Two PR-1 loci detected in the native cultivated potato Solanum phureja appear differentially expressed upon challenge by late blight

Plant pathogenesis-related proteins are toxic to invading pathogens. Among them, the subfamily PR-1 represents low-molecular weight proteins of unknown biochemical function. Here, we describe the cloning and isolation of two PR-1 genes (PR-1b1 (GenBank accession no. SPH493450) and PR-1b2 (SPH493451)) that encode predicted basic proteins. We isolated them from Solanum phureja, a native Andean potato with horizontal resistance to late blight, caused by the oomycete Phytophthora infestans. We demonstrate that the PR-1 genes belong to a small multigene family with an estimated copy number of 4–6 with one of them located on chromosome IX as determined by genetic mapping. The expression of PR-1 genes was different in late blight resistant and susceptible genotypes. Therefore, we propose that both PR-1 genes may play a role in horizontal late blight resistance of S. phureja.