Silicon-mediated mitigation of cadmium risk in peanut-growing soil depends on cultivar-specific defense strategies

Cadmium (Cd) contamination increases Cd bioavailability in agricultural soil and elevates the risk of Cd transfer into edible crop organs. Silicon (Si) amendment can achieve both objectives, yet the extent to which plant genotype modulates Si-based Cd mitigation effectiveness across different biological levels remains unclear. Here, two peanut ( Arachis hypogaea L.) cultivars with contrasting agronomic backgrounds were grown in Cd-contaminated soil (1 and 3 mg kg −1 added Cd) with or without Si (120 mg kg −1 ). Si treatment decreased soil bioavailable Cd and enhanced soil Cd retention capacity. Adsorption-desorption results suggested that soil-level Cd immobilization contributed to the reduction in Cd bioavailability. Seed Cd concentrations declined in a strongly cultivar-dependent manner (C-211: 51.1% reduction; B-202: 9.8%). Integrated transcriptomic and proteomic analyses revealed contrasting cultivar-specific defense strategies: B-202 was characterized by glutathione-mediated metabolic detoxification, whereas C-211 showed phenylpropanoid-associated structural defense and sequestration-related responses. These findings suggest that Si amendment reduces Cd bioavailability in contaminated soil and limits Cd transfer to edible organs, while the overall mitigation outcome is further shaped by genotype-dependent plant defense. Combining soil amendment with cultivar selection therefore offers a more reliable strategy for reducing seed Cd accumulation risk in Cd-affected agroecosystems.