A study on combining ability for six quantitative traits in the Silkworm, Bombyx mori L.

In this investigation، the effect of general combining ability and specific combining ability were estimated on six quantitative traits viz.، cocoon weight، shell weight، shell ratio، filament length، denier and renditta in silkworm، Bombyx mori L. utilizing two bivoltine races and two multivoltine races namely NB4D2، C108، Nistari and Pure Mysore، respectively. Combining ability analysis was carried out for six cocoon characters in an 4×4 diallel cross using Griffing’s Method-I، Model-I. The parents and their hybrids (F1) have compared together with using RCD design with three replications. The mean of genotypes variance was highly significant for all traits. Combining ability analysis revealed that specific combining ability variance was greater in magnitude and more important for the all cocoon characters except denier and renditta، indicating the involvement of non-additive type of gene action for the expression of these parameters. The GCA/SCA variance ratio exhibited that cocoon weight، shell weight and filament length was predominantly under additive control and other traits were under non-additive control. The ranking of parents according to the effect of GCA was almost are equal with the ranking of parent according to their mean values. The present results clearly indicate that we can predict the GCA values of parents based on their mean values and it is very important in silkworm breeding programme.