Furthering Elite Grape Rootstocks with Reduced Nematode Susceptibility. AVF Project #2024-2669.

Annual Progress Report Summary:

Vineyards are continuously at risk for infections by soil-borne pests and pathogens which have ample time and opportunity to establish, build-up in population densities, and cause damage.  Depending on the severity of infection, plant-parasitic nematodes can become major yield constraints.  In vineyard soils, soil-dwelling plant-parasitic nematodes can reproduce on susceptible plant roots.  Multiple species are often found at a location.  Meloidogyne spp. (root- knot nematodes), Mescocriconema xenoplax (ring nematode), Xiphinema americanum or X. index (dagger nematode), and Tylenchulus semipenetrans (citrus nematode) are most frequent and most damaging.  These can occur in various combinations within at least the upper 5-ft soil layers.  Utility of resistant rootstocks is challenged under these conditions of multiple species being present.  In a prior project, rootstock genotypes that had been selected under greenhouse conditions were tested under field conditions in nematode-infested soils following a >30-year- old ‘Thompson seedless’ vineyard.  Each rootstock selection was grafted to ‘Pinot Gris’ and cropped in 2022 and 2023.  Twelve genotypes were selected from these studies based on their propagation characteristics, vigor under nematode-infested conditions, and yield.  In the current project, dormant wood cuttings were bench-grafted to ‘Pinot Gris’ and planted to an experimental vineyard in early summer 2023.  In a second trial, plants that had been propagated late in 2022 were planted into a very similar trial alongside the larger one.  In 2024, stakes and a single-wire training system were installed.  The plants were trained to the stake and, depending on vigor, cordons were made.  Plant measurements including vine diameter and pruning weights were taken in winter 2025.