Cytogenotoxicity attributed to ioxynil octanoate exposure utilizing <i>Allium cepa</i> L as a model

Ioxynil octanoate, considered to be non-genotoxic, is widely used as a post-emergence herbicide. However, extensive agricultural usage might potentially adversely affect non-target organisms, indicating the need for a comprehensive toxicological reassessment. The aim of this study was to investigate the phytotoxic and cytogenotoxic effects attributed to exposure to this herbicide on <i>Allium cepa</i> L. examining germination, early growth, cell cycle progression, and genomic stability. Herbicide concentrations of 52, 209, 837, or 3350 ppm were tested. Distilled water was used as a negative control, while 10 ppm methyl methanesulfonate (MMS) served as a positive control in the comet assay. Parameters determined included germination, root and shoot growth, biomass accumulation, qualitative lipid peroxidation, mitotic index, chromosomal aberrations, and DNA fragmentation via the comet assay. All tested concentrations significantly reduced seed germination and seedling development, with 3350 ppm completely inhibiting normal growth. Histochemical analysis demonstrated significant oxidative stress. A mitodepressive effect exceeding 72% was observed after 72 hr exposure. DNA fragmentation induced by 837 and 3350 ppm was comparable to that of MMS. The association between comet assay results and the presence of micronuclei reinforces the compromise of genomic stability in <i>A. cepa</i> exposed to the compound. Data demonstrated that ioxynil octanoate, even at field-relevant concentrations, impaired cell division, and genomic integrity, indicative of significant cytogenotoxicity. These findings emphasize the need to reevaluate agricultural use of ioxynil octanoate, considering potential environmental risks to non-target organisms and the importance of complementary genotoxicological studies involving both target and non-target organisms.