Pcr-based Detection of Strobilurin Resistance in Cercospora Beticola*

Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola (Sacc.), is the most destructive foliar pathogen of sugarbeet worldwide. Control measures include the use of resistant varieties and crop rotation, but timely fungicide applications are essential for CLS management. Resistance to sterol demethylation inhibitor (DMI) fungicides (FRAC group 3) has been increasing in C. beticola populations, forcing growers to increase reliance on quinone outside inhibitor (QOI) fungicides (FRAC group 11). QOIs act by binding the quinol oxidation site of the cytochrome bc1 enzyme complex, which leads to an energy deficit in sensitive fungi. Point mutations in cytb that encode an amino acid exchange from phenylalanine to leucine at position 129 (F129L), glycine to arginine at position 137 (G137R), or glycine to alanine at position 143 (G143A) have been associated with resistance to QOI fungicides.