Effect of Drought stress on Resistant starch content and Glycemic index of rice (Oryza sativa L.)

Abstract Drought stress is the most devastating abiotic stress which severely affects starch biosynthesis, thus altering the glycemic index (GI) of rice grains. It shortens the period of grain filling by rapidly translocating assimilates to grains, thereby decreasing amylose content (AC), resistant starch (RS), and increasing GI value. Among 30 genotypes tested, ZHU‐11‐26, IR 20, and Annada differ in exhibiting a much lower reduction in AC and RS which result in insignificant change in GI (<1) under drought stress. Two genotypes (ZHU‐11‐26 and Pathara) are selected for granule bound starch synthase I expression analysis on the basis of their contrasting GI and RS content. The gene is highly and significantly expressed at the dough stage of grain development and shows a positive association between its expression and RS content. Drought is very common in most parts of the world in the present climate‐change scenario, where even mild terminal stress may affect grain filling rate and cause the increment in GI value of grains. In this context, identification of less responsive genotypes with a lesser change in GI under drought stress may help in developing rice varieties for the diabetics even grown under stress‐prone environments.