Common scab of potato caused by pathogenic Streptomyces species poses an economic burden to commercial potato cultivation. Despite decades of research, no molecular markers linked to this trait are currently available, making the development of scab resistant potato varieties inefficient. A primary pathogenicity determinant in common scab-causing Streptomyces genotypes is the production of the phytotoxin thaxtomin A. To identify candidate genes involved in common scab resistance we extracted RNA from tuber tissue of common scab resistant variety Kalkaska and susceptible variety Tundra in a time course 2, 4, 6, 8, 10, 18, 20 and 24 hours after Thaxtomin A treatment.