Combined effect of physical and chemical mutagens on mutation frequency in Aspergillus mdulans

Abstract

Combination treatments of EMS and gamma-rays have been shown to produce a synergistic effect on mutation frequency (methionine suppressors); the extent of synergism is dependent upon the order of application of the mutagens. Gamma irradiation followed by different doses of EMS showed synergistic effect of a higher magnitude at all the doses, whereas treatments with EMS prior to gamma-ray exposure produced the synergistic effect of a smaller order which declined at higher doses. In the light of available evidence, the synergistic effect has been attributed to the increased induction and fixation of the mutational events. The lesser synergism obtained in the pre-irradiation combination is probably caused by the radioprotective substances produced by the hydrolysis of EMS.