Varietal Differences in Maize (Zea mays L.) Responses to Soil Fomesafen Residues: Physiological Traits and Rhizosphere Bacterial Community Composition

Purpose This study compared the responses of fomesafen-tolerant (T) and -sensitive (S) maize ( Zea mays L.) seedlings exposed to the same soil residue levels to improve understanding of fomesafen carryover and its management in rotational cropping systems. Methods Pot experiments were conducted with T and S seedlings at soil fomesafen residue levels of 0, 0.2, 0.4, and 0.6 mg kg −1 . Soil fomesafen residues, plant accumulation, seedling growth, physiological injury, defense- and detoxification-associated responses, and rhizosphere bacterial composition were assessed. Results T seedlings maintained more stable growth, whereas biomass reductions in S seedlings reached 57.31%. Under the same fomesafen residue exposure, T seedlings exhibited a stronger glutathione-related Phase II response, with glutathione S-transferase activity increasing by 23.21-47.25% across the residue gradient; no comparable increase occurred in S seedlings. Rhizosphere bacterial composition also differed between varieties and residue levels, with selected genus-level differences involving Sphingobium , Massilia , and the Burkholderia-Caballeronia-Paraburkholderia complex. Conclusions Although fomesafen interferes with protoporphyrinogen oxidase in plants, the tolerance of T seedlings to soil fomesafen exposure was associated with stronger intracellular detoxification-related responses and distinct changes in rhizosphere bacterial composition. These findings provide critical ecological and physiological insights for mitigating herbicide carryover risks and ensuring agricultural sustainability.