ABSTRACT
University of Minnesota, Department of Plant Pathology, 495 Borlaug Hall/1991 Upper Buford Circle, St. Paul, MN 55108, USA; e-mail: jbradeen@umn.edu
The cultivated potato (Solanum tuberosum L.) is host to more than 60 diseases of contemporary signifi cance (Stevenson et al. 2001). Chief among these is late blight caused by the oomycete Phytophthora infestans. Late blight caused the European Potato Famine of the 1840s and today still ranks as the number one constraint of potato production worldwide, with annual losses and chemical inputs totaling billions of dollars (Kamoun 2001). Given the signifi cance of this disease, there has been concerted effort for 100 years to develop late blight resistant potato cultivars. While S. tuberosum lacks signifi cant resistance, many of the approximately 200 wild potato species are rich sources of late blight resistance (R) genes.
