Impacts of root-knot nematodes (Meloidogyne chitwoodi and M. hapla) on potato yield and quality in the Pacific Northwest

The root-knot nematodes, Meloidogyne chitwoodi and M. hapla, are important pests in potato production of the Pacific Northwest. Meloidogyne chitwoodi, is a quarantine pest and is known to cause galling and blemishes on the tuber flesh, resulting in crop rejection. Our work aims to understand the relationship between initial nematode density in soil and tuber yield and quality. A field was planted with three varieties of potato (‘Russet Burbank’, ‘Ranger Russet’, and ‘Clearwater Russet’) and inoculated with initial densities of either M. hapla (0, 50, and 200 eggs/250 cc of soil) or M. chitwoodi (0, 25, 50, and 200 eggs/250 cc of soil). At harvest, tubers were assessed for weight, total number, and external quality. After three months of storage, a subset (n = 10) from each treatment group was peeled and graded for damage caused by the nematodes. Two years of data indicate that M. chitwoodi caused increased severity of galling with increasing inoculation densities. M.chitwoodi also caused more than 10 nematode infections across all varieties at the 25 eggs/250cc of initial density. In the first year, M. chitwoodi reduced yield of ‘Clearwater Russet’ by approximately 40% at the highest initial density compared to the non-inoculated control (P = 0.025). Further, it was observed that M. haplainfected ‘Ranger Russet’ more readily and had greater than 6 infections at the highest inoculation density compared to other varieties. Overall, M. hapla had no impact on yield or tuber numbers. Results from this research will allow for a better understanding of the relationship between root-knot nematode densities in soil and their impacts on tuber yield and quality in the region.