Greenhouse Evaluation of Rootstocks Against the Northern Root-Knot Nematode (Meloidogyne hapla)

Background and goals The northern root-knot nematode (Meloido- gyne hapla) is a prevalent plant-parasitic nematode in northern grapegrowing regions. This nematode induces small galls on roots that restrict water and nutrient uptake, resulting in poor vine establishment or exacerbated decline in stressed vines. Rootstocks can be a viable option to manage vine decline caused by M. hapla in vineyards. Methods and key findings Nine Vitis spp. rootstocks (1616C, 99R, 44-53M, 140RU, Minotaur, SO4, SW, 5BB, and 1103P) and two Vitis vinifera own-rooted vines (Chardonnay and Cabernet Sauvignon) were evaluated against M. hapla in the greenhouse. Potted vines were inoculated with 5000 M. hapla eggs and destructively harvested after three months. Nematode reproduction factors (fina l population density/initial population density) were lower on the non-vinifera rootstocks than on the own-rooted V. vinifera vines. Only the rootstock 44-53M had a significantly greater reproduction factor value than the other non-vinifera rootstocks. Conclusions and significance This greenhouse evaluation provides a baseline resistance rating against M. hapla for several rootstock varieties. While many rootstocks are not fully resistant to M. hapla, the ability of M. hapla to reproduce on their roots relative to V. vinifera roots is several times lower. Rootstocks could improve longer-term management of M. hapla in Washington State vineyards.