Phylogenetic relationships within the family Potyviridae: Wheat streak mosaic virus and brome streak mosaic virus are not members of the genus Rymovirus.
The complete nucleotide sequence of wheat streak mosaic virus [wheat streak mosaic rymovirus] (WSMV) was determined based on complementary DNA clones derived from the 9384 nucleotide (nt) RNA of the virus. The genome of WSMV had a 130 nt 5′ leader and 149 nt 3′ untranslated region and was polyadenylated at the 3′ end. WSMV RNA encoded a single polyprotein of 3035 amino acid residues and had a deduced genome organization typical for a member of the family Potyviridae (5′-P1/HC-Pro/P3/6K1/CI/6K2/VPg-NIa/NIb/CP-3′). WSMV was assigned to the genus Rymovirus because, like ryegrass mosaic virus [ryegrass mosaic rymovirus] (RGMV), WSMV was transmitted by eriophyid mites. Phylogenetic analyses were conducted with complete polyprotein or NIb protein sequences of 11 members of the family Potyviridae, including viruses of monocots or dicots and viruses transmitted by aphids, whiteflies and mites. WSMV and the monocot-infecting, mite-transmitted brome streak mosaic virus [brome streak mosaic rymovirus](BrSMV) were sister taxa and shared a most recent common ancestor with the whitefly-transmitted sweet potato mild mottle virus [sweet potato mild mottle ipomovirus]. In contrast, RGMV shared a most recent common ancestor with aphid-transmitted species of the genus Potyvirus. These results suggest that WSMV and BrSMV should be classified within a new genus of the family Potyviridae and should not be considered species of the genus Rymovirus.