PCR detection of densonucleosis virus isolates in silkworm (Bombyx mori) from India and their nucleotide variability

Abstract

Densonucleosis virus (DNV) is one of the pathogenic viruses of the commercially valuable silkworm, Bombyx mori. It causes flacherie disease, mostly as combined infection with other pathogens like bacteria, which accounts for the significant loss of cocoons in sericulture. Two isolates of DNV from B. mori, DNV1 and DNV2 have been previously identified on the basis of their sequences. After infection with purified isolates of DNV in some commonly used silkworm strains, viz. Nistari, C’nichi, NB1 and Guangnnong Marked, the polymerase chain reaction (PCR) was conducted using DNV1 and DNV2 primers. DNV1 primers generated a distinct profile in the B. mori strains, whereas DNV2 produced single monomorphic band in all the screened strains. Sequence of one of the prominent fragments generated by the DNV1 primer exhibited very high degree of nucleotide variability from that of Japanese DNV1 isolate, but the sequence of DNV2 showed near to complete similarity. Besides, the study demonstrates that PCR technique could be used to diagnose the DNV presence/absence in silkworm strains without sacrificing the larvae and the results could be used in breeding programmes.