Identification and characterization of a novel carlavirus isolated from viburnum (Viburnum opulus) in Aotearoa New Zealand

The genus Viburnum includes more than 150 species of ornamental shrubs and trees cultivated worldwide. In Aotearoa New Zealand (NZ), V . opulus is the most popular species widely used in landscaping. To date, alfalfa mosaic virus (AMV) has been the only virus reported in viburnum in NZ. In this study, we report the identification and molecular characterization of a novel Carlavirus , tentatively named viburnum carlavirus 1 (VibCV1), from a V. opulus plant co-infected with AMV. The virus was characterized using high-throughput sequencing, transmission electron microscopy, and herbaceous indexing. The complete genome of VibCV1 is 8,444 nucleotides in length and encodes six open reading frames in a genome organization typical of members of the genus Carlavirus . Phylogenetic analyses revealed that VibCV1 is most closely related to Helleborus mosaic virus (HeMV), sharing 80.24% and 85.48% identity in the replicase and coat protein, respectively. These values lie on the borderline of current species demarcation criteria in the family Betaflexiviridae . Considering the distinct natural host range, limited distribution, and the phylogenetic divergence from HeMV, we propose that VibCV1 represents a novel species within the genus Carlavirus . The low incidence of VibCV1 in NZ viburnum populations is also discussed.