Getting help from the extended family: identification and genetic characterisation of novel resistance to Globodera pallida ‘Oberlangen’ in wild Solanum species

The potato cyst nematode Globodera pallida is a major agricultural pest that is responsible for significant potato yield losses on a global scale. The most effective and sustainable strategy to reduce damage caused by G. pallida is to cultivate nematode-resistant potato varieties. These varieties have been developed mainly by introgressing resistance genes from wild potato species. However, intensive reliance on limited and widely utilised sources of resistance against the predominant G. pallida pathotypes 2 and 3 (Pa2/3) has led to the emergence of virulent nematode populations that can overcome these defences. To address this issue, we undertook a comprehensive search for novel sources of resistance against this new virulent G. pallida type, ‘Emsland’, within wild Solanum species and identified several promising candidates. Three resistant accessions were further characterised with resistance loci mapped via a single-nucleotide polymorphism array in biparental progenies. Furthermore, one population was subjected to fine-mapping through genotyping-by-sequencing. A major resistance locus was identified in each of the three studied accessions: in a clone of Solanum gourlayi ssp. pachytrichum, resistance was mapped to the short arm of chromosome 5, whereas in clones of both S. hawkesianum and S. spegazzinii, resistance was traced to a locus on the long arm of chromosome 6. This study is the first to identify resistance loci controlling the new virulent G. pallida type, ‘Emsland’ (population ‘Oberlangen’). Our findings provide essential data for the introgression of these resistance loci into cultivated potato varieties, offering the potential to increase nematode resistance in potato crops.