Viral Disease in Silkworm – Nuclear Polyhedrosis Virus (Bombyx Mori L.)

Bombyx mori L (Lepidoptera: Bombycidae) is very important economically as a silk producer in sericulture, and the insect is used as a model in biotechnology (Goldsmith et al., 2005). The mulberry silkworm life cycle is affected by a number of diseases caused by viruses, bacteria, fungi and protozoa. The genetic resistance of the silkworm to viral diseases is mainly controlled by polygenic mechanism. Resistance of silkworm to nucleopolyhedrosis virus (BmNPV), cytoplasmic polyhedrosis virus (BmCPV) and infectious flacherie virus (BmIFV) is controlled by polygenes. BmNPV is considered to cause the dreaded viral disease in sericulture industry. In silkworm, gut proteases, lipase and red fluorescent protein plays a major role in the defense mechanism against viral pathogens. Earlier, techniques have been developed to detect this viral disease such as the enzyme-link immunosorbent assay (ELISA), DNA hybridization, colloidal textile dye-based dipstick immunoassay and western blot analysis.PCR is an extremely sensitive technique which amplifies target DNA sequences and PCR amplification of conserved fragment enabled the detection of low level of viral DNA. PCR technique and polyhedrin gene (polh) used to detect early infection of Grasserie virus (BmNPV) in silkworm.