P-392 - Pathogenicity of Phaeocytostroma ambiguum and Fusarium graminearum on Corn Seeds Under Controlled Conditions

Crown rot is an emerging disease of corn in the midwestern United States, and it is not clear what pathogens are causing the disease. In samples collected from across the Midwest, Phaeocytostroma ambiguum, was frequently recovered. This pathogen has been reported causing root and crown rot in South America and Europe. This study compared the pathogenicity of P. ambiguum with Fusarium graminearum, which was also commonly recovered from crown rot symptomatic plants, on corn seedings under controlled conditions. A randomized complete block design (RCBD) with three replications at 13°C, 18°C, and 23°C was used to assess pathogenicity Germinated seeds (four per plate) were placed in contact with each pathogen growing on ½ PDA in a Petri dish. Seeds placed on ½ PDA with no pathogen served as a control. Percent disease severity and seedling biomass reduction were recorded approximately seven days later. Disease severity increased with temperature, with F. graminearum causing significantly greater root rot and biomass reduction than P. ambiguum (P < 0.05). These findings provide new insights into the temperature-dependent pathogenicity of these fungi, and the potential role of P. ambiguum in crown rot of corn.