Marker-assisted selection for the broad-spectrum potato late blight resistance conferred by gene RB derived from a wild potato species

Potato (Solanum tuberosum L.) late blight, caused by Phytophthora infestans (Mont.) de Bary, is one of the most damaging diseases in any crop. Deployment of resistant varieties is the most effective way to control this disease. However, breeding for late blight resistance has been a challenge because the race-specific resistance genes introgressed from wild potato S. demissum Lindl. have been short lived and breeding for '' horizontal '' or durable resistance has achieved only moderate successes. We previously demonstrated that the high-level late blight resistance in a wild potato relative, S. butbocastanum Dunal subsp. bulbocastanum, is mainly controlled by a single resistance gene RB. Transgenic potato lines containing the RB gene have showed strong late blight resistance, comparable to the backcrossed progenies derived from the somatic hybrids between potato and S. bulbocastanum. Here we report the development of a polymerase chain reaction-based DNA marker for tracking the RB gene in breeding populations derived from the potato X S. bulbocastanum somatic hybrids. Several marker-positive breeding lines showed the expected late blight resistance in greenhouse evaluations. Our results demonstrate that marker-based selection will allow us to effectively transfer the RB gene into potato using traditional breeding methods, an alternative to deploying the RB gene through genetic transformation.