Genotoxic Effects of Herbicide Illoxan (Diclofop-Methyl) on Allium cepa L.

The genotoxic potential of the commercial herbicide Illoxan (containing 284 g/L diclofop-methyl) was determined by using chromosome aberrations in Allium cepa root tip cells. The EC_{50} value was determined as 150.00 mg/L using a root growth inhibition test and then the roots were treated with 37.50, 75.00, and 150.00 mg/L concentrations for 12, 24, and 48 h. The results indicated that Illoxan significantly increased the abnormal cell frequency at all concentrations and treatment periods when compared with their controls, and this increase was dose-dependent for the 24 and 48 h treatments. On the other hand, Illoxan significantly decreased the mitotic index (MI) in all treatments when compared with their controls. The decrease in the mitotic index was slightly dose-dependent for the 24 and 48 h treatments. Illoxan did not affect the percentage of mitotic stages. For the pretreated root tips, Illoxan (except 37.50 mg/L at 12 and 24 h) significantly increased the frequency of abnormal cells in a dose-dependent manner. This study indicates that Illoxan decreased the mitotic index and produced clastogenic and aneugenic types of abnormalities in Allium cepa root tip cells. The data obtained in this study showed that plant bioassays can be used as an important test battery to detect possible genotoxicity of chemicals.