Heterosis Studies on Hybrids of Cocoon Colour Sex-Limited Breed of the Silkworm, Bombyx mori L. Under Different Environments of Temperature

The commercial exploitation of hybrid vigour in silkworms has already been introduced since the beginning of the century in most developed countries. Breeds when reared over a series of environment exhibit less variation are considered stable. One of the main aims of the breeders is to recommend to farmers new breeds that are stable under different environmental conditions and yield level. In light of the above, the present study was undertaken to determine the heterosis of the hybrids of the new sex-limited breeds under different environments of temperature. The bivoltine cocoon colour sex-limited breed, Nandi (CSR2-SL), polyvoltine breeds viz., Pure Mysore, Nistari and ND7 and their nine hybrid combinations were selected as materials for the study. The silkworm rearing was carried out following the standard method with recommended temperature and RH conditions (Young age : 27-28°C and 80-85 % RH; Late age : 24-25°C and 65-70 % RH) till 2