Wines & Vines

48 practical winery & vineyard March 2015 They do not have a stake in any PD/GWSS research and are as impartial as possible when making recommendations. Possible solutions take root After many years of work and many dis- coveries about grapevine genetics and the mechanisms of how some other plants cope with the PD-causing Xf bacterium and survive, scientists began testing their theories — first in labs, then in green- houses and finally in real-world vineyards around the country. A few that seemed to work well in the lab or greenhouse failed when tested in field trials, but several have proved to be successful. Two are currently headed toward commercialization. One of the first solutions likely to be available to growers will be PD-resistant wine grape vines produced by traditional breeding methods. The work has been spearheaded by Dr. Andy Walker at the University of California (UC), Davis. The genes that made native North American grapevines (Vitis arizonica) resistant to PD were identified. Those vines were crossed with European wine grape varieties (Vitis vinifera) to pass that gene along. Using high-tech equipment, when the new plants are little more than seedlings in the green- house, a leaf is tested for the presence of the gene that provides the resistance to PD. Those that have the gene are advanced to the next level of breeding. Thanks to the use of high-tech equip- ment, traditional plant breeding that once took years can now be accomplished in only 18 to 24 months. Trial plantings to test fruit quality and for winemaking have proven that these grapes have retained flavor profiles to be expected from non-Xf- resistant wine grapes grown in California. Ten scions, along with three PD-resistant rootstocks, were released to the Foundation Plant Services at UC Davis, the first step in making them available to wine grape growers. Of note is that while these vines are PD-resistant, and the grapes look and taste like Chardonnay, Sauvignon Blanc or Zinfandel, genetically they are not the same, so they cannot be called by the same names. However, they can be planted in vineyards or areas of vineyard that have a history of PD and then used as blending grapes to maintain a desired flavor profile. What if you could give a shot to a grape- vine to give it the ability to prevent PD? Dr. Donald L. Hopkins of the University of Florida discovered a benign strain of the Xf bacterium on the East Coast and has used it as a biological control of PD. Vines planted in the southeastern United States were inoculated with this benign strain more than 10 years ago and have shown no symptoms of PD. "After reviewing the work completed over the past 15 years, it is reassuring to note that the funds generated by the growers and matched with both state and federal funding has been judiciously used for research and control of GWSS and PD. The upcoming referendum would show a support to the continuation of the work being done on GWSS and PD but also the expansion into research on European grapevine moth, vine mealybug, brown marmorated stink bug and grapevine red blotch associated virus (GRBaV). These other pests and diseases have the potential of having a devastating effect on the California grape industry. I fully support and encourage growers to vote positive in the upcoming referendum." —Nat DiBuduo, president/CEO of Allied Grape Growers G R A P E G R O W I N G

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