Changes in starch structure, function and enzyme activity in early-season indica rice under simulating high
Ruoyu Xiong1, Shiqi Yang2, Xiaofeng Ai2
1Ministry of Education and Jiangxi Key Laboratory of Crop Physiology, Ecology and Genetic Breeding, Jiangxi Agricultural University, Nanchang 330045, China; Key Laboratory of Germplasm innovation and genetic improvement of grain and oil crops, Co-construction by Ministry and Province, Ministry of Agriculture and Rural Affairs, Shanghai Academy of Agricultural Sciences, Shanghai 201403, China.
Abstract:
Early indica rice in Southern China frequently experiences high temperatures (HT) and strong light (SL) during grain filling, which accelerates grain maturity. In this study, two indica rice cultivars with different grain qualities under control (CK), HT, and HT + SL treatments to investigate their impacts on starch structure and physicochemical properties. The results demonstrated that HT and HT + SL treatments increased the amylopectin average chain length, long chain, relative crystallinity, large granule, and protein content (40.9 %-41.6 %), while decreasing amylose content (15.4 %-21.6 %) and branching degree compared to CK. This was due to a reduction in granule-bound starch synthase, soluble starch synthase, and starch branching enzymes, along with an increase in debranching enzyme activity, which altered the starch fine structure and diminished thermal stability and gelatinization viscosity. The HT + SL treatment exhibited a more pronounced impact, increasing the amylopectin middle chain (fb1) and relative crystallinity, while decreasing the branching degree and amylopectin short-chain length, indicating that SL exacerbated the deterioration of starch structure. Nevertheless, the starch physicochemical properties of high-quality cultivar were relatively less affected by the HT + SL conditions, suggesting a potential for improved utilization of starch in high-quality early indica rice in food processing.
