Backcross Breeding and Directional Selection of Two Multivoltines, N+p and Np of Silkworm, Bombyx mori L. for Higher Viability and Productivity in Eastern India

A new superior multivoltine breed of Bombyx mori L. (D+p) has been developed by crossing between two strains of Nistari Plain (Np) and Nistari Marked (N+p) which are the two most preferred strains of multivoltine breed at the farmer’s level of eastern India. Through standard breeding plan this needbased new breed, D+p was developed by adopting three steps: i) Development of Recurrent Backcross Line through backcross breeding for initial eight generations; ii) Improvement of developed RBL following directional selection process for the next twenty generations and ultimately iii) stabilization for next eight generations upto F40 generation at normal environmental conditions. Study of nine quantitative characters related to viability and productivity of the new breed in relation to its parents have been studied statistically and Heterosis%.