Grapevine Red Blotch Disease Research Articles

Effects of Grapevine Red Blotch Disease on Cabernet franc Vine Physiology, Bud Hardiness, and Fruit and Wine Quality

The effects of grapevine red blotch disease (GRBD) on vine performance were studied in a Cabernet franc vineyard in the Okanagan Valley, British Columbia, over two years. Vines with GRBD had lower pruning mass and were less winter hardy than non-GRBD vines, and produced lower yields comprising fewer clusters and larger berries with more seeds. GRBD reduced photosynthesis and stomatal conductance for asymptomatic leaves through the growing season, and more so for symptomatic leaves. Leaf fall was delayed or incomplete for GRBD vines. GRBD reduced berry soluble solids, anthocyanins, yeast assimilable N (YAN), and tannins, and increased berry pH and titratable acidity. Wine made from GRBD fruit had reduced anthocyanin and alcohol, lighter color, and more yellow hue. Effects of GRBD on wine sensory characteristics included less body and aftertaste, lower intensity of black and red fruit character, and increased acidity and intensity of vegetal character. Inclusion of low amounts, up to 20%, of GRBD fruit in wine reduced red fruit character in the first year, and increased astringency and vegetal character in the second year. The deleterious effects of GRBD on yield, fruit composition for winemaking, and bud hardiness, constitute a serious threat to grape growing regions in Canada and the United States. The degree of these impacts would be difficult to mitigate through management practices, which underscores the importance of planting virus tested vines to prevent the introduction and spread of GRBD.

First Report of Grapevine red blotch virus, the Causal Agent of Grapevine Red Blotch Disease, in Vitis vinifera in North Carolina

Grapevine red blotch virus (GRBV), genus Grablovirus, family Geminiviridae, is the causal agent for grapevine red blotch disease (GRBD) (Al Rwahnih et al. 2013; Yepes et al. 2018). GRBV has been found in several wine-grape growing regions in the United States (Krenz et al. 2014), as well as in germplasm repositories (Al Rwahnih et al. 2015). However, the incidence of GRBV in parts of the southeastern United States is unknown. Initial observations between August and October of 2017 in North Carolina (NC) vineyards revealed that the commonly grown red cultivars Vitis vinifera ‘Merlot’, ‘Malbec’, and ‘Cabernet franc’ frequently exhibited leaf symptoms similar to those associated with GRBD. The symptoms were seemingly unrelated to location, management, or age of the plants. A total of 80 grapevine samples were collected from eight blocks in six vineyards (10 vines per block) in three different wine-grape growing regions in NC (Upper Hiwassee Highlands American Viticultural Area [AVA], Crest of the Blue Ridge Henderson County AVA, and Yadkin Valley AVA), following the recommended sampling strategy from Foundation Plant Services (FPS, University of California–Davis) (http://fps.ucdavis.edu/samplecollection.cfm). All samples were collected in October 2018. Blocks were selected based on the cultivar and the visibility of symptomatic leaves. Ten vines with leaf symptoms were selected randomly within each block. 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. Following FPS protocols, total nucleic acid (TNA) was extracted from leaf petiole tissue using the RNeasy Mini Kit (Qiagen), and samples were analyzed by quantitative reverse transcription PCR (RT-qPCR) for a panel of viruses known to infect grapevine, including GRBV. GRBV was identified in 21 samples of cultivars Merlot and Malbec in Yadkin and Surry Counties, NC (both Yadkin Valley AVA). All positive vines showed GRBD symptoms. To confirm the RT-qPCR results, aliquots of TNA from GRBV-positive samples were run by end-point PCR for further sequencing. GRBV-specific primers as described by Al Rwahnih et al. (2013) were used. RT-PCR yielded products of the expected size (557 bp) for all positive samples, and they were directly sequenced. All the positive samples shared 100% identity with 22 GRBV GenBank accessions, with the top hit being an isolate from Washington state (MF795177), based on BLASTN analysis. Complete genomes of three representative GRBV samples, one from each positive vineyard, were amplified using Phusion Hot Start Flex 2× Master Mix (NEB) and overlapping primers, GRBV-OL-F (5′-ATTCCTGCAGTTCTAGTGAAAG-3′) and GRBV-OL-R (5′-TAGAACTGCAGGAATCGC-3′). Sequencing of the 3.2-kb amplicons was done and the sequences deposited in GenBank (accession nos. MN186403 to MN186405). The GRBV sequences from NC shared 97 to 99% complete genome identities with isolates from Washington State (MF795161 and MF795177). Phylogenetic analysis revealed the clustering of the three NC isolates into GRBV clade 2 (Krenz et al. 2014). This report is part of a comprehensive survey of NC vineyards to study grapevine virus incidence in the state. The source of the virus is unclear; however, studies are underway to determine source and potential vector capacity in NC. To our understanding, this is the first time GRBV is being reported in NC.

