrent selectIOn and direct selfing.

,

DISCUSSION

Question:

Ruhaihayo. I am seeking clarification, I think I missed out on what you do

with the progenies in the pedigree selection, did you say you self one and

recombine the best lines or did you say you continue selfing the progenies to

produce pure inbred line.

Answer:

Chumo. Selection starts from F2 and the selected plants are selfed and

within family selection is done in F 3 and by F4 selection is among families to

develop sister lines which will be used as SC in hybrid formation. Cross

formatIOn is also carried oUl at whatever stage the breeder chooses to

supplement the information on plant appearance selection.


122

Question:

Brhane. In your presentation it was not clear what attention you give to the

heterotic pattern of the component lines making the initial SCs. I assume

that the component lines must come from the same heterotic group. Please

comment on this issue.

Answer:

Chumo. Choice of the lines first and foremost will depend on the heterotic

groups, lines from the same heterotic group must be chosen. The lines are

chosen in such a way that one line has the good traits that the other line is

weak in.

Comment:

Ochieng. One of the roles of pedigree breeding would be to "incorporate"

the hi~ yield combinin~ ability of lines derived from advanced cycles of

selectiOn with traits deSIred either agronomically or for seed production'into

distinct inbred lines in different heterotic groups.


123

MAIZE IMPROVEMENT IN THE SOUTHERN HIGHLANDS OF TANZANIA

W.Y.F. Marandu; N.G. LyimoiA.E.M. Temu

and D. Kabungo •

ABSTRACT

The Southern Highlands ofTanzania occupy about 26% of the total

land area of the country and produ~es about 60% of the maize sold in the

market. Owing to its importance in the economy of the country the National

Maize Research Programme (NMRP) has always given a lot ofemphasis on

developing varieties and agronomic recommendations for the area. The

Maize Improvement Programme for the Southern Highlands (MIP) operates

from the Uyole Agricultural Centre as a sub-programme of NMRP with

emphasis on the development ofagronomic recommendations and varieties,

particularly hybrids, for high and mid-altitude areas.

Activities ofMIP are divided into breeding, agronomy and plant

protection.

Maize breeding work involves population improvement, inbred line

development and maintenance as well as variety testing. Working

populations were formed out of materials inherited from the former East

African Community research programmes and from CIMMYT, UTA, USA

as well as neighbouring countries.

Since 1985, several hundred inbred lines have been generated from

different populations and evaluated as lines per se and in some cases as test

cross progenies from which some lines have shown considerable potential as

parents for new commercial hybrids. One open pollinated variety, TMV-2,

has been released for high potential areas above 1500m. a.s.l. and several

promising experimental.varieties and hybrids are under test.

Agronomic work involves development of maize husbandry packages

relevant to the various agro-zones and farming systems of the Southern

Highlands. Blanket recommendations earlier given are constantly being

refined. Broad areas of research have been on field preparation techniques,

plant population studies, fertilizer use (organic and inorganic) weed control

(mechanical, chemical and integrated approach), soil fertility maintenance

and improvement ( use ofgreen manures, rotations, fallows, intercropping)

and studies on interaction of various management factors. Ofrecent,

recommendations have been given on the use ofCrotalaria spp as green

manure in a maize monoculture based system, and a new herbicide, Laddock

(bentazon + atrazine), for control ofweeds in maize and time and method of

application of urea under Southern Highland conditions.

Plant protection research concentrates on entomological problems in

maize, such as stalk borers, seedling and storage insects and monitoring of

armyworm outbreak. The timing ofcontrol of stalk borers using both

chemical, mechanical and biological extracts approaches have been

significant achievements in the recent past.

INTRODUCTION

The Southern Highlands ofTanzania which include the political regions of

Iringa, Mbeya, Rukwa and Ruvuma occupy about 26% of the total land area of the

country (Figure 1) and produce about 60% of the maize sold in the market. Since

1. Uyole Agricultural Centre, P.O. Box 400, Mbeya,

Tanzania


124

Fig.! TANZANIA: Southern Highlands demarcated

Agricultural Experimcntal Stations in the Southern lIighlands

Mbc)'i'

RC'J ion:

llukWJ Ih~'J i 011:

[ r i n":1 H


125

maize is the major staple food in Tanzania, changes in production of maize in the

Southern highlands have significant impact to the rest of the country.

A large proportion of the Southern Highlands has an altitude over 900 m.asl.

with unimodal rainfall fairly uniformly distributed, and exceeds the minimum

requirement for maize production. Areas below 900m. asl generally have unreliable

rainfall and maize production in these areas is insignificant.

Temperatures are near optimum throughout the growing season (usually

above 15°C). Periods of low temperatures and frost do occur in areas beyond 1800

m.asl., but the maize crop is not affected because it happens when the maize is past

physiological maturity.

Soils are variable with diverse origins and have moderate to low fertility;

often one or two nutrient elements being seriously deficient. However, water

holding properties and pH are good.

Maize production in the Southern Highlands started early in the century

mainly in Iringa region (Friis-Hansen, 1988) but significant expansion into Mbeya,

and Ruvuma occurred in the late 1960's and into Rukwa in the mid-1970's. The four

regions still have more land which can be used in the future for expansion of maize

production. Much of the maize is produced on small scale farms but a number of

large scale farms have also been in production for several years now. A large

proportion of maize is produced under monoculture, the rest being grown in

mixtures of various types.

Many farmers grow seed produced from the previous crop. There are,

however, no distinct local varieties maintained by the farmers mainly due to mixing

with improved varieties. The bulk of the crop can be described as population

mixtures derived from advanced generations of hybrids and local varieties.

Improved varieties have been in the hand of some large scale farmers for

some decades, but increased utilization of such varieties occurred after the

formation of the Tanzania Seed Company in 1973. Currently open pollinated

varieties as well as hybrids are grown. The area consumes over 60% of hybrid seed

sold in the country.

RESEARCH PROGRAMMES

Before 1974 research on maize was limited and uncoordinated. In that year

the National Maize Research Programme (NMRP) was initiated with Ilonga

Agricultural Research Institute serving as the co-ordinating centre. Activities of

NMRP were extended to the Southern Highlands extensively using the facilities at

Uyole and Njombe (Tanganyika Wattle Co. Ltd.- a private company which had

already initiated their own research programmes). Details of the NMRP were

presented in the Lusaka Workshop (Moshi and Marandu 1985).

As a result of the establishment of the Uyole Research Institute in 1970 with

a specific geographical area of mandate (Iringa, Mbeya, Ruvuma and Rukwa

regions) the need to have a fully fledged crop research pro~ammesfor the

Southern Highlands became necessary. Maize research actIvities at Uyole were

expanded in 1980 under the Southern Highlands Maize Improvement Programme

(MIP). The need to concentrate on maintenance and development of parental lines

for hybrid production, resulted into a new breeding programme being initiated in

1985 for hIgh altitude environments.

The MIP has 4 broad objectives.

1. To develop varieties suitable for the environment and farming

conditions of the highlands.

2. To maintain and improve parental lines of all current commercial

hybrids used in the country.

3. To research on agronomic practices suitable for all the agroecological

zones and farming systems in the Southern Highlands.


126

4. To monitor pests and diseases and recommend control strategy.

In order to achieve the above objectives the programme is divided into three

disciplines - breeding, agronomy and plant protection.

Breeding

Problems addressed by the breeding programme include:

grain yield

plant type particularly ear placement,

stalk lodging and prolificacy

grain type

adaptability particularly maturity, disease and insect pest resistance

Breeding work so far has concentrated on:

1. Population improvement and development of open pollinated

varieties and hybrids for intermediate and high altitude areas.

2. Development of inbred lines and testing them for combining ability.

3. Testing varieties from various sources for use by fanners or

incorporation in our populations.

Maintenance and production of breeders seed ofopen pollinated varieties

So far the programme maintains and produces breeders seed of one open

pollinated variety TMV-2 which was released in 1987 for use in high altitude areas.

TMV-2 is maintained using the method suggested by CIMMYT (1984) which

starts with about 500 half-sib ears from an isolation block as progenitors. The

pogenitor ears are planted in a half-sib isolation block with a balanced bulk of the

same ears as male rows.

Population Improvement

Population improvement work started at Ilonga when the NMRP was

initiated. A number of populations were formed and improved by the half-sib

method for the major zones and for various traits as described by Moshi and

Marandu (1985). The populations P62, P84, P301 (Ecuador 573) 'and P90 are now

being handled by MIP.

Unfortunately, not much information is available on the type and magnitude

of genetic variance or heterotic patterns of these materials; hence the chosen

method of population improvement was based more on available facilities,

manpower and curiosity of the breeders. Extrapolation of information available

from Kitale (Darrah ~ ill. 1972, ; Harrison, 1970) was helpful.

P62 and P84 have been undergoing improvement by half-sib recurrent

selection (which combines testing with recombination in an isolation block) and S2

selection procedures with the aim of extracting lines from them and eventually

comparing the two methods. P301 is being improved by Sl selection procedure

while P90 is bein~ maintained and improved by stratified mass selectIOn.

Activities 10 each population were begun in different years tl;Lallow

preparation time and to avoid peaks of pollination work and testing when

manpower was still limited. The different activities in each population are shown in

Table 1.

Preliminary Results

Half sib progeny tests.

Selection in P62 and P84 was done for a number of traits with emphasis on

grain yield, ear height, days to 50% silking and ear rots. In P84adaptation to

conditions in which blight could be a problem was considered important. The

progenies were planted at Uyole and Njombe for P62 and at Uyole and Ismani for

P84 then the results from the two sites were used to select entnes for next cycle as


127

Table 1:

Main activities in different populations

POPULATION

SEASON P62 P84 P301

----------------------------------------------------------------

1984-85(WET) Half-sib Half-sib

evaluation

evaluation

and selection

and selection

in isolation

in isolation

1985(DRY)

Selfing

from a bulk

1985-86(WET) Selfing in Half-sib

selected Sl

evaluation

families

and selection

in isolation

Selfing from

a bulk

1986-87 Yield test Selfing in Regenarate

of S2 families selected Sl from storage

]2!:l. ,g

families

Top-cross S2

families to a

line from Ec573

Half-sib

evaluation

and selection

in isolation

Half-sib

evaluation

and selection

in isolation

1987-88 Recombination Yield test Selfing from

of selected lines of S2 families a bulk

perse

Evaluation of

top-crosses

in a yield trial

at 2 locations

Half-sib

evaluation

and selection

in isolation

1988-89 Selfing from Recombination Yield test

bulk ofC1 of selected lines of S1 families

perse


128

well as experimental varieties. Table 2 shows the performance of progenies selected

to form two experimental varieties from P62. These varieties are now being

evaluated in the Tanzania Maize Variety Trials (High series).

Similarly two experimental varieties were formed from P84 using data from

1986-87 season.

