Nematologist Works on Resistant Grape Rootstocks
The IssueGrape vines are susceptible to diseases caused by various nematode species, including root-knot, root-lesion, ring, citrus, and dagger nematodes. Research has indicated that root-knot nematode species often adapt to invade previously resistant rootstocks within two to 14 years after planting. Once nematode populations develop the means to exploit one rootstock, they are then able to attack all the plantings using that rootstock. The damage caused by nematodes is economically significant, resulting in lost fruit and vine vigor for growers.
What Has ANR Done?Extension Nematologist Michael McKenry began in 1987 to characterize existing commercial rootstocks to determine their resistance and vigor levels. A USDA breeder made a cross between two rootstocks, Ramsey, a high-vigor rootstock which offered resistance to endoparasitic nematodes, and Schwarzmann, a low-vigor rootstock with resistance to several ectoparasitic nematodes. For nine years, Dr. McKenry evaluated about 800 vines produced from the seeds of the cross. The work identified two superior rootstocks produced by the cross: RS-3, a medium- to high-vigor rootstock, and RS-9, a low- to medium-vigor rootstock.
New Grape Rootstocks Provide Better Nematode ResistanceThe RS-3 and RS-9 rootstocks will be released to California nurseries in spring 2003, with growers expected to have them in two to three years. More than five years of grower field trials have indicated that the rootstocks offer resistance to a broad grouping of nematode species. RS-3 also has proven tolerant to grape fan leaf virus in commercial settings. In addition, the rootstocks offer two choices of vigor level. This is a desired quality because vines with too high vigor for a particular soil can produce fruit and wines of lower quality.
Supporting Unit:UCR Department of Nematology
Dr. Michael McKenry
Kearney Agricultural Center
9240 S. Riverbend, Parlier, CA 93648