Environmental Processing Modulates the Mutagenic Potential of Glyphosate: Evidence from Drosophila SMART Assay

Research Hypothesis: Environmental processing (soil interaction and microbial degradation) modulates glyphosate's mutagenic potential. While direct exposure to glyphosate-based herbicides is genotoxic, residues transformed by the soil matrix under aerobic or anaerobic conditions retain the capacity to trigger recombinogenic risk and genomic instability. Methodology: Data were gathered via the Drosophila melanogaster Somatic Mutation and Recombination Test (SMART). Third-instar trans-heterozygous larvae (mwh + / + flr³) were exposed to direct glyphosate concentrations (20%, 25%, 33.3% v/v), positive (1000 RAD X-ray) and negative (distilled water) controls, and aqueous extracts from treated soil incubated for three weeks under aerobic or anaerobic conditions. Adult wings were mounted and scored at 400× magnification for mosaic mutant clones, categorized as small/large single spots or twin spots. What the Data Shows: The dataset includes raw mutant counts (mwh, flr³, and twin spots), spot frequencies (n/N), and calculated induction frequencies (f) representing the probability of a mutational event per cell division. Statistical significance is determined by the Kastenbaum–Bowman conditional binomial test and exact Poisson tests across independent biological replicates. Notable Findings: Intrinsic Genotoxicity: Direct exposure (33.3%) is significantly mutagenic, reaching a frequency of 1.79 compared to a 0.275 baseline. Definitive LOH Evidence: Identification of twin spots in direct and soil-mediated groups provides definitive evidence that glyphosate acts as a recombinagen, inducing Loss of Heterozygosity (LOH). Environmental Modulation: Soil interaction significantly reduces mutation frequencies (to 1.33 for aerobic and 1.18 for anaerobic extracts) but does not neutralize the genotoxic risk. Benchmarks: Glyphosate’s induction frequency (9.85×10^−5) remains an order of magnitude lower than the 1000 RAD radiation benchmark (1.8×10^ −3 ). Interpretation and Use: This data provides a whole-organism perspective on how environmental matrices modify chemical hazards. Twin spots are critical indicators of reciprocal mitotic recombination, a key driver of carcinogenesis. The results demonstrate that while the soil matrix acts as a partial buffer, biologically active residues persist and remain capable of inducing complex genomic rearrangements.