Heterosis performance of yield and fibre quality in F1 and F2 hybrids in upland cotton

Because of the difficulty of producing F-1 hybrid seeds by hand emasculation and pollination, wide use of heterosis in cotton production has been limited in China. The objective of this study was to evaluate the potential of F-2 hybrids for yield and fibre quality. A half diallel involving eight parents and their F-1 and F-2 hybrids was grown in replicated studies at Linqing and Nanjing in 1999 and Nanjing in 2000. Yield and fibre quality was determined for all 64 entries. Fibre quality was also determined for parents and F(1)s, but only for Zhongmiansuo 28 (ZMS28), Xiangzamian 2 (XZM2) and Wanmian 13 (WM13) F(2)s. These three F-2 hybrids are extensively planted in China and provide experimental controls with which to compare the performance of new hybrids. Average yield heterosis for F(1)s and F(2)s was 15.9 and 9.2%, respectively. Inbreeding depression for yield varied but some F(2)s greatly out-yielded the best variety. Average F-1 heterosis was 6.7, 6.2 and 2.9%, respectively for number of bolls per unit area, boll weight, and lint percentage. The average F-2 heterosis for the same traits was 4.4, 3.3 and 1.6%, respectively. F-1 heterosis for fibre traits was low. In general, parental average was a good indicator of the yield and fibre quality of F-1 hybrids. These encouraging results suggest there is sufficient heterosis for yield to use F(2)s in China.