STUDIES ON SUITABILITY OF USING BIVOLTINE X MULTIVOLTINE SILKWORM HYBRID IN SEED CROP AND ITS UTILIZATION AS MALE PARENT FOR PREPARATION OF MULTI X (BIVOLTINE X MULTIVOLTINE) COMMERCIAL SILKWORM HYBRIDS IN TROPICAL CONDITIONS

Hybrids can tolerate variable climatic conditions and its rearing is easier than the parents due to hybrid vigour / heterogeneity. Bivoltine are edge over than multivoltine due to quality silk, besides its diapausing nature. Due to diapausing character, bivoltine seed can be prepared in favourable season and consigned in cold storage for longer period by which rearing during unfavourable seasons can be avoided. Utilizing these two advantageous tools i.e. hybrid vigour & diapause, an experiment was undertaken to study the performance of bi x multi hybrid in different seed crop seasons (Sep-Oct & Feb-Mar) and resultant commercial hybrids [Multi x (Bi x Multi)] in subsequent commercial crop seasons(Nov-Dec and Mar-April). Results showed a significant (P<0.001) increase in pupation (%) was observed during Sep-Oct (Unfavourable seed crop) in bi x multi hybrids (74.9 - 90.12 %) than the conventional bivoltine breeds, YB (36%) and NB4D2 (8%). In favourable seed crop season (Feb.Mar.), the pupation (%) and yield/ 10000 L (wt) ranged between 93 and 95% and 13.0 and14.5 kg respectively in bi x multi hybrids as compared to 86% and 74% pupation (%) with yield/ 10000 L (wt) of 10.7 kg and 9.4 kg respectively in YB and NB4D2(Control). During early summer commercial crop (April), Multi x (Bi x Multi) hybrids performed better as compared to single cross hybrids, whereas during autumn commercial (Nov-Dec) crop single cross hybrids performed better. Higher survival and yield observed in bi x multi crosses during different seed crop seasons and optimum performance of its hybrids in commercial seasons depicting it can be used as an alternative to bivoltine foundation crosses in seed crop seasons of tropical parts where variable and fluctuating climatic conditions prevails.