Novel Fusari- and Toti-like Viruses, with Probable Different Origins, in the Plant Pathogenic Oomycete .

To further classify the oomycete viruses that have been discovered in recent years, we investigated virus infection in the plant-parasitic oomycete in Japan. Double-stranded RNA detection, high-throughput sequencing, and RT-PCR revealed that the isolate UOP226 contained two viruses related to fusarivirus and totivirus, named Pythium ultimum RNA virus 1 (PuRV1) and Pythium ultimum RNA virus 2 (PuRV2), respectively. Phylogenetic analysis of the deduced amino acid sequence of the RNA-dependent RNA polymerase (RdRp) showed that fusari-like PuRV1 belonged to a different phylogenetic group than Plasmopara viticola lesion-associated fusari virus (PvlaFV) 1-3 from oomycete . Codon usage bias of the PuRV1 RdRp gene was more similar to those of fungi than and , suggesting that the PuRV1 ancestor horizontally transmitted to ancestor from fungi. Phylogenetic analysis of the deduced amino acid sequence of the RdRp of toti-like PuRV2 showed a monophyletic group with the other toti-like oomycete viruses from , and . However, the nucleotide sequences of toti-like oomycete viruses were not so homologous, suggesting the possibility of convergent evolution of toti-like oomycete viruses.