Diversity of Late Blight Resistance Genes in the VIR Potato Collection.

Late blight (LB) caused by the oomycete (Mont.) de Bary is the greatest threat to potato production worldwide. Current potato breeding for LB resistance heavily depends on the introduction of new genes for resistance to ( genes). Such genes have been discovered in highly diverse wild, primitive, and cultivated species of tuber-bearing potatoes ( L. section Dumort.) and introgressed into the elite potato cultivars by hybridization and transgenic complementation. Unfortunately, even the most resistant potato varieties have been overcome by LB due to the arrival of new pathogen strains and their rapid evolution. Therefore, novel sources for germplasm enhancement comprising the broad-spectrum genes are in high demand with breeders who aim to provide durable LB resistance. The Genbank of the N.I. Vavilov Institute of Plant Genetic Resources (VIR) in St. Petersburg harbors one of the world's largest collections of potato and potato relatives. In this study, LB resistance was evaluated in a core selection representing 20 species of seven series according to the Hawkes (1990) classification: (Rydb.) Hawkes, Buk., Buk., Bitt., (Rydb.) Hawkes, (Rydb.) Hawkes (wild and cultivated species), and Corr. LB resistance was assessed in 96 accessions representing 18 species in the laboratory test with detached leaves using a highly virulent and aggressive isolate of . The species notably differed in their LB resistance: Dun., Lindl., Lindl., and Hawkes stood out at a high frequency of resistant accessions (7-9 points on a 9-point scale). Well-established specific SCAR markers of ten genes-, , , , , , and -were used to mine 117 accessions representing 20 species from seven series. In particular, our evidence confirmed the diverse gene location in two American continents. The structural homologs of the , , and genes were found in the North American species other than , the species that was the original source of these genes for early potato breeding, and in some cases, in the South American species. The orthologs from and Schlechtd et Bché were restricted to genome B in the Mesoamerican series , and . The structural homologs of the gene that were initially identified in the South American species Hawkes and Hjert. were reported, for the first time, in the North American series of species.