Sequencing of a novel filamentous virus in the biocontrol agent Diachasmimorpha longicaudata

Parasitoid wasps are important agents of biological control, as their offspring develop inside or on the surface of host arthropods, ultimately killing the host and suppressing pest populations. Symbiotic relationships between some parasitoid wasps and viruses play a key role in the success of parasitoid wasp development. Numerous viruses have been identified in parasitoid wasps, although the functions of many remain unclear. For example, eight large double-stranded DNA viruses in the family Filamentoviridae have recently been sequenced from various parasitoid wasps. Using next-generation sequencing and viral discovery pipelines (DIAMOND, hifiasm-meta, Prokka, HMMER), we identified and assembled the complete genome of a novel filamentovirus from the parasitoid wasp Diachasmimorpha longicaudata, an important biological control agent of tephritid fruit fly pests. Comparative analyses with the NCBI online database revealed that this virus contains all 29 core genes conserved across filamentoviruses. Phylogenetic and synteny analyses further support its placement within the Filamentoviridae family. We propose to name the virus Diachasmimorpha longicaudata filamentovirus (DlFV). PCR and qPCR assays provide preliminary evidence that DlFV is present in both female and male wasps. This discovery broadens the known diversity of Filamentoviridae and further implicates parasitoid wasps as important hosts of these viruses. Understanding the function of this virus and its impact on D. longicaudata wasps may ultimately enhance the effectiveness of this species in fruit fly biocontrol programs.