Ecotoxicological assessment of the environmental risks of a glyphosate-based herbicide recently introduced in the Brazilian market: a perspective from plant-based bioassays

This study determined the phytotoxic and cytogenetic effects of two glyphosate-based herbicides (GBHs): XEQUE MATE HT IHARA® (restricted agricultural use – GBHn) and CITROMAX MAX 20 (used for gardening, sold for the general public – GBHg). Phytotoxicity bioassays were conducted using four non-target species (Lactuca sativa, Raphanus sativus, Pennisetum glaucum, and Hordeum vulgare) and one target species (Bidens pilosa). Both GBHs significantly reduced germination rate (G%), germination speed index (GSI), fresh mass (FM), and seedling growth (SG) in a dose-dependent manner. SG was the most sensitive endpoint with decreases over 99% at 480 mg/L for both GBHs. Bidens pilosa exhibited the highest sensitivity index (SI = 0.93 for GBHn, 0.8 for GBHg), confirming target specificity. Overall SI were similar (OSI = 0.75 for GBHn; 0.72 for GBHg), indicating comparable toxicity. Cytogenetic assays using Allium cepa demonstrated significant reductions in mitotic index (MI) at higher concentrations (> 40% decrease at higher doses), with limited chromosomal alterations but notable increases in micronuclei (MN) (up to 6 per 1,000 cells) for both GBHs. GBHn induced more MN formation than GBHg, suggesting greater genotoxicity. Despite similar phytotoxic profiles, GBHn's higher genotoxicity warrants concern. These results indicate the environmental risks posed by treatments with both formulations and emphasize the need for rigorous regulatory scrutiny for glyphosate-based herbicides.