In the future such EV's will be formed after two or three cycles of selection.

Emphasis will be placed on yield and adaptation to specific agro-ecological

conditions which have not been well covered in the past.

S2 Selection Scheme

Selection of S2 {Jrogenies to include in recombination in P62 and P84 was

based on preliminary YIeld tests of the lines per se for both populations as well as

yield test of top crosses from P62. The data indicated that there were strong

genotype X environment interactions for days to 50% silking which had some effect

on gram yield at the locations tested. About 10 - 15% of the S2 progenies were

selected and used in recombination.

Observations in the nursery and during testing suggested that both

populations were loaded with numerous undesirable recessive genes which were

revealed on selfing.

P84 also suffered serious inbreeding depression manifested by weak plants,

poor stands, barreness, and reduced plant height. The presence of numerous

undesirable genes is due to the fact that the populations bad not undergone any

selfing during development; and diversity of the original parents. P84 was

developed from various gene pools from the CIMMYT gene bank.

SI Selection Scheme

As a result of inbreeding depression observed in P84 and P62, it was decided

that P301 should be improved by Sl selection method. Also other materials

undergoing inbreeding are tested in preliminary yield trials, at 51 and combining

ability tests, at S3 and S4 depending on the material and available testers. 51

progenies from P301 are bemg tested in the 1988-89 season. Visual observations

su~est that the progenies did not suffer much inbreeding depression and a number

of hnes were very vigorous.

Mass Selection

This method Was chosen to be used with P90 which has been given low

priority in favour of P62. Emphasis is placed on visual selection for yield and grain

type.

variety evaluation

Three types of variety evaluation trials are envisaged. The first type includes

all evaluations which are of preliminary nature such as Experimental Hybrid Trials

and International Co-operative Trials. The entries to these trials are tested at a

limited number of locations and the best entries are selected for the next stage of

testing Tanzania Maize Variety Trial or used in the breeding nursery. The testing

period is usually one season and the number of locations varies depending on

availability of seed.

The second type of testing is the Tanzania Maize Variety Trials. This is the

formal trial from which variety release data is obtained. These are series of trials

grouped according to maturity and altitudes. The MIP conducts the series for high

and Intermediate altitude. The High series are confined to the Southern Highlands,

but the Intermediate series are tested at locations in and outside the Southern

Highlands as a joint effort between Ilonga and Uyole.


129

Table 2:

Perfomance of half-sib progenies selected to form

EV8562A and EV8562B.

------------------------------------------------------------

50% Ear Ear

Grai~eld(t/ha) silking ht. rot

ENTRY Uyole jombe MEAN (days) (em) %

------------------------------------------------------------

EV8562A

1- 2 8.3 10.0 9.2 108 146 15

1-78 9.2 10.1 9.6 105 150 7

II-77 9.8 10.4 10.1 106 152 10

II-35 9.1 9.7 9.4 108 152 14

II-49 8.7 11.6 10.2 107 142 6

II-48 9.1 11.6 10.4 109 156 8

11-62 8.8 10.7 9.8 106 139 6

II-85 8.5 11.2 9.9 105 147 15

II-91 9.5 9.7 9.6 108 154 5

Mean 9.3 10.5 9.8 107 149 10

EV8562B

II-53 9.8 11.3 10.5 107 154 5

11-48 9.1 11.6 10.4 107 156 8

11-49 8.7 11.6 10.2 107 142 6

11-62 8.8 10.7 9.8 106 139 6

1-48 10.4 8.9 9.6 106 155 8

1-78 9.2 10.1 9.6 105 150 7

11-91 9.5 9.7 9.6 108 154 5

11-68 9.1 9.7 9.4 107 145 5

1-25 8.1 10.5 9.3 108 161 2

Mean 9.1 10.6 9.8 107 149 10

All progenies (194)

-------------------

Highest 10.5 11.8 10.6 123 175 19

Lowest 3.8 4.9 6.4 104 125 1

Mean 8.6 8.6 8.5 109 149 8

Checks

H614 10.4 9.6 10.0 110 189 1

H6302 8.9 10.6 9.8 115 195 4

EV7990 9.1 8.9 9.0 110 174 9

------------------------------------------------------------


130

Because of the limited area below 900m.asl the low series of TMVf is not

usually planted in the Southern Hi~lands, but extrapolation of information is made

using data from trials planted outsIde the zone.

From these trials summaries are made over locations and seasons to obtain

information for variety release. So far several local and imported varieties have

been tested and one variety TMV-2 released from the high series (Table 3), while

similar information from the Intermediate series in the Southern Highlands was

combined with data from outside the Southern Highlands to support the release of

TMV-1 a streak resistant variety (Moshi ~ ill. 1987).

Table 3:

Mean grain yield (T/ha) of EV8290 in comparison

with check varieties in the TMVT across four high

altitude locations, over three seasons.

WCATIONS

VARIETY ----------------------------------------------

Uyole Mbimba Njombe Nkundi MEAN

------------------------------------------------------------

EV8290 7.31 6.32 7.03 9.34 7.50

H6302 8.09 6.16 7.34 9.60 7.80

H614 8.41 7.00 7.52 9.64 8.14

H632 6.95 5.23 6.68 8.97 6.96

SR52 7.94 6.54 6.26 8.68 7.36

UCA· 6.72 5.62 5.72 8.38# 6.36

• Mean of two seasons only.

# One season only.

The third group of trials include on farm trials, farmer managed trials, and

demonstration plots. This group of trials has not been very successfully done due to

shortage of facilities and manpower. However, arrangements have been done in

some cases to share information with other projects, particularly extension projects

such as FAO/Kilimo Fertilizer Project which has used TMV-2 as one of the

varieties for demonstration or verification depending on location.

This kind of feed-back from extension has been useful to reduce the demand

for independent facilities between Research and extension as well as sharing ideas

before variety release.

AGRONOMY

A~ronomic work has concentrated on broad areas with the aim of obtaining

informatIOn for immediate application in the Southern Highlands. This approach

was prompted by the rapid expansion of maize production in areas where there were

no appropriate recommendatIOns for efficient production of the crop.

The broad objectives are:

(a) To establish general recommendations for growing maize in the

Southern Highlands.

(b) To refine the general recommendations by ada{>ting them to specific

agro-ecological areas and socio-economic conditions.

(c) To investigate alternatives to the use of mineral fertilizers in order to

increase grain yield and maintain soil fertility.

To meet these objectives trials have been conducted in the following areas:

(i)

Methods of seedbed preparation


131

(ii) Variety testin~

(iii) Time of plantmg

(iV\ Use of inor~anic fertilizers

(v Crops rotatIOns

(vi Methods of weed control

(vii Use of organic manures and green manures

(viii Plant population density and planting configuration.

Results from most of the above trials were assembled together by Coon et al

1984 with recommendations based on agro-ecological zones found in the Southern

Highlands.

In general the major problems currently observed in the Southern Highlands

include:

low fertility particularly with respect to nitrogen and phosphorus

weed infestation, associated with long growingf period and slow rate

of growth for maize due 'to low temperatures particularly early in the

season.

dependence on inorganic fertilizers for high production despite high

cost, irregular supply and late delivery of this input.

Recently an attempt has been made to use Crotalaria zanziberica (c.

ochroleuca) as a green manure plant. Various ways of using the plant have been

considered including rotation, relay cropping and intercropping. However, up to

date only the rotation method appears to be of considerable importance.

Temu (1986) indicated that if C. zanziberica was ploughed under at flowering

time then a maize crop followed, in the second season, savings of up 80 kgjha N

could be realized (Fig. 2). However, this method ties up land and requires extra

labour to establish and incorporate the green manure.

Planting C. zanziberica in the same field as maize resulted in a number of

problems which contributed to poor performance of maize. These included:

(i) slow growth of C. zanziberica under cool conditions allowing serious

weed competition

(ii)

(iii)

obstruction during maize harvesting if seeded in all rows

serious competition with maize in warm areas

To solve some of the above problems an attempt has been made to include

C. Zanziberica into the Matengo pit farming system which takes advantage of the

bio-mass weeded during the establishment of pits.

Weed control has been singled out as a major problem in recent years due to

increased use of fertilizers as well as continuous maize production with little or no

rotation.

Approaches to weed management in maize have been:

(il mechanical (hand weeding and interrow cultivations)

(Ii herbicides (pre- and post- emergence and contact)

(Iii cultural (rotations, intercropping)

(iv) integrated weed management

Testing of these methods of control has been done with some success. The

results of such trials were summarized by Temu 1988.

It is recommended that for effective weed control the frequency o1"hand

weeding should be at least twice during the critical period of weed competition.

For farmers who can afford to purchase herbicides, Primagram (atrazine and

metolachlor), Gesaprim (atrazine) Laddock (atrazine and bentazon) at rates up to

5.1 of the product per hectare are recommended. These herbicide should be

complemented by other methods of control such as hand-pulling, interrow

cultivation or use of a contact herbicides (like para~uat). To augument efforts to

minimize weed infestation, cultural practices includmg early and proper seedbed


132

F i 9 .2: EFH1.[ OF CROTALARIA ON ~L.vZE

10000

to

J:

&1))

filll'PONSE TO NITROGEN

~

........ Em) / /'

OJ cr / _..--t'

X

"0 ,.'~

4C1XJ

v

>- /

xco

..

I

--

Maize

after maize

Maize after Crotalaria

i ncorporu t ed

Maize after Crotalaria cut and

removed

(j

(; iO if) l:il leD

N-ra' e

(kg/ha)


133

preparation, rotations, clean seeds, early planting and fertilizer placement are

recommended.

Recommendations on fertilizer use (N and P) in the Southern Highlands

have been established. In the higher rainfall areas (>800mm p.a.), up to 150

KgN/ha can be applied, while in areas where rainfall is moderate or limiting an

applIcation of 60 - 80 KgN is adequate. Rate of phosphorus needed for maize

production is 20 - 40Kg/ha. The higher rates bemg recommendations for the more

P deficient areas like Mbozi district. Split applicatIOn of N half at planting under

seed and the rest at 80 cm is the best option for small farmers. All P is applied at

planting under seed.

Methods of application of urea, which is a relatively new fertilizer to farmers

in the Southern Highlands, have been discussed by Temu (1989). Split application,

broadcastin~ and incorporation or placement in furrows along maize rows were

possible options for small or large scale operations.

PlANT PROTECTION

So far most of the plant protection work relates to entomological problems.

Stalk borers, particularly Buseolafusca,cutwormsAgrotis spp. and stor~e pests such

as Sitophilus spp. are the major pests. However, recently other pests which pose

considerable threat to maize seedlings have appeared. These include Tanymecus

spp, Heterostylus spp. Systates spp. and chafer grubs (Heteronychus spp.).

The control of B. fusca has been dealt with using chemical and cultural

methods. An attempt has also been made to monitor the movement of the moth by

using sex pheromones.

