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Abstract
In the last five years the intensity of Cylindrocladium black rot (CBR) of peanut has increased in Georgia and outbreaks have been observed in previously uninfested fields. One explanation for this trend might be changes in the population structure of the causal agent, Cylindrocladium parasiticum. To investigate this trend genetic analysis and pathogenicity studies were conducted using C. parasiticum isolates from the southeastern U.S. Genetic analysis revealed low levels of diversity within the population and while there were statistically significant differences in aggressiveness between isolates, these differences did not correlate to the geographical origin. Overall, the data suggest that recent trends of increasing CBR intensity in Georgia are not due to changes in population structure. Alternatively, it is likely that the trends can be explained by undetected inoculum accumulation in soil and local distribution of inoculum as fewer farmers produce peanuts on larger farms