Complete genome sequence of a German isolate of spartina mottle virus supports its classification as a member of the proposed genus “Sparmovirus” within the family Potyviridae

Spartina mottle virus (SpMV), an unassigned member of the family Potyviridae, has been known since 1980, when it was first described in England and Wales in symptomatic plants of the genus Spartina. In infected cells, flexuous particles and pinwheel inclusion bodies were found that resemble those of potyvirids. To date, the NCBI database contains only two partial sequences of a German (Nessmersiel) and an Italian (Assisi) isolate, suggesting that SpMV could be the first member of a new genus, called “Sparmovirus”, in the family Potyviridae. In this study, the first complete genome sequence of the German SpMV isolate (SpMV Ger) was determined. The genome of SpMV is a single-stranded, monopartite, polyadenylated RNA consisting of 9376 nucleotides. Sequence analysis revealed a genome organization similar to that of classical potyviruses, including many conserved features. In phylogenetic analysis, SpMV could not be assigned to any of the known genera, but it showed the closest relationship to rymoviruses and common reed chlorotic stripe virus (CRCSV, unassigned). Sequence comparisons confirmed that a new genus should be established containing SpMV, CRCSV, and three Bermuda grass mosaic virus isolates, which are considered divergent strains of SpMV.