38th Annual Meeting of the Society for Invertebrate Pathology

Natural populations of the spruce budworm, Choristoneura fumiferana, are regulated by various natural enemies, including the ichneumonid wasps Tranosema rostrale (subfamily Campopleginae) and Glypta fumiferana (subfamily Banchinae). These endoparasitoids oviposit at different times of their host’s life cycle: G. fumiferana females lay their eggs in pre-diapause 2^nd instars, while T. rostrale wasps parasitize post-diapause instars. At oviposition, both parasitoids inject a polydnavirus (PDV) that is believed to be required for successful parasitization. Sequences obtained to date for genomes of PDVs isolated from ichneumonid (Ichnovirus; IV) and braconid (Bracovirus; BV) wasps indicate that the two groups differ with respect to gene content and families. Here, we show that among IVs, differences are also observed between the virus of the campoplegine T. rostrale (TrIV) and that of the banchine G. fumiferana (GfIV). The latter has a virion morphology distinct from that of campoplegine IVs, and its genome segments are both smaller and more abundant. In addition, sequence analysis indicates that while TrIV contains genes similar to those found in other IVs, the genes identified in GfIV are more similar to those of BVs. These singularities may reflect differences in phylogenetic lineages and/or in selection pressures experienced by the two wasps.