Tnals testing various insecticides have been conducted for a number of years

and several insecticides have been found suitable for the control ofB. fusca. Among

the suitable insecticides are: Fenitrothion+ Fenvalerate 1.80, (Sumicombi),

Cypermethrin lOEC (Ripcord), Phenthoate+ Oimethoate 410:110 gil (Rogodial)

and Endosulfan 40 (ThlOdan 40). It was also confirmed that an extract from

Tephrosia sp. used by farmers (when other chemicals are not available or

affordable) was an effective way of controlling B. Fusca.

Since B. fusca survives in maize stover to the next cropping season, it was

envisaged that management of maize stover could offer a solution to the control of

the pest. A trial to test different ways of stover management was conducted at Uyole

for three seasons .. It was observed that maize stover left standing in the field had

high larval survival rates compared to stover slashed and chopped into short pieces

left on the surface and buried (Fig.3). It was concluded that chopping maize stover

at the end of the season was a feasible method of reducing infestation in the

following season if practiced by a large number of farmers.

The maize grain weevils (Sitophilus spp.) and maize grain moth (Sitotroga

Cerellela) infest maize, often starting in the field carried to stores, causing

considerable loss. Kynakil 1% (Malathion) has been used for a long time to control

these pests. However, the product looses efficacy within a few weeks after

application, making it difficult to store maize until the next harvest. Testing of other

chemicals has been done at Uyole with encouraging results. Actellic 50EC and

Sumithion 50EC have been found to give good protection if used on the bag along

or on both the grain and the bag at a rate of 10 ppm.

Other activities include monitoring of armyworms and the larger grain borer

(Prostephanus trancatus) which appear sporadically in the Southern Highlands.

FUTURE PLANS

While the Maize Improvement Programme will maintain its objectives as

they are now, the relative importance given to some of the problems may change

depending on availability of facilities and manpower. It is mtended to consider the


134

Fig. J. Er~ect o~ stover management on control o~

B. fusca.

m

00

.cJ

~

ll.

-

10

~ ~ dead larvae

1

dead pupae

B

2 "

~

"

dead insects

6 3

')

o

2

3

4

Key:

1. stover slashed and le~t on the ground

2. Stover left standing

J. Stover slashed and buried in normal land preparation

4. Stover slashed, chopped into about JO em. lengths and

left on the ground


135

problem of Maize Streak Virus Disease in mid - and high altitude areas more

seriously by incorporating streak resistance into some of the important parental

lines.

We also think that knowledge of the genetic variances and type of gene

actions in our populations would greatly aid decision making in the future.

The problem of weevils will be studied systematically as from next season in

order to find suitable lasting solutions.

REFERENCES

CIMMYT 1984. Development, Maintenance, and Seed Multiplication of Open­

Pollinated Maize Varieties. The International Maize and Wheat

Improvement Center (CIMMYT); Mexco D.F. pp. 11.

Croon, I; Deutsch, J; and Temu ARM. 1984. Maize Production in Tanzania's

Southern Highlands: Current status and recommendations for the future.

CIMMYT, Mexico DF. pp. 102.

Darrah L.L.; S.A Eberhart and H. Penny, 1972. A maize breeding methods study in

Kenya. Crop Sci. 12: 605-608.

Friis-Hansen E. 1988. Seeds of wealth - seeds of risk? The Vulnerability of hybrid

maize production in the Southern Highlands of Tanzania. CDR, Project

paper 88.2. Copenhagen, Denmark. pp. 63.

Harrison, M.N. 1970. Maize Improvement in East Africa. In: Crop Improvement in

East Africa Edited by C.L.A Leakey. CAB Farnham Royal, England. p.21­

59.

Moshi, AJ. and W.Y.F. Marandu 1985. Maiz~ Research in Tanzania. In: B. Gelaw

(ed) 1986; To Feed Ourselves: Proc. IS Eastern. Central and Southern

Africa Maize Regional Workshop, Lusaka, March, 1985. CIMMYT, Mexco

D.F.

__...,...,,:-:-and Z.O. Mduruma. 1987. A proposal for release of two maize varieties.

Presented to the National Variety Release Sub-Committee, Tanga, 21 st

November 1987. Mimeo.

..,

Temu, ARM. 1986. Effect of Crotalaria zanziberica as a previous crop on grain

yield of maize. Uyole Agricultural Bulletin Vol. 1:7-14.

1988. Weeds amd Weed rontrol in the Southern Highlands of

--....,·.... I'a::-:nza=-=rna. Presented to the IS National Maize Research Workshop, Arusha,

Tanzania; June 1988.

_____....,......-1989. Effect of methsd of placement of urea fertilizer on grain yield of

maize. Presented to the 3 r Eastern Central and §outhern Africa Maize

Regional Workshop, Nairobi, Kenya: Sept. 17-22° , 1989.


136

DISCUSSION

Question:

Chumo. Have you carried out research to find out how effective Tephrosia is

compared to the commercial insecticides in controlling stalk borer.

Answer:

Marandu. Yes, we tested 4% and 8% of leaf crude extract and found that

the higher concentration was effective to reduce damage to economic levels;

though not as effective as commercial insecticides. We still need to look at

the extract in more detail so that we establish its properties and possibly find

a way of concentrating the active ingradient.

Question:

Chivatsi. In Kenya advanced generations of maize hybrids are not

recommended for planting although farmers do it. Is it the same in your

country?

Answer:

Marandu. Same only in that small scale farmers unable to buy certified seed

and lateness of seed In circulation leads to this.

We recommend to our farmers that they should buy fresh seed of hybrids

each season, and after 3-4 years for open pollinated varieties. However,

because of insufficient supply of improved seed and late delivery, the farmers

tend to select seed from previous crop which may be a hybrid. Further,

because the fields are usually small, whatever the farmer selects from

previous crops there are high chances that the crop will have been

contaminated by improved varieties from nearby fields. Hence the resulting

planting is like a mixture of populations which have high yield. The farmers

have therefore tended to keep the mixture because they dont see much

difference between the mixture and late planted improved varieties.


137

EVALU TION OF ELITE COMPOSITE MAIZE VARIETIES

FOR THEIR RELATIVE AFFINIlY

Benti Tolessa, Kebede Mulatu, Legese ~olde

Gezahegne Bogale and Assefa Areta

ABSTRACT

Eight parental composites and the resulting 28 F1 crosses were

evaluated in a randomized complete block design with four replications in

four environments. Five parental composites namely, Bako composite n,

UCA, KCC, Alemay Composite and EAH-75 maintained nearly equal yield

potential. The lowest yielders in aU environments were Awasa - Jima (C 4 )

and KCB. Genotypes and genotype X environment interaction for grain yield

based on two environments represented by years and locations, were

significant and represented high yielding (HYE) and low yielding (LYE)

environments. A few F~_l!1brids recorded yield superiority over the best

composite only under RYE. Frequency of F1hybrids with negative heterosis

was much higher under LYE compared to RYE. Hetero-dist analysis

suggested that composites 1 (UCA) and 5(KCB) were most divergent, while

composite 8(Alemaya composite) had close affinity with parents 4(Awasa­

Jima (C4), 3(EAH-75), and 2 (Bako Composite II). Cluster score further

supported the trend recorded from hetero-dist analysis. Dat from the

present study as well as information available from other sources suggest

that the elite composites under study are associated with a marked genotype

x environmentinteractioD. The magnitude of superiority of F1 hybrids over

parent is rather limited to favorable environments. Data suggested the need

for introgressing more diverse germplasm for developing more productive

crop varieties.

INTRODUCTION

In Ethiopia both high yieldin~ hybrids and composite varieties are

commercially grown. Eight of the high yielding full season composite varieties

currently under commercial use in Ethiopia were either introduced from abroad or

synthesized from indigenous or indegenolls exotic germplasm (1) (Table 1). Some

of these composites partly related by descent and grown for several generations

under

similar agro-ecological conditions with limited directed and natural selection in the

~ountry are likely to provide similar performance for a set of agronomic characters

of major economic importance. Some maize breeder nd seed producers thus

believe that some of these high yielding composites may no longer be considered as

distinctly different cultivars. An alternative viewpoint held is that these high

yielding varieties are distinct and diverse with regard to per se performance and

adaptability and can thus be profitably exploited by selective intercrossing. Taking

note of these view points the present study was undertaken to evaluate eight elite

composite varieties of maize for their genetic affinity.

MATERIALS AND METIIODS

Eight elite composite varieties of maize with high yield potential and wide

genetic base were used in the present study (Table 1). Five of them, namely 2

1. National Maize Team Leader, Breeder. Assistant

Research Officers, respectively. Balm Research Centre,

P.O. Box 3, Bako, Shewa, Ethiopia.


138

(Bak6 composite II), 7(Bako composite (~), 8(Alemaya composite), 3(EAH-75),

4(Awasa-Jima (C_ 4 ), were developed indigenously while the other three were

introduced froin Kenya 6(KCC), 5(KCB) and Tanzania l(UCA). These eight

composites and their 28 all possible F1 crosses excluding reciprocals, were evaluated

in a randomized complete block design during the rainy seasons of 1985 and 1986 at

Bako and Didesa. In each environment the study had three replications. Each plot

comprised four rows, 3 metre long. Middle two rows were used for the record of

yield and other data. Spacings of 75 and 30 cm were respectively used between and

within rows.

Table 1. Background information on the parents

Parent

Country of

origin of

composite

variety

Country of origin of component

materials

Year of release

and recommended

areas of

cultivation

1 UCA

2 Bako Composite II

3 EAH-75

4 Awasa.Jima (C4)

5 KGB

6 KGG

7 Bako Composite (C ) 2

8 Alemaya composite

Tanzania

Ethiopia

Ethiopia

Ethiopia

Kenya

Kenya

Ethiopia

Ethiopia

Kenyan/U.S./Latin American

Synthesized from Kenyan hybrids

Local Ethiopian material

Local Ethiopian material

Superior local Kenyan material

Latin American

Local/East African/Latin American

Local/East African/Latin American

early 1970s, W.Z.

not released

not known, E & W.Z.

late 1960s, S.Z.

early 19705, W.Z.

early 19705, W.Z.

mid 1970, W.Z.

early 19705, E & S.Z

W.l. : Western zone

E : Eastern zone

S.Z. : Southern zone

Data on grain yield, days to 50 per cent silk emergence, plant height, ear

hei~bt and per cent lodging were recorded. Grain yield per plot was adjusted for

vanation in plant stand through analysis of covariance, and for grain moisture. Data

on per cent lodging was subjected to "arc sine angular" transformation before

analysis. Data over the four environments were pooled by considering the

environments as random variables. Following the analysis of the design of the

experiment mid-parent heterosis for yield was computed for each of the ~ ur

environments. Mid-parent heterosis was used to analyse genetic affinity among

parents following the "hetero-dist" analysis and AlP - array hetero-score of Singh ~

aI. (2) and Singh (personal communication).

