Journal
PLANT DISEASE
Volume 105, Issue 1, Pages 175-182Publisher
AMER PHYTOPATHOLOGICAL SOC
DOI: 10.1094/PDIS-11-19-2395-RE
Keywords
fruit; fungi; grape; pathogen detection; powdery mildew; QoI resistance; TaqMan; strobilurin resistance; Vitis vinifera
Categories
Funding
- American Vineyard Foundation
- California State University Agricultural Research
- Michigan State University Project GREEEN
- United States Department of Agriculture (USDA) Specialty Crop Research Initiative FRAME project [2018-03375]
- USDA Agricultural Research Service Current Research Information System [5358-22000-041-00D]
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The study identified the most common genetic mutation causing resistance in grapevine powdery mildew, developed accurate diagnostic tools to detect this resistance, and achieved good results in field sampling.
Grapevine powdery mildew (GPM), caused by the fungus Erysiphe necator, is a constant threat to worldwide production of grape berries, requiring repeated use of fungicides for management. The frequent fungicide applications have resulted in resistance to commonly used quinone outside inhibitor (QoI) fungicides and the resistance is associated with single-nucleotide polymorphisms (SNPs) in the mitochondrial cytochrome b gene (cytb). In this study, we attempted to detect the most common SNP causing a glycine to alanine substitution at amino acid position 143 (i.e., G143A) in the cytb protein, to track this resistance using allele-specific TaqMan probe and digital-droplet PCR-based assays. Specificity and sensitivity of these assays showed that these two assays could discriminate SNPs and were effective on mixed samples. These diagnostic assays were implemented to survey E. necator samples collected from leaf and air samples from California and Oregon grape-growing regions. Sequencing of PCR amplicons and phenotyping of isolates also revealed that these assays accurately detected each allele (100% agreement), and there was an absolute agreement between the presence or absence of the G143A mutation and resistance to QoIs in the E. necator sampled. These results indicate that the developed diagnostic tools will help growers make informed decisions about fungicide selections and applications which, in turn, will facilitate GPM disease management and improve grape production systems.
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