~ 1079 ~ International Journal of Chemical Studies 2019; 7(6): 1079-1083 P-ISSN: 2349–8528 E-ISSN: 2321–4902 IJCS 2019; 7(6): 1079-1083 © 2019 IJCS Received: 13-09-2019 Accepted: 24-10-2019 DK Hadimani Department of Sericulture College of Agriculture Bheemarayangudi. UAS Raichur, Karnataka, India MC Devaiah Department of Sericulture, UAS, GKVK, Bangalore, Karnataka, India KC Narayanaswamy Department of Sericulture, UAS, GKVK, Bangalore, Karnataka, India RN Bhaskar Department of Sericulture, UAS, GKVK, Bangalore, Karnataka, India Radha D Kale Department of Agril. Entomology (Zoology), Bangalore, Karnataka, India KR Shreeramulu Department of Agril. Microbiology UAS, GKVK, Bangalore, Karnataka, India Corresponding Author: DK Hadimani Department of Sericulture College of Agriculture Bheemarayangudi, UAS Raichur, Karnataka, India Studies on mulberry silkworm cocoon traits due to Bm NPV infection DK Hadimani, MC Devaiah, KC Narayanaswamy, RN Bhaskar, Radha D Kale and KR Shreeramulu Abstract Silkworm diseases are caused by a number of pathogens that results in drastic reduction in the quantity and quality of cocoon crop. This ultimately has a direct effect on the farming community of the country due to reduced returns. Thus viral diseases of silkworm pose a serious problem in sericulture industry which need to be checked to the maximum possible level. Therefore, no serious attempts have been made systematically to screen different improved breeds and hybrids of mulberry silkworms for cocoon traits to BmNPV infection. In this direction, to screened the tolerance of BmNPV infection was under taken. The effective rate of rearing was significantly maximum in PM × CSR2 (62.50%), which was on par with that of MH1 × CSR2 (61.11%)). Similarly, the effective rate of rearing varied from 88.00 per cent in CSR2 × CSR4 to 93.00 per cent in PM × CSR2 of uninfected batches. Among the viral dilutions, the effective rate of rearing differed significantly in improved breeds and hybrids. The effective rate of rearing was significantly maximum in control batch (90.16%) followed by 10 -6 PIBs (40.76%) and 10 -3 PIBs concentration (37.04%).The cocoon, pupal and shell weights were found to be non-significant except shell ratio in improved breeds and hybrids of silkworm. The shell ratio was significantly maximum in CSR2 (22.64%). It was significantly minimum in PM × CSR2 (18.60%). Among the PIBs concentrations tested, the cocoon (1.30 g), shell (0.271g) and pupal weights (0.92 g) and shell ratio (20.64%) were significantly maximum at viral dilution of 10 -6 PIBs followed by 10 -3 PIBs (1.17g, 0.216g, 0.86g, 18.60 per cent, respectively) compared to the control (1.75g, 0.39g, 1.29g and 22.03 per cent, respectively).Among the interactions, the cocoon, shell and pupal weights and shell ratio were found to be non-significant. Keywords: Mulberry silkworm, cocoon traits, BmNPV, infection Introduction Silkworm is one of the most important domesticated insects where the growth and development is greatly influenced by environmental conditions. Success of silkworm breeds/hybrids largely depends on their adaptability to the environment in which it is destined to be reared. The biological as well as cocoon-related characters are influenced by ambient temperature, rearing seasons, quality mulberry leaf, and genetic constitution of silkworm strains. It is a well-established fact that under tropical conditions, unlike polyvoltines, bivoltines are more vulnerable to various stress like hot climatic conditions of tropics, poor leaf quality, and improper management of silkworm crop during summer that is not conducive for bivoltine rearing for technologically and economically poor farmers of India. Though the nature of silkworm healthiness is unclear, healthy silkworm varieties are important for the stabilization of silkworm crops. The use of commercial silkworm hybrids resistant to important silkworm diseases is economical and better option particularly in tropical areas. Due to fluctuating climatic conditions, inadequate silkworm disease management practices and poor quality mulberry leaf, frequent crop losses are witnessed especially due to grasserie disease with the farmers in tropical areas. The rate of disease induction is perhaps controlled by the host’s developmental stage, particularly moulting period, indicating that physiological changes in silkworms may also play an important role in the induction of viral diseases. Sericulture is economically very important for farming community especially for rural areas. Among the silkworm diseases, nuclear polyhedrosis virus (NPV) of Bombyx mori (BmNPV) is known to occur in all larval instars and more commonly in 4th and 5th instars during all seasons and causing 20-50% cocoon crop losses. In viral diseases two common diseases are found these are nuclear polyhedrosis and cytoplasmic polyhedrosis.