Response of Silkworm (Bombyx mori L.) Breeds to Temperature and BmNPV Stress

Silkworm Bombyx mori L. is one of the most important domesticated insects, which produces luxuriant silk thread in the form of cocoon by consuming mulberry leaves during larval period. The growth and development of silkworm is greatly influenced by environmental conditions. The seasonal differences in the environmental components considerably affect the genotypic expression in the form of phenotypic output of silkworm crop. Bombyx mori nucleopolyhedrovirus (BmNPV) is a pathogen that causes great economic losses in sericulture. In the present investigation, twelve bivoltine silkworm breeds (WM, ND5, NB4D2, U-4, PO1, ND3, U-6, CSR2, SH6, SPO, U-3 and NSP) were studied for temperature and BmNPV stress. After third and fourth moult silkworm larvae were treated with BmNPV inoculum at 25±1⁰C and 30±1⁰C temperature respectively. Increased mortality was observed at 30±1⁰C when compared to 25±1⁰C. However, with respect to breeds the highest total mortality was recorded in breed PO1 and least in breed U-3. Silkworm breed U-3 may have the ability to tolerate BmNPV incidence and can be exploit for evolving disease-tolerant silkworm hybrids.