Physiological and Rhizosphere Microbial Community Responses of Rapeseed (Brassica napus L.) to Antimony Stress: Implications for Phytoremediation and Seed Safety

Antimony (Sb) contamination in agricultural soils threatens the safety of rapeseed production, yet the mechanisms driving cultivar differences in seed Sb accumulation remain unclear. A pot experiment was conducted with two Sb-tolerant cultivars showing contrasting accumulation patterns, Nanyouza 1 (high-accumulating) and Fengyou 958 (low-accumulating), grown under increasing Sb levels. (1) Sb stress inhibited growth and reduced photosynthetic performance in both cultivars; antioxidant enzymes showed a “low stimulation–high inhibition” response and MDA increased under high Sb, indicating aggravated oxidative damage beyond the tolerance threshold. (2) Nanyouza 1 accumulated more Sb in vegetative tissues and exhibited stronger root-to-shoot translocation than Fengyou 958, whereas seed Sb remained relatively low in both cultivars and bioconcentration/translocation efficiencies declined with increasing Sb. (3) At maturity, rhizosphere bacterial communities shifted along the Sb gradient, and taxa associated with Sb differed, with Ramlibacter and Bacillus positively correlated. These findings provide mechanistic insights supporting the integration of cultivar selection and rhizosphere regulation to achieve both safe production and phytoremediation in Sb-contaminated farmland.