UC Davis

Two novel negative-stranded (ns)RNA viruses were identified by high throughput sequencing in grapevine. The genomes of both viruses, named grapevine Muscat rose virus (GMRV) and grapevine Garan dmak virus (GGDV), comprise three segments with each containing a unique gene. Based on sequence identity and presence of typical domains/motifs, the proteins encoded by the two viruses were predicted to be: RNA-dependent RNA polymerase (RdRp), nucleocapsid protein (NP), and putative movement protein (MP). These proteins showed the highest identities with orthologs in the recently discovered apple rubbery wood viruses 1 and 2, members of a tentative genus (Rubodvirus) within the family Phenuiviridae. The three segments of GMRV and GGDV share almost identical sequences at their 5' and 3' termini, which are also complementary to each other and may form a panhandle structure. Phylogenetics based on RdRp, NP and MP placed GMRV and GGDV in the same cluster with rubodviruses. Grapevine collections were screened for the presence of both novel viruses via RT-PCR, identifying infected plants. GMRV and GGDV were successfully graft-transmitted, thus, they are the first nsRNA viruses identified and transmitted in grapevine. Lastly, different evolutionary scenarios of nsRNA viruses are discussed.