Abstract
BackgroundIn recent years, the Ontario grape and wine industry has experienced outbreaks of viral diseases across the province. Little is known about the prevalence of viruses and viral diseases in Ontario. Since 2015, we have conducted large-scale surveys for major viruses in commercial wine grapes in order to obtain a comprehensive understanding of the prevalence and severity of viral diseases in Ontario.MethodsA total of 657 composite leaf samples representing 3285 vines collected from 137 vine blocks of 33 vineyards from three appellations: Niagara Peninsula, Lake Erie North Shore and Prince Edward County. These samples covered six major red cultivars and five major white grape cultivars. Using a multiplex RT-PCR format, we tested these samples for 17 viruses including those involved in all major viral diseases of the grapevine, such as five grapevine leafroll-associated viruses (GLRaV-1, 2, 3, 4, 7), grapevine red blotch virus (GRBV), grapevine Pinot gris virus (GPGV), grapevine rupestris stem sitting-associated virus (GRSPaV), grapevine virus A (GVA), grapevine virus B (GVB), grapevine fleck virus (GFkV), arabis mosaic virus (ArMV), tomato ringspot virus (ToRSV), trapevine fanleaf virus (GFLV), among others.ResultsFourteen of the 17 viruses were detected from these samples and the predominant viruses are GRSPaV, GLRaV-3, GFkV, GPGV and GRBaV with an incidence of 84.0, 47.9, 21.8, 21.6 and 18.3%, respectively. As expected, mixed infections with multiple viruses are common. 95.6% of the samples included in the survey were infected with at least one virus; 67% of the samples with 2–4 viruses and 4.7% of the samples with 5–6 viruses. The major grape cultivars all tested positive for these major viruses. The results also suggested that the use of infected planting material may have been one of the chief factors responsible for the recent outbreaks of viral diseases across the province.ConclusionsThis is the first such comprehensive survey for grapevine viruses in Ontario and one of the most extensive surveys ever conducted in Canada. The recent outbreaks of viral diseases in Ontario vineyards were likely caused by GLRaV-3, GRBV and GPGV. Findings from this survey provides a baseline for the grape and wine industry in developing strategies for managing grapevine viral diseases in Ontario vineyards.
Highlights
In recent years, the Ontario grape and wine industry has experienced outbreaks of viral diseases across the province
Fourteen viruses were detected in Vitis vinifera wine grapes in Ontario We used the multiplex RT-PCR system we developed to screen for 17 viruses separated into five groups, which included five viruses that are associated with leafroll (GLRaV-1, − 2, − 3, − 4, − 7), three that are involved in rugose wood (GRSPaV, grapevine virus A (GVA), and grapevine virus B (GVB)), three nepoviruses that are causal agents of the infectious degegneration and decline (ArMV, grapevine fanleaf virus (GFLV), and tomato ringspot virus (ToRSV)), and four viruses that are associated with the fleck complex (GFkV, grapevine asteroid mosaic-associated virus (GAMaV), grapevine Syrah virus − 1 (GSyV-1) and grapevine rupestris vein feathering virus (GRVFV))
Using a multiplex RT-PCR format we recently developed, we have tested for 17 viruses from 657 composite samples representing 3285 vines collected from the three major grape-growing regions in the province
Summary
The Ontario grape and wine industry has experienced outbreaks of viral diseases across the province. A new disease, grapevine red blotch, caused by the DNA virus ‘grapevine red blotch virus’ (GRBV) was discovered in the USA [8, 9] and Canada [10, 11]. Another new virus, grapevine Pinot gris virus (GPGV) was identified in grapevine plants showing symptoms of chlorotic mottling and leaf deformations [12] and was soon reported worldwide from many countries in Europe, Asia, South and North America [13]. In Canada, GPGV has been reported in Ontario and British Columbia [14, 15]
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