Identification and characterization of a new vitivirus from grapevine

Abstract

New virus-like sequences, TvAQ7 and TvP15, were found in a Japanese grapevine accession of OKY-AQ7 (cv. Aki Queen) and of OKY-P15 (cv. Pione) by nested RT-PCR to simultaneously amplify a segment of the RNA-dependent RNA polymerase (RdRp) gene from members of the genera Vitivirus and Foveavirus. The TvAQ7 genome, except for an exact 5′ terminus, is composed of about 7.6 kb containing five potential open reading frames. The genomic organization resembles those of grapevine virus A and other known vitiviruses. The 199-amino-acid sequence deduced from the ORF4 of TvAQ7 has 38.5–54.0% identity with the coat protein (CP) of known grapevine vitiviruses and 86.9% identity with TvP15. Phylogenetic analysis based on amino acid sequences of the CP showed that TvAQ7 and TvP15 were closely related to the vitiviruses. In addition, we confirmed that TvAQ7 and TvP15 were transmitted from infected grapevine to healthy seedlings by the mealybug Pseudococcus comstocki Kuwanae. On the basis of our findings, TvAQ7 and TvP15 should be considered isolates of a new species of the genus Vitivirus, and both isolates are probably genetic variants of the new species. We propose to name this virus grapevine virus E (GVE).