The goal of this project is to determine the level of variation existing in populations of the sudden death syndrome pathogen (F. virguliforme) in Iowa. Ten isolates were selected from within six haplotypes for aggressiveness on three soybean varieties. Two susceptible and one resistant variety were inoculated with the isolates and rated for foliar disease severity over a period of 30 days. At the end of the experiment, data was collected on root rot severity, shoot height and weight, and dry root weight. Significant differences (P < 0.0001) were found among isolates in causing leaf scotch and root rot. Shoot height, shoot fresh weight, and root dry weight were also affected by the aggressiveness...