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ARS Home » Northeast Area » Geneva, New York » Grape Genetics Research Unit (GGRU) » Research » Publications at this Location » Publication #213373
Title: Ontogenic resistance to Uncinula necator varies by genotype and tissue type in a diverse collection of Vitis spp

Author
item GEE, CHRISTOPHER - CORNELL UNIVERSITY
item GADOURY, DAVID - CORNELL UNIVERSITY
item Cadle-Davidson, Lance

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2008
Publication Date: 7/1/2008
Citation: Gee, C., Gadoury, D., Cadle Davidson, L.E. 2008. Ontogenic resistance to Uncinula necator varies by genotype and tissue type in a diverse collection of Vitis spp. Plant Disease. 92:1067-1073.

Interpretive Summary: As plants or plant tissues age, their susceptibility to pathogens changes via a phenomenon known as ontogenic resistance. Grapevine berries susceptible to grapevine powdery mildew become ontogenically resistant approximately 2 to 3 weeks post-bloom, as demonstrated in several cultivars of Vitis vinifera and in V. labruscana ‘Concord.’ To identify genetic variation for ontogenic resistance, we screened a diverse collection of species and interspecific hybrids maintained in the USDA-ARS cold-hardy Vitis germplasm collection in Geneva, NY. Of the 79 genotypes whose fruit clusters were screened for susceptibility to powdery mildew under field conditions, 50 were resistant to powdery mildew irrespective of the stage of berry development at the time of inoculation. Of the susceptible genotypes, 23 exhibited a statistically significant gain of ontogenic resistance as berries aged. These 23 genotypes with ontogenic resistance included four species as well as several interspecific hybrids of Vitis spp. Typically, ontogenic resistance functioned by reducing the frequency of successful penetration by U. necator. Some genotypes developed ontogenic resistance earlier or later than most. Ontogenic resistance ratings of the rachis and pedicels did not match those for the berries for the majority of genotypes studied. Despite the broad conservation of the presence of ontogenic resistance, one genotype (V. rupestris ‘R-65-44’) remained persistently susceptible well past the onset of ripening, over one month later than reported previously for V. vinifera and V. labruscana. The genetic variation identified in ontogenic resistance could facilitate further study of ontogenic resistance through characterization of new genetic resources.

Technical Abstract: Berries of grapevine (Vitis spp.) have a limited window of susceptibility to Uncinula necator, the causal agent of grapevine powdery mildew, corresponding to approximately 2 to 3 weeks post-bloom. This phenomenon has been demonstrated in several cultivars of V. vinifera and in V. labruscana ‘Concord’, which all exhibited a similar temporal distribution of susceptibility. To identify novel genetic variation for ontogenic resistance, we screened a diverse collection of species and interspecific hybrids maintained in the USDA-ARS cold-hardy Vitis germplasm collection in Geneva, NY. Of the 79 genotypes whose fruit clusters were screened for susceptibility to powdery mildew under field conditions, 50 exhibited a high basal level of resistance to powdery mildew and did not develop more than trace levels of disease when inoculated, irrespective of the stage of berry development at the time of inoculation. Twenty-three genotypes exhibited a statistically significant gain of resistance as berries aged. This ontogenic resistance was conserved across four species and several interspecific hybrids of Vitis spp., though the timing of the onset of ontogenic resistance varied by genotype. The mechanism of ontogenic resistance was assayed for three of the genotypes and reduced the frequency of successful penetration by U. necator on each. Despite the broad conservation of ontogenic resistance across species, one genotype (V. rupestris ‘R-65-44’) remained susceptible past the onset of ripening, over one month later than reported previously for V. vinifera and V. labruscana. Variation in the resistance phenotype was observed between the rachis, pedicels and berries within clusters of the majority of genotypes studied. The multiple facets of genetic variation identified in ontogenic resistance could facilitate further study of the inheritance and molecular basis of ontogenic resistance.