COMBINING ABILITY AND HETEROSIS STUDIES IN BIVOLTINE STRAINS OF SILKWORM BOMBYX MORI (L.)

Heterosis, general and specific combining abilities (GCA and SCA) was estimated fore m cally important quantitative traits for JD, SF, YS, SH, SH, and NND, six bivoltine of mulberry silkworm Bombyx mori L. maintained at Univoltine Research Station, Majra Pradesh. Hybrid vigour was found significant for traits-silk cocoon yield, survival of single cocoon weight, Denier and larval duration. Significant G A variance for cocoon single cocoon weight, filament length and Denier (size of the silk filament) indicates additive gene action is more important for these traits. Both GCA and SCA variances significant for other economic traits-single shell weight, silk shell ratio % and larval di indicating both additive and non-additive gene action important for them. Reciprocale (maternal) were found significant for single shell weight, denier and larval duration. GCSCA variance magnitudes were discussed in relation to selection and comparison with voltine races. Heritability estimates in the narrow sense were found moderate for cocoon single cocoon weight and denier, and slightly higher for larval duration, shell weight, and %. Four crosses SFX SH, SFXYS, SHXSF and SHxYS, found promising for c. ercial exploitation for increased silk production, in temperate regions of Uttar Pradesh other parts of India.