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Poster: Diseases of Plants: Disease Detection & Diagnosis


The prevalence of grapevine leafroll and red blotch diseases in Washington vineyards
J. ADIPUTRA (1), P. Swamy (1), B. Donda (1), B. Bagewadi (1), N. Natra (1), R. Naidu (1) (1) Washington State University, U.S.A.

Grapevine leafroll disease (GLD) is a significant constraint to the production of wine grapes (Vitis vinifera) in Washington State. Grapevine leafroll associated virus (GLRaV) 1, 2, 3, and 4 have so far been documented, with GLRaV-3 being the most widely distributed in Washington vineyards. However, recent reports of the occurrence of grapevine red blotch disease (GRBD) have raised concerns about the extent of its distribution in Washington vineyards. Since the symptomatology of GLD and GRBD is highly similar in wine grape cultivars, reliable information on the prevalence of these two diseases is necessary for deploying appropriate disease mitigation strategies. Towards this objective, surveys of vineyards were conducted during 2014 and 2015 seasons in seven American Viticultural Areas of Washington. A total of 1,469 samples collected from fourteen red-berried and five white-berried wine grape cultivars were tested for the presence of GLRaV-3 and Grapevine red blotch-associated virus (GRBaV) by polymerase chain reaction (PCR)-based diagnostic assays. The PCR results were further confirmed by cloning and sequencing of virus-specific amplicons. The combined data showed that 83.7% and 13.7% of samples were positive for GLRaV-3 and GRBaV, respectively, indicating that GLD is predominant relative to GRBD in Washington vineyards. A multiplex PCR assay has been optimized for high throughput testing of grapevine samples for the presence of GLRaV-3 and GRBaV.