Late Blight Resistance Profiles of Elite Potato Germplasm in the United States

Pyramiding resistance genes ( R genes) in potato generally provides improved field resistance against late blight (LB). Potato breeders may implement pyramiding by targeting breeding schemes according to LB genetic profiles. This study interrogated LB resistant elite germplasm for pyramided late blight R genes using DNA-based markers, which were then challenged against contemporary LB races. Five late blight R gene markers were used in this study. LB resistance ratings were determined using detached leaf assay (DLA) and field data from multiple locations and years. The clone J117, found to have the Rpi-blb1/RB gene , showed high resistance against US-23 in the laboratory and field. Several varieties positive for the R3b gene showed at least moderate resistance in the DLA and in the field. While two varieties were found to be pyramided with the R1 and R3b genes and also showed good field resistance, DLA results indicate that the combination is likely non-additive. LB resistance may be broadened by incorporating novel R gene combinations.