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178Inheritance of resistance to scabSchroeder and Christensen (11)reported that <strong>the</strong> resistance of wheat tohead scab was a quantitative charactercontrolled by polygenes. In recentyears. Chinese workers have alsoshown that resistance of wheat tocolonization by G. zeae is controlled bypolygenes (27). The resistance of Fistends to resemble <strong>the</strong> resistant parent.and exhibits obvious heterosis.Backcrossing with resistant parentstends to increase resistance. XiaSui-shing. Zhou Chau-fei and Quia Cunming(personel communication) studied<strong>the</strong> inheritance of scab resistance inSu-mai 3 and Wang-shui-bai andobtained similar results. Yu Yu-jin (26)studied <strong>the</strong> inheritance of resistance ofSu-mai 3 by monosomic analysis;results indicated that at least five pairsof genes which determine resistance tohyphal spread were located onchromosomes lB. 2A. 5A. 6D and 7D.Chen Chu-huo (2). using a 4 x 4 halfdiallelscheme with two resistant andtwo susceptible parents to study <strong>the</strong>inheritance of resistance in wheat.suggested that Su-mai 3 and WangzhouHong-he-shang (Red Monk) might havemore dominant genes for controllingresistance: <strong>the</strong>y demonstrated highgeneral combining abll1ty for redUcing<strong>the</strong> rate of diseased spikelets in <strong>the</strong>irprogenies. It appears that <strong>the</strong>inheritance of resistance to scab ismainly governed by additive genes. butnon-additive genes also have asignificant effect. The genes controllingresistance were partially dominant. Itwas found in diallel crosses that <strong>the</strong>rewas a significant positive correlationbetween resistance and plant height orspike length. and a significant negativecorrelation between resistance andspikelet density in F2 populations.Various workers have suggested that<strong>the</strong> heritabll1ty of resistance of wheat toscab is low.Sources of resistance to scabThe studies of <strong>the</strong> cooperative researchteam have demonstrated that sources ofscab resistance come mainly fromcommon wheats. Some Chinesevarieties with high and stable resistancehave been <strong>the</strong> best available sources ofresistance among <strong>the</strong> world collection;<strong>the</strong> resistance in exotic varieties has notexceeded <strong>the</strong> resistance of <strong>the</strong>sevarieties. Su-mai 3 has been introducedinto many countries of <strong>the</strong> world. and<strong>the</strong>re has been no report that itsresistance is equal to or better thanlocal varieties in those countries.Nanjing 7840. a new source ofresistance. is derived from crosses of(Aurora x Anhui 11) F2 x Su-mai 3. andmany resistant varieties or lines withgood agronomic characters have beenderived from it (29).Crosses between moderately resistantand susceptible varieties may yieldhybrids with higher resistance than<strong>the</strong>ir parents. The well-known resistantvariety Su-mai 3 was bred through <strong>the</strong>hybridization of <strong>the</strong> moderatelysusceptible varieties. Funo and Taiwanwheat. The crossing of <strong>the</strong> moderatelyresistant varieties. Jingzhou 1 and Sumai2. also produced progenies withhigh and stable resistance.Some materials of <strong>the</strong> genus Secale areano<strong>the</strong>r source of resistance. Jingzhou1 was derived from <strong>the</strong> hybrid of Nanda2419 and Jingzhou rye. Jingzhou 66(MS-MR) was derived from <strong>the</strong>combination (Funo x durum) (Nanda2419 x rye). Jingzhou 1 has beenadopted as a common parent in <strong>the</strong>breeding programs for resistance toscab in South China.EpidemiologyOccurrence of scabcUsease in <strong>the</strong> fieldA rice-wheat cropping system is foundin most of <strong>the</strong> regions of <strong>the</strong> middle andlower reaches of <strong>the</strong> Yangtse River. Theinitial inocula of scab usually comesfrom <strong>the</strong> peri<strong>the</strong>cia on rice stubble.
