Resistance risk and mechanism of fludioxonil against Exserohilum turcicum, the causal agent of northern corn leaf blight.

BACKGROUND Northern corn leaf blight (NCLB), caused by Exserohilum turcicum, is one of the most important fungal diseases in corn production worldwide. The current study explored the resistance risk and mechanism of fludioxonil against E. turcicum. RESULTS The median effective concentration (EC50) values of fludioxonil against 100 isolates of E. turcicum was in the range 0.0032-0.1809 μg mL-1, with a mean of 0.0447 μg mL-1. Eight fludioxonil-resistant mutants of E. turcicum were acquired. Compared with their wild-type strains, the resistant mutants showed decreased biological fitness. A fungicide sensitivity test showed that fludioxonil resistance mutations of E. turcicum also reduced the sensitivity of mutant strains to fluazinam. Importantly, a new point mutation D905N in the EtOs1 gene was detected. Molecular docking further showed that this point mutation led to a decreased binding affinity between histidine kinases and ATP. Moreover, the activity of histidine kinases in the resistant mutants decreased remarkably. Field tests showed that fludioxonil at 20 g ha-1 exhibited >80% efficiency against NCLB. CONCLUSION These data indicated that the resistance risk of fludioxonil against E. turcicum is low. Fludioxonil is a promising alternative fungicide for controlling NCLB. © 2025 Society of Chemical Industry.