The impact of grapevine red blotch disease on Vitis vinifera L. Chardonnay grape and wine composition and sensory attributes over three seasons.

Grapevine red blotch virus (GRBV) is a recently discovered DNA virus, which was demonstrated to be responsible for grapevine red blotch disease (GRBD). Its presence has been confirmed in the United States, Canada, Mexico, and South Korea in white and red Vitis vinifera cultivars, including Chardonnay. It has been shown that the three-cornered alfalfa treehopper (Spissistilus festinus) was able to both acquire the GRBV from a grapevine infected and transmit it to healthy grapevines in glasshouse conditions. Studies found that GRBD impacts fruit price, grapevine physiology, and grape berry composition and metabolism in red cultivars. This study evaluated the impact of GRBD on V. vinifera L. Chardonnay grape and wine composition and sensory properties from one vineyard during the 2014, 2015 and 2016 seasons. Grapes from symptomatic red blotch diseased grapevines were lower in total soluble solids, flavan-3-ol, and total phenolic content, and higher in flavonol content when compared to grapes from healthy grapevines. Wines made with grapes from symptomatic grapevines resulted mostly in lower ethanol content and higher pH when compared to wines made from healthy grapevines. Analysis of volatile compounds and descriptive analysis demonstrated that GRBD can impact wine style by altering aroma, flavor, and mouthfeel attributes. The impacts of GRBD on grape composition directly influenced wine chemistry. The decreased ethanol content impacted not only the levels of volatile compounds but the sensory perception during descriptive analysis. The extent of GRBD impact on the grape composition and wine composition and sensory attributes varied between seasons. © 2019 Society of Chemical Industry.

Impact of Grapevine Red Blotch Disease on Grape Composition of Vitis vinifera Cabernet Sauvignon, Merlot, and Chardonnay.

Grapevine red blotch disease (GRBD) is a recently recognized viral disease that affects grapevines ( Vitis vinifera L.). Currently little is known about its impact on grape composition. This study focused on the impact of GRBD on grape primary and secondary metabolites (mainly phenolic compounds) of three Vitis vinifera L. cultivars during two seasons. Grapes from symptomatic red blotch diseased vines (RB (+)) mostly had lower concentration of total soluble solids (TSS) and higher titratable acidity (TA) levels when compared to grapes from healthy vines (RB (-)) at harvest. GRBD impacted grape phenolic composition by mostly decreasing anthocyanin and increasing flavonol and proanthocyanidin (PA) contents in berry skins. No major impacts were observed on seed phenolics. RB (+) grapes contained more amino and carboxylic acids, while RB (-) grapes contained more oligosaccharides, polyols, and some specific monosaccharides at harvest. The impact of GRBD on grape composition was variable and dependent on the cultivar, site, and season.

