EPPO Global Database

EPPO Reporting Service no. 05 - 2015 Num. article: 2015/093

Grapevine red blotch-associated virus: addition to the EPPO Alert List

Why: Grapevine red blotch-associated virus (GRBaV) is a newly identified virus of grapevine (Vitis vinifera) and a putative member of a new genus (which remains to be characterized) within the family Geminiviridae. This virus is associated with red blotch disease that was first reported in California in 2008, and then found in the major grape-growing areas in North America. As GRBaV causes an emerging disease which affects the profitability of vineyards by substantially reducing fruit quality and ripening, the EPPO Panel on Phytosanitary Measures suggested its addition to the EPPO Alert List.

Where: for the moment, GRBaV has only been reported from North America. Although, reported recently, it is thought that GRBaV has been present in North American vineyards for a long time. The symptom similarity to leafroll viruses probably explains the delay in recognizing and characterizing the causal agent of red blotch disease.
EPPO region: absent.
North America: Canada (Ontario), USA (Arizona, Arkansas, California, Georgia, Idaho, Maryland, New Jersey, New York, North Carolina, Oregon, Pennsylvania, Texas, Virginia, Washington).

On which plants: grapevine (Vitis vinifera). The disease affects red cultivars (e.g. Cabernet franc, Cabernet sauvignon, Malbec, Merlot, Mourvèdre, Petit Verdot, Petite Syrah, Pinot Noir, Zinfandel), white cultivars (e.g. Chardonnay, Riesling), as well as table grapes and some rootstocks. GRBaV has been detected in grapevine collections, nursery stock and established vineyards.

Damage: in red grapevine cultivars, foliar symptoms consist of red blotches, marginal reddening, and red veins. In white cultivars, foliar disease symptoms are less conspicuous and generally involve irregular chlorotic areas that may become necrotic late in the season. Some white cultivars, such as Sauvignon Blanc may remain asymptomatic. Foliar symptoms first appear on older leaves at the base of the canopy in June and July and progressively move toward the top of the canopy in later months. Symptoms caused by GRBaV resemble those of leafroll viruses, but GRBaV does not cause leaf rolling, the red discolouration remains blotchy and irregular, and the smaller veins become red instead of remaining green. In addition to foliar symptoms, GRBaV affects fruit quality by delaying fruit ripening and reducing sugar content at harvest (i.e. grapes are slow to develop sugar levels sufficient for winemaking and some never fully mature).

Transmission: GRBaV is graft-transmissible and the most likely source of contamination of new vineyards is infected plant material. Although spread of GRBaV by a vector has not been confirmed, the patchy distribution of infected vines in vineyards and the increase in the number of diseased vines over time suggests that a vector is involved in disease spread. Glasshouse experiments have shown that GRBaV could be transmitted by Erythroneura ziczac (Hemiptera: Cicadellidae - Virginia creeper leafhopper) from infected to healthy vines. However, further studies are needed to understand how the virus is spread under field conditions and determine the role of the leafhopper(s) in disease epidemiology.

Pathway: plants for planting of grapevine from countries where GRBaV occurs.

Possible risks: grapevine is a crop of major economic importance in the EPPO region. GRBaV has been shown to negatively affect grapevine production and in particular, the quality of the berries. As the epidemiology of red blotch disease remains to be clarified, and in particular the role of possible vectors, the main control measures rely on the use of healthy planting material, and in some cases on the elimination of diseased plants. At present, the presence of GRBaV has been confirmed only in North America. However, in a study conducted in the National Clonal Germplasm Repository (NCGR) in California, grapevine accessions originating from countries outside North America (including European countries) tested positive for the virus. It cannot be concluded from these results that the virus occurs in those countries, but it seems wise that grapevine-growing countries verify the presence or absence of GRBaV in their crops, and eventually include this new virus in certification schemes to prevent its spread.

EPPO RS 2015/093
Panel review date -
Entry date 2015-05


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