Validation for drought tolerance genotypes in SURIN1 backcross introgression lines

Abstract

Rice growing areas in northeast Thailand are mostly is under rainfed lowland condition. Grain yield is low and vary depends on amount and distribution of rainfall. Drought is a major problem which can occur any time during growing period, early, mid and late season. Late season drought commonly occurs, causing significant yield reduction. Therefore breeding program emphasis on tolerance to late season drought (flowering stage) for maintaining yield production under drought condition will be evaluated. In collaboration between Rice research institute and BIOTEC Thailand, Surin1 drought tolerant rice population had been developed by molecular backcrossing. So far, the population had been advanced generation to BC3F5. In this study, total of 90 lines from this population was evaluated for under late season drought at Chum Phae Rice Research Center, Khon Kaen. There were 2 growing conditions, well water and drought stress at flowering stage. Under drought stress condition, water was drained out from experimental plot at panicle initiation stage (PI) for inducing drought stress. Under drought condition there was severely drought development which grain yield reduction was 91% in comparison to well water condition. Mean leaf water potential at 40 days after inducing stress was -19.1 Pa. In comparison to well water condition, there were reduction in filled grain percentage for 48%, panicle number and plant height. Flowering time was also delayed. Among genotypes, there were no significant (P>0.05) variation in grain yield, days to 75% flowering and flowering delay under both well and drought stress conditions, except grain yield under well water condition. Correlation between grain yield and days to 75% flowering was negatively significance only under drought stress condition, suggested that under drought stress condition days to flowering has significant effect on grain yield, early genotypes could be able to produce higher grain yield than late genotypes. There were found also under drought stress condition that delay in flowering has significant negative correlations with grain yield (-0.49, P<0.01) and filled grain percentage (-0.38, P<0.01). The correlation suggested that less delay in flowering was desirable character for drought tolerance at flowering stage.