Sowing Date Regulates Starch Metabolism of Glutinous Rice via Altering High-Temperature Duration to Modify Flavor...

Adjusting sowing date effectively regulates rice growth and grain quality amid climate warming. Here, a field experiment was conducted in the Jianghan Plain to investigate how four wine-making glutinous rice sowing dates (21 May, 28 May, 4 June, and 9 June) regulate starch metabolism and grain quality via temperature, and subsequent effects on sensory quality and metabolome of brewed rice wine. The results showed that delayed sowing significantly reduced grain-filling high-temperature stress duration by up to 60.65% while maintaining stable grain yield. With postponed sowing, key starch synthase activities changed obviously; glutinous rice amylose content decreased from 1.6% to 1.3%, and gel consistency and alkali spreading value increased remarkably. Further fermentation tests indicated that glutinous rice sown on 4 June had the optimal raw material quality, and the brewed rice wine possessed the highest sensory score (29.9% higher than the early-sown treatment T1), as well as abundant volatile compounds. Metabolomic analysis differentiated metabolites across treatments, and correlation analysis verified that high-temperature duration indirectly regulated rice wine quality via grain physicochemical traits. In conclusion, moderate sowing delay alleviates high-temperature stress, optimizes raw grain quality and enhances rice wine flavor. The best sowing time for wine-making glutinous rice here is 4 June.