RESULTS AND DISCUSSION

Mean performance over the four environments for grain yield, ear height,

plant height and lodging are recorded in Table 4.

Even though the error variance for grain yield were homogeneous, the

variance ratio for genotype and genotype X environments were not sign.ificant.

Average yields for the four environments were, however, significant and showed

wide variation (Table 2) and were respectively 83.91, 72.64, 40.00 and 48.30

quintals/ha for Bako 1985, Bako 1986. Didesa 1985, Didesa 1986. Data for two

environments (Didesa 1985 and Bako 1986) fOf which F-test for genotypes was

significant were further pooled. In this analysis both genotypes and genotypes X

environment interaction were found to be significant. Bako 1986 and Dicfe-sa 1985


Table 2. Mean grain yield (q/ha) ot composites and their F 1

crossesln.tour environments

1.

2.

3.

4,

5.

6.

7.

8.

UCA

Bake comp.1I

EAH-75

Awasa-Jima (C 4

)

KCB

KCC

Bake compo (C/!

AlemaY8 compolite

l' 2 3 4 5 6 7 8

84.8 a 87.3 84.0 78.8 14.8 85.7 79.1 96.2

70.0 b 65.7 84.8 74,2 87.1 68.4 71,1 68.4

5O.6c ' 41,5 41.3 51.5 39.3 58,0 46.6 37.7

46.0 d 38,6 50.8 54.6 46.6 51.3 57.7 43,1

62,0 e 58,4 65.3 54.9 62.0 66.0 63.8 61.3

82.4 90.6 86.0 98.6 92.8 70.4 84,4

78.8 75.3 73.3 76.6 62.4 66.4 75.3

49.1 48.4 46.0 31.7 38.6 38,8 28.2

49.7 44.0 52.6 52.8 46.2 50.2 48.6

65.1 54,7 54.4 65,1 60.0 56.4 59.1

72.4 79.5 82.0 80.6 80.8 74.2

76.0 69.3 78.8 86.0 66.8 66.2

54.6 38,4 36.4 23.7 37.5 32.4

47.3 39.1 49,1 57.1 43.3 53.3

62.4 56,7 61.6 62.0 57.1 56.7

70,6 68.6 92.8 104.6 79.7

58,2 78.0 68.6 62.8 63.5

50,0 16.6 29.3 42.2 31.5

38.4 44.2 54.8 48.8 48,2

54.4 52.0 61.6 54.7 5;).8

76.4 77.5 86.6 99.7

58.8 78.6 67.5 72.6

34.2 24.6 27.5 38.6

52.0 55.3 40.4 51.7

55.3 59.1 55.6 65.8

83.1 71.5 104.0

83.3 74.4 78.0

37,7 38.8 46.4

50.8 36.4 60.2

63.8 55.3 72.2

69.1 90.2

69.5 72.4

44.4 36.8

57.7 49.1

Environment

a- Bako 1985

b - Bako 11186

c· 0Ide.. 1985

d • Olde.. 11186

•• Pooled analyala

Mean YIeld

!ILl!!

83.91

n.M

40.00

48.30

e1.33

C.O. at 5%/S.E.M CV%

7.47

16.70

1e.01

7.12

3.24

15.32

13.51

25.16

24.80

18.35

60.2 62.2

85.7

83.3

60.2

42.2

~

W

1.0


140

respectively represented high (HYE) and low yielding environments (LYE) and

were helpful in further study of the various genotypes included in the study,

particularly with regard to grain yield. Based on mean performance over two

environments (Table 3) the parent KCB was at par with Jima-Awasa (C4) and Balco

com{'osite (Cz) and gave significantly lower yield than other parents. None of the

hybnds, however, recorded higher grain yield than EAH-75 which gave highest

YIeld. Varied behavior of the parents under two environments (HYE, LYE) as

noted from genotype X environment interaction was further evidenced by the

performance of Alemayacomposite and composite KCC which were respectively

low and high yielders in Bako 1986 reversed their position in Didesa 1985 test

(Table 2). It was likewise true for Awasa-Jima (C4)' This observation is further

supported by the performance of some elite F1 hybrids namely DCA X KCB, EAH­

75 X KCC, and DCA X EACH-75 recorded L8 to 4.6% hi~her grain yield than the

best composite during Bako 1986 (HYE), none of the hybnds gave better yield than

the best composites at Didesa 1985, in fact above named three hybrids were among

the low yieldmg entries under LYE. In contrast to these observations parents like

Bako composite II, DCA and EAH-75 were grouped among high yielders under

each of the two environments. Composite KCC, the second highest yielding parent

under HYE took 80.8 days to produce silks in 50 per cent of the plants (Table 4).

The hybrids compared to their parents in general were intermediate to early in

flowering suggesting partial dominance for earliness.

Per cent mid-parent heterosis for grain yield for the two environments

showed considerable variation. It ranged from 35.17 per cent to -23.01 per cent for

DCA X KCB and Bako composite II X KCC for Bako 1986 and 31.16 per cent to­

60.42 per cent for DCA X KCC and Awasa-Jima (C4) X KCB for Didesa 1985

respectively. Frequency of hybrids with ne~ative estlmates of heterosis was 26 and

10 for Didesa 1985. and Bako 1986, respectively, these two respectively represented

the low and high yielding environments. Mid-parent heterosis based on two

environments ranged from 18.30 per cent to -22.38 per cent for DCA X KCB and

EAH-75 X Alemaya composite respectively, and 19 crosses recorded negative

estimates of heterosis.

Parents associated with high negative heterosis showed closer affinity and

lack of diversity. On the other hand parents associated with high positive heterosis

were considered to be diverse and unrelated. Cluster score was established by the

number of rays emanating from each parent in the hetero-dist diagram. Cluster

scores are recorded in Table 5.

Data from Didesa 1985 and Bako 1986 presented a contrast, while in the

former environment all parents (except two involved in one hybrid) had negative

cluster score while in the latter environment all parents had positive cluster scores

(except 2 parents involved in one hybrid).

Cluster score (Table 5) for Didesa 1985 (LYE) data suggested that parents

8(Alemaya composite) and 4(Awasa-Jima (C 4 ) respectively had score of -5 and-4

su~estingtheir closer affinity with other parents. Parent I(DCA) with score of 0

indicated its divergence from other parents. This conclusion was further supported

by a positive cluster score of 3 from Bako 1986 (HYE) as well. KCB recorded a

score of 4. Overall cluster score indicated that parents I(DCA) and 5(KCB) were

most divergent while parent 8(Alemaya composite) was least divergent from others.

Thus parents 8(Alemaya composite), 4(Awasa-Jima (C 4 ) 3(EAH-75) and 2(Bako

composite II) could form one closely related group. Divergence between parents

I(DCA) and 5 (KCB) and affinity between the above named parent is expected on

the basiS of the parental materiafs included in their initial synthesis and related past

history of selectIOn.

ArrayIparental mean (AlP) data combined over two environments (Table 6)

were used to further study the relationship among parents. The AlP ratio helped to


Table 3. Mean grain yield of parents and their crosses In two environments (q/ha) (Didesa 1985 and Bako 1986)

2 3 4 5 6 7 8

1. UCA 60.33 53.66 63,10 62,88 63.22 63.22 58.88 53.11

2, Bako comp." 63.99 61.88 59.66 54.22 SO.55 52.66 51.77

3, EAH·75 65.33 53.88 57.68 54.88 52.22 49.33

4. Awasa-Jima (C4) 54.11 47.33 49.00 52.55 47.55

5. KCB 46,55 51.68 47.55 55.68

6. KCC 60.55 56.66 62.22

7, Bako compo (C 2

) 57.00 54.66

8. A1emaya composite 61.77

C.D. at 5% 11.09 (q/ha)

C.V,% 17.42

.r= .....


Table C Mean perforllance of parents and their crosses based on four environll8nts for grain yield, Q/ha (a),

days to m silk (b), plant height, CII (c), ear height, CII (dl, and lodging arc sine percent (e).

f 2 3 4 5 6 7 8

UCA Bako cOllO, II EAH-75 Ama-Jilla tCl) KCB KCC BakO-illLll..L-_AJuU..L.C.o.DIJi,

UCA

62.9 a 84.6 b 58.4 8~, 3 65,3 82.2 64,9 83.9 62.0 8402 66.0 84.0 63.8 83.3 61.3

83.2

293,5 C 293,2 288.1 287.9 308,0 310.5 283.3 286,0

181.9 174.7 172,1 176,1 188.3 184.6 173,8 170.2

. .3.1..L 29..l. 38.4 2403 31.3 .. 31,6 .-2.L.8 ._..J..t_6.

Bako comp, II 65.1 64',7 64,4 65,1 60.0 56,4 59.5

62,9 82,7 81.8 8U 82,0 81.5 8U

302.5 290.6 294.0 299.2 302.4 272,1 291.2

184,0 173.0 170,3 181.0 173,4 157,8 161.6

____~.8..J. .2..L..L. 22.6 ---12..L 1i...L 1!.LL ...Jl,A.

EAH-75

62,4 82.1 56.7 80.7 61.6 81.9 62,0 80.2 57,1 79,5 56,7

92.1

275.6 27403 304.5 m,7 282.0 304, I

167.5 158.0 177,8 176,3 16402 185.2

ZhL lUI -ll,_L__. . ..2.L1-.__..__J.l.~L._. ..__._._.lU

Awasa-Jima (Cd

54.4 52,0 61.6 64.7 5U

82.8 83.5 8U 8U 82.2

275,7 30E,2 293.1 274.; 281.4

.__. . .__. .__. . ... . 154,5 181.7 163.1 152,5 1l..L__---1U ---'-4....1 z.,_L~ 161.3

u.a

1.

2,

3.

4.

5, KCB 55.3 a 59, i 55,5 65.8

82.3 a 8U 83.5 a1.8

289.4 a 289,3 282,7 292,8

166.8 a 17U 169.8 182,:

_..__... . .._.__.__._. ._.._....__. . . 1t...La._. .12.....L. . __ ._UL~_. ..--._..;.3_,.S.

6. KCC 62.8 55.3 ;202

80.8 61.2 8i ,0

302,6 285.C 292.0

174.3 17~,C' i72,2

7-:--Bak;-~~~p.(.c~i-.-.----.---------.------ ..---- --.-.-.-.--.-----.- ---..-.- -.--------.-----.-.-..--- 1Z.,_2__.__.__.2...4..,J _ . .. ._14..,l

SO.2 62.2

8, Alemaya composlt£

E.D1Lrn.Ifle.n.t.. . ... _C.J.Lal_.5J.LS_LL.~.

a - Yield Q/ha

b - Days to 50~ siH

c .. Plan height

d - Ear eight

e - Loeg ng (Are, sine percent)

± 3, 23E

C•955 ~

15.4(

i I. ~3

US

c.u

IUS

U3

5,59

3.26

~U5

81. ;

282. r

158.2

.8.3

82.3

2" ,6

:51,1

24.3

fU

-SZ,7

292.0

180.0

2S .:

.r=

IV


Table 5. Cluster score

Pooled over 2

Parents Dideaa 1985 Bako 1986 Environment environments CNerall

(-) (+) Total (-) (+) Total Total (-) (+) Total Score

----------------------------------------------------------------------------

1 ·1 1 0 0 3 3 3 .


