High-Throughput Sequencing Indicates a Novel Marafivirus in Grapevine Showing Vein-Clearing Symptoms

A putative new marafivirus was identified in a 'Jumeigui' grapevine exhibitting obvious vein-clearing symptoms by high-throughput sequencing, which tentatively named grapevine-associated marafivirus (GaMV). The nearly complete genomic sequence of GaMV was amplified by reverse transcription PCR, and the terminal sequences were determined using the rapid amplification of cDNA ends method. The nearly complete genome of GaMV is 6346 bp long, excluding the poly(A) tail, and shows 51.2-62.3% nucleotide identity with other members of the genera Marafivirus, Maculavirus and Tymovirus in the family Tymoviridae. Additionally, it includes five functional domains homologous to those found in members of these genera. A phylogenetic analysis showed that GaMV clustered with other species-related marafiviruses. These data support GaMV being a representative member of a novel species in the genus Marafivirus. Furthermore, GaMV was graft-transmissible and 26 of 516 (5.04%) grapevine samples from five provinces in China tested positive by reverse transcription PCR. The coat protein of GaMV isolates shared 91.7-100% and 96.7-100% identities at the nt and aa levels, respectively. The coat protein-based phylogenetic trees revealed three well-defined clusters.