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An assessment of new bivoltine races and their hybrids was conducted to identify the best-performing hybrid. Five thermotolerant pure breeds (B1, B2, B4, B6 and B8) and four popular CSR breeds (CSR2, CSR27, CSR6, CSR26) were used to develop six foundation crosses and eight double hybrids. These breeds and hybrids were evaluated based on eight important economic traits. Among the parental races, B4 excelled in four traits viz., single cocoon weight (1.69 g), cocoon yield/10,000 larvae (16.42 kg), filament length (1347.14 m) and filament weight (0.31 g). CSR27 recorded the highest shell weight (0.34 g), shell ratio (22.18%) and denier (2.49). In foundation crosses, B1 × B4 had the highest single cocoon weight (1.81 g), cocoon yield/10,000 larvae (17.98 kg), filament length (1319.06 m) and filament weight (0.33 g). FC2 excelled in shell weight (0.38 g), shell ratio (22.33%) and denier (2.45). Among double hybrids, (B1 × B4) × (FC1) recorded the highest single cocoon weight (2.67 g), cocoon yield/10,000 larvae (25.87 kg), filament length (1434.29 m) and denier (2.85). FC2 × FC1 performed best in shell weight (0.38 g), shell ratio (22.33%) and filament weight (0.47 g). Thus, new breeds B1 and B4, foundation crosses B1 × B4 and B1 × B2 and double hybrids (B1 × B4) × (FC1) show promise for commercial exploitation after multi-location trials, offering alternatives to established CSR breeds and hybrids.
Thrilekha et al. (Sat,) studied this question.