the Symposium on Wheats for More Tropical Environments - cimmyt

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104Leaf areaThere should be a small leaf area interms of number and/or size. Althoughit is not easy to generalize. thischaracteristic seems to be essential inorder to reduce evapotranspiration and.hence. enhance drought tolerance (19).TilleringSince <strong>the</strong> number of tillers depends on<strong>the</strong> number of leaves (as tillers areinitiated in leafaxils). it follows that <strong>the</strong>drought-tolerant variety should havereduced tillers (19).Water utilizationThe drought-tolerant line should have<strong>the</strong> ability to efficiently utilize availablewater. Such a variety should maintainits photosyn<strong>the</strong>sis and growth at lowwater availability. The developmentalplasticity of <strong>the</strong> variety should be suchthat it gives an economic yield underwater stress. as well as best yield undergood moisture situations. Thisincreased efficiency in water use couldresult from a restriction on <strong>the</strong> relativeability of <strong>the</strong> plant to extract waterfrom <strong>the</strong> soil during early crop growth.leaving more water to support <strong>the</strong> plantin <strong>the</strong> grain-filling stage. Thischaracteristic might be developedthrough selection of plants with erectleaves and reduced tillering (6).Density toleranceDow (5) showed that maize hybridsresistant to density stress were alsomore drought tolerant. Thus. densitytrials may also help in selection fordrought tolerance. as plants resistant todensity stress should have a relativelygreater ability to withdraw water from<strong>the</strong> soil.Root systemsA good root system is necessary fortolerance to both drought and moisturestress. because it enhances early plantestablishment. as well as efficiency in<strong>the</strong> water-uptake capacity of <strong>the</strong> plant.ConclusionsIn Nigeria. high temperature anddrought constitute problems for wheatproduction. Fortunately, <strong>the</strong>seproblems are not as erratic as are someproblems under rainfed conditions ino<strong>the</strong>r tropical countries. Hightemperatures mainly affect <strong>the</strong> plantduring establishment and tillering andduring <strong>the</strong> grain-filling stage. Hightemperatures are <strong>the</strong> main limitation towheat production in sou<strong>the</strong>rn Nigeria.Drought, on <strong>the</strong> o<strong>the</strong>r hand. is periodic.Drought-tolerant lines/varieties willinvariably enhance water economy.Thus. both heat and drought toleranceare desirable characteristics to beincorporated into Nigerian selections, inorder to stabilize yield and increaseproduction.Performance of adapted wheatgermplasm indicates that yieldsranging from 3 to 4 tlha are possibleunder optimum conditions. Therefore.heat and drought-tolerant lines yielding1.5 to 2.5 tlha under stress conditionsand up to 4 tlha under optimumconditions should be selected. It isdifficult to generalize as to genetic traitswhich enhance heat and droughttolerance, but some of <strong>the</strong>characteristics described above havebeen shown to be relatively effective infield crops. and in wheats in particular.
106References1. Anonymous. 1972. Wheat. InGenetic Vulnerability of MajorCrops. Division of Biology andAgriculture National ResearchCouncil. National Academy ofScience.Washington. D. C..USA. Pp. 151-152.2. Aremu. J.A.• and F.C. Orakwue.1983. Plant Breeding AnnualReport 1982-83. Department ofPlant Science. Ahmadu BelloUniversity. Zaria. Nigeria.3. Asana. RD. 1974. Physiologicalresponses of wheat to early sowingunder non-irrigated cultivation andlate sowing under irrigation. IndianJournal of Genetics 34:109-96.4. Blum. A. 1979. Geneticimprovement of drought resistancein crop plants: A case of sorghum.In Stress Physiology in Crop Plants.H. Mussel and RC. Staples. eds.Wiley Interscience. New York. NewYork, USA. Pp. 429-445.5. Dow. E.W. 1981. Resistance todrought and density stress inCanadian and European maize (Zeamays L.) hybrids. M.Sc. Thesis.University of Guelph. Ontario,Canada.6. Evans. L.T.. I.F. Wardlaw andRA. Fischer. 1975. Wheat. In CropPhysiology: Some Case Histories.L. T. Evans. ed. CambridgeUniversity Press. Cambridge,England. Pp. 101-149.7. Fischer. RA.. and R Maurer. 1978.Drought resistance in wheatcultivars: 1. Grain yield response.Australian Journal AgriculturalResearch 29:897-912.8. Fischer. K. S .• E.C. Johnson andT.O. Edmeades. 1983. Breeding andselection for drought resistance intropical maize. CIMMYT. EI Batan.Mexico.9. Friend. F.D.C. 1966. The effect oflight and temperature on <strong>the</strong>growth of cereals. In The Growth ofCereals and Grasses. F. L. Milthorpeand J.D. Ivins. eds. Butterworths.London. England. Pp. 181-199.10. Levitt. J. 1972. Responses of Plantsto Environmental Stresses.Academic Press. New York. NewYork. USA.11. MacDowall. F.D.H. 1973. Growthkinetics of marqUiS wheat versusmorphogenic dependence.Canadian Journal of Botany51:1259-65.12. May. L. H.. and RL. Milthorpe.1962. Drought resistance of cropplants. Field Crop Abstracts15:171-179.13. Olugbemi, L.B. 1973. Wheatresearch in Negeria. In Proceedingsof <strong>the</strong> Fourth FAOlRockefeUerFoundation Wheat Seminar.Tehran. Iran. May 21-June 5. 1973.Pp.92-96.14. Olugbemi. L.B.. F.C. Orakwue andE.V. Aguda. 1981. Preliminarystudies on <strong>the</strong> effects of varieties.seed rates and levels of nitrogenfertilizers on <strong>the</strong> yield attributes ofwheat (Triticum aesttvum L.) underNigerian conditions. Smari Journalof Agricultural Research 1:95-99.
