Laila Fayyaz, Summaira Riaz, Rong Hu, and Andrew Walker*
*UC Davis, Dept. Viticulture and Enology, University of California, Davis, CA 95616 (awalker@ucdavis.edu)

The cultivated grape species Vitis vinifera is highly susceptible to powdery mildew (PM), caused by the fungal pathogen Erysiphe necator. One of the primary objectives of grape breeders is to identify and breed natural sources of PM resistance into cultivated grapevine to mitigate the costs of PM management and promote health and environmental benefits.  In this project, we aim to develop a physical map of the Ren6PM resistance locus, which was previously identified in the Chinese species, V. piasezkii. While comparing the resistance responses of the Ren6, Ren4, and Run1resistance loci, we found that Ren6 provides resistance against a broader array of fungal isolates. We propose using a map-based cloning approach to identify the candidate resistance ® genes with the help of bacterial artificial chromosome (BAC) libraries. The physical map will help us identify putative resistance genes in the Ren6 locus and allow us to compare the functionality of this gene(s) with PM resistance genes from different genetic backgrounds. Cloning PM resistance genes will help us understand different plant-pathogen gene interactions and may allow combination of PM resistance genes with different functionality to produce more durable resistance.

Funding Support: Louise Rossi Endowed Chair in Viticulture AIP USAID