A Rapid Microtiter Assay to Evaluate Fungicide Sensitivity to Colletotrichum falcatum Isolates

Chemical control of sugarcane red rot, caused by Colletotrichum falcatum, forms part of integrated management of the disease. A rapid microtiter bioassay based on the colorimetric changes of resazurin dye was developed to evaluate the sensitivity of C. falcatum to the main chemical fungicide groups, including strobilurin, triazole, benzimidazole, isophthalonitrile and dithiocarbamate. There was no significant difference among the isolates in terms of growth inhibition for any of the active ingredients tested (α = 0.01). The C. falcatum isolates showed almost similar sensitivity to various fungicides. The active ingredients varied in relation to fungitoxicity. Doses that inhibited 50% of C. falcatum growth were calculated as a percentage of resazurin reduction due to various fungicides. The colorimetric method used to assess the fungitoxicity of active ingredients to C. falcatum, combined with resazurin, proved a fast practical and efficient method. © 2022 Friends Science Publishers