Toxic chemicals-induced genotoxicity detected by random amplified polymorphic DNA (RAPD) in bean (Phaseolus vulgaris L.) seedlings.

Assessment of genotoxins-induced DNA damage and mutations at molecular level is important in eco-genotoxicology. In this research, RAPD was used to detect DNA damage in the roots and leaves of bean (Phaseolus vulgaris L.) seedlings exposed to toxic chemicals of Hg, B, Cr and Zn (HgCl(2), H(3)BO(3), K(2)Cr(2)O(7) and ZnSO(4)7H(2)O) at concentrations of 150 and 350 ppm for 7 d. Inhibition of shoot and root growth and increase of Hg, B, Cr and Zn element contents in the roots and leaves were observed with an increase in the concentration. For the RAPD analyses, 12 RAPD primers of 60-70% GC content were found to produce unique polymorphic band profiles and subsequently were used to produce a total of 120 bands of 263-3125 bp in the roots and leaves of untreated and treated seedlings. Polymorphisms became evident as disappearance and/or appearance of DNA bands in 150 and 350 ppm treatments compared with untreated control treatments. The DNA changes in RAPD profiles were more in the roots than in the leaves. The highest polymorphism was observed in boric acid treatments among the toxic chemicals. In a dendrogram constructed based on genetic similarity coefficients, the treatments were grouped into three main clusters: (a) root-B-150 ppm treatment grouped alone, (b) root-350 ppm-Hg, B, Cr and Zn treatments clustered together, and (c) the others including untreated control treatments merged together. We concluded that DNA alterations detected by RAPD analysis offered a useful biomarker assay for the evaluation of genotoxic effects of Hg, B, Cr and Zn pollutions on plants.