Identification of quantitative trait loci for four morphologic traits under water stress in rice (Oryza sativa L.).

Late season drought coinciding with the rice booting to heading stage affects the development of plant height, panicle exsertion, and flag leaf size, and causes significant yield loss. In this study, a recombinant inbred line population derived from a cross between paddy and upland cultivars was used for data collection of the morphologic traits under well water and drought stress conditions. Drought stress was applied at the stage of panicle initiation in the field in 2002 and at the booting stage in PVC pipes in 2003. The data from stress conditions and their ratios (trait measured under stress condition/trait measured under well water condition) or differences (trait measured under stress condition minus trait measured under well water condition) were used for QTL analysis. Totally, 17 and 36 QTLs for these traits were identified in 2002 and 2003, respectively, which explained a range of 2.58%-29.82% of the phenotypic variation. Among them, six QTLs were commonly identified in the two years, suggesting that the drought stress in the two years was different. The genetic basis of these traits will provide useful information for improving rice late season drought resistance, and their application as indirect indices in rice late season drought resistance screening was also discussed.