A Potential New Source of Extreme Resistance to Potato Virus Y in the Potato Variety Bistra

Potato virus Y (PVY) is a common and devastating pathogen of potato worldwide and insecticide control alone for aphid vectors is not effective due to the rapid transmission of the virus by aphids following probing. Three Ry genes for extreme resistance to PVY have been identified and are used in potato breeding programs for the development of PVY-resistant varieties. Tightly linked molecular markers have been developed for all three genes and are used for marker-assisted selection (MAS). However, some varieties with known extreme resistance to PVY do not amplify any molecular markers for these resistance genes. Sante and its progeny Bistra are examples of two varieties with extreme resistance to PVY and yet have no amplification of Ry associated molecular markers. The source of PVY resistance in Bistra was mapped using SNP genotyping of 190 of its progeny which had been characterized for response to PVY infection using a N-Wilga strain. A major QTL was found on the proximal end of chromosome 11, in close proximity to Ry(adg), one of the three known extreme resistance genes for PVY. However, no known markers which detect Ry(adg) amplify in Sante or Bistra which indicates they may possess a currently unidentified resistance gene, or the genetic linkages of molecular markers typically associated with the presence of Ry(adg) no longer exist due to recombination between the gene and its associated molecular marker primer annealing sites.