Performance of cotton F1 hybrids and its relation to the mean yield of advanced bulk generations

Abstract

The performance of intraspecific (Gossypium hirsutum) and interspecific (G. hirsutum × G. barbadense) F1 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 F1 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 F1s and their F2 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 F5 bulk) was included.Intraspecific F1 hybrids outyielded the best variety at both locations. Lint yield of the F1 hybrids ranged from 99 to 158% with a mean value of 122%. Useful F1 heterosis (hybrids with higher values than the best check cultivar) was also expressed for boll weight and Verticillium wilt infestation. The latter was more pronounced in hybrids derived from tolerant parents.All F1 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 F2 through F5 generations, with plant height, boll weight, earliness, fiber quality and wilt tolerance moving toward the hirsutum values.In the F2 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 F1s intraspecific hybrids maintained part of their useful heterosis in the F2. From the F3 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 F1 intraspecific hybrids yielded progressively less in subsequent generations, and in the F5 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 F1 did not predict the yield of the bulks in the following generations. Yet, the combined performance of the hybrids in the F1 and F2 generation could be a good indicator to identify the most promising populations to be utilized either as F2 hybrids or as a source population for further selection.