PD-Resistant Vinifera Vines Ready to Bear Fruit

UC Davis researchers to taste-test wines this year

by Jane Firstenfeld
Davis, Calif. -- The first vinifera hybrid vines developed by researchers at UC Davis to genetically resist infection from Pierce's disease (PD) are expected to bear sufficiently this fall to permit a minuscule first harvest and wine quality evaluation. If the results are favorable, PD-resistant vinifera crosses may be certified for release within two or three years, according to Dr. Andrew Walker, the UC geneticist who heads the project.

Walker told Wines & Vines that he and his team are performing separate research on methods to predict wine quality using only a few clusters from cultivars that are 87.5% Chardonnay, Syrah and other winegrapes, crossed with a variety of PD-resistant grape species.

 "We used many vinifera species in the crosses," Walker said. "We chose vinifera cultivars from a broad range of flavors, colors, tannin structure and production levels so we could advance the resistant-winegrape breeding program on many fronts."

The research, funded by the California Department of Food and Agriculture PD/GWSS board, first identified DNA markers for the locus of genes that resist PD in certain species of native American grapevines. "It is best referred to as a 'locus,' since it may be a region with several genes. The locus functions as a single dominant gene," Walker explained. "The only form of resistance that functions as a single dominant gene is in a form of Vitis Arizonica from Monterrey, Mexico," he said. The crosses, classically bred and hybridized, included many native American species with resistant gene loci. Research to characterize the gene or genes involved is underway.

The hybrid vines will be patented and released through UC Davis. "They might well be certified for release at FPS in two to three years, but they will have to be bulked up and made available from nurseries," Walker said. "There will be better material, with higher levels of vinifera on the heels of the first releases at 87.5%," he added.
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