Determination of general and specific combining ability of cotton Genotypes by 7*7 Diallel Drossing Method

High seed cotton yield is ultimate objective of any crop-breeding program. In order to achieve this goal, hybrid development is an important step. Diallel cross method of producing hybrid seed cotton, is one of the most common approaches. In this study, in order to determinate the general and specific combining ability in cotton, seven cotton genotypes were crossed by unilateral Diallel. The study was conducted during two years. Crosses were done in the first year and in the second year, seven parents with the resulting diallel hybrids (totally 28 genotypes) were evaluated in order to investigate the success rate of hybridization and heterosis calculation based on randomized complete block (RCB) design with three replications. Studied genotypes were included Lambright،Tabladilla، B -557، Sindos-80، Zeta -2، Tashkand-2 andNO.200.In this study, some of quantitative and morphological traits of cotton including percentage of fruiting plants, plant height, boll weight, average number of boll, total seed cotton yield and earliness percentage were evaluated. Statistical analysis showed that NO.200*Tashkand-2 hybrid by total seed cotton yield b of 5139Kg per hectare was the first class and the best among all. However, B-557*Tabladilla, Tashkand-2*Tabladilla and No.200*B-557 with 80%, 78% and 77% early maturity had higher earliness than others, respectively. In terms of heterosis percentage, Sindos-80*Lambright hybrid had higher yield at the rate of 33.4% and in terms of early maturity, NO.200*Lambright hybrid by 26.5% higher than high parent were the best hybrids. Among the parents, Lambright and Tashkand-2 were the good general combinatory in view of yield and early maturity. However, among the hybrids, NO.200*Tabladilla and Tashkand-2*Tabladilla were the best specific combinatory in terms of yield and early maturity