Development of SCAR markers to the PVY resistance gene Ryadg based on a common feature of plant disease resistance genes

Sequence-characterized amplified regions (SCARs) were developed, based on nucleotide differences within resistance gene-like fragments isolated from a potato plant carrying the Ry(adg) gene, which confers extreme resistance to potato Y potyvirus (PVY). It originates from Solanum tuberosum subsp. andigena, and a susceptible potato plant. SCARs were tested using 103 potato breeding lines and cultivars with diverse genetic backgrounds derived from Europe, North America, and Japan. Two markers showed high accuracy for detection of the Ry(adg) gene. The SCAR marker RYSC3 was generated only in genotypes carrying Ry(adg). The SCAR marker RYSC4 was detected in all genotypes carrying Ry(adg) but also in four PVY-susceptible genotypes. Neither marker was detected in genotypes carrying other Ry genes originating from different species than S. tuberosum subsp. andigena. Therefore, these SCAR markers should be powerful tools in marker-assisted selection for Ry(adg) in potato breeding programs, and should also be useful for cloning of the Ry(adg) gene.