Differential genotoxicity of ethyl methanesulphonate, N-ethyl-N-nitrosourea and maleic hydrazide in tobacco seedlings based on data of the Comet assay and two recombination assays.

The purpose of this study was to determine if mutagen-induced DNA damage is correlated with the frequency of induced recombination events. The alkylating agents ethyl methanesulphonate (EMS) and N-ethyl-N-nitrosourea (ENU), and the plant growth regulator and herbicide maleic hydrazide (MH) were compared in tobacco seedlings for their ability to induce DNA damage measured by the Comet assay, and recombination activity measured by the GUS gene reactivation assay, and by the somatic twin sectors assay. While EMS and ENU induced a dose-dependent increase in DNA damage in leaf nuclei, MH had no significant effect. By contrast, MH induced a 6-fold higher frequency of homologous recombination as expressed by the GUS assay and a 2.8-fold higher frequency of somatic twin sectors than after EMS treatments.