Effects of imidacloprid and iprodione, isolated and in mixture, were assessed by using seed germination and root growth test, flow cytometry, and chromosomal aberrations test on Allium cepa root meristem. The highest concentrations of imidacloprid, including field concentration, increased the frequency of sub-G1 particles, decreased the frequency of nuclei in G2/M, increased the coefficient of variation of G1 (CVG1) and the frequency of aberrant cells, and inhibited the mitotic index culminating in the reduction in root length. All doses of iprodione also presented cytogenotoxic action. The highest concentration of the fungicide affected the growth of A. cepa roots. In response to exposure to pesticide mixtures, the cell cycle of A. cepa was blocked in the G1 phase. The mixtures with low doses of the pesticides significantly decreased the mitotic index, and as a consequence, the genotoxicity was reduced. In the mixtures with the highest doses of the agrochemicals, the blockage of the cell cycle was insufficient for damage repair, resulting in a significant increase of chromosomal aberrations. The results suggest caution in the use of pesticides doses that induce cytological abnormalities in non-target organisms.
Keywords: Adherent chromosomes; Chromosomal aberrations; Flow cytometry; Micronuclei; Phytotoxicity.