Induction of mitotic and chromosomal abnormalities on Allium cepa cells by pesticides imidacloprid and sulfentrazone and the mixture of them.

To evaluate the cytotoxic and genotoxic effects of low concentrations of pesticides in non-target organisms, seeds of Allium cepa were exposed for 24 h to the imidacloprid insecticide, sulfentrazone herbicide and to the mixture of them, followed by recovery periods of 48 and 72 h. Imidacloprid results indicated an indirect genotoxic effect by inducing different types of chromosome aberration (CA), mainly bridges and chromosomal adherences. Cells with micronucleus (MN) were not significant in the analyzed meristems. Moreover, the 72-h recovery tests indicated that the two lower concentrations of the insecticide (0.036 and 0.36 g L(-1)) had their genotoxic effects minimized after discontinuation of treatment, differently to the observed for the field concentration (3.6 g L(-1)). Sulfentrazone herbicide at field concentration (6 g L(-1)) caused cytotoxic effects by inducing nuclear fragmentation and inhibition of cell division. The other concentrations (0.06, 0.6 and 1.2 g L(-1)) indicated genotoxic effects for this herbicide. The concentration of 0.06 g L(-1) induced persistent effects that could be visualized both by the induction of CA in the recovery times as by the presence of MN in meristematic and F1 cells. The induction of MN by this lowest concentration was associated with the great amount of breakage, losses and chromosomal bridges. The mixture of pesticides induced genotoxic and cytotoxic effects, by reducing the MI of the cells. The chromosomal damage induced by the mixture of pesticides was not persistent to the cells, since such damage was minimized 72 h after the interruption of the exposure.