Tagging quantitative trait loci associated with grain yield and root morphological traits in rice (Oryza sativa L.) under contrasting moisture regimes

Plant breeding for drought-prone habitats envisages a favorable combination of grain yield and drought resistance. Though several components enhancing drought resistance have been identified in rice,their association with grain yield, under low-moisture stress, has been established in very few instances. We attempt to study the associations between rice grain yield and root system parameters both at phenotypic and genotypic levels. The doubled haploid population of IR64/Azucena was evaluated for root related traits at peak vegetative stage and grain yield related traits under both low-moisture stress and non stress conditions. ‘Mean environment’ was computed for yield related traits. Correlation and QTL mapping was attempted to find out the associations. The correlation between maximum root length and grain yield was positive under stress and negative in non stress. Genotypes with thicker and deeper roots, manifested higher biomass and grain yield under stress. Only one QTL found to increase days to flowering in non stress was also found to influence root volume and dry weight negatively under stress. The study suggests that loci enhancing grain yield and related traits were not pleiotropic with loci for desirable root morphological traits studied under low-moisture stress at vegetative stage, in the genetic material used in the study. It is thus possible to combine higher grain yield and desirable root morphological traits, favorably, to enhance productivity of rice under low-moisture stress. In rainfed ecologies, where deep roots contribute to enhanced drought resistance in rice, the results indicate the possibility of combining drought resistance with higher levels of grain yield. This revised version was published online in August 2006 with corrections to the Cover Date.