Submitted to: Phytopathology Supplement; APSnet (Plant Pathology Online)
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2006
Publication Date: 6/1/2006
Citation: Hanson, L.E. 2006. What we know about the genetics of fungicide resistance in Cercospora and Mycosphaerella. Phytopathology Supplement; APSnet (Plant Pathology Online). Interpretive Summary:
Technical Abstract: One of the major management methods for Cercospora leaf spot is fungicide sprays. However, resistance or reduced sensitivity has been found to several fungicides in Cercospora beticola. While resistance to fungicides has been observed in the tin, benzimidazole, DMI, and strobilurin classes, the genetics of resistance has not been extensively investigated in C. beticola. Recently benzimidazole-resistant (BR) isolates of C. beticola were examined. Isolates from different years and production regions in the United States all had a mutation in the beta-tubulin gene at that corresponded to mutations that confer benzimidazole-resistance in other fungi. This same mutation confers sensitivity to N-phenylcarbamates (NPC). When isolates were tested for sensitivity to an NPC fungicide, BR isolates were sensitive to the NPC, while benzimidazole-senstive isolates showed little sensitivity to the NPC. While the genetics of resistance to other fungicides is not known in C. beticola, work in Mycosphaerella has shown two types of resistance to strobilurin fungicides, including activation of an alternative oxidase system, and mutations in the mitochondrial cytochrome b gene, which might be active in Cercospora. Alterations in target genes, as well as altered uptake and secretion mechanisms, have been observed in relation to fungicide resistance in other Ascomycetes, and these also should be investigated in Cercospora.