Furthering Elite Grape Rootstocks With Reduced Nematode Susceptibility

The long-time plantings of vineyards are continuously at risk for infection by soil-borne pests and diseases.  These 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 planting of ‘Thompson seedless’ grape.  They were grafted to ‘Pinot Gris’ and produced yields in 2022 and 2023.  Twelve genotypes were selected from these studies based on their propagation characteristics, vigor under nematode-infested conditions, and productivity of grape ‘Pinot Gris’.  In the current project year, dormant wood cuttings were made, bench-grafted to ‘Pinot Gris’, and planted to an experimental vineyard in early summer 2023.  Cleanliness from virus (GFLV, GLRaV-3, GRBV) of these cuttings was attested by Plant Foundation Services (FPS) before propagation.