Molecular characterization of a novel partitivirus with four segments isolated from Fusarium solani, the causal agent of citrus root rot

We report here the identification of a dsRNA virus, obtained from <i>Fusarium solani</i> strain Newher-7, tentatively named <i>F. solani</i> partitivirus 3 (FsPV3). It consists of four dsRNA segments (dsRNA1-4) with lengths of 1961, 1900, 1830 and 1830 bp, respectively. Sequence analysis showed that dsRNA1 encodes an RNA-dependent RNA polymerase (RdRp), dsRNA2 encodes a capsid protein (CP), dsRNA3 encodes a hypothetical protein of unknown function and dsRNA4 encodes two hypothetical proteins of unknown function. Amino acid sequence comparisons showed that the RdRp of FsPV3 is most similar to that of Hulunbuir Parti tick virus 1. In contrast, the CP of FsPV3, as well as the hypothetical protein encoded by ORF3 of dsRNA3, was most similar to cognate proteins encoded by <i>Colletotrichum</i>-associated partitivirus 2. However, the two hypothetical proteins encoded by dsRNA4 showed no significant similarity to the available sequences in the National Center for Biotechnology Information database and encoded no apparent conserved domains. Phylogenetic analysis of the RdRp and CP showed that FsPV3 clustered together with other species in the genus <i>Alphapartitivirus</i>. Given that proteins encoded by FsPV3 are not sufficiently highly homologous to a single known virus and that it encodes two novel proteins, we suggest that FsPV3 should be regarded as a new member of the genus <i>Alphapartitivirus</i> in the family <i>Partitiviridae</i>. This is the first report of FsPV3 infecting <i>F. solani</i>.