Combining Ability of Diallel Crosses of Bivoltine Silkworm, Bombyx mori L.

General and specific combining ability effects of six bivoltine breeds of silkworm (Bombyx mori L.) were evaluated for six quantitative characters through diallel method wherein parents, $F_{1}s$ and reciprocals are involved. The breeds $APS_{11}\;and\;APS_{2}$ were found to be the best general combiners for most of the traits studied. The high estimates of specific combining ability (sca) variance (${\sigma}^{2}s$) compared to general combining ability (gca) variance (${\sigma}^{2}g$) indicated the predominant role of non-additive gene action in the control of all the characters. Positive sca effects for majority of the traits were expressed by the combinations $APS_{13}{\times}APS_6,\;APS_{13}{\times}APS_2,\;APS_{11}{\times}APS_6\;and\;APS_5{\times}APS_2$ out of 15 crosses. Among the 15 reciprocal crosses studied, the combination $APS_8{\times}APS_{13}$ showed positive reciprocal effects for all the six traits. With both the parents $APS_5\;and\;APS_2$ being good general combiners the hybrid $APS_5{\times}APS_2$ showing high sca effects is recommended for commercial use.