Wheat production is adversely affected by drought stress in many regions of the world. Traditional wheat breeding techniques have only achieved about half the yield progress in affected areas relative to areas receiving adequate moisture. This study was initiated to study trait associations contributing to sustained yield performance under reduced moisture and identify possible quantitative trait loci (QTL) contributing to that performance. To this end, a population of 140 lines from a 'Dharwar Dry' x 'Sitta' cross was grown in Ciudad Obregon, Sonora, Mexico, under different water regimes for two years. Water stress reduced grain yields by about 41% from the 3-irrigation to the 1-irrigation (stressed), and by 28% from the 3-irrigation to the 2-irrigation regime. Line means for grain yield were similar under the 3-irrigation regime but differed under the other regimes. Grain yield was mainly associated with spike density, biomass, and grains m-2 under stress and negatively associated with drought susceptibility index (DSI). Single marker analyses showed that Xwmc48 was significantly associated with DSI values for the stressed regime. Composite interval mapping revealed a coincidence of QTL for grain yield, grain fill rate, spike density, grains m-2, biomass production, biomass production rate, and DSI on chromosome 4A. Chromosome 4A microsatellite marker Xwmc89 was associated with all significant QTL and, in most cases, explained the most phenotypic variation under the stressed regime. The QTL for DSI and grain yield explained up to 41 and 20% of the phenotypic variation, respectively. Microsatellite marker Xwmc89 could be used for marker assisted selection to introgress important gene(s) for production under drought stress from Dharwar Dry.
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