144

divide the parents into three group (a) parents I(UCA), 5(KCB), (b) parents

4(Awasa-Jlma (C 4 ), 6 (KCC), 7(Bako composite (c,); and (c) parents 3(EAH-75),

8(Alemaya composite), 2(Bako composite II). The A/P ratio and parental mean

ranks were closely related in inverse order. Standard deviation associated with

array mean broadly followed the order of A/P. Array hetero-score (Table 6)

further suggested that the parents I(UCA) and 5 (KCB) were more divergent than

other parents.

Besides yield, data on other agronomic characters also provided an

opportunity to study affinity among parents. Composites KCC and KCB provided

an interestlllg situation. Even though the two parents significantly differed in days

to silk, F1 crosses of these parents involving five common testers (parents 1(UCA),

2(Bako composite II) 3(EAH-75), 7(Bako composite (C,), and 8(Alemaya

composite) provided nearly similar mean values for plan1 height, ear height, and

lodglllg (Table 4). Moreover crosses of KCB and KCC with parents I(UCA) and

8(Alemays composite) also yielded similar mean values for days to silk. Mid parent

heterosis for yield among these parents was 3.53 per cent. These data suggest that

even though these materials were developed from divergent materials (Table 1) the

present seed stocks under study over a prolonged period of selection (directed and

natural has led to a loss of genetic divergence, however mutual introgression

through outcrossing at some occasion cannot be ruled out.

Data from the present study suggest that several of the elite composites

under evaluation are related and associated with marked genotype-environment

interaction. Most of these composites are better adapted to favourable

environments. The superiority of F1 hybrids over parents is better expressed under

high yielding environments. ibis suggests the need for introgressing additional

germplasm from diverse genetic sources into the locally available well adapted

population to synthesize superior composite varieties for extensive exploitation

through systematic breeding programme involving evaluation at selected diverse

environments in the country.

ACKNOWLEDGEMENT

The help of Dr Joginder Singh in the statistical analysis of data and

interpretation IS gratefully acknowledged.

REFERENCES

Benti Tolessa, 1986. Better and stable performance of maize through genetic

improvement at Bako. Agricultural Research, Vol. 1 No.1, 11-12. Addis

Ababa.

Singh, J., N.N. Singh, N.P. Gupta, I. Singh, S.B. Singh and R.D. Singh. 1986. Choices

of selection sites in the development of improved versions of composite

Diara of maize. Proceedings of National Seminar on Integrat~d

Management of Approach for Maximizing Crop Production in"Rainfed and

Problem areas; JARI, New Delhi.


145

PROGRESS IN MAIZE (ZEA MAYS 1..) POPULATION IMPROVEMENT

FOR TIlE EASTERN HIGHLANDS OF ETIlIOPIA

Dejene Makonnen 1

ABSTRACf

Maize is one ofthe major cereals in Ethiopia and ranks first in yield

per unit area and total production as compared to other cereal crops.

Improved open pollinated varieties by and large are very important to the

fanning community. Hybrids which do require higher inputs have not yet

established themselves as basic commodity among the peasants.

Nevertheless, there is a growing demand for clean and improved

seeds of populations. Open pollinated improved composites are being

developed from local collections and introductions. Further selection

continues on the locally developed and introduced composites to improve

plant types and yield. SI fonnation, half-sib recombination and full-sib

selection methodologies are duly applied. In the recent past, experimental

varieties have been developed and tested. Hence, one of the experimental

varieties is in the process of multiplication and distribution.

Hybrid varieties have very limited demand, except by the Ministry of

State Fanns Development. Minimal effort is being placed to develop lines

and hybrids.

INTRODUCfION

Maize (Zea mays L.) is one of the principal and popular cereal crops grown

in Ethiopia. It has the highest yielding potential as compared to other cereals. It

ranked first in yield per hectare and total grain yield. The major maize growing

areas of Ethiopia are Western, Southern, South-Western and Eastern regions. The

national average yield of maize in Ethiopia is generally low ranging fromg 11 to 19

quintals per hectare (Dejene Makonnen, 1979). Efforts to improve maize at

Alemaya University of Agriculture have been underway for many years. This task

was undertaken in cooperation and collaboration with national and international

organizations and institutions. This paper outlines the major tasks undertaken in

population improvement and the progress and achievements attained.

Demand for Improved Cultivar

A positive percentage of growth rate of area under maize production has

been obtained in the last decade. As maize became popular and its area of

production increased the demand for seeds of improved varieties became

significantly high. Many small farmers and producers' cooperatives started

requesting for Improved seeds in most parts of the Eastern Highlands. Therefore, to

meet the demands of improved seeds improvement of varieties becomes a

prerequisiteo

By and large the highest percentage of farmers are small holders. Many of

these farmers are not well prepared to use hybrid varieties that require higher

inputs and management Mirustry of State Farms and Development, whicn

comprises a very small sector of the farming system (5%) does require hybrid seeds.

Hence, major attention is given for the development of open pollinated Improved

populations that can meet the demand of farmers. To a lesser extent effort has also

been placed for the development of hybrid varieties.

1. Alemaya University of Agriculture, P.O. Box 138,

Dire Dawa, Ethiopia.


146

Population Improvement Methodology

Source materials were mostly obtained from Kenya, Tanzania, Zimbabwe,

Mexico and local collections. Different techniques of selection were employed in

the improvement of diverse germplasm. The objectives and/or goals of the

improvement program were to develop:

stable and high yielding varieties

superior lines and hybrids

the optimum cultural practices

To achieve the objectives the selection methodologies depicted in Charts 1-3

have been used. The followin~strategies are also believed to be instrumental for

achieving the goals and objectives set up. These are:

~ooper~te With national and international organizations and

InstitutIOns

involve graduate students for their thesis research

involve selected farmers for on-farm trials

make use of off-season nurseries

Results and Discussion

. Po~ulations a.t various st~ges of improvement have been introduced from

nelghbounng countnes. These mcluded KCC, KCB, DCA, DCB, KCE, ZCA, ICA

and EC573 among others. These long cycle populations were tested for their

adaptability at various sites including the Eastern Highlands. These introductions

showed very good prospect and promise to be used as recommended cultivars with

some improvement on their agronomic traits (Benti, 1986).

Local collections were recombined with some of these introductions to

produce one of the outstanding composites, Alemaya composite for the Eastern

highlands and other similar locations. Alemaya composite was initially produced

through mass selection. A steady selection and progress of improvement has been

attained within the composite. The composite has particularly performed well at

Alemaya in the Eastern highlands, Kulumsa, Awassa and Jirnma. Hence it is being

multiplied by Ethiopian Seed Cooporation for large scale distribution among the

farming community. The composite is characterized as beirlg tall, about 300 cm in

height. It produces attactive ears, 34 cm long with 12 to 16 rows. The kernel are

mixtures of small, medium and large in size; flint, semi-dent and dent with white

endosperm. The composite performed well, yielding as high as 100 quirltals per

hectare under optimum experimental conditions.

The other improved population developed for the Eastern highlands and

ot er similar location is EAH-75. This variety is also very popular, it is multiplied in

large quantities by the Ethiopian Seed COf{>oration for large scale distribution. The

plants are about 250 cm in height. The vanety produce, large sized ears 33 cm long

with 12 to 16 rows of 50 seeds per row. It haskS cleanly and easily. The kernels are

mixtures of small, medium and large in size, semi-dent to dent With white

endosperm. The variety performs well under optimum experimental conditions.

Other series of composites which constitute Mexican germplasm designated

CA series have been developed and tested. Some of these composites are early in

maturity. However, the vaneties did not extend beyond experiment level.

Mostly a white endosperm maize is preferred, nonetheless, a yellow

endosperm improved population from local collections through mass selection and

ear to row half-sib family selection was developed. The population, known as

Bakuri has a maturity rating of 120-135 days; and plant height of 200 cm. The

kernels are mixtures of small, medium and lar~e SlZe, generally flint with yellow

endosperm. This improved population is distnbuted around Alemaya at a limited

scale.


CHART 1. DEVELOPMENT OF STABLE AND HIGH YIELDING MAIZE VARIETIES

GENERAL BREEDING APPROACH

POPULATION IMPROVEMENT

ADAPTATION YIELD POTENTIAL

HIGH LAND

MEDIUM ALTITUDE

RUST

BLIGHT

IMPROVED

PLANT TYPE

MATURITY

FOUR-FIVE MONTHS

IMPROVED

SILK

RECURRENT

SELECTION

MULTI LOCATION

TESTING

.l:O

"'-J


CHART 2. POPULATION IMPROVEMENT AND HYBRID DEVELOPMENT

- SOURCE POPULATION

- COLLECTIONS

- INTRODUCTIONS

Mass S.

E.T.S.

H.S.

Sl-T

I IMPROVED VARlETY 1

LINE DEVELOPMENT

H.S.

F.S.

TESTING OF

IMPROVED VARIETY

....

"..,

I VARIETY J

....

.... .... " " , .... 1....

....

, .... ....

....

TOP CROSS

PRE. TESTING

DIALLEL CROSS

TESTING LINES

.l:"

co


CHART 3. SPECIFIC BREEDING APPROACH

ILINE DEVELOPMENT I

J

TESTING OF LINES PERSE

TESTING

DEVELOPED SYNTHETICS

7

RELEASE FOR COMMERCIAL

PRODUCTION

.s:=


150

The traditionally preferred and commercially produced maize types are

white in color, dent and semi-dent in texture. The flinty pop com is not well known

and grown by the peasant sector. Nonetheless, pop com is very popular at the urban

centers. Very linuted amount of pop com has been imported for urban

consumption in the past few years. Attempts have been made to develop a pop com

variety that can meet the urban needs and substitute import.

Local collections and some introductions from North America have served as

a source material for the development of the pop com variety. Through S1 and haJf

sib family selection the current pop com variety was developed. The variety

matures within 90 to 120 days and yields 40-50 quintals per hectare. It is well

adapted to Alemaya, Bako, and Awassa regions. The variety is being multiplied at

Alemaya and has been distributed to interested institutions and individuals. The

variety tillers, particularly when widely spaced. It produces small ears, the kernels

being mixtures of rice and pearl types WIth white endosperm.

