Metatranscriptomic sequencing reveals there were abundant and diverse viruses in the midgut of diseased silkworm (Bombyx mori) with soft rot symptoms

To date, six viruses belonging to genera Alphabaculovirus, Cypovirus, Iflavirus, Iteravirus, Bidensovirus and Maculavirus were harbored in the silkworm (Bombyx mori) and in the cultured BmN cells. Diseased silkworms with unknown etiology often create economic losses to the farmers. In the present investigation, the abundance and diversity of viruses in the midgut of diseased silkworms with soft rot symptoms were assessed by meta-transcriptomic sequencing in order to screen the potential pathogenic virus of the silkworm, B. mori. After removal of undefined reads, clean reads were assembled, and the obtained 76 viral unigenes were annotated to 43 viruses. Among these viruses, the B. mori cypovirus, Pieris rapae virus, Nodaviridae sp., B. mori bidensovirus, Pseudomonas virus pf16, Pseudomonas phage Skulduggery, Klebsiella phage KPN U2874, Equid gamma-herpesvirus 2, fowlpox virus and Xestia c-nigrum granulovirus were dominant virus species. These metatran-scriptomic sequencing results provided new clues for screening and identifying novel pathogenic virus of the silkworm.