Differences in Starch Components and Related Enzymes Activity in the Grains of Different Wheat Cultivars

Nine wheat cultivars with similar total starch content and different amylose and amylopectin content in mature stage were classified into three groups: low amylose, medium amylose and high amylose. The dynamic changes in ratio of amylose to amylopectin, and the activity changes of four enzymes in relation to starch biosynthesis and their relationships to the amylose and amylopectin accumulated during grain filling period were examined. The results showed that the ratio of amylose and amylopectin of wheat cultivars from group of high amylose was significantly higher than those of the other groups in the 28 d and 35 d after anthesis, and that the different ratio of amylose to amylopectin of variant wheat cultivars was caused by different amylose and amylopectin accumulation rate during middle and late stages of grain filling. Wheat cultivars, from group of low amylose, also with low granule bounded starch synthetase (GBSS) activity during filling stage and with low adenosine diphosphate glucose pyrophosphorylase (ADPGPPase) and uridinediphosphate glucose pyrophosphorylase (UDPGPPase) activity during middle stage and late stage of filling, produced less amylose in grains. High soluble starch synthetase (SSS) activity enhanced accumulation of amylose and amylopectin in the early stage of filling, but it would accelerate amylopectin accumulation and decelerate amylose accumulation in the late stage of filling.