First Report of Grapevine Red Blotch Virus in Mexico

Grapevine red blotch virus (GRBV) (Al Rwahnih et al. 2013) is a member of the recently recognized genus Grablovirus in the family Geminiviridae (Varsani et al. 2017). GRBV is the causal agent of grapevine red blotch disease (Yepes et al. 2018), affecting viticulture in North America and some other regions around the world (reviewed in Sudarshana et al. [2015]). In this study, we sampled grapevine plants displaying red blotch symptoms in the major wine producing region of Mexico: Ensenada, Baja California, in 2016 and 2017. A total of 46 samples from cultivars Vitis vinifera L. ‘Pinot Noir’ and ‘Merlot’ were tested in 2016 by end-point polymerase chain reaction (PCR) using primers GRBV-V2F (5′-ATGGGTTAGGGGATGAGGCT-3′) and GRBV-V1R (5′-CGGCAATGACTCCTGCGGCT-3′). Results showed amplification of the expected 798-bp product from 31 samples. One of these amplicons was cloned, sequenced, and compared with reported sequences through a BLASTn search. The fragment had high nucleotide sequence identity (98%) with GRBV isolate BCRB5 from Canada (GenBank accession no. KX234092). The presence of GRBV was corroborated using the AmplifyRP Acceler8 kit (Agdia, Elkhart, IN), which detects the GRBV genome by isothermal recombinase polymerase amplification (RPA). In 2017 symptomatic V. vinifera ‘Nebbiolo’ plants were tested by multiplex PCR to amplify a region of the replicase-associated protein (Rep) gene with primers Repfor/Reprev (expected product 318 bp) and a fragment from the coat protein (CP) gene with primers CPfor/CPrev (expected product 257 bp) (Krenz et al. 2014). Amplicons from a positive sample were cleaned using a GenJet PCR purification kit (Thermo Fisher Scientific, Waltham, MA) and analyzed by Sanger sequencing. Both Rep and CP fragments shared >99% nucleotide sequence identity with GRBV isolates ONRB7 (KY316025) and ONRB4 (KY316022) from Canada (Poojari et al. 2017). To gain a deeper insight into the phylogeny of local GRBV isolates, we sequenced the full-length viral genome of 2016 and 2017 representative isolates. Each genome was amplified by high-fidelity PCR in two fragments, combining primers CPfor/Reprev (expected product 1.8 kb) and Repfor/CPrev (expected product 1.9 kb). After Sanger sequencing, the genomes were assembled in the GeneStudio sequence analysis software version 2.2.0.0 (GeneStudio, Suwanee, GA). A phylogenetic tree constructed after comparing the local isolates GRBV-Gpe-JGB (MH557096) and GRBV-Gpe-JCT (MH557095) to GRBV isolates from Canada and the United States grouped the Baja Californian isolates with clade 1 isolates. To our best knowledge, this is the first report of GRBV in Mexico.

Mitigating the Economic Impact of Grapevine Red Blotch: Optimizing Disease Management Strategies in U.S. Vineyards

Grapevine red blotch disease (GRBD) is a recently-recognized viral disease found across some of the major grapegrowing regions in the United States. Vineyard managers were surveyed to (i) estimate the economic impact of GRBD on Vitis vinifera cv. Cabernet Sauvignon in Napa and Sonoma Counties in California and on V. vinifera cv. Merlot in eastern Washington and Long Island in New York, and (ii) to identify cost-minimizing management strategies under various disease incidence rates, price penalties for suboptimal fruit composition, timing of disease onset relative to vineyard age, and costs of control. The economic cost of GRBD was estimated to range from $2213/ha in eastern Washington, when disease onset occurs at a low initial infection level and there is a low price penalty, to $68,548/ha in Napa County, when initial infection rates and quality penalties are both high. Our results further suggest that roguing symptomatic vines and replanting with clean vines derived from virus-tested stocks minimize losses if GRBD incidence is low to moderate (below 30%), while a full vineyard replacement should be pursued if disease incidence is higher, generally above 30%. These findings should help vineyard managers in the four examined viticultural regions adopt optimal GRBD management strategies.

Effects of Grapevine red blotch-associated virus (GRBaV) infection on foliar metabolism of grapevines

Grapevine red blotch-associated virus (GRBaV), which causes grapevine red blotch disease, is an emerging problem for grapevine production in the United States. However, little is known about how viruses, such as GRBaV, affect host physiology even though it is crucial to understanding host-pathogen interactions, symptom development, and potential effects on other pathogens and insect pests including potential vectors. Thus, foliar levels of amino acids, sugars, phenolics and terpenoids were examined in healthy or GRBaV-infected ‘Cabernet Franc’ (CF) or ‘Cabernet Sauvignon’ (CS) grapevines both before and after development of red blotch symptoms, in July and September of 2014, respectively. Particular amino acids were increased both before and after symptom development in both cultivars, with some of these amino acids having previously defined associations with host defences. Fructose and glucose were increased in GRBaV-infected CF at both sampling times. However, for CS only, glucose was increased in infected grapevines and only when pre-symptomatic. Phenolic levels were greater in GRBaV-infected CF and CS after symptom expression. Terpenoids were greater in infected CF in July, with no other apparent differences. Taken together, these results demonstrate the effects of GRBaV infection on host physiology, with shifts potentially associated with symptom development and changes in resistance to other organisms.

Grapevine red blotch-associated virus Is Widespread in the United States.

