RESUMEN
Assessment of the sensitivity of non-sporulating fungi to fungicides through amended-media assays is labor intensive. As an alternative, we developed an absorbance assay using 96-well microplates to assess the sensitivity of Clarireedia jacksonii, a non-sporulating fungus, to the fungicide propiconazole based on the change in absorbance corresponding to fungal growth. This microplate assay can allow for the assessment of multiple isolates of C. jacksonii at different concentrations of a fungicide with many technical replications in a single plate. Three methods for inoculating microplate wells were compared. The "microplug" method was the simplest to perform, requiring only a micropipette with 1 ml tips. EC50 values from this microplate assay were compared to those of a traditional amended agar assay using 30 isolates of C. jacksonii with varying sensitivity to propiconazole. The non-transformed relationship between the two assays was low but weakly significant (R2 = 0.137, p = 0.037). However, correlation of log10 transformed EC50 values from both assays revealed a stronger and highly significant relationship (R2 = 0.56, p < 0.001). Additionally, the microplate assay appears to be more sensitive in detecting resistance (EC50 > 0.1 µg/ml), and revealed five of the assessed isolates to be resistant to propiconazole that were not found as such with the amended agar assay. These results imply that EC50 results from the microplate assay were not exactly equivalent to the amended agar assay for estimating EC50 values, but it may be useful in assigning or confirming general sensitivity classifications.