Isolation and identification of a new Bombyx mori nucleopolyhedrovirus strain isolated from Yunnan, China

Bombyx mori nucleopolyhedrovirus (BmNPV) is a silkworm pathogen that causes serious economic losses in sericulture. In this study, a new BmNPV strain, designated as BmNPV-YN1, from Yunnan (China), was isolated and identified through molecular identification. Sequence analysis results revealed that polyhedrin (polh) presented the highest identity among various BmNPVs; this gene indicated that BmNPV-YN1 is a BmNPV strain. The baculovirus repeated-ORF (bro) genes of this isolate were different from those of six BmNPV strains (BmNPV-T3, BmNPV-ZJ, BmNPV-GX, BmNPV-India, BmNPV-Cubic, and BmNPV-Brazilian). The BmNPV-YN1 bro family includes bro-a, bro-b, bro-c, bro-d, and bro-e, which are similar to those of BmNPV-T3. Sequence alignment results further showed the differences in the composition and sequences of the bro family members among various strains. The bro-d sequences were also phylogenetically analysed. Results demonstrate that BmNPV-YN1, BmNPV-Cubic, and BmNPV-India are closely related. Despite this close relationship, BmNPV-YN1 belongs to a distinct cluster. The BmNPV DNA was subjected to restriction endonuclease analysis and the obtained results provided additional evidence supporting the identity of the novel BmNPV-YN1 strain. Indeed, BmNPV-YN1 isolated from Yunnan is a new BmNPV strain. The proposed method can be used to rapidly and accurately detect and identify BmNPVs strains.