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POSTERS: Fungicide and antibiotic resistance

Rapid sampling techniques to monitor quinone outside inhibitor fungicide resistant Erysiphe necator
Sarah Lowder - Oregon State University. Walter Mahaffee- USDA ARS, Timothy Miles- Michigan State University, Michelle Moyer- Washington State University, Tara Neill- USDA ARS

Quinone outside inhibitor fungicide resistant Erysiphe necator can be monitored using a previously developed competitive TaqMan qPCR assay. However, it is unclear how to sample vineyards to accurately assess resistance in a field population. A visual assessment with observed colonies collected by rubbing a cotton swab over the leaf surface (leaf swab) was compared to rubbing a swab over worker gloves (glove swab). Over 1500 samples from 326 row transects were collected throughout the 2018 season from 12 commercial Oregon vineyards via a linear stratified sampling pattern where each sample type was collected from the same row. For each row, the leaf swabs were aggregated. Comparing presence-absence of leaf vs glove swabs, there was a 65% agreement between techniques. In 31% of sampled rows, glove swabs detected the presence of E. necator without visual detection, indicating that glove swabs may be able detect disease at lower levels than traditional disease scouting. When E. necator was detected via both leaf and glove swab, the samples agreed 98% of the time for presence of the resistance genotype at the row level. Cooperating growers also collected glove swab samples and results agreed 77% of the time with the researcher glove samples. These results indicate that swabbing vineyard worker gloves may be a viable technique for E. necator sampling and fungicide resistance monitoring with minimal interruption to grower production practices or added collection costs.