Cytogenotoxicity and morphophysiological changes in the myxomycete Fuligo septica (Myxomycota, Physarales) caused by glyphosate

The myxomycetes are important components of edaphic microbiota, contributing to nutrient cycling and the regulation of microbial communities. However, toxicological studies involving these organisms remain scarce, and little is known about their responses to xenobiotics widely used in agriculture. In this study, we evaluated the cytogenotoxic effects of the glyphosate formulation Roundup® Transorb R on Fuligo septica (L.) Wiggers through spore germination assays, comet assay in myxamoeba, and morphophysiological analyses of the plasmodium. Spores were exposed to glyphosate concentrations ranging from 0.003 to 1.50 mg mL −1 . Germination was progressively reduced at intermediate concentrations (0.03–0.20 mg mL −1 ), while concentrations ≥ 0.50 mg mL −1 strongly inhibited germination, reaching 100% inhibition at 1.50 mg mL −1 . Genotoxicity was assessed after exposing myxamoeba to concentrations between 0.02 and 2.00 mg mL −1 , revealing significant concentration-dependent increases in DNA damage, with levels at 1.00–2.00 mg mL −1 comparable to or greater than the positive control (5 mM hydrogen peroxide). Morphological alterations, including reduced motility and encystment, accompanied the observed genetic damage. Plasmodia exposed to concentrations between 0.25 and 4.00 mg mL −1 showed significant mass loss and severe structural alterations, including thinning of plasmodial veins, darkened regions, and cytoplasmic leakage. Statistical analyses indicated significant differences among treatments ( p < 0.001). These findings provide the first robust evidence of glyphosate-induced cytotoxicity and genotoxicity in myxomycetes.