Tight Physical Linkage of the Nematode Resistance Gene Gpa2 and the Virus Resistance Gene Rx on a Single Segment Introgressed from the Wild Species Solanum tuberosum subsp …

Comparative mapping studies within several plant genera have shown that genes for resistance to taxonomically diverse pathogens are often co-localized on the maps of these genotypes. Here we describe the genetic analysis of such a gene cluster on chromosome 12 of potato. This cluster harbors the resistance loci Gpa2 and Rx, which confer resistance to the potato cyst nematode Globodera pallida and potato virus X (PVX), respectively. By screening two mapping populations with 10 CAPS (cleaved amplified polymorphic sequence) markers derived from AFLP (amplified fragment length polymorphism) markers and the ends of overlapping bacteria) artificial chromosome (BAC) clones, it is demonstrated that Gpa2 and Rx are tightly linked. From a recombination fraction of 1/3386, found after screening two different mapping populations, a genetic distance of 0.02 cM between Gpa2 and Rx was calculated. The …