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288sorghum. can be calculated. This maybe useful for agronomists and breederswhen planning visits to experiments atvarious locations.Van Keulen (12.19.20) developed acalculation method for estimating cropyields at Production Level 2 where. attimes during <strong>the</strong> growing season. watermay be a limiting factor. The degree ofwater shortage for <strong>the</strong> crop. duringdifferent periods. can be calculated.This gives an indication of whatamount of irrigation water is necessaryto achieve potential production andwhen to apply supplemental irrigation.Existing simulation models forProduction Level 3 are still in apreliminary stage. for use only byspecialized scientists (12.22).DiscussiuDOne of <strong>the</strong> problems in interpreting <strong>the</strong>results of long-term yield trials is <strong>the</strong>assessment of <strong>the</strong> relative influence ofgenotype characteristics. environmentalfactors and management practices on<strong>the</strong> final results in a particularsituation. This difficulty limits <strong>the</strong>possibilities for extrapolation of resultsto o<strong>the</strong>r areas. where less-detailedexperiments have been carried out orfor generalization over longer timeperiods. The use of models. in which<strong>the</strong> influence of such factors isdescribed quantitatively. may behelpful in analyZing experimentalresults and applying <strong>the</strong>m for <strong>the</strong>purpose of prediction. At present.simple models at Production Levels 1and 2 may be useful to agronomists.breeders and planners.Table 1 shows that <strong>the</strong> total heat sumfor <strong>the</strong> development of wheat fromemergence to maturity is considerablylower than for rice. One interestingchallenge to breeders could be toincrease this total heat sum: this mightfacilitate <strong>the</strong> introduction of wheat intowarmer areas. Preventive breeding mayalso be an important element of overallcrop improvement. in order to prevent<strong>the</strong> increase of minor pests andpathogens already present in <strong>the</strong>ecosystem and to preclude futureproblems (2).In <strong>the</strong> model by Van Keulen and deMilliano (21). actual grain numbers arenot simulated: ra<strong>the</strong>r. a function isintroduced in <strong>the</strong> model representingthis sink-effect. When <strong>the</strong> maximumtemperature is above 25°C in <strong>the</strong> tendayan<strong>the</strong>sis period. only a fraction ofavailable carbohydrates is translocatedto <strong>the</strong> grain. This fraction declines withincreasing temperatures. reaching 0 at35°C. This model worked well forZambia. but not for Niger. In Niamey.Niger. maximum air temperatureduring an<strong>the</strong>sis is between 35 and40°C. In reality. a grain yield of 2.4 Uhacan be achieved. which is more thantwice <strong>the</strong> amount calculated by <strong>the</strong>model (1.1 Uha). even if <strong>the</strong> influence ofmaximum air temperature on seed setis removed. EVidently. <strong>the</strong> model needsfur<strong>the</strong>r improvement for widerapplication. especially for areas wheremaximum air temperatures during <strong>the</strong>growing season exceed 30°C.How existing cultivars behave underhigh temperatures is still a subject ofstudy (10.11.24). Vernalization andphotoperiod sensitivity can delay <strong>the</strong>rate of plant development untilan<strong>the</strong>sis. but <strong>the</strong> delay may not bematched with an increase in number ofgrains per spikelet or per spike (10).Genotypes which are relativelyinsensitive to vernalization andphotoperiod and. hence. early. appearto be best at many locations. especiallyat hotter. lower elevations (11). Most of<strong>the</strong> models mentioned here apply togenotypes (bread and durum wheats)which are relatively insensitive tovernalization and photoperiod andfollow <strong>the</strong> universal heat sum well. Careshould be taken with <strong>the</strong> application ofdata and experience collected inwestern high-input systems to o<strong>the</strong>ragricultural systems (6.17). Therefore.local research should precedeproduction.
