Cytogenetic effects of quizalofop-p-ethyl herbicide on the root meristem cells of allium cepa L.

In this research, toxic and cytotoxic effects of quizalofop-P-ethyl (QPE) on roottips of Allium cepa L. were investigated. The effects of different concentrations ofQPE herbicide and exposure times on root growth, mitotic index, anaphase-telophase chromosome aberrations, and formation of micronuclei at interphasewere determined. The control treatments were performed in distilled water. In alltreatments, the onions which homogeneously rooted in distilled water for 24 hwere used. In Allium root growth inhibition test, effective concentration (EC50)value of QPE herbicide was found approximately 1.5 ppm. In cytotoxicity test,onions were grown at distilled water (control), and at EC50 (1.5 ppm), half of theEC50 (EC50/2=0.75 ppm), double the EC50 (2×EC50=3 ppm) concentrations of QPEherbicide for 24, 48, 72 and 96 h. Following these treatments, the slides wereprepared from the root tip samples for microscopical investigations. Mitotic indexwas significantly decreased by increasing the concentration of QPE herbicide(P<0.05). QPE herbicide induced anaphase-telophase chromosome aberrations indifferent ratios. These aberrations were detected such as stickness (%38.57),bridges (%28.42), vagrant chromosomes (%16.67), c-anaphase (%14.10),multipolarity (%1.60) and fragments (%0.64). Stickness was significantlyincreased at 3 ppm compared to other concentrations, while no stickness wasobserved at control treatments. Bridges, vagrant chromosomes and c-anaphaseswere significantly increased at 0.75 and 1.5 ppm compared to control. Theincrement in total chromosome aberrations were found at significant level in allconcentrations compared to control. According to the micronuclei formation atinterphase, differences among periods in each concentration were foundinsignificant. The micronuclei formation was significantly increased at only 3ppm according to the means of all periods in each concentration.2006, 67Key words: Allium cepa, quizalofop-P-ethyl herbicide, root growth, effectiveconcentration, mitotic index, chromosome aberrations, micronuclei