Performance of cotton F-1 hybrids and its relation to the mean yield of advanced bulk generations

The performance of intraspecific (Gossypium hirsutum) and interspecific (G. hirsutum x G. barbadense) F-1 cotton hybrids and its correlation with the mean yield of advanced bulk generations was assessed under Greek environmental conditions. For this, 14 intraspecific and five interspecific cotton F-1 hybrids were evaluated at two locations (Sindos and Vardates) during the 1985-88 period. In addition, two interspecific hybrids (5, 6), the three best (8, 7, 11) and two among the worst (4, 10) intraspecific F(1)s and their F-2 bulks were also evaluated at Sindos in 1986. This evaluation was repeated in the following years. In each successive year the new generation (up to the F-5 bulk) was included. Intraspecific F-1 hybrids outyielded the best variety at both locations. Lint yield of the F-1 hybrids ranged from 99 to 158% with a mean value of 122%. Useful F-1 heterosis (hybrids with higher values than the best check cultivar) was also expressed for boil weight and Verticillium wilt infestation. The latter was more pronounced in hybrids derived from tolerant parents. All F-1 interspecific hybrids were dominated by the barbadense phenotype and had its superior fiber lint quality, lower lint percentage, and resistance to Verticillium wilt. In addition, they expressed positive heterosis for lint yield at Sindos and negative at Vardates, compared with the check variety. The frequency of the hirsutum phenotype progressively increased in the F-2 through F-5 generations, with plant height, bell weight, earliness, fiber quality and wilt tolerance moving toward the hirsutum values. In the F-2 generation yield dropped dramatically (> 50%) in the interspecific hybrids, whereas in the intraspecific hybrids inbreeding depression was much less and varied from hybrid to hybrid. The good F(1)s intraspecific hybrids maintained part of their useful heterosis in the F-2. From the F-3 onwards the yield improved in the interspecific crosses and stabilized around 75% of the yield recorded in the best check variety. In contrast, the highest yielding F-1 intraspecific hybrids yielded progressively less in subsequent generations, and in the F-5 they produced the same yield as the best cultivar, whereas the yield of the lowest yielding intraspecific hybrids was stabilized around 95% of the yield recorded in the best cultivar. It was concluded that yield of the F-1 did not predict the yield of the bulks in the following generations. Yet, the combined performance of the hybrids in the F-1 and F-2 generation could be a good indicator to identify the most promising populations to be utilized either as F-2 hybrids or as a source population for further selection. (C) 1999 Elsevier Science B.V. All rights reserved