Fungicide Resistance in Cercospora kikuchii, a Soybean Pathogen.

Isolates of Cercospora kikuchii, a soybean (Glycine max) pathogen causing Cercospora leaf blight and purple seed stain, were tested to determine baseline sensitivities (n = 50) to selected quinone outside inhibitor (QoI) fungicides by conducting radial growth assays on fungicide-amended media. Baseline effective fungicide concentration to inhibit 50% of fungal radial growth (EC) values were compared with EC values for isolates collected in 2011 (n = 50), 2012 (n = 50), and 2013 (n = 36) throughout soybean-producing areas in Louisiana. Median EC values for isolates subjected to QoI fungicides were significantly (P = 0.

Assessment of Lineages of Cercospora kikuchii in Louisiana for Aggressiveness and Screening Soybean Cultivars for Resistance to Cercospora Leaf Blight.

Cercospora leaf blight (CLB) became much more prevalent in Louisiana beginning in 1999. A previous study showed that the Louisiana population of Cercospora kikuchii, the causal agent, was dominated by a new lineage that differed from those collected in other locations at earlier times. In this study, we tested whether the dominance of the new lineage was caused by higher aggressiveness and screened soybean cultivars for resistance to CLB.