Evaluation orthe Populations

Introduced and locally produced long cycle populations are tall and late in

maturity. They are in general susceptible to lodging under high wind and stormy

conditions. Due to lod~ing reduction in yield is recorded. Furthermore, much of

the photosynthate is Utilized for the development and maintenance of the lar~e

vegetative part of the populations. Many of the composites have similarities III plant

type and seed texture. They seem to have shared common gene pools. Hence, It is

better to have one or few populations that represent the different composites for

different growing sites than having duplicates or similar-types.

The improved populations, Alemaya composite, KCC, KCB and DCA were

test crossed with EC573. The crossed progenies and including the checks Alemaya

composite and EAH-75 were tested at Alemaya, Bako, Jimma, KuJumsa and

Awassa. The crosses performed well yielding very high at A1emaya (Table 1). The

result indicated that there was no significant difference among the crossed progenies

at the specific location.

The four composites; namely: A1emaya composite, KCC, KCB and UCA

were pooled together to serve as source material for the improvementper se. The

main objective of the improvement program was to develop a stable and high

yielding population with reduced to plant type and ear height.

Sl plants were developed from the source materials in the first generation.

Half-sib recombination among the selected Sl plants was accomplished in the

following generation and subsequently, full-sibS were developed from the half-sibs.

250 full-sib families and six local checks were tested in a 16 by 16 lattice design for

yield and other agronomic characteristics at more than one location. The top ten

best performin~ families were recombined to constitute elite experimental variety.

The elite expenmental varieties were advanced to F 2 and F 3 generations at an

isolation before they were tested for yield. The improvement process takes longer

time. Hence, to reduce the period and accelerate the progress an off-season nursery

is used for the recombination and constitution of families.

Using the source materials, AI. Comp., KCC, KCB and DCA three

experimental varieties have been generated at Alemaya. The parental components

that constituted EV-1, EV-2, and EV-3 are given in Tables 2,3 and 4, respectively.

The selected full-sib families have desirable agronomic characteristics including

high yield.

The experimental varieties were tested for yield and other agronomic

characteristics. They have out performed the origmal source populations; namely:

AI. Comp., KCC, KCB and UCA. The experimental varieties yielded hi~b and bave

low plant and ear height (Table 5). Experimental Variety-1 is now multlplied on a

10 hectare field of the University farm. Starting next year it will be advanced to on-


Table 1. Grain Yield (O/ha) of !op-cfOR test results (1984)

No. Entries Alemaya Bako Jimma Kulumsa AWMlIlI Mean

1 AI. Comp. x EC573 104 76 75 97 89 88

2 KCCx EC573 104 64 61 93 87 86

3 KC8xEC573 130 91 68 102 88 96

4 UCAx EC573 107 76 44 115 74 83

5 EAH-75 105 76 59 92 90 64

6 Alemaya Comp. 92 72 54 52 76 69

Mean 107 79 60 92 64 64

Table 2. Grain yield In q/ha and other agronomic traits of full-sib families (parental components of EV-1)

Height (cm)

No. Families Days to

silk

Plant Ear Plant

aspect

Ear

aspect

Yield

q/ha

1 KCC-29-2-6 x KCB - 4-2-6 99 202.0 96.5 1.5 1.5 119.0

2 KCB-21-5-5-x AJ.Comp.-19-4-3 97 179.0 97.0 2.0 1.5 108.0

3 UCA-OO-5-4 x KCB ·17-1-2 93 188.5 85.0 1.5 1.0 101.0

4 UCA-27-3-2- x KCC-5-3-2· 95 179.0 n.5 2.0 2.0 103.0

5 UCA·29-1-4 x KCC-47-2-1 97 293.0 99.0 2.0 2.0 104.0

6 KCC-23-3-1 x KCB-21-2·1 95 195.0 98.0 1.5 1.5 112.0

7 AI.Comp. 38-1-3 x KC8-35-1-1 98 195.0 94.8 1.5 1.0 108.0

8 KCC-30-1·1. x KCB-40-2·1 93 186.0 92.5 1.5 1.5 104.0

9 KCCt6-1-2- x UCA·56-1-6 94 179.5 83.5 1.5 1.5 107.0

10 UCA-31·3-1 x KCB-1-1-3 95 199.5 105.0 2.0 1.2 105.0

U1


Table 3. Grain yield in q/ha and other agronomic traits of full-sib families (parental components of EV-2)

Days to Height (em)

No. Families Tassel Silk Plant Ear

Plant

aspect

Ear

aspect

Yield

q/ha

1 I>J. Comp.-5S-2-1 x KCG-9-5-2 87 91 240.0 134.0 2.0 2.0 124.38

2 KCG-15-1-16 x UCA-14-1-4 86 91 200.5 111.5 1.5 2.0 117.97

3 KCB-40-2·5- x I>J. Comp. 4-1-1 89 96 204.0 110.5 1.25 2.25 112.30

4 UCA-23-3-3-2-x I>J. Comp. 5-3-1 91 97 219.5 115.5 1.5 2.75 112.20

5 KCB-32-1-J.Comp. 9-3-2 85 92 218.0 101.0 2.0 1.75 111.60

6 I>J.Comp. 69-5-1-x KCG-12·1·1 85 90 218.0 127.5 1.75 2.25 109.81

7 KCG-4-2-1 x UCA - s-3-1 89 96 220.0 137.5 2.0 2.25 107.28

8 UCA-64-5-4 x KCB - 34-3-3- 91 97 207.0 121.0 1.75 2.0 103.68

9 I>J.Comp.22-1-3- x KCB-34-3-3- 91 97 207.0 121.0 1.75 2.0 103.68

10 KCG-9-1-2 x KCB-12·2121 90 96 246.5 140.5 1.5 2.5 102.85

Table 4 Grain yield and other agronomic traits of full-sib families (parental components of EV-3)

-----------------------------------------~------------ ------------------------------

Days to Height (em)

No. Families Tassel Silk Plant Ear Plant

aspect

Ear

aspect

Yield

q/ha

1 I>J.Comp.59-2-1 x KCG-9-5-2 87 91 240.0 184.0 2.0 2.0 124.38

2 KCB-40-2-5 x I>J. Com~1-1 89 96 204.0 110.5 1.25 2.25 112.30

3 UCA-23-3-2 x I>J. Comp.5-3-1 91 97 219.5 155.5 1.5 2.50 112.20

4 KCB-35-1·2· x KCG-16-1-4 91 100 249.5 146.0 1.75 2.5 109.81

5 AJ.Comp.-60-2-2 x KCB-24-4-3 91 97 212.0 121.5 1.75 2.25 108.55

6 KCG-4-2-1 x UCA-J.Comp-21-1-3 94 102 206.0 186.0 1.75 2.75 103.54

9 I>J.Comp.-46-4-1 x UCA-


\ Table 5. Grain yield and other agronomic traits 01 open-pollinatedNarietles of maize (ba mays l.)

Days to

0i..a8ll8

(0-5 scale)

-----------,.;..--

Height (em) tOOO Kernel Yield

No. Name Tassel Silk Rust Blight Plant Ear wt(grains) qjha

t EV-l 88 92 0.50 0.50 t56 n 448.7 119,4

2 EV-2 88 92 0.75 0.50 160 84 481.5 107.2

3 EV-3 87 92 0.25 0.00 164 89 448.0 '00.56

4 AI. Composite 92 98 0.00 0.50 189 106 468.85 98.0

5 KCB 94 99 0.75 0.75 244 148 478.1 98.2

6 KCC 88 94 0.25 0.75 205 109 513.7 83,78

7 EAH-75 94 103 0.75 0.50 188 102 438.85 88.3

8 UCA 89 98 0.25 1.00 195 109.5 487.0 104.56

------------------------~----------------------------- -------------------------------------------

Vl

W


154

farm demonstration trial. It will hopefully replace the very tall, late maturing and

lodging susceptible composites in the Eastern Highlands and similar agro-ecological

zones of Ethiopia.

Hybrids

Hybrids have high demand by the Ministry of State Farm and Development.

To meet the demand, efforts have been made in the development of hybrid . Large

number of lines were developed from the composites using the conventional method

of selfing. Lines at various stages of selfin~were top crossed with a well established

broad based population to test their combming abilIty. Through top cross test

potential lines were screened. For further evaluation selected lines have gone to

diallel cross to determine both general and specific combining ability. Diallel cross

studies have partly been undertaken by graduate students for their M.Sc. theses

research requirement. Lines that are Identified to be good combiners and have had

good performances have been multiplied and maintained.

Large number of single cross and double cross hybrids have been generated

from the lines and tested for various agronomic characteristics in experiment

stations.

The lines AI.28B, Ba.D, AI.29, AI.30, AI.31, AI.32, AI.33 and AI.34 appeared

to be very good in their combining ability and performance. Four single cross

hybrids designated Alemaya 79A, Alemaya 79B, Alemaya 79C and Afemaya 79D

have been developed using these lines. These hybrids are ready for verification test

and release. Some double cross hybrids are also being produced, and they are being

tested including this crop season.

Agronomic Practices

For the maximum potential expression of the varieties developed the

optimum agronomic practices need to be maintained. Thus, density per unit area,

date of planting, fertility requirement and others practices were studIed and

established for the varieties developed.

REFERENCES

Benti Tolessa, 1986. Better and stable performance of maize through genetic

improvement at Bako. lAR VoU, No.I.

Dejene Makonnen, 1979, 1983, 1985. Maize improvement progress report.

Alemaya University of Agriculture.

DISCUSSION

Question:

Brhane. The seeds of the CA series you showed in your slides had white and

yellow seed mixtures. Are you concerned about the color mixture of the

seeds when you consider the final product for release to farmers?

Answer:

Dejene. The seed color is a major concern. The CA serious composites are

kept under experiment station because of their seed color mixture (t.h.U; is one

of the reasons). Attempts wiIl be made to select for one seed color type.


155

TIlE ROLE AND CONTRIBUTION OF CIMMYfjllTA TO MAIZE

RESEARCH IN UGANDA

Denis T. Kyetere 1 and George Bigirwa 2

Maize production in Uganda has existed for more than 100 years.

Cultivation was mainly for subsistence until the early 1970s. At that time maize was

considered a cash crop. Currently it is called a non-traditional cash crop, principally

earmarked as an imI?0rtant commodity for barter trade with other countries. Maize

bas also become an lIDportant food crop in many areas of the country.

Maize research is documented as having its beginnings in 1927, though on a

limited scale. This has included participating in the East African Maize Variety

Trials and International Maize Variety Trials. During the years of 1955 to 1977

Uganda participated in the Annual East African CooperatIve Maize Variety Trials.

Participation in the CIMMYT/IITA maize trials has been intermittent since 1971

with the objectives of testing varieties, elite populations, inbred lines and h¥brids

across their adaptability for utilization indirectly as research materials or directly as

released products.

