Technical Abstract: Potato leafroll virus (PLRV) is a major virus pathogen of potato. Infection of potato can result in substantial reductions in yield as well as tuber quality via the expression of net necrosis. Solanum etuberosum, a wild relative of cultivated potato, is highly resistant to PLRV as well as other potato diseases and insect pests. Reproductively isolated from cultivated potato, S. etuberosum, was somatically hybridized with a S. tuberosum haploid x S. berthaultii hybrid. Successive backcrossing of the somatic hybrid to cultivated potato has produced progeny with improved agronomics and PLRV resistance from S. etuberosum. Segregation of PLRV resistance in a BC3 population suggests a monogenic trait. Using RFLP and CAPS markers, previously mapped in potato and tomato, PLRV resistance was localized to chromosome 4 in the segregating BC3 population. Having localized the genomic region associated with PLRV resistance, we report on our efforts in the identification of PCR-based molecular markers that may be used for marker-assisted selection for PLRV resistance.