Integrative Approaches to Dissecting Yield QTL for Drought Tolerance in Rice.

The International Rice Research Institute estimates that it takes about 1,432 liters of water to produce 1 kg of rice, which accounts for 34-43% of the global irrigation resources. Drought stress is a major constraint to rainfed rice production that affects ~23 million ha worldwide. Drought during the reproductive stage can reduce rice yield up to 80%. Under the current and imminent climate change scenarios, scarcity of quality water resources will become an increasing threat to rice production and productivity. Drought tolerance is a polygenic trait. Identifying genes controlling drought tolerance traits will provide clues to designing strategies for developing varieties with improved water use efficiency through gene introgression. Advanced generation progeny of two bi-parental populations (Cocodrie x Vandana; Cocodrie x N-22) and the Rice Diversity Panel 1 (RDP1) were screened in two replications under 15 days of reproductive stage drought stress under field conditions at Crowley, LA. Yield traits, such as panicle number, fertile seed number and seed weight were measured from the populations. Genotyping was performed using 187 SSR markers distributed across the 12 chromosomes. Genetic mapping showed that the phenotypic variance explained by the quantitative trait loci (QTL) for all traits ranged from 6.0 to 12.4%. QTL for seed weight were detected on chromosomes 9 and 12 that accounted for 8.1 and 7.3% of the phenotypic variance, respectively. QTL for seed number were co-localized on the same chromosomes with R² of 12.4 and 9.0%, respectively. Through comparative analysis of the genes within QTL regions with the drought-induced transcriptome data, a number of candidate genes with possible roles in drought stress tolerance were identified. These genes are being investigated for their expression pattern among the extreme drought-resistant and sensitive lines selected from both the bi-parental populations as well as the RDP1. The results will be presented in detail.