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Poster: Biology & Disease Mgmt: Chemical Control


Resistance to quinone outside inhibitor fungicides in Cercospora sojina in Ohio
L. WEBER (1), A. Dorrance (1) (1) The Ohio State University, U.S.A.

Quinone outside inhibitor (QoI) fungicides are a common class of fungicides used to manage the fungus Cercospora sojina, the causal agent of frogeye leaf spot in soybean. Soybean leaf samples exhibiting symptoms of frogeye leaf spot were sent to the Soybean Pathology lab from across the state of Ohio during the summer of 2015. Cercospora sojina conidia were recovered from lesions to test their sensitivity to QoI fungicides. Potential C. sojina samples were confirmed by ITS sequencing then tested for the presence of the G143A mutation in the cytochrome b gene, the most commonly observed mutation in QoI-resistant fungi. QoI fungicide resistance was detected in two C. sojina samples in a mixed population of sensitive and resistant spores, while all other samples were sensitive to QoI fungicides. Fast and efficient identification of fungicide resistant C. sojina in Ohio will be useful in minimizing potential soybean yield loss as frogeye leaf spot incidence in Ohio increases in the warm, moist conditions and mild winters that favor the pathogen.