A study on straight and reciprocal crossing in F1 hybrids using bivoltine and multivoltine silkworm, Bombyx mori L. (Lep., Bombycidae) races

The effects of straight and reciprocal crossing on F1 hybrids were estimated on six quantitativetraits viz., cocoon weight, shell weight, shell ratio, filament length, denier and renditta in the silkworm, Bombyx mori L. utilizing two bivoltine races and two multivoltine races namely N 4D2, C108, Nistari and Pure Mysore, respectively. In order to understand the genetics of cross breeding system between multivoltine and bivoltine races, a hybridization experiment was conducted by crossing females of multivoltine races (Pure Mysore and Nistari) with males of bivoltine races (C108 and NB4D2) and its reciprocals during 2009. The twelve straight and reciprocal hybrids were reared under standard laboratory condition. The data of the hybrids was analysed for the estimation of six economical traits to study the crossing effects, between the hybrids. The straight and reciprocal crossing of C108 × NB4D2 has shown maximum cocoon weight (0.37 gr) whereas PM × Nistari has recorded minimum cocoon weight (0.2 gr) among the hybrids. Superiority of strait crosses between multivoltine and bivoltine races only have been shown for denier trait in PM × NB4D2 hybrid. In bivoltine × multivoltine hybrids, characters such as cocoon weight, shell weight, filament length and denier showed high significant difference.