First report of grapevine rupestris vein feathering virus in Vitis vinifera L. from Japan

The production of wine grapes is gaining widespread popularity and being carried out on approximately 2,200 hectares of land in Japan. Scions grafted onto rootstocks generally have been imported from the EU, USA, New Zealand, and Australia into Japan. Unfortunately, viruses have spread in Japanese vineyards by slipping through the net of plant quarantine. Grapevine rupestris vein feathering virus (GRVFV), which was detected in a Greek grapevine accessions, is a member of genus Marafivirus in family Tymoviridae (El Beaino et al. 2001). GRVFV has been detected in many countries such as USA, Canada, Australia, New Zealand, Italy, Spain, Switzerland, Czech Republic, Uruguay, and Pakistan (Jo et al. 2015; Eichmeier et al. 2016; Xiao and Meng 2016; Blouin and MacDiarmid 2017; Reynard et al. 2017; Cho et al. 2018; Mahmood et al. 2019; Wu et al. 2020). Herein we report GRVFV infection in Vitis vinifera L. grapevines from Japan. In February 2021, dormant canes from 18 V. vinifera cv. Cabernet Sauvignon with leafroll-like disease symptoms, growing in a vineyard located in Kanagawa Prefecture, were collected. No typical vein banding symptom by GRVFV were observed in the grapevines during the growing season. Total RNA was isolated from the canes using an RNeasy Plant Mini Kit and QIAshredder (Qiagen, Valencia, CA), and subjected to cDNA synthesis using a PrimeScript 1st Strand cDNA Synthesis Kit (Takara Bio, Shiga, Japan). RT-PCR was performed with GRVFV_6156F and GRVFV_6600R primers for GRVFV detection (Reynard et al. 2017). The expected 445 nucleotides (nt) amplification product was obtained from four of 18 grapevines. Sequence analysis of the products revealed 91% identities to corresponding sequences of GRVFV isolates CHASS (KY513702) and Mauzac (KY513701) from Switzerland. Genome walking to determine the whole-genome sequence of the GRVFV isolates from the four grapevines was performed. Briefly, the upstream and downstream of the 445 nt amplification product were amplified from first-strand cDNA using gene-specific primers designed from the product and CHASS-specific primers. Each amplified fragment was Sanger sequenced. Next, gene-specific primers were designed to obtain the complete genome of GRVFV as 13 overlapping DNA fragments from each of the four grapevine samples. An identical complete genome of 6,704 bp was assembled from the overlapping DNA fragments using MEGA 10 software and named as NA1 isolate (DDBJ accession no. LC619667). Phylogenetic analysis of the NA1 genome and corresponding sequences of GRVFV from other countries showed that NA1 formed a cluster with isolate NZ ChTK0004 from New Zealand (MF000326; Supplementary Figure 1). In pairwise comparisons, the complete NA1 genome was most identical at 88% and 87%, respectively to isolates NZ ChTK0004 and Mauzac. The predicted amino acid sequences of NA1 polyprotein shared high homologies (96%) to the corresponding polyprotein sequences of NZ ChTK0004 and Mauzac, suggesting that NA1 is genetically similar to GRVFV isolates from New Zealand and Switzerland. The NA1-infected Cabernet Sauvignon was co-infected with Grapevine leafroll-associated virus 3, Grapevine virus A, and Grapevine rupestris stem pitting-associated virus according to RT-PCR assay for grapevine virus detection (Nakaune and Nakano 2006). The results underscore the importance of intensifying quarantine measures to prevent introduction of exotic viruses via contaminated wine grape vegetative cuttings.