Dr. Ron Runnebaum, asst. professor, Dept. of Viticulture & Enology, UC Davis, has prepared the update below. This project receives funding from the Oregon Wine Board as part of its viticulture and enology research grant program.Click edit button to change this text.

Importance to the Oregon wine community: Powdery mildew is historically the number one disease challenge of viticulture in Oregon. A serious infestation can defoliate a vineyard and destroy the fruit. Wrotham Pinot noir, a little-known clone brought to the U.S. from England by winemaker Dick Peterson in the early 1980s, has been observed to exhibit grape powdery mildew (PM) resistance. A Pinot noir clone with PM resistance would be highly valuable to the Oregon wine industry by reducing fungicide spraying, labor and vehicle use.

Progress: Cuttings for grafting and meristem isolation have been harvested, documented, and are undergoing viral and disease elimination at Foundation Plant Services (FPS). The clone has received approval to be permanently housed in the 100-acre Foundation Vineyard established on fumigated soil in an isolated location. The clone will be regularly inspected and retested by FPS and CDFA. This testing typically requires two years. Initial testing has shown the field cuttings to be infected with Red Blotch virus. Two of the three remaining acres of this clone will be removed this year. The remaining acre is located in Gonzales, CA and was planted approximately 25 years ago. The vineyard owner has indicated he is interested in not spraying a section of the Wrotham vines this year to observe PM field resistance. The owner has also indicated he will remove the vines in the near future.

A half ton of fruit each from three clones (Wrotham along with 115 and 777, as control clones) of Pinot noir
were harvested from Tondre Vineyard in Gonzales, California. Due to a 116° F heat spike in September, the Brix levels spiked to 26, 26 and 28 degrees respectively. The fruit was fermented and processed under established Pinot noir fermentation protocols in the Robert Mondavi Teaching and Research Winery. Nine fermentations, which includes three replicates per clone, were produced. The wines are currently in stainless steel vessels awaiting bottling in March. After bottling, the wine will remain in temperature-controlled storage until sensory studies are conducted. Due to scheduling difficulties, sensory studies, conducted in Prof. H. Heymann’s laboratory, will not be completed until summer.

Wrotham Pinot noir has been tested twice with a common strain C of Powdery mildew (PM) and has shown susceptibility to this strain of PM. It has been decided to conduct a broader disease trial to determine degree of susceptibility to the tested strain and two others. Wrotham Pinot noir will be compared to Pinot noir clone 667, Pinot Meunier, PM susceptible Carignane, semi PM resistant Karazandl and fully PM resistant NC 615 with three strains of PM. The strains will include a common strain (C), a weaker branching strain and a virulent strain. In mid-August, cuttings were taken from the different varieties and propagated. Out of 20-24 cuttings, as many as 10 and as few as 2 cuttings survived from each variety. Due to the lignification of the cuttings and two month dormancy of the growth buds, poor rooting has required new green cuttings to be propagated. The additional cuttings are ready and PM trials will commence on March 22nd.

Genetic screening will commence after spring budbreak to compare two Pinot noir clones and Pinot Meunier to Wrotham Pinot noir. Existing SNP primers will be utilized on DNA extracted from leaf tissue to determine the genetic heritage of Wrotham. The SNP primers are Pinot noir and Pinot Meunier specific.

Principal Investigator: Ron Runnebaum, asst. professor, Dept. of Viticulture & Enology, UC Davis.

Researchers: The work for this research project is being conducted by second year Master’s candidate Kara Leong under the guidance of professors Ron Runnebaum, Dario Cantu and Andrew Walker.