Abstract Michelle MoyerMaria MirelesKatherine EastBernadette GagnierInga Zasada

Field Response of Rootstocks to Northern Root-Knot Nematode

Michelle Moyer,* Maria Mireles, Katherine East, Bernadette Gagnier, and Inga Zasada
*Washington State University, 24106 North Bunn Rd, Prosser, WA, 99350 (michelle.moyer@wsu.edu)

Management of plant parasitic nematodes in Washington State vineyards undergoing replanting has been dominated by preplant soil fumigation. Our past work showed this approach does not result in long-term suppression. In 2015, we established a trial evaluating rootstocks in a commercial vineyard undergoing replanting after 20+ years of production. The rootstocks were planted in replicated plots of fumigated (metam sodium), nonfumigated, and nonfumigated inoculated with Meloidogyne hap­la (northern root knot nematode). By fall 2021, all evaluated non-vinifera “resistant” rootstocks (101-14 MGT, 1103P, Harmony, Teleki 5C) supported M. hapla development; however, Teleki 5C and 1103P supported fewer M. hapla than the own-rooted Vitis vinifera control vines (eightfold fewer nematodes; p = 0.02). While not statistically different than own-rooted V. vinifera, Harmony and 101-14 MGT supported threefold fewer nematodes. When considering the multi-year chronic exposure to M. hapla (nematode dosage), all evaluated rootstocks had reduced M. hapla dosage than own-rooted V. vinifera. This M. hapla dosage comparison also provides a means to vi­sualize nematode “tolerance”: 1103P and Teleki 5C supported the fewest M. hapla over time, followed by Harmony and 101-14 MGT, with own-rooted V. vinifera supporting significantly more M. hapla over time (p < 0.0001). The rootstocks evaluated in this study had heavier pruning weights than own-rooted V. vinifera after three growing seasons (p < 0.0001). Among the non-vinifera rootstocks, some supported more nematodes than others, but after seven growing seasons, there was not a statistical difference between rootstock choice and influence on dormant pruning weights (p < 0.05). This enforces the concept of tolerance: though a rootstock might support M. hapla development, there is not a discernable phenotype difference. The use of non-vinifera rootstocks, while still supporting some M. hapla development, are still a sustainable long-term solution for M. hapla management.

Funding Support: 80% Washington State Grape and Wine Research Program, 10% USDA National Institute of Food and Agriculture, Hatch project #1016563, 10% USDA-ARS Current Research Information System 2072-22000-043-00D