Phylogenetic justification for splitting the Rymovirus genus of the taxonomic family Potyviridae

The Potyviridae family has been divided into four genera on the basis of vector transmission, as follows: Potyvirus genus (aphid), Rymovirus genus (mite), Bymovirus genus (fungus) and Ipomovirus genus (whitefly). However recent sequence comparisons of the coat protein and 3' NCR regions of the potyviruses have demonstrated that the rymoviruses appear to be a group of two unrelated clusters namely Ryegrass Mosaic Virus (RGMV), Agropyron Mosaic Virus (AgMV) and Hordeum Mosaic Virus (HoMV) in one group and Wheat Streak Mosaic Virus (WSMV) and Brome Streak Mosaic Virus (BrSMV) in the second group. We therefore propose that RGMV, AgMV and HoMV remain in the genus Rymovirus and WSMV and BrSMV form a separate genus, possibly the Whestrevirus genus.