Differences in the two-crop yields and main-crop rice qualities among different hybrid mid-season rice varieties in the ratooning rice region of southern Sichuan, China

Due to high temperature forced ripening, the yield of hybrid mid-season rice is low and rice quality is poor in the high temperature and drought-prone areas of south Sichuan. Therefore, it is important to make full use of the autumn temperature and light resources to improve grain yield and the quality of ratooning rice. A total of 12 new hybrid mid-season rice varieties, approved between 2015 and 2016, were used as materials to study the effects of environment on the yield and quality of main crop and ratoon in Longchang, Jiangan, Fushun, and Yibin, which are ecologically representative sites in southern Sichuan, China. The results showed that the difference in the main crop, ratooning rice, and total yields of two seasons among four sites was extremely significant. The main crop and ratooning rice yields of 12 rice varieties were significantly different, but the difference in total yields was not significant. There were 7 varieties ('Chuangliangyouhuazhan' 'Nei5you 907' 'Yixiang 4245' 'Luxiangyou 104' 'Huayou 357' 'Nei6A/Mianhui 138', and 'Longliangyou 1813') with more than 11 000 kg·hm^-2 yield over two seasons. There were no significant differences in gelatinization consistency of 6 rice varieties, but the other five traits were very significantly different among four sites. The rice quality in Yibin and Jiang'an were slightly better than in other two sites. The quality differences among 12 rice varieties and four sites were very significant, and the overall rice quality was relatively good for 'Chuangliangyou Huazhan' and 'Longliangyou 1813' varieties. There was a significant negative correlation between ratooning rice yield and main crop yield. However, there were no significant correlations between main crop yield and head milled rice rate, chalky rice rate, and chalkiness. The results showed that there was no obvious contradiction between high yields and three quality characters (milled rice rate, chalky grain rate, and chalkiness degree), indicating that improving the three quality characters under specific ecological conditions in southern Sichuan does not impeded rice yield increase. Varieties with a large grain length-width ratio had a reduced chalky grain rate, chalky degree, and amylose content, but an increased gel consistency.