| The heterosis and the genetic effects of combinations of upland cotton varieties with different ripening stage (early, medium, mid-late) were investigated so as to determine the combination types with the features of early ripening,higher yield and better quality. The results showed that the early×medium type and the medium×medium type of upland cotton had stronger hetorosis in ripening stage, yield and fibre quality. In the early×early combination of upland cotton, more transgressive early hybrids were found, yet its yield and quality were inferior to other types of combination. Transgressive early hybrids were also obtained in the combinations of early×mid-late, medium×mid-late and mid-late×mid-late, but their growth period was generally longer than the early×medium and medium×medium hybrids, and their yield and quality were below the medium×medium and early×medium hybrids. |