A highly divergent isolate of tomato blistering mosaic virus from Solanum violaefolium

The complete genome of a tymovirus infecting Solanum violaefolium was sequenced. The genome comprised 6284 nt, with a 5'-UTR of 137 nt and a comparatively longer 3'-UTR of 121 nt. Sequence analysis confirmed three ORFs encoding a movement protein, a polyprotein, and a coat protein (CP). The isolate was considered to be the Tomato blistering mosaic virus (ToBMV) based on a CP amino acid sequence identity of 95.3 %. The nucleotide sequence of the complete genome of the S. violaefolium isolate, however, differed markedly from the other two reported ToBMV isolates, with identities of 76.6 and 76.3 %, below one of the demarcation criteria of the genus Tymovirus (overall genome identity of 80 %). No recombination signals were detected in the genome of this isolate. The high identity of the CP amino acid sequence and similar host responses suggest that the S. violaefolium isolate belongs to the same species as the Tomato blistering mosaic virus. The sequence analysis of this ToBMV isolate thus suggests that the demarcation criterion of 80 % overall genome sequence identity in the genus Tymovirus may require revision.