|ACHALA, K - Oregon State University
|GREENE, M - Oregon State University
Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 3/21/2019
Publication Date: 4/3/2019
Citation: Achala, K.C., Greene, M.M., Martin, R.R. 2019. Seasonal sampling procedure for increased accuracy of grapevine red blotch virus detection. Abstract for Oregon Grape Day on April 3, 2019 in Corvallis, OR.
Technical Abstract: For the confirmation of grapevine red blotch virus (GRBV) infection, it is recommended that vines be tested for virus and not rely on symptoms as we do for other disease diagnosis. We conducted virus detection trials in southern Oregon to identify the best tissues to use for sampling and optimal vine phenology to best detect GRBV during the growing season. In the summer of 2018, we tested five infected and five non-infected grapevines in a vineyard with a history of GRB disease. Four leaf petioles were collected from the base, middle, and top of vine canopies at three phenological stages including fruit set, verasion, and harvest. Total nucleic acids were extracted from petiole samples and amplified using standard primer sets via polymerase chain reaction (PCR). Petioles from non-infected vines were all negative regardless of phenological stage or position in the vine canopy. From 180 tests of infected vines, only 53% of were positive for GRBV in the PCR assay used. From the infected vines, the accuracy of test results were consistently high (90 to 100%) for the samples collected from base of canopies and low (0-10%) from the samples collected from top of the canopy. Samples collected from the base of the canopy at harvest from infected vines were all (20 of 20) positive for GRBV. During fruit set, 95% of the petioles collected from the base of the canopies were positive, but that number decreased significantly in medium and top petioles, where only 15 and 5% of vines tested positive, respectively. During veraison, detection from the mid-canopy increased to 90% of the sampled petioles, whereas all petiole samples from the top of the canopy were negative. During harvest, GRBV detection from the middle and tops of canopies did not differ significantly from detection at veraison. These results suggest that older petioles are more suitable tissues for testing GRBV and that the accuracy of test results increases with samples collected later in the season.