HERBICIDE GENOTOXICITY REVEALED WITH THE SOMATIC WING SPOT ASSAY OF Drosophila melanogaster

Abstract

The genotoxicity of the herbicides clomazone, linuron and simazine was detected using the somatic wing spot assay of Drosophila melanogaster . For the evaluation of the mutagenic and recombinogenic activities induced by the herbicides two crosses were used: the standard cross (ST) which expresses basal levels of cytochrome P450 enzymes and the high bioactivation cross (HB) with overexpression of P450 genes conferring increased sensitivity to promutagens and procarcinogens. Third-instar larvae were exposed by chronic feeding (48 h) to three different concentrations of each herbicide. The frequencies of spots per individual in the treated series were compared to the negative concurrent control series (water or 5 % ethanol solution depending on the herbicide). Clomazone showed positive results for small and total spots in both the ST and the HB crosses. Linuron was positive at all concentrations tested for small and total spots in the ST cross while only positive for small and total spots at the highest concentration assayed in the HB cross. Simazine did not produce positive results in the ST cross while it was positive in the HB cross. The bifunctional cross-linking agent mitomycin C (MMC – 0.15 mM) was used as positive control and produced as expected a significant increase of all types of spots in both crosses. In conclusion, the positive results were due to induced mutations and not by recombinogenic activity, furthermore the significant increase in the frequency of total spots was mainly due to the induction of small single spots.