Resistance to Quinone Outside Inhibitor Fungicides Conferred by the G143A Mutation in Cercospora sojina (Causal Agent of Frogeye Leaf Spot) Isolates from South Dakota Soybean Fields

Abstract

Resistance to quinone outside inhibitor (QoI) fungicides was detected in Cercospora sojina (causal agent of frogeye leaf spot) isolates collected from soybean (Glycine max) fields in four South Dakota counties during the 2018 growing season. A discriminatory dose assay was used to detect QoI-resistant isolates, and a follow-up polymerase chain reaction assay was used to determine the presence of the G143A mutation in QoI-resistant isolates. This is the first report of resistance to QoI fungicides in C. sojina isolates from South Dakota.