A Survey of Viruses Found in Grapevine Cultivars Grown in Missouri

In 2017 a survey was initiated of vineyards throughout Missouri for the presence of 19 different grapevine viruses. A total of 400 samples were collected from 25 grape cultivars, with a sample consisting of 16 petioles (four petioles from four different vines). Sampling within vineyard blocks was random, 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 rupestris stem pitting-associated virus, which was found in 59% of the samples, followed by grapevine leafroll-associated virus 3 (53%), grapevine red blotch virus (35%), grapevine virus E (31%), grapevine leafroll-associated virus 2 (19%), grapevine virus B (17%), grapevine fleck virus (13.5%), grapevine leafroll-associated virus-2 Redglobe (9%), grapevine vein clearing virus (8%), grapevine virus A (0.5%), and grapevine leafroll-associated virus 4 strain 5 (0.2%). Two or more viruses were detected in ~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.