Determination of genotoxic effects of copper sulphate and cobalt chloride in Allium cepa root cells by chromosome aberration and comet assays

We used the anaphase–telophase chromosome aberration and comet (Single Cell Gel Electrophoresis, SCGE) assays to evaluate the genotoxic effects of copper sulphate (CS) and cobalt chloride (CC) chemicals prepared in two concentrations (EC50, 2xEC50), using methyl methanesulfonate (MMS) as a positive control and untreated cells as a negative control. In Allium root growth inhibition test, EC50 values for CS and CC are 1.5 and 5.5 ppm, respectively. Mitotic index (MI) decreased in all concentrations tested of CS and CC compared to the control at each exposure time. The bridge, stickiness, vagrant chromosomes, fragments, c-anaphase and multipolarity chromosome aberrations were observed in anaphase–telophase cells. The total chromosome aberrations were more frequent with an increasing in the exposure time and the concentrations of both chemicals. The genotoxicity of CS and CC in Allium cepa root cells was analyzed using a mild alkaline comet assay at pH 12.3, which allows the detection of single strand breaks. In all the concentrations, CS and CC induced a significant increase (P < 0.05) in DNA damage. No significant difference was found between positive control (300 ± 5.81) and 3 ppm CS (280 ± 4.61). The methods used are applicable for biological monitoring of environmental pollutants.