Reducing chalkiness and enhancing quality and yield in hybrid indica rice at the middle panicle position through optimal water and nitrogen management.

Chalkiness considerably impacts rice quality and is influenced by water and fertilizer management. This study investigates the regulatory mechanisms of water and nitrogen management on yield and chalkiness across different panicle positions. Compared to the upper and lower panicle positions, grain yield from the middle panicle position was significantly increased by 8.58-55.63 %, especially significantly increased the starch branching enzyme (SEB), adenosine diphosphate glucose pyrophosphorylase (ADPG), protein content, B chain (DP13-24) and 1045/1022 cm, which were responsible for chalkiness reduction. The water and nitrogen management pattern of implementing straw mulching promoted ADPG and SEB activity 0.12-29.68 %, decreased granule-bound starch synthase activity 2.26-50.49 %, increased small starch granules 2.03-11.81 % and relative crystallinity 1.41-9.69 %, contributed to high yield 9825.91-10,314.64 kg ha and chalkiness reduction 2.78-14.23 %, and affected to enhance gelatinization enthalpy 8.23-38.88 %. Overall, optimized water and nitrogen management increased grain yield and reduced chalkiness by improving starch synthase activity, protein content and multi-level structures in grains at the middle panicle position.