289The computer has become a valuableassistant to <strong>the</strong> agronomist (16), and isa useful tool for performing simulations.The thinking, data interpretation andsyn<strong>the</strong>sis, however, still need to bedone by man. Where money is alimiting factor, time is usually not aslimiting. In <strong>the</strong>se areas, <strong>the</strong> calculationmethods mentioned can be performedwith a desk calculator.The use of simulation models foragrometeorological purposes indeveloping countries was recognized by<strong>the</strong> World Meteorological Organization.In 1983, <strong>the</strong>y organized a workshop inWageningen, Ne<strong>the</strong>rlands, to trainstudents from various tropical countries(20). The Centre for World Food Studiesalso developed simulation models fordifferent countries, such as Bangladesh,Thailand and Indonesia. Some of <strong>the</strong>models are available in a simple formfor use by individuals and researchcenters.AcknowledgementsThe authors wish to thank CIMMYT forinviting <strong>the</strong>m to present this paper, andR Villareal and S. Waddington forcritical review of <strong>the</strong> article.References1. Azzi, G. 1927. Le climat du ble dansIe monde: les bases ecologiques de laculture mondiale du ble. FAO.Rome, Italy.2. Buddenhagen, I.W., and O.M.B. DePonti. 1983. Crop improvement tominimize future losses to diseasesand pests in <strong>the</strong> tropiCS. FAO PlantProtection Bulletin 31:11-30.4. Ciccarone, A. 1947. II problemadelle ruggini dei grani in Etiopia.Tre anni di osservazioni (1938,1939, 1940). Instituto Agronomicoper l'Africa Italiana, Florence, Italy.5. CIMMYT. 1983. World Wheat Factsand Trends Report 2. CIMMYT,Mexico.6. De MUUano, W.A.J. 1983.Improvement of wheat in Zambiausing incomplete resistance againstrusts. PhD Thesis. State AgriculturalUniversity, Wageningen,Ne<strong>the</strong>rlands.7. Fuggles-Couchman, N.R 1951.Wheat production in Tanganyika.World Crops 3:183-187.8 . Harrington, L.W., S. Sat-thapornand C. Chavewong. 1984. GroWingwheat in Thailand: An overview ofeconomic issues. 1984 AnnualWheat Workshop, Chiang Mai,Thailand, January 21-22, 1984.9. Hurd, E.A. 1981. Status of researchand production, Zambia. InProceedings of <strong>the</strong> Wheat Workshop,J.A. Toogood, ed. Mount MakuluResearch Station, ChUanga, Zambia.10. Midmore, D.J., P.M. Cartwright andRA. Fischer. 1982. Wheat intropical environments: I. Phasicdevelopment and spike size. FieldCrops Research 5: 185·200.11. Midmore, D.J., P.M. CartWright andRA. Fischer. 1~84. Wheat intropical environments. II. Cropgrowth and grain yield. Field CropsResearch 8:207.227. I3. Ca<strong>the</strong>rinet, M., and M. Miche. 1967.Le ble dans les pays d'Mriquecontinentale tropicale d'expressionFrancaise. L'Agronomie tropicale22:933-979.
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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
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53Table 3. Average yield of best wh
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Selection of Wheats forSubtropical
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Nigeria is high temperature. South
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59Wheat Production in Bangladesh:It
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61Research PrioritiesVarietal devel
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63Wheat Improvement Programsfor <st
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65In India, a series of wheat varie
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67in temperature are capable of cau
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69primarily due to a lack of financ
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71Triticale ImprovementRegular bree
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73The climate in this region is war
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75Recently, the pe
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77Variety improvement must also bec
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79those areas that are suitable for
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Wheat Growing in the</stron
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83Thailand Winter Cereals ProgramP.
