1a.Objectives (from AD-416):
Provide Pacific Northwest (PNW) grape growers with more information about the damage potential and management of plant-parasitic nematode.
1b.Approach (from AD-416):
1) Screen grape variety/clone combinations against Meloidogyne hapla in the greenhouse;. 2)Determine macro and micro spatial dynamics of plant-parasitic nematodes in established PNW vineyards; and. 3)Determine the impact of M. hapla on variety/clone establishment and productivity in a field setting.
This research was conducted in support of NP303 objective 2 "Identify plant germplasm and cultivars of small fruits resistant to economically-important soilborne diseases" of the parent project. Plant-parasitic nematodes are commonly encountered in soil samples collected from Washington vineyards; however, little is known about the biology, distribution, and impact of these root parasites in the second largest grape producing region in the United States. Greenhouse and field experiments were conducted to begin to address these questions, with the end goal of providing Washington grape growers with information about plant-parasitic nematode upon which to base management decisions. In greenhouse trials evaluating the host status of own-rooted grape variety/clones to the root-knot nematode Meloidogyne hapla, it was discovered that the white varieties Chardonnay and White Riesling were better hosts to the root-knot nematode than the red varieties Syrah, Cabernet Sauvignon, and Merlot. In general, White Riesling clones were the best hosts for root-knot nematode while Merlot clones were the poorest hosts for the nematode. Also as part of this research, the horizontal and vertical distribution of plant-parasitic nematodes in semi-arid vineyards was determined. In a Chardonnay vineyard it was found that root-knot and ring, Mesocriconema xenoplax, nematode population densities were weakly to moderately related to soil moisture and fine roots. There was a trend towards root-knot nematodes being aggregated around irrigation wetting zones, while ring nematodes were aggregated around vines. Vertically, root-knot nematode, ring nematode, and root-lesion nematode, Pratylenchus, were concentrated in the upper 18 inches of soil. These results provide the first indication that plant-parasitic nematodes may be managed in Washington vineyards through variety selection. There may also be the opportunity to target areas within a vineyard where plant-parasitic nematode populations are high during pre-plant management.