A broad Nematode Screen to Evaluate Four Potential Nematode Resistant Rootstocks
In 1993 we were unable to secure as many plants of 10-17A, 10-23B and 6-19B as we would have liked. We did, however, have enough for six replicates of each rootstock in the presence of two X. americanum populations and one A”, index population. May 1994 root observations reveal tip galls by X. index on the Cabernet Sauvignon and Sauvignon Blanc comparisons but not on the above three rootstocks. May 1994 soil samples revealed inadequate nematode populations to determine the levels of resistance in the rootstocks. This technical problem can be solved with time and more sampling. Sixteen Ramsey x Schwarzmann seedlings are currently being screened against a dozen different nematode species. Two of the 16 seedlings exhibit poor rooting ability. All work should be completed by the target date of January 1995. One can see from Table 1 how some of the more interesting rootstocks performed in comparison to industry standards of Ramsey, Freedom, Teleki 5C and Harmony. In the screening process a number of farm advisors provided us with vineyard soil having root knot nematode problems. These mixed populations revealed that although 8-1 OB performed well against three of our most aggressive root knot populations it did not succeed against common field populations of root knot. It also shows the results of a two-year study involving those rootstocks and ring nematodes indicating that each has performed at least as well as Harmony. Our data for other ectoparasites will be available within months. Based on the numbers in Table 1 we have three rootstocks with very broad nematode resistance. These include 10-17A, 10-23B, and 6-19B. Each of these has differing parentage which is an asset when it comes time to make rootstock decisions at the farm level. The 6-19B rootstock roots well but may have some vigor problems. To have a successful rootstock one must be able to protect against all root knot populations present in the field. That is the “lofty” goal of this work.