The effect of alternate wetting and drying (AWD) on spikelet fertility, grain traits and the biosynthesis of 2-acetyl-1-pyrroline (2-AP) in rice grown under high temperature.

BACKGROUND: High temperature attributed to climate change is a major obstacle to rice production. This study examined how alternate wetting and drying (AWD) irrigation can mitigate the effects of high temperatures on rice production. Three indica rice cultivars-Ye Xiang You You Si (YXYYS), Jing Zhan 1 (JZ1), and Qing Xiang You Yi 19 (QXYY19)-with varying heat susceptibility levels were used to analyse the impact of AWD on spikelet fertility, grain traits, and the biosynthesis of 2-acetyl-1-pyrroline (2-AP) from heading to harvest in rice grown under high temperature. RESULTS: The findings revealed that AWD significantly reduced spikelet fertility in all cultivars, but its effect on spikelet fertility depends on the heat susceptibility level of each cultivar. AWD alleviated the negative effect of high temperature on the biosynthesis of 2-AP and increased 2-AP content in leaves and grains of rice. This study also provided new insights on the effect of starch granules and brown rice grain width on chalkiness and demonstrated that starch granule arrangement and airspaces-not starch granule size-as well as brown rice grain width influenced chalkiness in rice. It also revealed that rice husk affected grain shape. Cooked rice elongation and rice whiteness were significantly increased by AWD, but it reduced the seed germination rate. CONCLUSIONS: This study presents a roadmap for the improvement of spikelet fertility in rice grown under high temperature. It also presents a simplified and cost-effective means to further increase the biosynthesis of 2-AP, proffered solutions for the reduction of chalkiness, and proposed methods for the improvement of grain shape by targeting genes, quantitative trait loci (QTLs), and signalling pathways associated with those traits in rice.