ABSTRACT
A half diallel set of crosses of seven Egyptian cotton cultivars (G. barbadense L.) was conducted and evaluated in the F2-generation for two years under early and late planting to study the effects of planting date on the performance and type of gene action controlling seed cotton yield, number of bolls, boll weight and seed index. The combined reduction due to late planting in seed cotton yield/plant was 71.21% for the parents and 65.17% for the F2-generations. The average reduction in number of bolls/plant, boll weight and seed index was 69.72, 9.11, and 12.67% for the parents, and 63.42, 9.95 and 12.37% for the F2-generations; respectively. Both of additive and non-additive effects of genes were operating in the inheritance of all traits, and the non-additive effects were very large compared to additive gene effects. Epistatic gene effects were found in all traits in the second season. The dominant and recessive genes were not equally distributed among the parents. The graphics of Wr/Vr analysis indicated that the distribution of the parents around the regression line was not consistent from early to late planting and from year to year for seed cotton yield/plant and number of bolls/plant. Negative intercept of the regression line to the Wr axe was found for seed cotton yield in three cases and for number of bolls/plant in all cases, indicating over-dominance. The non-additive effects of genes were reflected in the departure of narrow from broad sense heritability in seed cotton yield, number of bolls/plant and boll weight. Therefore, pedigree and recurrent selection methods could be effective in late segregating generations of these material. The promising F2-populations for the studied traits to select lines adapted to early and late plantings were Giza 90 x Giza 86, Giza 92 x Giza 86, Giza 88 x Giza 86 and Giza 86 x Giza 80.