Revisiting Orthotospovirus phylogeny using full-genome data and testing the contribution of selection, recombination and segment reassortment in the origin of members of new species.

The family Tospoviridae of the order Bunyavirales is constituted of tri-segmented negative-sense single-stranded RNA viruses that infect plants and are also able to replicate in their insect vectors in a persistent manner. The family is composed of a single genus, Orthotospovirus, whose type species is Tomato spotted wilt orthotospovirus. Previous studies assessing the phylogenetic relationships within this genus were based on partial genomic sequences, resulting in unresolved clades and a poor assessment of the roles of recombination and segment reassortment during mixed infections. Full genome sequences of members of recognized Orthotospovirus species are now available at NCBI. In this study, we examined 67 complete genome sequences from members of 22 species. Our study confirms the existence of four phylogroups (A to D), grouped in two major clades (A-B and C-D) within the genus. We found strong evidence that within-segment recombination events and reassortment of segments during mixed infections have been involved in the origin of new orthotospoviruses. Also, selection pressures were analyzed for each gene, and evidence of positive selection was found in all genes.