Threat of Brown Rot of Potato and Existing Resistance

Brown rot of potatoes caused by Ralstonia solanacearum is common in developing countries. Historically, brown rot losses in the United States have been restricted to southern states. This trend will most likely change with new Ralstonia introductions and temperature variability. A cold tolerant Ralstonia strain was used in this study to compare resistance between 18 wild accessions from eight species , nine accessions from the International Potato Center (CIP), and seven common US cultivars. Testing was done at both 18 °C and 30 °C. Of the wild potato species tested, S. commersonii and S. microdontum were the most resistant. CIP accessions varied from moderately resistant to very resistant. Four of the US cultivars were also moderately resistant. With certain accessions temperature played a role in resistance with high temperatures usually increasing severity of disease and cool temperatures promoting the occurrence of asymptomatic plants. The resistance observed appears to be partial, multigenic resistance.