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United States Department of Agriculture

Agricultural Research Service


Location: Grape Genetics Research

2013 Annual Report

1a. Objectives (from AD-416):
Our contribution to this proposal is in phenotyping powdery mildew resistance in 15 breeding populations in order 1) to develop markers linked with resistance loci and 2) to have standardized assessment of the strength, mechanism, race-specificity, and unique biological features of each resistance.

1b. Approach (from AD-416):
(1) Phenotype the parents and 20 progeny (maintained in Geneva greenhouse) for resistance segregation using a single isolate of E. necator. a. If resistance is not observed, screen with a panel of 4 isolates to identify avirulent isolates. (2) Challenge resistant individuals with a panel of 8 diverse E. necator isolates to identify virulent and avirulent isolates. a. If no virulent isolates are found, repeat with more diverse panel and with natural infection in E. necator center of origin. (3) For each uniquely avirulent isolate in (2), phenotype entire mapping population for resistance, with 10 conidial droplets on 4 leaves per progeny. (4) With virulent and avirulent isolates on 2 susceptible and 4 resistant progeny of each population, quantify penetration success rate, host necrosis, microcolony success rate, and hyphal length at 72 hours post-inoculation for standardized phenotyping of resistance mechanism and strength in the presence and absence of virulence.

3. Progress Report:
In Year 2, six mapping populations were maintained in good health for use in the project. From these, 3,239 vines have been sampled for DNA isolation and genotyping by the project; over 1,000 leaves were sampled for powdery mildew resistance phenotyping by the project; 250 cuttings and 200 seed were prepared for phenotyping; and over 1,100 vines were measured for other traits, including fruit quality and resistance to fungi or nematodes. The resulting data, including an estimated 200 million genotypic data points and 200,000 phenotypic data points, are ready for analysis of the genetic control of traits. Techniques developed for the genotyping and phenotyping of populations helped us to be consistent in our scientific approaches in spite of populations being grown in such different regions as New York and California. Funding provided for this project enabled us to maintain these populations in breeding programs with space and time limitations that would otherwise have required the populations to be eliminated or drastically reduced by selection. Without maintaining these complete populations, the project could not be completed successfully.

4. Accomplishments

Last Modified: 05/27/2017
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