Abstract:

Starch is the major component of wheat endosperm and an important source of carbon and energy in human food and animal fodder. Starch consists of amylose and amylopectin. Starch synthesis and accumulation takes place during grain filling in wheat. Many enzymes take part in starch synthesis, including sucrose synthase (SS), ADP-glucose pyrophosphorylase (AGPP), granule-bound starch synthase (GBSS), soluble starch synthase (SSS), starch branching enzyme (SBE), starch debrabching enzyme (DBE) and so on. According to the present studies, AGPP, starch synthase and SBE were the key enzymes controlling starch synthesis. Many scientists had studied the changes of enzymes activities，involved in starch synthesis in the grain in the grain filling. But to date there have been no report about the dynamic changes of starch accumulation and enzymes relating to starch synthesis in the grain during grain filling of winter wheat cultivars with different quality types. For this reason, three winter wheat cultivars with different quality types，Gaomai 8901（strong gluten），Yumai 49（medium gluten） and Luomai 1（weak gluten）cultured in the soil pool，were used for the research. Starch content was measured by the method of Xu et al. Starch accumulation was obtained by multiplying starch content with grain weight. The rate of starch accumulating was determined by the amount of starch accumulated over time. AGPP activity was tested according to the method described by Douglas et al. SSS and SBE activities were measured according to the methods described by Nakamura et al. ^[12] Main results indicated that the amylopectin synthesis was synchronous with the amylose synthesis（Fig.1），and the amylopectin was synthetised faster than the amylose during the medium to later grain filling. The accumulating rates of amylose，amylopectin and starch in the grain of Yumai 49 were higher than that of other two cultivars. Changes in activities of AGPP，UGPP，SSS，GBSS and SBE of different cultivars all showed a single-peak curve. The peak level of the enzymes in Yumai 49 was higher than that in other two cultivars（Fig.2，Fig.3），and most of the tested enzymes kept higher activities during the medium to later grain filling. It suggests that the medium gluten cultivar Yumai 49 has stronger ability for starch synthesis，compared with Gaomai 8901 and Luomai 1.

Key words: Winter wheat, Quality type, Starch, Accumulation development, Enzyme activity