Genetic Variation and Combining Ability for Yield and Fiber Traits among Cotton F1 Hybrid Population

The experiment was conducted to detect genetic variation and genetic effects associated with cultivars. Seven varieties of upland cotton (G. hirsutum L) representing a broad array were crossed in all possible combinations in diallel fashion, the parents and F1 progenies were sown in replicated experiment. Hayman diallel cross analysis was employed to investigate the nature of action and interaction of genes involved in the inheritance of character while the Griffing techniques was used to estimate general and specific combining ability of parents and genetic components of the variance for traits under study. Diallel analysis revealed that all the characters were polygenetically inherited and exhibited the greater part of genetic variation is due to dominant effect for all traits as (H1/D)1/2 value is more than one and the dominant gene effect H1, H2 is also significant for all traits under study. The H1 value is almost equal to H2 for all the traits, which indicate the occurrence of equal gene frequency at all loci. The ratio H1/4H1 is also nearly equal 0.25 for all traits except for node of first fruiting branch, seed cotton yield and staple length, which reflected that positive and negative alleles are equally distributed among the parents for all traits. Significant estimates for General Combining Ability (GCA) and Specific Combing Ability (SCA) effect is significant for all traits but GCA mean square were smaller than SCA indicating dominant gene action for the traits under study and it is possible that hybrid vigour for these traits can be utilized. From the GCA value, it is estimated that LRA-5166 is the best combination for NFB, boll number and monopodial branches while FH-945 is best combiner for plant height, number of nodes/plant, staple length. From SCA effect it is observed that cross FH-901 X MNH554, LRA5166 X FH-945 were good cross combination for selecting the genotypes having lower NFB and M.B values, in segregating generation while the cross combination LRA5166 X CIM499 has the reasonable SCA effect for seed cotton yield, GOT% which indicated that the progenies of this cross should be used for improving yield, yield components with early maturing traits like less monopodial branches and lower value of NFB. The estimate of heritability broadsense (Hbs) and narrow sense (Hns) indicated that the main portion of genetic variation among the population under study was due to dominant gene effect.