P-174 - Phenotypic characterization of Exserohilum rostratum isolated from Northern Corn Leaf Blight lesions on Maize in Florida

Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is the most prevalent disease on maize in Florida. Recently, we recently identified E. rostratum in NCLB like lesions from field and sweet corn commercially grown in Suwannee, Columbia, Palm Beach, and Miami-Dade counties, raising questions about its potential role and etiology in the NCLB disease. This study aims to determine the pathogenicity and phenotype of E. rostratum isolates collected from NCLB lesions. Sequences of tef1, LSU and ITS were used to identify the isolates as belong to the species E. rostratum. Thus, 12 E. rostratum isolates were selected to represent the counties where they were collected. Then they were tested alongside a positive control of E. turcicum. Sweet corn plants at the V2/V3 growth stage were inoculated with a spore suspension (10⁴ spores/mL), with eight replicates per treatment in a greenhouse experiment. Immediately after inoculation, plants were placed in a humidity chamber for 48 hours. The experiment was performed in a randomized complete block design in a greenhouse setting. The severity and phenotype of the lesions was assessed 14 days after inoculation and pathogen re-isolated in PDA media. These findings enhance our understanding of NCLB in Florida and the Exserohilum pathosystem, providing valuable insights into disease management.