Determination of genotoxic effects of 2,4-d and dicamba herbicides in bean (Phaseolus vulgaris L.) roots by rapd and comet assays

The present study was undertaken to evaluate genotoxic potential of two auxinic herbicides; 2,4-dicholorophenoxy acetic acid (2,4-D) and 3,6-dichloro-2-methoxybenzoic acid (dicamba) in the root tissue of bean (Phaseolus vulgaris L.) seedlings. Two-day old bean seedlings were exposed to distilled water (negative control), methyl methanesulfonate (MMS, positive control) and three sublethal concentrations (0.1, 02 and 0.3 ppm) of 2,4-D and dicamba for 96 h. The root growth, total soluble protein content, DNA damage in individual cells (comet assay) and randomly amplified polymorphic DNA (RAPD) profiles were used as endpoints of genotoxicity. 2,4-D and dicamba EC50 values of root growth were calculated as 0.17 and 0.24 ppm, respectively. Total soluble protein content in the root tissue of the seedlings was significantly decreased at MMS treatment and at high concentrations (0.2 and 0.3 ppm) of dicamba, while 0.2 and 0.3 ppm 2,4-D treatments increased the protein content (P ? 0.05). Dose-dependent single strand DNA breaks in the root nuclei of bean seedlings were determined for 2,4-D and dicamba as revealed by comet assay. In comparison to negative control, RAPD polymorphisms became evident as disappearance and/or appearance of RAPD bands in treated seedlings. The diagnostic and phonetic numerical analyses of RAPD profiles obviously indicated dose-dependent genotoxicity induced by 2,4-D and dicamba. According to sensitivity of parameters to 2,4-D and dicamba toxicity, the above indicator rank in the following order: comet assay > root growth > RAPD profiles > total soluble protein content.2009, 78 PagesKey words: Phaseolus vulgaris, 2,4-D, Dicamba, Comet Assay, RAPD, Genotoxicity.