Plants are direct recipients of agro-toxics and therefore important materials for assessing environmental chemicals for genotoxicity. Three doses, representing ¼, ½ and EC50 of hormoban, storm killer, villa, fungi-nil, bexadust, aphicide, karbadust and basagran were assessed for cytotoxic and genotoxic effects to onion root tip cells in the root tip chromosome aberration assay after 24 h exposure. Cytotoxicity was inferred when the Mitotic index (dividing cells/1000 scored) of treated cells was£ ½ negative control. All the pesticides were toxic. Genotoxicity was measured by analyzing 30 to 100 anaphase-telophase cells per dose of chemical for, chromosome fragments, bridges, vagrant chromosome, c-anaphase, multipolarity and stick chromosomes and comparing the percentage of aberrant cells at each dose with that of the negative control using the Chi-squared test. With the exception of basagran, the pesticides were genotoxic (P < 0.05). The C-anaphase and Stick chromosomes types of aberrations predominated which was evidence of the action of the pesticides on the mitotic spindle and the coiling of chromosomes during anaphase to telophase.
Key words: Allium cepa, cytotoxicity, genotoxicity, pesticides, root tip meristem cells.
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