Virulence Diversity of Peruvian and United States Potato Cyst Nematode Populations Across a Panel of Potato Resistance Sources

Potato cyst nematodes (Globodera pallida and G. rostochiensis) are quarantine pests that threaten global potato production. While European and North American populations often exhibit limited genetic diversity, native Andean populations possess a broader virulence spectrum. This study evaluated the virulence of 10 Peruvian Globodera populations compared to U.S. reference populations (G. pallida Pa2/3 from Idaho and G. rostochiensis Ro1 from New York) using a panel of potato genotypes comprising standard differentials, breeding clones, and commercial varieties. While the U.S. populations displayed expected virulence profiles, the Peruvian populations exhibited high diversity and complex virulence phenotypes. We identified a distinct "Pa1-like" G. pallida lineage (PER10) that was avirulent on H2 resistance in clone P55/7, a differential typically susceptible to the U.S. G. pallida population, and partially overcame the Pa2/3 resistance in the variety ‘Maria Huanca’. Furthermore, specific Andean G. pallida populations (e.g., PER22) were virulent, overcoming partial resistance in the H3 breeding clone 12674ab1 with significantly higher reproduction than the U.S. G. pallida population. In contrast, the H1 gene in clone NY121, which confers resistance to G. rostochiensis Ro1, remained effective against the Andean G. rostochiensis population (PER26). These findings quantify a significant virulence gap between the U.S. and Peruvian Globodera populations, indicating that current U.S. resistance sources may be vulnerable to specific Andean Globodera lineages. The results underscore the necessity of strict quarantine measures and the pyramiding of diverse resistance genes to manage the virulence reservoir present in these native populations.