Abstract: 【Objective】The present study was carried out to characterize the changing activities of key enzymes during grain filling in two wheat cultivars differing in gluten under irrigated and rainfed conditions. This information will help to elucidate the enzymatic mechanisms of starch synthesis in wheat cultivars with different gluten. 【Method】The starch accumulation, sucrose metabolism and related enzymes activities were investigated in strong gluten type cultivar, JM20, and weak gluten type cultivar, BY535, in Taian and Dezhou experimental locations. 【Result】The soil water deficit led to an increase at early grain-filling period and decrease during late grain-filling, respectively, in starch accumulation rate and activities of key enzymes involved in starch synthesis, especially AGPase, SSS, and SBE. Water deficit enhanced grain starch accumulation in two wheat cultivars. It suggests that rainfed treatment increased the physiological activities during early grain filling, and promoted starch accumulation. Furthermore, the change of starch accumulation rate was consistent with SS，AGPase，SSS and GBSS. The results suggested that these enzymes play a key role in starch synthesis and the decrease of photosynthate produced in source organ is not the factor inhibiting starch accumulation.【Conclusion】The soil water deficit led to an increase at early grain-filling period and decrease during late grain-filling, respectively, in starch accumulation rate and activities of key enzymes involved in starch synthesis, especially AGPase, SSS, GBSS and SBE. It indicated that water deficit can increase the sink activities and promote starch synthesis and accumulation.

Key words: Wheat (Triticum aestivum L.), Starch synthesis, Irrigation, Rainfed cultivation