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The International Maize and Wheat I
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3AcknowledgementsThe Tropical Wheat
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5Wheat Production in Bangladesh: It
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7Chemical Control ofHelmtn.thosport
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1 9PrefaceThe international worksho
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uToluca, a high-elevation station a
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13In Bangladesh. many farmers' fiel
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global cooperation that permits apo
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17Recognizing the
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19With UNDP assistance. CIMMYTexpan
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4 21Introduction to the</st
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23grain-filling stages are required
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Table 1. Countries growing whut in
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27Month of sowing and month afterfl
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29. Table 3. Correlation coefficien
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31Earliness-Earliness is needed if
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33requires more than technical solu
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3~from other crops
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37Table 2. Advanced lines selected
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39If Bol1via does not radically cha
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41Table 5. Water efficiency utiliza
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4320-year period. Also indicated ar
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Table 2. (Con't)Cross and pedigreeN
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47respectively. for central AlaJuel
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49Table 1. Climatological data, Fra
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51Wheat Research in the</st
Page 55 and 56: 53Table 3. Average yield of best wh
Page 57 and 58: Selection of Wheats forSubtropical
Page 59 and 60: Nigeria is high temperature. South
Page 61 and 62: 59Wheat Production in Bangladesh:It
Page 63 and 64: 61Research PrioritiesVarietal devel
Page 65 and 66: 63Wheat Improvement Programsfor <st
Page 67 and 68: 65In India, a series of wheat varie
Page 69 and 70: 67in temperature are capable of cau
Page 71 and 72: 69primarily due to a lack of financ
Page 73 and 74: 71Triticale ImprovementRegular bree
Page 75 and 76: 73The climate in this region is war
Page 77 and 78: 75Recently, the pe
Page 79 and 80: 77Variety improvement must also bec
Page 81 and 82: 79those areas that are suitable for
Page 83 and 84: Wheat Growing in the</stron
Page 85 and 86: 83Thailand Winter Cereals ProgramP.
Page 87 and 88: Many farmers are now exploring <str
Page 89 and 90: 87crop is present, and known. at pl
Page 91 and 92: 6 ~89Contributed PapersI. BreedingB
Page 93 and 94: 91area at flowering. Vegetative vig
Page 95 and 96: 93of the plants se
Page 97 and 98: Screening for tropical adaptationTh
Page 99 and 100: 97Table 3. Best advanced lines of b
Page 101 and 102: 99Table 4. Highest yielding advance
Page 103 and 104: 101very late, high temperatures at
Page 105: 103hence, select for drought tolera
Page 109 and 110: 107Breeding Wheats for Heatand Drou
Page 111 and 112: 109unit area. However, looking at s
Page 113 and 114: 111Identifying Wheats Adapted to Mo
Page 115 and 116: 113standard date for sowing. In spi
Page 117 and 118: 115transferred into high-yielding a
Page 119 and 120: 117Table 1. Chemical properties of
Page 121 and 122: 119• Resistance to shattering•
Page 123 and 124: 121References1. Araujo. J.E.G. 1949
Page 125 and 126: 123hours of sunlight monthly. Altho
Page 127 and 128: 125Screening Wheats for QualityA. A
Page 129 and 130: 127Wide Crosses and New Genesfor Wh
Page 131 and 132: 129The introduction of alien geneti
Page 133 and 134: 131averaged about 2.5 tonslha. Howe
Page 135 and 136: 133must also demonstrate a yieldadv
Page 137 and 138: 135II. Diseases and Disease Control
Page 139 and 140: 137beaker with 200 ml sterilized di
Page 141 and 142: 139Table 1. (Cont'd)Resistance reac
Page 143 and 144: 141Identification ofSources of Resi
Page 145 and 146: 143References1. Adlakha, K, RD. Wil
Page 147 and 148: Breeding Wheats with Resistanceto H
Page 149 and 150: 147conditions. whereby infectionper
Page 151 and 152: 149CIMMYT Methods for Screening Whe
Page 153 and 154: 151Selection under Field Conditions
Page 155 and 156: 153February. Environmental conditio
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156Each trla1 had two replications
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157References1. De Milliano. W.A.J.
