An alphabaculovirus isolated from dead Lymantria dispar larvae shows high genetic similarity to baculovirus previously isolated from Lymantria monacha - An example of adaptation to a new host.

A new isolate of baculovirus, Lymantria dispar multiple nucleopolyhedrovirus-BNP (LdMNPV-BNP), was found in dead gypsy moth (L. dispar) caterpillars collected in the Biebrzanski National Park in Poland. Here, we examined its biological activity, structure, genetic content and phylogeny. Multiple nucleocapsids of LdMNPV-BNP are enveloped together in 2-26 virions embedded in occluded bodies (OBs) very similar to the OBs previously described in viruses infecting Lymantriinae. This isolate kills pest larvae in a relatively short time (LT50 of approximately 9days for a dose of 2×10(7)OBs/ml), highlighting the possibility for its use as a biopesticide. Next-generation sequencing of LdMNPV-BNP revealed gene content (e.g. DNA photolyase) that is not present in any LdMNPV isolate sequenced to date. The genome is 157,270 base pairs long and has a notably lower G+C content in comparison to other LdMNPVs (50.3% G+C content compared to an average of 57.4% among other LdMNPVs). According to our phylogenetic analysis based on 37 core genes, LdMNPV-BNP is a member of group II alphabaculoviruses, which are closely related to LdMNPV and LyxyMNPV (Lymantria xylina multiple nucleopolyhedrovirus). Molecular evolution inference based on the partial sequence of lef-8, lef-9 and polh genes shows that LdMNPV-BNP and isolates of Lymantria monacha nucleopolyhedrovirus (LymoNPV) may share a very recent common ancestor or be isolates of the same virus species. LdMNPV-BNP, like other baculoviruses, could be beneficial as an active component of biopesticides that can be used during forest integrated pest management.