Evaluation location: Wisconsin, United States
Fifteen plants per accession and three tubers per plant were evaluated for soft rot resistance. Accessions were representative of a broad geographic area and a wide range of habitats. P. carotovorum isolate WPP14 was cultured and 3 ul of prepared bacterial suspension was inoculated into each tuber in a hole with a depth of 5 mm created by a pipette tip (34). Then, the diameter of decay was measured after a 72-h incubation in the dark at 100% relative humidity and 25 degrees C. An average of the measures was calculated. Smaller measures are more resistant.