Effects of different irrigation regimes on grain yield and water use efficiency in japonica-indica hybrid rice cultivar Yongyou 1540.

The objective of this study is to understand how different irrigation regimes affected on grain yield and water use efficiency (WUE) of japonica-indica hybrid rice cultivar Yongyou 1540 and its physiological bases. In the present study, Yongyou 1540 was used and three irrigation regimes were set up during the whole growth period, including continuous flooding (CF), alternate wetting and moderate drying (AWMD), and alternate wetting and severe drying (AWSD). The results showed that compared with CF, both AWMD and AWSD significantly improved WUE, with the increase of 22.6%-25.6% and 18.2%-23.1%, respectively. AWMD significantly increased yield by 8.6%-10.0%, while AWSD significantly decreased yield by 6.0%-7.5%. Compared with CF, AWMD significantly reduced the number of tillers, shoot dry weight and leaf area index (LAI) at the jointing stage, and reduced leaf area duration (LAD) from transplanting to heading, and the crop growth rate (CGR) from transplanting to jointing. However, AWMD significantly increased the percentage of productive tillers, CGR from jointing to heading, root length density, deep root ratio, root to shoot ratio, specific root length, root total absorbing area, and activity absorbing area during the whole growth period, and increased the net photosynthetic rate of flag leaves, root oxidation activity, and Z+ZR content in both roots and leaves, key enzymes involved in sucrose-starch metabolism in grains at two soil re-watering stages at grain filling stage. In conclusion, these results indicated that AWMD could increase both grain yield and WUE, promote root and shoot growth, and improve plant physiological activity at grain filling stage, and achieve high yield and high WUE, which was the best irrigation regime in this study. [ABSTRACT FROM AUTHOR]