The synergistic effect of variety improvement and alternate wetting and drying irrigation on yield, water use efficiency and lodging resistance in rice

Dwarfism in rice has reduced plant height, enhancing lodging resistance and supporting high grain yields. Alternate wetting and drying irrigation (AWD) has proven effective for water conservation in rice production. However, the impact of AWD on grain yield and lodging-resistant stem characteristics during rice variety improvement is not well understood. This study evaluated eight mid-season indica rice varieties from Jiangsu province spanning the last 80 years, across two years under conventional irrigation (CI) and AWD. We observed that grain yield and water use efficiency (WUE) increased with variety improvement under both CI and AWD irrigation regimes. However, AWD significantly boosted yield and WUE compared to CI, with increases of 10.32 % in early tall, 9.37 % in dwarf, 20.33 % in semi-dwarf, and 25.22 % in semi-dwarf hybrid types, respectively. Concurrently, stem breaking resistance, parenchyma and mechanical tissue thickness, and silicon content in the second basal internode of the stem were significantly enhanced, while the lodging index decreased with variety improvement. Internode length initially decreased and then stabilized, and the contents of soluble sugar, starch, lignin, and cellulose in the stem and sheath rose, then decreased, and eventually stabilized. AWD improved the morphological, mechanical, physicochemical characteristics, and anatomical indicators in the second basal internode, and reduced the lodging index. Correlation analysis revealed a close relationship between yield, WUE, lodging index, and stem characteristics. Notably, modern hybrid rice varieties with low lodging indices achieved high yields and WUE under AWD, attributed to the enhanced characteristics of the second basal internode.