The partial sequence of RNA 1 of the ophiovirus ranunculus white mottle virus indicates its relationship to rhabdoviruses and provides candidate primers for an ophiovirus-specific RT-PCR test.

A 4019 nucleotide sequence was obtained for RNA 1 of Ranunculus white mottle virus (RWMV), genus Ophiovirus, representing an incomplete ORF of 1339 aa. Amino acid sequence analysis revealed significant similarities with RNA polymerases of Rhabdoviridae and a conserved domain of 685 aa, corresponding to the RdRp domain of the Mononegavirales. Phylogenetic analysis indicated that the genus Ophiovirus is not related to the genus Tenuivirus or the family Bunyaviridae, with which it has been linked, and probably deserves a special taxonomic position, within a new family. A pair of degenerate primers was designed from a consensus sequence obtained from a relatively conserved region in the RNA 1 of two members of the genus, Citrus psorosis virus (CPsV) and RWMV. The primers, used in RT-PCR experiments, amplified a 136bp DNA fragment from all the three recognized members of the genus, i.e. CPsV, RWMV and Tulip mild mottle mosaic virus (TMMMV) and from two tentative ophioviruses from lettuce and freesia. Amplicons obtained were sequenced and compared with the corresponding sequences of CPsV and RWMV and phylogenetic relationships were evaluated. Genus-specificity was confirmed using extracts from plants infected by viruses belonging to the genera Tospovirus, Tenuivirus, Rhabdovirus and Varicosavirus.