Effect of high temperature on grain filling period, yield, amylose content and activity of starch biosynthesis enzymes in endosperm of basmati rice

BACKGROUNDHigh temperature during grain filling affects yield, starch amylose content and activity of starch biosynthesis enzymes in basmati rice. To investigate the physiological mechanisms underpinning the effects of high temperature on rice grain, basmati rice was grown under two temperature conditions-32 and 22 degrees C-during grain filling. RESULTSHigh temperature decreased the grain filling period from 32 to 26 days, reducing yield by 6%, and caused a reduction in total starch (3.1%) and amylose content (22%). Measurable activities of key enzymes involved in sucrose to starch conversion, sucrose synthase, ADP-glucose pyrophosphorylase, starch phosphorylase and soluble starch synthase in endosperms developed at 32 degrees C were lower than those at 22 degrees C compared with similar ripening stage on an endosperm basis. In particular, granule-bound starch synthase (GBSS) activity was significantly lower than corresponding activity in endosperms developing at 22 degrees C during all developmental stages analyzed. CONCLUSIONResults suggest changes in amylose/amylopectin ratio observed in plants grown at 32 degrees C was attributable to a reduction in activity of GBSS, the sole enzyme responsible for amylose biosynthesis. (c) 2014 Society of Chemical Industry