179How <strong>the</strong> pathogen oversummers andoverwinters after <strong>the</strong> wheat harvest andhow <strong>the</strong> peri<strong>the</strong>cia reproduce areimportant factors for forecasting scabepidemics. Xu Run-cheng and HuangZhen-xing (21) suggested that G. zeaecan only survive for a short time underflooding; <strong>the</strong>refore. <strong>the</strong> organism cannotoversummer on <strong>the</strong> soil surface inpaddies after rice has been harvested.although it can survive on <strong>the</strong> plantbase. leaf sheaths and rice grains and<strong>the</strong>n be transferred to <strong>the</strong> soil (5). LiangXun-yi and Wang Qing-sheng (personalcommunication) have confirmed that<strong>the</strong> pathogen can oversummer on rice.on dry soil surfaces. on <strong>the</strong> shady sideof piles of wheat straw and on <strong>the</strong>remains of wheat stems and grainsscattered over <strong>the</strong> threshing ground. aswell as on rice straw and wi<strong>the</strong>red rapestems in fields.Research of <strong>the</strong> Hunan AgriculturalCollege suggests that <strong>the</strong> pathogenaffects not only wheat and barley. butalso such crops as corn. sorghum andcotton. It may also infect weeds, suchas Cynodon dactylon (L.) and Pers. andproduces peri<strong>the</strong>cia on <strong>the</strong> debris.The Shanghai Academy of AgriculturalSciences (1975 to 1977) and <strong>the</strong>Suzhou Institute of AgriculturalSciences (1977 and 1980) made a seriesof observations on <strong>the</strong> dissemination ofmature ascospores. The resultsindicated that aerial ascospores couldbe trapped throughout <strong>the</strong> year. Thisindicates that infected rice stubble.grains and wheat debris remaining infields and aerial ascospores which havefallen on <strong>the</strong> soil are all sources ofinoculum. causing peri<strong>the</strong>cia formationon rice stubble early in <strong>the</strong> spring. Thepathogen overwinters as mycelia onrice stubble.Ye Hua-zhi (24) studied <strong>the</strong> biology ofG. zeae and showed that <strong>the</strong>temperature for peri<strong>the</strong>cial formationranged from 5 to 35°C and. forascospore production. 13 to 33°C. withan optimum of 25 to 28°C. Thedischarge of ascospores is controlled bymoisture and precipitation. Thenumber of ascospores released isgreater at night (8 p.m. to 8 a.m.) thanby day (8 a.m. to 8 p.m.), and is greateron rainy days. The peak for sporedischarge is from 10 p.m. to 8 a.m.and. more specifically. from midnight to6 a.m. Germination of ascosporesoccurs at 4 to 35°C. with an optimumof 25 to 28°C. Germination percentagemay reach more than 90% within 4 to8 hours at a temperature of 25 to 30°C.The ascospore can germinate withoutfree water. but germination is markedlyinhibited when relative humidity is low;it doesn't occur below 81%.ForecastingVarious ma<strong>the</strong>matical models havebeen established in China forforecasting scab epidemics overdifferent'areas. The best is <strong>the</strong> oneproposed by <strong>the</strong> workers in HubeiProvince (6). Mter haVing qualitativelyanalyzed <strong>the</strong> key factors causingepidemics. and haVing quantitativelydefined <strong>the</strong> relationship between <strong>the</strong>degree of epidemic and <strong>the</strong> keymeteorological factors in GuangjiCounty over a period of 21 years. <strong>the</strong>cooperative group suggested thatepidemics depend on <strong>the</strong> interaction of<strong>the</strong> pathogen and <strong>the</strong> host with fourmeteorological factors. rainfall (R), daysof rain (Rd). relative humidity (Rh). andsunlight hours (S). The statistical modelfor calculating <strong>the</strong> incidence of diseasewas established as:Y:;:[sin (47.72 IgQ-33.64»). whereQ :;: RRdRhISThis indicates that <strong>the</strong> outbreak ofepidemics varies according to climaticand atmospheric conditions, but <strong>the</strong>semeteorological factors can be utilized toforecast epidemics for a province or fora certain area.From 1975 to 1981, short-termforecasting of scab epidemics was doneby <strong>the</strong> Shanghai Academy of
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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
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
Page 157 and 158: 156Each trla1 had two replications
Page 159 and 160: 157References1. De Milliano. W.A.J.
Page 161 and 162: 159Shinchunaga and descendants). se
Page 163 and 164: 161Wheat Breedingfor Scab Resistanc
Page 165 and 166: 163References1. Andersen. A.L. 1948
Page 167 and 168: 16526. Luzzardi. G.C.. C.R. Pierobo
Page 169 and 170: 18748. Nisikado. Y. 1958. Studies o
Page 171 and 172: Head Scab Screening Methods Used at
Page 173 and 174: 171Wheat spikes are spray-inoculate
Page 175 and 176: 173Reference.1. Bekele. G.T. 1984.
Page 177 and 178: 1'71SThe species and varieties with
Page 179: 177suspension. This method has prov
Page 183 and 184: 18112. Takegami, S. 1961. Proceedin
Page 185 and 186: 183Documented Foot RotDlseaBes in W
Page 187 and 188: 185References1. Anderson. N.A. 1982
Page 189 and 190: 187against leaf rust by the
Page 191 and 192: -188Distribution and Importance ofR
Page 193 and 194: 191Surprisingly. little or no stem
Page 195 and 196: 193temperatures. but this differenc
Page 197 and 198: 19~14. Lapis. D.B. and M.C. Kamatoy
Page 199 and 200: 197According to a new criterionesta
Page 201 and 202: 199Loss in yield is directly propor
Page 203 and 204: Chemical Control ofHelminthosportum
Page 205 and 206: 203H. sattvum on foliage and heads
Page 207 and 208: 205Table 1. Mean number of lesions
Page 209 and 210: 20'7Table 4. Effect on lelf spot in
Page 211 and 212: 209III. AgronomyPhysiological Limit
Page 213 and 214: Table 1. Actual and pouible wheat1l
Page 215 and 216: 213Table 2. Wheat yield determinati
Page 217 and 218: 216unpublished). A role of thumb de
Page 219 and 220: 217seasonally and cloudiness persis
Page 221 and 222: 219developmental periods. to around
Page 223 and 224: 221Growth at high temperaturesEarly
Page 225 and 226: CertainlY crop growth rates in exce
Page 227 and 228: 225rice, another C
Page 229 and 230: 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
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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
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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
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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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