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POSTERS: Population biology and genetics

Survey of viruses found in grapevine cultivars grown in Missouri
James Schoelz - University of Missouri. Dean Volenberg- University of Missouri, Maher Al Rwahnih- University of California-Davis, Vicki Klaassen- Foundation Plant Services, Mustafa Adhab- University of Missouri - Columbia

In 2017 a survey was initiated of vineyards throughout Missouri for the presence of 26 different grapevine viruses. A total of 400 samples were collected with a sample consisting of 16 petioles (4 petioles from 4 different vines). A total of 26 grape cultivars were sampled. Vineyard blocks were sampled randomly without regard to the presence or absence of symptoms. After nucleic acids were extracted from petiole samples, nucleic acid samples were analyzed using reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) to detect viral RNA/DNA. At least one virus was detected in 90% of the samples. The most common virus detected in the survey was Grapevine stem pitting-associated virus, which was found in 59% of the samples, followed by Grapevine leafroll-associated virus 3 (in 53%), Grapevine red blotch (in 35%), Grapevine virus E (in 31%), Grapevine leafroll-associated virus 2 (in 19%) and its closely related variant Grapevine leafroll-associated virus 2RG (in 9%), Grapevine virus B (in 17%), Grapevine fleck virus (in 13.5%), Grapevine vein clearing virus (in 8%), Grapevine virus A (in 0.5%), and Grapevine leafroll-associated virus 4 strain 5 (in 0.2%). Two or more viruses were detected in approximately 65% of the samples, with an upper limit of seven viruses detected in one sample. An analysis of the survey results indicated that each grapevine cultivar appears to be infected by specific virus combinations that are for the most part, unique to that cultivar.