Genetic analysis of yield and some associated traits in upland cotton (Gossypium hirsutum L.) genotypes

In this study six genotypes of upland cotton (G. hirsutum L.) were crossed in a half diallel (6×6) mating fashion. The parents and F1s were planted in a complete randomized block design with three replications at the Hashemabad Cotton Research Station (Gorgan) in 2005. Cotton yield and some agronomic traits were evaluated. Analysis of variance showed that differences due to genotypes were significant (P≤0.05) for yield, plant height, boll weight, monopodial branch number and maturity coefficient (earliness). Also, the correlation coefficients between cotton yield and above indicated traits were significant. The diallel analysis results showed that plant height, monopodial branch numbers and earliness exhibited additive gene effects. Both additive and non-additive gene effects were important in controlling of cotton yield and boll weight. The parental genotypes of Cok. 349, V.S.O and No: 200 genetyp exhibited significant General combining Ability (GCA) for yield and boll weight. Bolgar539 exhibited significant GCA for earliness. The Cok. 349 × NO: 200 and Asland × NO: 200 have exhibited higher and positive specific combining ability (SCA) for yield. Dominance and recessive allele frequencies were not in equilibrium with respect to traits studied. The average degree of dominance value was greater than 1 (d>1) for all studied traits. Frequencies of dominant alleles were more than recessive alleles in parental genotypes. According to our data, increase of cotton yield is obtained by exploitation of both additive and non-additive gene effects. For this purpose, recurrent selection in order to accumulate desirable additive genes, as well as exploiting of dominance variance through hybrid production would be more appropriate in future cotton breeding programs.