BACKGROUND: Fludioxonil is a broad-spectrum fungicide widely used for the management of seed-borne and postharvest fungal diseases. This study aimed to characterize the dose–response relationships of phytopathogenic fungi exposed to fludioxonil. Six fungal pathogens including; Fusarium fujikuroi, Alternaria alternata, Botrytis cinerea, Colletotrichum gloeosporioides, Colletotrichum acutatum, and Sclerotinia sclerotiorum were selected to evaluate their response-to-dosage curves (RTDCs) to fludioxonil.

RESULTS: The response-to-dosage curves (RTDCs) of the six plant pathogens to fludioxonil varied among species. In fludioxonil-sensitive isolates, Fusarium fujikuroi exhibited a fluctuating response, while Alternaria alternata, Botrytis cinerea, Colletotrichum gloeosporioides, C. acutatum, and Sclerotinia sclerotiorum displayed typical sigmoidal (S-shaped) dose–response patterns. Among resistant isolates, B. cinerea and F. fujikuroi maintained S-curve responses at higher concentrations, whereas resistant A. alternata isolates did not follow this pattern.

CONCLUSION: Among the six phytopathogenic fungi examined, Fusarium fujikuroi exhibited a distinctive response-to-dosage curve, highlighting the diversity of RTDCs among plant pathogens in response to MAPK (mitogen-activated protein kinase) inhibitors.

Keywords: six phytopathogenic fungi, fludioxonil, response-to-dosage curves (RTDC), Fusarium fujikuroi, fluctuating sensitivity.