|BROOKS, SIRAPRAPA - Foreign Agricultural Service (FAS, USDA)|
|GADOURY, DAVID - Cornell University - New York|
|KOZMA, PAL - University Of Hungary|
|REISCH, BRUCE - Cornell University - New York|
Submitted to: Vitis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2011
Publication Date: 12/15/2011
Citation: Cadle Davidson, L.E., Brooks, S., Gadoury, D., Kozma, P., Reisch, B. 2011. Natural infection of Run1-positive vines by naïve genotypes of Erysiphe necator. Vitis. 50:173-175.
Interpretive Summary: Some Muscadine grapevines are naturally resistant to powdery mildew infection due to the Run1 resistance gene. This gene is being used in traditional grape breeding programs around the world. Because similar resistance genes from other crops are not typically long-lasting, we tried to determine whether Run1 would be an exception. From 2008-10 in Geneva, NY, we carefully monitored a vineyard of breeding lines known to have the Run1 resistance gene. In October 2010, signs of powdery mildew infection were readily observed on a portion of Run1 vines, although the severity of disease was reduced relative to vines lacking Run1. We observed the sexual phase of the pathogen, indicating the presence of at least two genetically different individuals. This was surprising since the pathogen population in NY had never seen Muscadine grapes or Run1, and indicates that Run1 is not likely to be long-lasting by itself. We encourage grape breeders, grape pathologists, and grape growers to work together to protect Run1 for future use by considering these results in light of long-term grape breeding strategies, commercial deployment of resistance genes, and disease management of resistant vines.
Technical Abstract: The dominant powdery mildew resistance gene Run1 from Muscadine grapes (Vitis rotundifolia) confers strong resistance characterized by rapid programmed cell death. Grape breeders around the world are introgressing Run1 into their breeding lines; however, similar resistance genes from other crops are not typically long-lasting. To detect a decrease in Run1 efficacy in the center of origin of the pathogen, from 2008-10 we carefully monitored a Geneva, NY, vineyard of breeding lines known to have Run1 resistance. In October 2010, signs of powdery mildew infection were readily observed on 14 of 113 progeny with molecular markers for Run1 (12.4%) versus 100% incidence on vines lacking Run1. For vines infected by powdery mildew, average disease severity was also lower for Run1-positive progeny (2.5) than for Run1-negative seedlings (3.8) or for susceptible and moderately susceptible controls (4.0-4.8). We observed mature cleistothecia on Run1 leaves, indicating the presence of at least two virulent pathogen genotypes. Because the pathogen population in NY has not co-evolved with Muscadine grapes, these observations suggest rapid selection for virulence on Run1. We encourage grape breeders, grape pathologists, and grape growers to work together to protect Run1 for future use by considering these results in light of long-term grape breeding strategies, commercial deployment of resistance genes, and virulence management on resistant vines.