Evaluation of Reproductive and Growth Performance in New Breeds and Hybrids of Bivoltine Silkworm (Bombyx mori L.)

This study aimed to evaluate the reproductive and growth performance of recently developed bivoltine silkworm parental breeds and their hybrids to improve silk production and ensure the long-term sustainability of sericulture. Utilizing five thermotolerant pure breeds (B1, B2, B4, B6 and B8) and four popular CSR breeds (CSR2, CSR27, CSR6 and CSR26), six foundation crosses and eight double hybrids were developed and evaluated for ten traits. Results showed that B1 exhibited superior performance in fecundity (524.00), hatching percentage (98.67%), dead eggs (1.33%), pupal weight (1.31 g), pupation rate (96.84%) and cumulative survival index (CSI) (93.84%). The foundation cross B1 × B2 excelled in fecundity (553.67), larval mortality (2.67%), pupal weight (1.53 g), ERR (97.33%) and CSI (93.27%) while FC2 performed better in hatching percentage (97.60%), dead eggs percentage (2.40%), fifth instar larval duration (157.21 h), fifth instar larval weight (35.64 g/10 larvae) and pupation rate (96.33%). Among the double hybrids, (B1 × B2) × (FC1) demonstrated superior performance in fecundity (614.33), larval mortality (1.41%), pupal weight (2.06 g), ERR (98.59%) and CSI (97.24%). FC2 × FC1 excelled in larval duration (141.11 h), fifth instar larval weight (51.96 g/10 larvae) and pupation rate (98.94%). Double hybrids showed significant improvements compared to parental breeds and foundation crosses, indicating potential for field testing and further development. These results indicate the potential of using the newly identified breeds and foundation crosses in silkworm breeding, particularly in developing new double hybrids as an alternative to established CSR breeds and hybrids.