the Symposium on Wheats for More Tropical Environments - cimmyt

Selection of Wheats forSubtropical EnvironmentsFor <strong>the</strong> past several years. a cooperativeprogram for <strong>the</strong> genetic improvement ofwheat has been conducted by INIA.Mexico. and CIMMYT at <strong>the</strong> CIANOexperiment station in Ciudad Obregon.Sonora: <strong>the</strong> objective has been <strong>the</strong>development of germplasm tolerant tohigh temperature and drought. Thestrategy utilized has been that of <strong>the</strong>selection of early generations in <strong>the</strong>Yaqui Valley of Sonora. These materialsare sown early in October whentemperatures are high (23°C meantemperature). Irrigation is applied atgermination and again. after 72 days. atflowering. Individual plant selection ispracticed with regard to agronomic typeand disease resistance. Advancedgenerations are evaluated in subtropicalenvironments. in sou<strong>the</strong>rn Sinaloa andcentral Tamaulipas. As a result of <strong>the</strong>setrials. <strong>the</strong> experimental lineBuckbuck"S"-PVN"S" has beendeveloped. In subtropical San LorenzoValley. its yield has been 3630 kg/hat15% above <strong>the</strong> mean of presentcommercial varieties.ConclusionsAs a result of research in MeXico. it ispossible to obtain wheat yields of morethan 4 Uha under subtropicalenvironments. It is necessary to fur<strong>the</strong>rimprove <strong>the</strong> yield potential ofcommercial varieties for <strong>the</strong>se areasthrough breeding. Selection must bemade for high yield and better toleranceto high temperature and diseases. Thetrials must be conducted underappropriate types of environmentalconditions.Wheat yields in <strong>the</strong> subtropics can alsobe improved substantially by improvingagronomic practices. especially suchfactors as planting date and density.fertilization and insect and weedcontrol.Wheat cultivation in San Lorenzo.Sinaloa. and <strong>the</strong> Huasteca inTamaulipas. covering an area of about200,000 hectares in a subtropicalclimate. represents a productionpotential of approximately one milliontons of wheat annually. 19% ofMexico's entire annual production.Table 1. Yields of selected commercial varieties in <strong>the</strong> traditional wheat-growing areas of<strong>the</strong> nonhwest and three subtropical environments of MexicoYield (kg/ha)NorthwestSubtropical environmentsYaqui Valley Culiacan San Lorenzo SantiagoVariety Valley Valley ValleyUres 81 7,300 6,700 3,100 700Sonoita 81 7,200 4,500 1,900 400Seri 82 7,000 6,100 3,900 900Glennson 81 6,900 5,700 2,900 800Genaro 81 6,900 6,000 3,700 600Mean 7,100 5,800 3,100 700