Abstract

In order to understand the genetics of cross breeding system between multivoltine and bivoltine race, a hybridization experiment was conducted by crossing females of multivoltine Pure Mysore race (PM) with males of a bivoltine race C₁₀₈ and its reciprocals. The F₁ and F₂ progenies of the above crosses were derived in order to study the economic traits and biological characters. The results of the analysis of the thirteen economic traits in the F₁ progeny between the regular and reciprocal crosses clearly indicated that wherever PM is participated as female partner the values of the economic traits are on the higher side than the reciprocals. In regard to the studies on the biological characters, the F₁ progeny of a cross of females of PM with males of C₁₀₈ produced non-diapause eggs exhibiting 23 - 24 days of larval duration and spinning light green cocoons. On the other hand a cross between females of C₁₀₈ with males of PM produced only diapause type of eggs having larval duration of 22 days which is shorter by 1 - 1.5 days compared to regular cross. The F₂ progenies involving both the crosses produced 3:1 ratio diapause: non-diapause eggs and green: white cocoons indicating Mendelian pattern of inheritance for voltinism and cocoon colour. The authors in the present investigation discussed the importance of hemizygous and heterozygous individuals of F₁ progeny and its utility in genetics and breeding of silkwormBombyx mori.

Key words: Regular and reciprocal crosses, Bombyx mori, Economic traits, biological characters.