Abstract
Meloidogyne chitwoodi, commonly known as the Columbia root-knot nematode (CRKN), is a major threat to potato production in the Pacific Northwest (Idaho, Oregon, and Washington) of the United States. The nematode damages both roots and tubers, significantly lowering tuber market value. In Washington and Oregon's Columbia Basin, the two main M. chitwoodi populations are race 1 and a pathotype of race 1 known as Roza. While resistance to race 1 is present in the potato breeding line PA99N82-4, this resistance is ineffective against Roza. To assess virulence differences, both populations were tested on Arabidopsis thaliana and tomato roots. Results showed that Roza was more virulent on these two susceptible hosts. Furthermore, infection assays on tomatoes carrying the Mi-1.2 resistance gene revealed that both populations can overcome this resistance, indicating that Mi-1.2 does not confer protection against either M. chitwoodi race 1 or Roza.