Detection of point-mutation mutagens in Aspergillus nidulans: comparison of methionine suppressors and arginine resistance induction by fungicides.

In the present study we describe the effect of 4 fungicides on the induction of point mutations in strains biA1 methG1 (induction of methionine suppressors) and 118 (induction of arginine resistance) of Aspergillus nidulans. Captan, which was used as a known mutagen, Daconil 2787 and Dithane M-45 were effective in inducing these mutations, whereas the fungicide Cercobin caused no significant increase in the induction frequency of the point mutations selected. Actually, a decrease in the frequency of methionine suppressors was observed in relation to those occurring spontaneously. However, this effect could not be considered antimutagenic because the revertants were more sensitive to the fungicide than the biA1 methG1 strain. Although the induction of methionine suppressors was more convenient because it permits the visualization of several morphological types, the 118 strain system also proved to be effective in detecting point-mutation induction.