Globodera pallida virulence on major potato resistance has a common genetic basis across Western Europe.

The potato cyst nematode Globodera pallida poses a major threat to potato production in Western Europe. Current management strategies largely depend on the use of potato varieties carrying the genetic resistance GpaVvrn. However, reports from multiple West-European countries indicate a steady rise in virulence against GpaVvrn-containing potato varieties, raising serious concerns about G. pallida control. Although recent studies have resolved the genetic basis of virulence in two Dutch G. pallida populations, it remains unclear how conserved this genetic adaptation is in populations from different regions. To investigate this, we first selected eight Dutch G. pallida populations on the GpaVvrn-containing potato variety Seresta and confirmed a previously identified virulence locus. Second, by analysing the allele frequencies of four virulence-associated SNPs in Dutch, British, and French GpaVvrn-selected G. pallida populations, we found that the same allele is consistently selected by GpaVvrn across Western Europe. Third, we analysed the propagation of eight G. pallida populations on 26 GpaVvrn-containing potato varieties and showed that a population's allele frequency of a single SNP (T173N) accurately reflects its reproduction on GpaVvrn. Fourth, we developed an allele-specific quantitative PCR (AS-qPCR) assay to determine a population's alternative allele frequency (AAF) of T173N and showed that AS-qPCR-based AAFs reliably indicate virulence levels on GpaVvrn in Dutch and German G. pallida populations. Together, these findings suggest that a common allele is consistently selected by GpaVvrn in populations from different regions across Western Europe. The AS-qPCR assay developed in this study provides a practical tool to estimate G. pallida virulence on GpaVvrn in the field, enabling field-tailored and sustainable resistance management strategies for farmers.