Time to flowering is an essential component of the adaptation and productivity of cotton (Gossipium hirsutum) in various agro-ecological zones. This article presents a study of the genetic control of this trait in two crosses obtained from different early-maturity parental lines. In each cross, multiple generations including P 1 , F 1 , P 2 , B 1 , B 2 and F 2 were evaluated under two natural field conditions in 2004 and 2005. The data on time to flowering in the F 2 populations had a continuous distribution but deviated from normality. A joint segregation analysis (JSA) revealed that time of flowering in upland cotton was controlled by a mixture of an additive major gene and additive-dominant polygenes. The first-and second-order genetic parameters were all calculated based on the mixture of major gene and polygene inheritance models using JSA. These results suggested that there was considerable genetic diversity and complexity in days to anthesis in upland cotton. This variation can be used to formulate the most efficient breeding strategy and to design cotton for a particular environment.

SU MMARYGenetic manipulation of leaf architecture may be a useful breeding objective in cotton (Gossypium spp.). The present study reports quantitative genetic analysis of leaf traits from two intraspecific crosses of inbred lines in upland cotton (Gossypium hirsutum L.) viz. Kang3rChaoji463 and Han109rJi98. Six leaf morphological traits (leaf area (LA), leaf perimeter (LP), main lobe length (LL) and width (LW), petiole length (PL), and main LL/LW ratio) were recorded from multiple generations (P 1 , F 1 , P 2 , BC 1 , BC 2 , and F 2 ) in the two crosses. Generation mean analyses were conducted to explain the inheritance of each leaf morphological trait. The six-parameter model showed a better fit to an additive-dominance model for LA, main LW, PL, and main LL/LW ratio in the two crosses, suggesting the relative importance of epistatic effects controlling leaf morphology. A simple additive-dominance model accounted for the genetic variation of the main LL in the Kang3r Chaoji463 cross. Different models were selected as appropriate to explain LP in the two crosses. The differences between broad-and narrow-sense heritability values for the same trait were not constant in the two crosses. The estimated minimum number of genes controlling each leaf morphological trait ranged from 0 to 2 for both the crosses. Moreover, the sums of the minimum number of genes controlling leaf morphology were 6 and 2 in the Kang3rChaoji463 and Han109rJi98 populations, respectively. Most data suggested that there existed a substantial opportunity to breed cottons that transgress the present range of leaf phenotypes found.