Potato Virus Y (PVY) is an important virus of potato due to the non-persistent mode of transmission by aphids causing yield losses. Genetic resistance is the recommended control since insecticides cannot adequately control the spread of PVY by aphids. The gene Ryadg from S. tuberosum ssp. andigena provides resistance to all strains of PVY. This gene has genetically been mapped to chromosome XI, and linked polymerase chain reaction (PCR) based DNA markers have been identified. This study identified PVY resistant progeny by the use of the molecular sequence-characterized amplified region (SCAR) marker RYSC3. The RYSC3 marker allowed a simple and fast approach to determine if the Ryadg gene was present in the seedling family populations evaluated. The RYSC3 marker identified 16 families with progeny segregating for the Ryadg gene. Progeny segregated 1:1 for PVY resistance, fitting the model simplex (Ryryryry) for the Ryadg allele.