Performance of new double hybrids of bivoltine silkworm derived from high temperature and muscardine tolerant foundation crosses

Seven new double hybrids were developed using high temperature and muscardine tolerant silkworm foundation crosses and commercial foundation crosses (FC2 and FC1). The results revealed that 4 double hybrids, viz., FC2 × FC1 (59.32), (B1 × B2) × (FC1) (59.12), (B1 × B4) × (FC1) (58.91) and (B2 × B4) × (FC1) (50.57) scored a mean evaluation index (EI) above 50 for all twelve traits assessed. Among these, (B1 × B2) × (FC1) scored second highest mean EI value for five parameters and ranked 2nd next to FC2 × FC1 which recorded highest mean EI value due to its elevated performance for larval weight (69.10) and denier (69.00) only. Furthermore, (B1 × B4) × (FC1) scored highest mean EI value for five parameters. Thus, two double hybrids, (B1 × B2) × (FC1) and (B1 × B4) × (FC1) recorded superior performance over commercial double hybrid (FC2 × FC1) for most of the economic parameters evaluated with an added advantage of high temperature and muscardine disease tolerance, thereby enhancing productivity.