Recently, the resistance gene Gpa2 was cloned from potato. This R-gene confers resistance against specific populations of the potato cyst nematode Globodera pallida.
Interestingly, Gpa2 is highly homologous to the tightly linked resistance gene Rx1 which confers resistance against a completely distinct pathogen viz. the potato virus X (PVX).
The strong structural relationship between both genes at the one hand and the recognition of totally different pathogens at the other hand is unique. Both genes are localized in the same cluster on chromosome 12 of potato. Currently we are studying the molecular evolution of these R-genes by looking for new homologues in several Solanaceae spp. Phylogenetic analysis will be performed based on sequence data to determine the mutual relationships of the homologues and to understand the mechanism of diversifying selection of R-genes.