Assessing the impact of nuclear polyhedrosis virus (Grasserie) on economic traits of bivoltine silkworm (Bombyx mori L.) breeds under temperate climatic conditions

The present investigation was carried out to assess the impact of nuclear polyhedrosis virus (Grasserie) on economic traits of bivoltine silkworm (Bombyx mori L.) breeds under temperate climatic conditions. Ten mature larval weight was recorded (40.9g) in case of SANISH8 and it was minimum (35.6g) in APS4. Among the cocoon traits SH6 recorded the maximum cocoon weight of 1.49g, NB4D2 recorded highest shell weight of 0.30g and shell ratio of 20.12 per cent. However in susceptible breed cocoon traits found minimum cocoon weight of 1.38 g (CSR4), shell weight of 0.26 g (APS4) and shell ratio of 18.56 per cent (APS4). Breeds which were less susceptible to BmNPV viz., NB4D2 and APS8 yields more cocoons by weight. Among the improved breeds of silkworm the average filament length, filament size and raw silk were found significantly in BmNPV inoculated. However, the maximum average filament length of 816 m (DUN-6), filament size of 2.61 (DUN-22) and raw silk of 29.17% (DUN-6) was noticed. However, in susceptible breeds average filament length of 709 m (APS4), filament size of 2.28 (APS4) and raw silk of 24.58% (CSR2). Genotypes APS8 and NB4D2 has showing better economic characters as compared to other silkworm genotypes.