Induction and Characterization of <i>Penicillium caseicolum</i> Mutants Resistant to Ergosterol Biosynthesis Inhibitors

Abstract

The isolation of Penicillium caseicolum mutants resistant to different fungicides which inhibit ergosterol biosynthesis is reported. Mutational frequencies for resistance were high (3 x 10 to 3 x 10). The levels of resistance toward the inhibitors of sterol C-14 demethylation were always low (<10), whereas high values were obtained with mutants resistant to inhibitors of sterol Delta14 reduction or Delta8-->Delta7 isomerization, or both. Generally, there was a positive cross-resistance between fungicides showing the same biochemical mode of action but not between compounds of two different groups. Mycelial growth rate and sporulation were tested; several mutants were not affected for these characteristics. We conclude that resistance to ergosterol biosynthesis inhibitors may be used as a good marker for genetic studies through protoplast fusion.