A breakthrough in understanding grapevine powdery mildew resistance in V. amurensis
image: Vitis amurensis “PI 588631” exhibits a rapid and strong resistance response associated with host necrosis at attempted powdery mildew penetration sites.
Credit: Horticulture Research
Throughout evolution, plants and pathogens have engaged in an arms race, with plants developing resistance genes like nucleotide-binding site leucine-rich repeats (NLRs) to counteract pathogen effectors. Historically, eastern North America has been identified as a diversity hub for Erysiphe necator, the causative agent of grapevine powdery mildew (GPM). Consequently, most Vitis species native to this region show GPM resistance, often linked to NLR loci. Interestingly, Vitis species from Eurasia also manifest resistance, pointing to the same NLR loci. A parallel situation is observed with Plasmopara viticola, another grapevine pathogen. Although some resistance mechanisms against GPM in V. amurensis are known, the genetic basis for others remains elusive. Therefore, it is urgent to develop DNA marker technology to assist the identification of resistance candidate genes and genetic improvement of grapes.
In March 2023, Horticulture Research published a research paper entitled by “Discovery and genome-guided mapping of REN12 from Vitis amurensis, conferring strong, rapid resistance to grapevine powdery mildew ”.
To understand the resistance mechanism and specificity against grapevine powdery mildew (GPM) in V. amurensis “PI 588631”, a series of E. necator isolates were used in controlled inoculation experiments. Results at 48 hours post-inoculation showed that all isolates were highly resistant, with more than 97% of conidia being halted before or immediately after emergence of a secondary hypha from appressoria. This resistance indicated a decreased penetration success rate and decreased hyphal branching, both suggestive of a programmed cell death response in the host. Assessment of grapevine powdery mildew resistance in individuals naturally infected with Vitis amurensis 'PI 588631' × V. vinifera 'Valley Pearl' F1 generation in vineyards showed an increase in disease severity in all tissue types each year. Computer-aided assessments of controlled inoculations using a neural network to track hyphal growth validated these field observations. In the genetic analysis using 2,000 rhAmpSeq core genome markers, 874 markers showed polymorphism in F1 progeny, revealing a high degree of genetic alignment among the parent plants. A consistent resistance locus named REN12 mapped to chromosome 13 between 22.8 and 27.0 Mb. This locus accounted for 86.9% of the observed phenotypic variation in leaves, independent of tissue type. The accuracy was further improved by shotgun sequencing of recombinant vines using skim-seq technology, which narrowed the locus to a 780 kb region of 25.15-25.93 Mb. RNASeq analysis showed allele-specific expression of four resistance genes (NLRs) in the resistant parent. Furthermore, a genome alignment with another V. amurensis variant highlighted structural differences and an increased number of potential resistance genes in the examined locus.
In summary, this study identified and examined a new GPM resistance source in V. amurensis “PI 588631”, holding promise for the genetic enhancement of grapes, offering valuable germplasm for future grapevine improvements. Effective conservation of resistance resources can be achieved in the future by stacking resistance loci and combining them with other suppression strategies to minimize the selection of virulent isolates.
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References
Authors
Surya Sapkota1, Cheng Zou2, Craig Ledbetter3, Anna Underhill4, Qi Sun2, David Gadoury1 and Lance Cadle-Davidson1,4,*
Affiliations
1. School of Integrative Plant Science, Cornell AgriTech, Cornell University, Geneva, NY, 14456, USA
2. BRC Bioinformatics Facility, Institute of Biotechnology, Cornell University, Ithaca, NY, 14853, USA
3. United States Department of Agriculture (USDA)-Agricultural Research Service (ARS), Crop Diseases, Pests and Genetics Research Unit, San Joaquin Valley Agricultural Sciences Center, Parlier, CA, 93648, USA
4. USDA-ARS, Grape Genetics Research Unit, Geneva, NY, 14456, USA
About Lance Cadle-Davidson
He is an adjunct associate professor in the School of Integrative Plant Science, Plant Pathology, and Plant-Microbe Biology Section Cornell AgriTech at Cornell University. His research interests include sustainable management of fungal and oomycete diseases in grapevine, host-pathogen co-evolution and disease resistance, and the use of genomic tools to enhance breeding.