Estimation of Genetic Parameters for Traits Effective on Earliness in Cotton Using Diallel Crosses

To study inheritance of morphological traits associated with earliness and their relationship with yield, six genotypes of cotton were studied in a half diallel cross in 2003 in Darab. Fifteen F1 and six parents were evaluated in a complete block design with three replications. The results showed that differences among treatments were significant for seed cotton yield, earliness, plant height, date of first squire and mean maturity data. General and specific combining ability (GCA and SCA) effects were estimated by the method 2 of the Griffing’s model I. Mean square of general combining ability (GCA) was significant for all studied traits. Specific combining ability (SCA) was significant only for yield. GCA/SCA ratio was significant for all studied traits except for yield. Determination of genetic parameters, statistical indices and graphical analysis by Jinks–Hayman method showed that gene actions for yield and earliness were over-dominance, while plant height, days to first squire and mean maturity data showed partial dominance. All of the traits had high board sense heritability. Narrow sense heritability was also high for all traits except yield.