Apart from germplasm development, training, advisory services, distribution

of technical information and logistics are other contributions from CIMMYT and

IITA Training goes back as early as 1981. A good number of maize and wheat

scientists plus farm managers have received training at CIMMYT headquarters,

Mexico. Technical information has been through CIMMYT staff exchanging ideas

or through publications. Logistics have ranged from a vehicle, field and laboratory

equipment plus chemicals and provision of a personal computer and its accessories.

A few people have also received training at lITA, Nis.eria.

Much emphasis will be given to the first contnbution from CIMMYTlIlTA

named above and that is gerrnplasm because it forms the major component of maize

research in the country and the main source of diverse genetic materials for the

country's breeding program. Kawanda Composite B (KWCB) is composed of

materials tested and selected under this collaboration, i.e. it was developed from

materials of Central and South American origin though it was never released.

Kawanda Composite A (KWCA) the present variety being grown by farmers had

streak resistance incorporated

at rITA Due to the upheavals in Uganda, maize research was affected likewise.

The 1985 heavy looting of Kawanda Research Station the then headquarters of

Maize research, saw the end of previous years wor!).. Records, facilities and

germplasm assemblage that had been made got destroyed. Starting with 1986, a

short term strategy of obtaining and screening varieties that are high yielding,

resistant to maize streak, other diseases, pests and with other de irable attributes

was launched. Focus was on CIMMYT and UTA materials and so far a good

number of useful varieties has been identified (Tables 1 and 2).

Following the susceptibility of most of the introduced materials to H.

turcicum leaf bli~ht, it wa decided to start a program to solve this problem. Some

seeds of Population 42 (ETO-Illinois) which IS supposed to have blight resistance

were received from CIMMYT Mexico and the material is to be multiplied this year

second season. If the material is found promising it will be intercrossed with OUI

adapted gerrnplasm.

1. Maize Breeder and Acting Head of National Maize Program

2. Pathologist Maize Program, Namulonge Research Station,

P.O. Box 7084, Kampala, Uganda.


156

Table 1. Agronomic data for ELvr-18A planted at Namulonge in 1988B

Entry Name

Plant

Height

em

Ear

Height

em

Blight

Score

1-5

Yield in

KgfHa*

Across 8443

Across 8329

G. Aragua 8443

Piura 8336

Guarare 8427

Tocumen (1) 8424

Palmira 8425

Across 8328 RE

Cagua 8425

Across 7729 RE

San Cristobal 8424

KWCA certified (check)

CV%

228

215

205

205

213

207

2)J7

235

231

213

254

284

5.97

132

122

106

122

109

110

99

107

98

148

146

170

2.0

2.2

1.6

2.3

2.0

2.0

1.4

1.7

1.7

1.7

1.8

1.5

31.84

8086 a

7647b

7342 be

7lf)2 cd

7097 cde

7000 cde

6903 de

6876 e

6808 ef

6806 ef

6477 fg

6189 g

12.72

" Entries with different letters have significant yield

differences at the 5% level.

Table 2. Agronomic data for Uganda Maize Variety Trials

planted at Namulonge in 1988B

Entry Name"

Plant

Height

em

Ear

Height

em

Blight

Score

1-5

Yield in

KgfHa"

Ikenne (1) 8149-SR 224 115 1.5 6921 a

Ev. Across 83 TZ M-SR-W 223 173 1.7 6786 a

Gusau TZB-SR 127 123 1.7 6634 a

KWCA certified (check) 301 176 1.5 6513 ab

tv. Gwebi (1) TZM-SR-W 232 124 1.7 6177 be

Ev.8428-SR 237 121 3.2 6016 cd

Ev.8442-SR 243 133 2.2 5671 d

Ev Ml. MakuJu (1) TZM-SR-W 1&5 90 1.7 5582d

CV% 5.39 921 24.88 13.88

* Entries 6&71u1d reduced plant populations (50%) due to

harsh seed trcatmen1.

*. Entries with different letters have significant yield

differences at Lhe 5% level.

In our H. turcicum evaluation work we used two locations Kamenyarrtiggo

DFI (hot spot area) and NamuloD,ge Research Station. Leaves heavily infected with

blight and approaching full maturIty were collected from three different ecological

zones at end of last year.


157

Just before inoculation, the dry leaves were ground into a meal of about the

coarseness of wheat bran. Inoculation was done at 6-8 leaf stage by placing a pinch

of leaf meal (a leafed thimbleful) into the whorl of each plant. TIus was followed by

application of water into the whorl. Ten days later a second inoculation was made

usmg two methods; a meal of ground leaves and spore suspension (60,000

spores/plant).

Portions of the lesions around their edges were cut, surface sterilized, washed

in distilled water and placed in acidified potato dextrose agar (APDA) using aseptic

techniques and incubated at 25-30°C. From these samples a culture of the

pathogen was transferred to APDA Two to three weeks after the fungus mycelia

had covered the surface of the agar. About 10-20 ml of sterile distilled water were

added onto the place and the spores including the mycelia on the surface of the

agar, were scrapped off using a rubber tipped spatula. The suspension was strained

through a layer of muslin cloth.

Evaluations were done three times during the growing season. Disease

reactions were evaluated using a scale of 1 to 5. Intermediate ratings between two

numerals were in some cases used (Table 3).

Table 3. H. turcicum evaluation at Kamenyamiggo DF!

10.5.89 20.6.89 T7.7.89 Plant

score SCOre score Aspect

------------------------------------------------------------

KWCAcert 1.5 2 2.5 3.

5

Gusau TZB-SR 2 3.5 3.5 3.

5

Ikeone (1) 8149 3 3.5 4 3.

5

EV8429-5R 2 3 3.5 3.

5

KWCA-SR 1.5 2.5 2.5 3.

5

EV. Babungo (3) TZ MSR-W 1.5 2 3 3.

5

E",. JOS (1) TZ MSR-W 2 3.5 4 4

Ev. Across 83 TZ MSR 1.5 2.5 3 3

Ev.8428-SR 2.5 3.5 3.5 3

Ev.8443-SR 2 3 3.5 3

1 = Very slight infection

2 = Light infection

3 = Moderate infection

4 = Heavy infection

5 = Very heavy infection

DISCUSSION

Question:

Njuguna. How well is the Kawanda streak resistant composite (KWCA-SR)

holding for streak resistance? 'Is it adapted to mid-altitutde?

Answer:

Bigirwa. It has high resistance against maize streak and is wen adapted to

the mid altitudes.


158

THE PERFORMANCE OF INTRODUCED MAIZE HYBRIDS

AT KAWANDA RESEARCH STATION

Elizabeth Byanjeru Rubaihayol

ABSTRACT

The objective ofthis trial was to evaluate the performance ofeight

different white hybrid maizes from UTA under Uganda conditions. The

eight hybrids included were 8321·18, 8321·21, 8322-13, 8428.19, 8505·1, 8505·

3,8505-5, Samaru-83-TZSR-W-1. Two local varieties namely Kawanda

Composite A and K8, selected their high local performance were included as

checks. The last variety is excellent for marginal rainfall areas. Fifteen

characters were studied including plant stand; plant height, ear height,

number ofdays to SO% silking, root and stalk lodging, husk cover, diseases,

plants harvested, ear rot, plant aspect, ear aspect, field yield and moisture

percentage at harvest. The main emphasis was on yield and how all the

other characters affect it. The results indicated that root and stalk lodging,

rust (Puccinia polysora) and ear rot reduced yield significantly as their

intensity increased. Blight (Helminthosporium turcicum) had insignificant

effect on yield. Yield increased linearly as the number of harvested ears

increased for all entries. The overall results indicated that the hybrids

evaluated in this trial were superior to the local varieties in almost all the

traits except resistance to blight where KWCA was superior.

INTRODUCTION

Since the introduction of maize breeding and intensive production in Uganda

in the early fifties, a number of hybrid varieties have been imported into the

country, mainly from Kenya. So far, no local hybrids have been developed by maize

breeders in Uganda. However, the farmers have become increasingly aware of the

advantages, particularly in yield, of hybrid maize over the open poIfinated varieties.

Efforts by Uganda breeders to develop hybrid maize have been hampered by

unavailability of cold storage to maintain a large stock of inbred lines and where

promising inbred lines have been identified and hybrids like KWCA x MCI and

KWCA x KWCB developed, the National Seed Company has not been in a position

to produce seed of the established variety KWCA let alone produce seeds of a

second open pollinated variety, Kawanda Composite B.

The strife the country has gone through led to the loss of all breeders inbred

lines and other maize materials. Hence an effort to introduce hybrid materials

from willing countries and organizations for testing under Uganda conditions was

made. The intention being to temporarily continue to import hybrid seed while the

breeders carry out an intensive programme to develop local hybrids with emphasis

on high yield, disease and pest resistance. It is in this context that eight white maize

hybrids were introduced from UTA and tested at Kawanda Research Station in

1985. The 1985 trial was abortive due to the liberation war but,the same trial was

repeated in 1986. The objectives were to evaluate the performance of these eight

hybrids at Kawanda and compare them with one synthetic variety and one

composite variety. The long term objective was to evaluate these varieties in

different maize growing areas of Uganda for their yield potential and resistance to

pests and diseases. The ultimate goal was to produce them commercially in areas

where they would be found suitable.

1. Senior Maize Breeder & Director of Research, Kawanda

Research Station, P.o. Box 7065, Kampala, Uganda.


159

MATERIALS AND METHODS

The following eight white maize hybrids were introduced from the

International Institute of Tropical Agriculture (lITA) and planted during the second

season of 1986 at Kawanda Research Station. Two leading local varieties were

included in the trial:

Variety Name

8321-18

8321-21

8322-13

8428-19

8505-1

8505-3

8505-5

Samaru-83 TZSR-W-l

Kawanda Composite A (KWCA)

K8 (Synthetic Variety)

Entry Number

1

2

3456789

10

The experiment was planted in a fairly uniform field located at Kawanda

Research StatIOn, in the Lake Victoria Basin with a ferralitic red clay loam soils of

Buganda Catena. The mean annual rainfall is 1132 rom which is well distributed but

has two reaks, one durin~ March-April and the second peak in October-November.

The tria was conducted In the second rains. The environment was kept fairly

uniform so that the variations observed would be as far as practicable due to the

differences in the genotypes.

The entries were planted in a randomized complete clock design with four

replications. Plot size was 2.25 m wide by 5 m long with a spacing of 75 em between

rows and 50 em within each row. There were four rows with 11 hills per row. Three

seeds were planted per hill and thinned to two seedlings per hill, giving a perfect

stand of 22 plants per row and 88 plants per plot. The estimated plant density was

53,333 plants per hectare.

