An article in the April 2022 SACAPP Potato Bulletin discussed PCN tolerance versus resistance and included the diagram below which shows the 4 possible combinations of these two characteristics. In the real world, a variety might sit between these 4 categories. Tolerance is the ability of a potato variety to maintain yield despite the presence of PCN while resistance is the ability of a variety to limit PCN multiplication. They are often confused as being the same trait but they are different.