First report of grapevine red blotch virus, the causal agent of grapevine red blotch disease in vitis vinifera in North Carolina

Authors: HOFFMANN, MARK - North Carolina State University; TALTON, WIN - North Carolina State University; NITA, MIZHUHO - Virginia Tech; TAYLOR, JONES - Virginia Tech; AL RWAHNIH, MAHER - University Of California, Davis; Sudarshana, Mysore; ALMEYDA, CHRISTIE - North Carolina State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2019
Publication Date: 4/1/2020
Citation: Hoffmann, M., Talton, W., Nita, M., Taylor, J., Al Rwahnih, M., Sudarshana, M.R., Almeyda, C. 2020. First report of grapevine red blotch virus, the causal agent of grapevine red blotch disease in vitis vinifera in North Carolina. Plant Disease. 104(4):1266-1266. https://doi.org/10.1094/PDIS-07-19-1539-PDN.
DOI: https://doi.org/10.1094/PDIS-07-19-1539-PDN

Interpretive Summary:

Technical Abstract: Grapevine red blotch disease (GRBD) was first described on Vitis vinifera cv. ‘Cabernet Sauvignon’ at the University of California Oakville Research Station in 2008 and since then has been affecting North American grape production (Krenz et al., 2014). Grapevine red blotch virus (GRBV, Genus Grablovirus, Family Geminiviridae) was consistently isolated from symptomatic grapevines (Al Rwahnih et al., 2013). Recently, Koch’s postulates have been fulfilled therefore proving that GRBV is the causal agent of Grapevine red blotch disease (Yepes et al. 2018). GRBV has been found throughout the United States (Krenz et al., 2014), as well as in germplasm repositories (Al Rwahnih et al. 2015). However, the incidence of GRBV affecting grapes in parts of the southeast of the US is unknown. Initial observations over the second half of 2017 in North Carolina (NC) vineyards revealed, that the commonly grown red varieties V. vinifera cv. ‘Merlot’ and cv. ‘Cabernet franc’ frequently exhibited leaf symptoms similar to those associated with leafroll and red blotch disease. Those symptoms were seemingly unrelated to location, management or age of the plants. A total of 240 grapevine samples were collected from 8 commercial vineyards (10 vines per vineyard) in 3 different wine-grape growing regions in NC, following the recommended sampling strategy of the Foundation Plant Services (FPS, UC Davis) (http://fps.ucdavis.edu/samplecollection.cfm). Three samples per grapevine were collected, sampling both cordons. Samples were directly stored at 4°C and shipped overnight to the NC State University Micropropagation and Repository Unit for further processing. One out of three samples were processed at the day of arrival, and two samples were stored at -80°C for further processing. Samples were tested by RT-qPCR for a panel of viruses known to infect grapevine, including GRBV. Total RNA was extracted from leaf petiole tissue using a modified RNeasy Mini Kit (Qiagen). The RNA was analyzed for the presence of the GRBV genome by qPCR. Among the 80 vines tested, GRBV was identified in 21 samples of V. vinifera cv. ‘Merlot’ and ‘Malbec’ in Yadkin and Surry Counties, NC. Infections with other common grapevine viruses were also identified in these samples. To confirm the qPCR results, fresh aliquots of RNA from GRBV positive samples were run by conventional RT-PCR and sequenced (GenBank accession number: MK573562). The reaction used GRBV-specific primers as described by Al Rwahnih et al. (2013). PCR yielded products of expected size (557 bp) and were directly sequenced. The sequenced regions were compared to other GRBV sequences by Basic Local Alignment Search Tool (BLAST) and shared 100% identity to 22 GRBV accessions (GenBank accession number top hit MF795177.1). This report is part of a comprehensive survey of NC vineyards to study grapevine virus incidence in the state. GRBV was found in the premium wine making region of NC, the Yadkin Valley AVA. To this date the source of the virus is unclear, however studies are underway to determine the local vector capacity. To our understanding, this is the first time GRBV is being reported in North Carolina. This study was partly funded by the North Carolina Grape and Wine Council.