General agronomy included the application of single super phosphate at a

rate of 125 kg/ha in the seed bed, a day before planting. Nitrogen in the form of

Calcium Ammonium Nitrate was applied when the CrOp was knee high at the rate of

250 kg/ha. A minimum of ten guard rows surrounded the trial to reduce edge

effects. The trial was hoe-weeded three times during its wowing period to keep it

weed-free. No measures were taken against pests and arumal damage. The trial

was guarded against bird damage which were scared away daily from the time the

trial was in the milk stage to hard green maturity. Data on most important

agronomic traits were collected only on two central rows.

RESULTS AND DISCUSSION

The results reported were obtained in the second rains. The environment

was kept fairly uniform so that the variations observed would be as far as practicable

due to the differences in the genotypes. PLant stand ranged from 50% to 97.7% with

hybrid 8505-5 having the Lowest stand of 50% closely followed by K8 at 68% and the

remaining entries faUln~ between 90% and 97.7%. The differences observed were

significant. Plant height measures indicated the entries were generally memum to

very tall ranging from 172.5 em in 8505-3 to 230.8 cm in Kawanda Composite A

(KWCA). These differences were highly significant. Ear height to a large extent

was linearly related to plant height in that tall plants had high placed ears. Again

8505-3 had the lowest placed ear at 69.3 em and KWCA had the highest placed ear

at 137.5 em from the ground and the differences were significant.


Table 1. Agronomic Data of the IITA White Hybrid Maize Trial

at Kawanda Aee.earch Station, 1986, Second Season.

------------------------------------------------------------------------------------------

ENTRY PLT PLT EAR DAYS LODGING HUSK DISEASE PLT EARS EAR YIELD MOIS- PlANT EAR

NO. STAND HT HT TO ROOT STAlK COVER RUST BUGHT AT HARV- ROT FIELD TURE ASPECT ASPECT

CM CM SILK HARVT ESTED WT(KG)

-----------------------------------------------------------------------------------------

t 41 195.8 100.8 71 2.3 1.4 1.5 2.5 3.5 37 39 141.0 8,40 15.13 3.3 2.8

2 42 195,8 75.8 71 1.7 1.0 2.3 1.8 3.0 42 42 1.0 9.20 15.25 2.0 2.5

3 43 181,3 90.0 75 2.2 2.9 1.5 3.3 5.0 38 39 1,5 5.65 14,73 3.5 4.3

4 40 191.3 86.8 69 2.0 2,9 1.3 2.2 4.8 33 37 1.2 7.33 14.80 3.3 .3.0

5 42 185,0 89.0 76 2.1 2.0 1,5 1.8 3.3 37 38 1.3 8.30 18.20 2.3 3.3

6 42 172.5 69.3 71 2.2 2.7 1.8 2.5 4,8 37 38 1.3 6.10 14,80 4.0 3.5

7 28 176.0 78.5 74 1.5 1,8 1.3 2.5 3,8 26 30 1.2 5.28 15.35 3,3 3.5

8 40 207,8 98.5 76 2.0 1,8 2.0 2.3 3.3 36 37 1.3 7.35 14.38 2.8 2.8

9 40 230.8 137,5 37 2.7 2,5 2,3 3.3 2,5 30 27 1.9 5.20 15.93 4,0 3.8

10 31 178.8 87.3 56 1.7 3,0 4,3 3.0 3.0 27 21 2.0 2.43 14.78 4.8 4.3

-----------------------------------------------------------------------------------------

39 188.3 91.2 71

"an

2.0 2,2 2.0 2.5 3.7 34 35 1.3 6.52 15.13 3.3 31.4

LSD 5% 3.2 13.5 13.0 3.0 N.S N,S N.S 0.5 0.5 3.4 3.2 0.3 1.04 0.61 0.5 0,5

tv'll. 9.79 8.42 16.72 4.93 41.3 47,25 32.13 22.19 16.78 11.64 10.94 24.51 18.75 4.76 16.39 17.33

-----------------------------------------------------------------------------------------

0

en


161

The number of days to 50% silking were also significantly different with K8

being the earliest to silk at 56 days after planting and was followed by 8428-19 at 69

days. The two being significantly different, but the latter was not significantly

different in silking date from hybrids 8321-21, 8505-3 and KWCA 8505-1 and

Samaru-83-TZSR-W-1 were the latest to silk. This could be of significant

implications especially in the second rains which are short. The farmers who plant

late would lose the crop. That is if late silking is positively correlated with late

maturity. In this particular trial maturity date was not recorded.

Both root and stalk lodging were moderate in all entries. There were

significant differences among entries for both traits but the coefficient ofvariation

was over 40% and very high making the results unreliable.

In general, all the hybrids had good husk cover. Although the score for K8

was bad (4.3) it was still not significantly different from 8505-5 with a score of 1.3.

However, these results are highly unrelIable as the coefficient of variation was very

high.

For diseases evaluation, only the results for blight and rust are available.

Rust was present on all entries being severe on entries 8322-13, KWCA and K8 and

mild on 8321-21 and 8505-1 with identical lowest score. Blight was moderate to

severe with only KWCA being more resistant than the remaining entries. Although

the results indicate that blight was more severe than rust, blight developed late on

most entries and did not apparently affect yield. Plants harvested ranged from 59%

to 95% of the perfect stand. 8505-5 had the lowest stand closely followed by K8 at

67%. Entry 8321-21 had the highest percentage of plants harvested at 95%. The

differences observed affected yteld as discussed later.

Number of ears harvested was mainly to indicate the presence or absence of

single eared, double eared and barren plants. Except for KWCA and K8 where the

number of ears harvested was lower than the number of plants harvested, the

remaining entries generally indicated the majority of plants had one ear, but in a

few entries one or two plants had more than one ear. It is surprising to note KWCA

had less ears harvested than the number of plants harvested because this composite

has a naturally high tendency for double ears. Entry 8321-21 had the highest

number of ears harvested corresponding to its high percentage of plants harvested.

The differences between varieties were highly significant.

Ear rot was negligible in all entries except in KWCA and K8 where it was

moderate and the differences among entries were significant. The hybrids were

more resistant to ear rot than the local varieties.

Differences among entries for field yield were highly significant. The

observed yield-by-entries interaction indicated the yield potential was not the same

f9r each entry. The field yield was adjusted for mOisture content. Separating the

mean field yield showed K8 was the lowest yielder and significantly different from

all other entries. It was followed by KWCA, 8505-5, 8322-13 and 8505-3 which were

not significantly different from each other. These were followed by 8438-19,

Samuru-83-TZSR-W-1 and 8505-1 which had similar yields but were significantly

higher yielders than the former group. 8321-18 and 8321-21 were the highest

yielding group in that order and were significantly different from the rest of the

entries. The hybrids outyielded the local varieties K8 and KWCA According to

hybrid evaluatIOns of the early and mid - seventies Kawanda Composite A and

Kawanda Composite B were performing better than the Kenya Hybrids such as

H632, H5013, H5014 etc. but there were environment by vanety interactions as

hybrids tended to perform better in Eastern Uganda (Rubaihayo 1975). The 1986

results seem to suggest that the local composite has deteriorated or the liTA hybrids

are Superior to the Kenya hybrids when grown in Uganda. However, no conclusions

can be drawn as the results In this paper were from one location and one season, yet

the results of the seventies were multilocational and for a number of seasons.


162

Entries varied significantly for moisture content and that is why the field

yield was adjusted for moisture content. Entry Samaru-83-TZSR-W-1 had the

lowest moisture content but was among the best 4 yielders, although the high

number of plants and ears harvested could have contributed to this high yield inspite

of the low moisture content. However, it did not vary significantly from 8322-13, K8,

8505-3 and 8428-19. Entries K8, 8505-3, 8429-19 did not vary significantly from

entries 8321-18, 8321-21 and 8505-5. Entries KWCA and 8505-1 had the highest

moisture content and yet KWCA was the second lowest yielder. This could be

attributed to the low number of ears harvested but as indicated the yields were all

adjusted for moisture content. So other factors were most important in affecting

yield results.

Plant aspect was a general score of "look" or "appeal" of the plants in each

entry. 8321-21 was best looking closely followed by 8505-1. Entries 8505-3, KWCA

and K8 had the worst looking plants. The differences among entries were

significant. Ear aspect was also "look" and "appeal" and entries differed

significantly. The best looking ears were of entries 8321-18, 8421-21, 8428-19 and

Samaru-83-TZSR-W-1. The worst "looking" ears were of entries 8322-13 and K8.

CORRELATION OF SOME TRAITS

Highly significant correlations were observed between field yield and some

selected traits and also between plant height and lodging. Significant negative

correlations were observed between yield and stalk lodgmg (r =0.7(0), yield and

rust disease (r = -0.751) at 5% probability level. This indicated that yIeld tended to

decrease as the intensity of stalk lodging, rust and ear rot increased. Root lodging (r

= 0.096) and blight (r = 0.021) did not appear to affect yield much. As discussed

earlier blight developed late on most of the entries. Probably this is why it had little

effect on yield. There was significant positive correlation of yield with the number

of ears harvested (r = 0.875, which could indicate yield increase with increase in

number of ears harvested.

Significant positive correlation (r = 0.596) was observed between plant

height and root lodging indicating that root lodging increased as plant height

increased. On the contrary stalk lodging showed negative correlation (r = 0.207)

~ndicating there was a tendency for stalk lodging to decrease as the plant height

mcreased.

The overall results indicated that hybrids evaluated in this trial were superior

to the local varieties KWCA and K8 in almost all the traits except resistance to

blight where KWCA was superior. More evaluation will be continued to verify

the~e results and recommendations made accordingly.

ACKNOWLEDGEMENTS

The author thanks Sarah Nanziri and Margaret Nabasirye for technical

assistance.

REFERENCES

Rubaihayo, E.B. Maize Breeding Annual Reports 1972-1976 and 1986.

DISCUSSION

Question:

Hikwa.

1. You indicated variations in plant stand from 50% to 97%. What

caused such low plant stands (50%) when (according to your

introduction) moisture was not limiting?


163

2. Data on several of your linear regression graphs (dipictinS some

parameters you recorded) seemed to be very scattered, WIth a lot of

outliers, indicating that linear regressions were not the best. What

were your correlation coefficients like?

Answer:

Rubaihayo:

1. There was poor germination in K8 and 8505-5 otherwise the

remaining entries ranged from 90-97.7%.

2. Although the data was scattered the general trend was linear either

upwards or downwards or level. The correlation coefficients were

either strongly negative or positive; slightly positive or slightly

negative. The r values are given in the main paper.


164

OVERVIEW OF THE BURUNDI MAIZE BREEDING PROGRAM

Emmanuel Rufyikiri 1

ABSTRACT

The Burundi Maize Breeding Program has concentrated its efforts on

selection for high yield, earliness and disease resistance. The seleCtion

program is based on population improvement of both local and exotic maize

materials with a view ofdeveloping ope~-pollinated maize cultivars currently