Grapevine red blotch disease has been recognized since 2008 as affecting North American grape production. The presence of the newly described Grapevine red blotch-associated virus (GRBaV) is highly correlated with the disease. To more effectively detect and monitor the presence of the virus, a sample processing strategy and multiplex polymerase chain reaction assay were developed. A total of 42 of 113 vine samples collected in or received from seven of the United States were shown to harbor the virus, demonstrating the virus is widely distributed across North America. Phylogenetic analyses of a viral replication-associated protein (Rep) gene fragment from the 42 isolates of GRBaV demonstrated distinct clades of the virus (1 and 2), with clade 1 showing the greatest variability. The full-length genome of six virus isolates was sequenced, and phylogenetic analyses of 14 whole genomes recapitulated results seen for the Rep gene. A comparison of GRBaV genomes revealed evidence of recombination underlying some of the variation seen among GRBaV genomes within clade 1. Phylogenetic analyses of coat and replicase-associated protein sequences among single-stranded DNA viruses showed GRBaV to group within the family Geminiviridae. This grouping is distinct from members of the families Nanoviridae and Circoviridae, with limited significant affinities to both recognized genera and novel plant-infecting, gemini-like viruses.

Association of a DNA Virus with Grapevines Affected by Red Blotch Disease in California

In the Napa Valley of California, vineyards of 'Cabernet Franc' (CF) clone 214, 'Cabernet Sauvignon' clone 337, and 'Zinfandel' clone 1A (Z1A) with grapevines exhibiting foliar symptoms of red blotches, marginal reddening, and red veins that were accompanied by reduced sugar accumulation in fruit at harvest were initially suspected to be infected with leafroll-associated viruses. However, reverse-transcription polymerase chain reaction (PCR) tests were negative for all known leafroll-associated viruses, with the exception of Grapevine leafroll-associated virus 2 in Z1A. Metagenomic analysis of cDNA libraries obtained from double-stranded RNA enriched nucleic acid (NA) preparations from bark scrapings of dormant canes on an Illumina platform revealed sequences having a distant relationship with members of the family Geminiviridae. Sequencing of products obtained by PCR assays using overlapping primers and rolling circle amplification (RCA) confirmed the presence of a single circular genome of 3,206 nucleotides which was nearly identical to the genome of a recently reported Grapevine cabernet franc-associated virus found in declining grapevines in New York. We propose to call this virus "Grapevine red blotch-associated virus" (GRBaV) to describe its association with grapevine red blotch disease. Primers specific to GRBaV amplified a product of expected size (557 bp) from NA preparations obtained from petioles of several diseased source vines. Chip bud inoculations successfully transmitted GRBaV to test plants of CF, as confirmed by PCR analysis. This is the first report of a DNA virus associated with red blotch disease of grapevines in California.

Perspectives in neuro-ophthalmology.

<h3>Abstract</h3> Grapevine red blotch disease (GRBD) is an emerging disease caused by grapevine red blotch virus (GRBV). It is widespread in a majority of wine grape production regions in the United States and differential spread dynamics have been reported between the regions. In this study, we surveyed eight vineyard sites in southern Oregon over four years for the progression of GRBD incidence. The surveyed vineyards included five sites that were five years or older and three sites that were three years old. The disease incidence in the older blocks ranged from 2.81 to 58.78%; whereas in the younger blocks it ranged from 0.29 to 1.11%. Some of these vineyards implemented frequent disease scouting, removing, and replanting. The disease incidence in these blocks remained less than 5% over the survey period. However, in the vineyards that did not implement any roguing and replanting, the disease incidence increased by nearly 30-fold after three years. We analyzed the spatial distribution of the disease in vineyards surveyed in 2020 and found that the disease distribution is highly aggregated based on Spatial Analysis by Distance Indices (SADIE). In a separate study, we also tested the GRBV infection status of asymptomatic vines next to symptomatic vines to aid in the decision making process when roguing and replanting. Out of 410 asymptomatic vines, surrounding 41 symptomatic vines, only two tested positive for GRBV. Additionally, in 2020 and 2021, we tested the GRBV status on previously identified possible alternative host species, blackberries (<i>Rubus armeniacus</i>) and wild/feral grapes (<i>Vitis riparia</i>) collected from areas surrounding the four survey sites. We observed that GRBV was present in 10 to 70% of the wild grape samples in both years and 10% of the blackberry samples in 2020. However, the virus titer was low in blackberry samples and it was not detected in 2021 samples. These results indicate the potential importance of wild grapes as alternative hosts on GRBD incidence and spread in southern Oregon vineyards, while blackberry is unlikely to be an alternative host with epidemiological significance.