A Genetic Study of Resistance to Thiabendazole and Sodium O-Phenylphenate in Penicillium italicum by the Parasexual Cycle

Abstract

Mutants of Penicillium italicum resistant to 0.5 mg/liter of thiabendazole (TBZ) were obtained only after mutagenizing sensitive conidia. Although mutagenized sensitive conidia did not yield mutants resistant to 7 or 500 mg/liter TBZ, such mutants were recovered after mutagenizing conidia from a strain resistant to 0.5 mg/liter TBZ The three levels of resistance were termed low (L), intermediate (I), or high (H). Diploids heterozygous for H mutants had H resistance; diploids heterozygous for L or I mutants had L resistance. Resistance to 50 mg/liter of sodium o-phenylphenate (SOPP) was determined by a dominant mutation, and diploids heterozygous for SOPP resistance were resistant. Haploid segregants from 14 diploid strains with different combinations of TBZ and SOPP sensitivity or resistance were genetically analyzed and indicated that L, I, and H resistance to TBZ probably results from a mutation in two or three closely linked loci. Resistance to TBZ or SOPP, two mutations for different conidia colors, a...