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Many farmers are now exploring <str
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87crop is present, and known. at pl
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6 ~89Contributed PapersI. BreedingB
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91area at flowering. Vegetative vig
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93of the plants se
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Screening for tropical adaptationTh
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97Table 3. Best advanced lines of b
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99Table 4. Highest yielding advance
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101very late, high temperatures at
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103hence, select for drought tolera
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106References1. Anonymous. 1972. Wh
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107Breeding Wheats for Heatand Drou
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109unit area. However, looking at s
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111Identifying Wheats Adapted to Mo
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113standard date for sowing. In spi
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115transferred into high-yielding a
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117Table 1. Chemical properties of
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119• Resistance to shattering•
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121References1. Araujo. J.E.G. 1949
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123hours of sunlight monthly. Altho
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125Screening Wheats for QualityA. A
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127Wide Crosses and New Genesfor Wh
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129The introduction of alien geneti
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131averaged about 2.5 tonslha. Howe
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133must also demonstrate a yieldadv
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135II. Diseases and Disease Control
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137beaker with 200 ml sterilized di
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139Table 1. (Cont'd)Resistance reac
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141Identification ofSources of Resi
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143References1. Adlakha, K, RD. Wil
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Breeding Wheats with Resistanceto H
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147conditions. whereby infectionper
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149CIMMYT Methods for Screening Whe
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151Selection under Field Conditions
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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
Page 239 and 240: 237applied without increasing <stro
Page 241 and 242: The Cerrados: Future WheatProductio
Page 243 and 244: 241there is utiliz
Page 245 and 246: 243• Ammonium sulfate [(NH4)2S04]
Page 247 and 248: 245Physical Soil ProblemsThe soils
Page 249 and 250: 247program. these
Page 251 and 252: 249References1. Commisao Norte Bras
Page 253 and 254: 251was rather poor
Page 255 and 256: 253Tolerant vartettes-The yield ofv
Page 257 and 258: 255Alternative locations-An evaluat
Page 259 and 260: 257Wheat Production Constraintsand
Page 261 and 262: 259numerical grading which showed <
Page 263 and 264: 261directed towards minimum loss of
Page 265 and 266: '.2636. Cheng, C.P. 1977. Wheatprod
Page 267 and 268: Wheat in Rice...BasedCropping Syste
Page 269 and 270: 267Rice varietiesAs mentioned above
Page 271 and 272: 269A problem of declining yields ha
Page 273 and 274: 271_.z.:::-~:J.."•._,:.\--_.r+++v
Page 275 and 276: 273Agronomic Practices and Problems
Page 277 and 278: 275water percolation in rice. For w
Page 279 and 280: 277Rice-Wheat Cropping Systemsin So
Page 281 and 282: 279Table 1. Yield and economic retu
Page 283 and 284: 281was higher with the</str
Page 285 and 286: 283to compete with othe</st
Page 287 and 288: for tropical environments. Highesta
Page 289: 287can be used. The computer is a u
Page 293 and 294: 291IV. SeedWheat Seed Production,St
Page 295 and 296: 293On average, no more that 100 mm
Page 297 and 298: 295Storage in 20-liter biscuit or k
Page 299 and 300: Production, Storageand Marketing of
Page 301 and 302: 299true to type. are selected and t
Page 303 and 304: 301discussed and ascertained; <stro
Page 305 and 306: 303V. EconomicsWheat in the
Page 307 and 308: 305than in Asia and Africa (about 1
Page 309 and 310: 307wheat consumption). However, <st
Page 311 and 312: 309These changing consumption patte
Page 313 and 314: 311Finally. it should be clarified
Page 315 and 316: 313in areas where wheat yields arer
Page 317 and 318: 31510. FAO. 1982. The bread economy
Page 319 and 320: 317Lowlands withinadequate dry-seas
Page 321 and 322: 319Table 1. Private and social prof
Page 323 and 324: The Local-Use Approach to t
Page 325 and 326: 323fired oven has been used at oneu
Page 327 and 328: 325ControlliDg fungal diseasesThe i
Page 329 and 330: The Relative Priority andEconomics
Page 331 and 332: 329Comparative MarketPrices of Stap
Page 333 and 334: 331References1. Agricultural Extens
Page 335 and 336: Table 1. Area, average yield and to
Page 337 and 338: Table 3. Annual domestic wheat prod
Page 339 and 340: 337Table 5. Financial costs of whea
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Comments'D.L. WiDkelmaDll, DIrector
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7341------_1Closing Remarks, <stron
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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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