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159Shinchunaga and descendants). se
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161Wheat Breedingfor Scab Resistanc
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163References1. Andersen. A.L. 1948
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16526. Luzzardi. G.C.. C.R. Pierobo
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18748. Nisikado. Y. 1958. Studies o
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Head Scab Screening Methods Used at
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171Wheat spikes are spray-inoculate
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173Reference.1. Bekele. G.T. 1984.
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1'71SThe species and varieties with
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177suspension. This method has prov
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179How the pathoge
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18112. Takegami, S. 1961. Proceedin
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183Documented Foot RotDlseaBes in W
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185References1. Anderson. N.A. 1982
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187against leaf rust by the
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-188Distribution and Importance ofR
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191Surprisingly. little or no stem
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193temperatures. but this differenc
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19~14. Lapis. D.B. and M.C. Kamatoy
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197According to a new criterionesta
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199Loss in yield is directly propor
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Chemical Control ofHelminthosportum
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203H. sattvum on foliage and heads
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205Table 1. Mean number of lesions
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20'7Table 4. Effect on lelf spot in
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209III. AgronomyPhysiological Limit
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Table 1. Actual and pouible wheat1l
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213Table 2. Wheat yield determinati
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216unpublished). A role of thumb de
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217seasonally and cloudiness persis
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219developmental periods. to around
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221Growth at high temperaturesEarly
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CertainlY crop growth rates in exce
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225rice, another C
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227105% that of C306 for th
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22913. Fischer. RA.. I. Aguilar. R
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Soil Management as an Alternativefo
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233water content in the</st
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23~Tolerance to soil aciditySoil ac
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237applied without increasing <stro
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The Cerrados: Future WheatProductio
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241there is utiliz
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243• Ammonium sulfate [(NH4)2S04]
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245Physical Soil ProblemsThe soils
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247program. these
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249References1. Commisao Norte Bras
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251was rather poor
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253Tolerant vartettes-The yield ofv
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255Alternative locations-An evaluat
Page 259 and 260:
257Wheat Production Constraintsand
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259numerical grading which showed <
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261directed towards minimum loss of
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'.2636. Cheng, C.P. 1977. Wheatprod
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Wheat in Rice...BasedCropping Syste
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267Rice varietiesAs mentioned above
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269A problem of declining yields ha
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271_.z.:::-~:J.."•._,:.\--_.r+++v
Page 275 and 276:
273Agronomic Practices and Problems
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275water percolation in rice. For w
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277Rice-Wheat Cropping Systemsin So
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279Table 1. Yield and economic retu
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281was higher with the</str
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283to compete with othe</st
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for tropical environments. Highesta
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287can be used. The computer is a u
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289The computer has become a valuab
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291IV. SeedWheat Seed Production,St
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293On average, no more that 100 mm
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295Storage in 20-liter biscuit or k
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Production, Storageand Marketing of
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299true to type. are selected and t
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301discussed and ascertained; <stro
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303V. EconomicsWheat in the
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305than in Asia and Africa (about 1
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307wheat consumption). However, <st
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309These changing consumption patte
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311Finally. it should be clarified
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313in areas where wheat yields arer
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31510. FAO. 1982. The bread economy
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317Lowlands withinadequate dry-seas
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319Table 1. Private and social prof
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The Local-Use Approach to t
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323fired oven has been used at oneu
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325ControlliDg fungal diseasesThe i
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The Relative Priority andEconomics
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329Comparative MarketPrices of Stap
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331References1. Agricultural Extens
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Table 1. Area, average yield and to
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Table 3. Annual domestic wheat prod
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337Table 5. Financial costs of whea
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Comments'D.L. WiDkelmaDll, DIrector
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7341------_1Closing Remarks, <stron
Page 345 and 346:
343Table 1. Probleml for th
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345While efforts to develop wheatge
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347Appendix IIWheat Pests and Disea
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349Appendix IIIParticipants. <stron
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351NigeriaMr. Ahmed M. FalakiResear
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353CIMMYT Staff. MexicoMr. Robert D
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