Classification of tospoviruses based on phylogeny of nucleoprotein gene sequences

The nucleotide sequences of the nucleoprotein (N) genes of seven tospovirus isolates representing three serogroups were determined and used to establish phylogenetic parameters to delineate species within the Tospovirus genus of the Bunyaviridae. A high sequence divergence (55.9% identity at the nucleotide level) was observed between isolates of serogroup I (tomato spotted wilt virus) and isolates of serogroup III (Impatiens necrotic spot virus). The serogroup II isolates take an intermediate position. Their N genes have 75% identity with those of serogroup I isolates and 57% with those of serogroup III isolates. Whereas the isolates within serogroups I or III have almost identical sequences, the two isolates BR-03 and SA-05 of serogroup II diverged significantly from each other (82.1% sequence identity). The results obtained support the conclusion that, in addition to the species TSWV and INSV, the serogroup II isolates BR-03 and SA-05 have to be considered as distinct species within the genus Tospovirus for which the names tomato chlorotic spot virus and groundnut ringspot virus, respectively, are proposed.