A Search for More Durable Resistance

During 1996 soil samples were collected and analyzed from existing rootstock trials in Kern County (500), Mendocino County (50), Gilroy (30), Kearney Ag Center (150), Fresno area (60), Merced County (20), and Monterey County (20). These results are still being tabulated and compared to previous findings from the same vineyards. We have focused more in this area this year because there is value to such work, but also because after eight months into this project I have still not found a post-doctorate or other scientist to conduct the microscopic studies we proposed. That search is still underway. We do have young vines of the five rootstocks (10-17A, 10-23B, 6-19B, RS-2, and RS-3) inoculated into microplots with 10 reps each in the presence of root knot populations that break resistance of Ramsey, Freedom, and Harmony. We are also initiating this winter the microplot evaluations of ectoparasites against 110R, 101-14, and 5BB. In spring 1997 we will plant conventional rootstocks in the presence of aggressive root knot populations using a split-root technique with half of each root system growing in the presence of pin nematode or ring nematode only. This project is being funded equally by the American Vineyard Foundation, the California Table Grape Commission and the Grape Rootstock Commission. Our support is ample and the work we still expect to complete within our three-year goal. On a side note, we are initiating a large field trial using these five rootstocks after various soil treatments with Thompson Seedless as the scion.