Arbuscular mycorrhizal fungi and phosphate-solubilizing bacteria synergistically enhance growth and cadmium accumulation of hyperaccumulator Sedum plumbizincicola

Arbuscular mycorrhizal fungi (AMF) and phosphate-solubilizing bacteria (PSB) are commonly found in cadmium (Cd)-contaminated soils and have the potential to enhance phytoremediation. However, the synergistic effects and underlying mechanisms of AMF and PSB on plant growth and Cd accumulation in hyperaccumulators remain largely unclear. A pot experiment was conducted using Sedum plumbizincicola grown in Cd-contaminated soil (8.99 mg kg⁻¹) to investigate the effects of single inoculation and co-inoculation with AMF ( Funneliformis mosseae ) and PSB ( Serratia marcescens ). Inoculation with AMF and PSB, especially co-inoculation, significantly improved nutrient availability and acid phosphatase activity in the rhizosphere soil, root morphology, and leaf mineral nutrient accumulation, thereby promoting plant growth. Compared with the control, co-inoculation (AMF + PSB) increased shoot and root biomass by 79% and 46%, respectively. Co-inoculation also decreased rhizosphere soil pH and markedly enhanced Cd bioavailability, with a 250% increase in CaCl 2 ‑extractable Cd concentration. Meanwhile, co-inoculation upregulated the expression of Cd detoxification-related genes ( SpMT2 , SepPCS , and SpHIPP45 ) by 6–9%, leading to 182% and 113% higher Cd accumulation in shoots and roots, respectively. Partial least squares path modeling (PLS-PM) indicated that the synergistic association of AMF and PSB contributed to enhanced Cd accumulation, which was linked to improved plant growth and increased rhizosphere soil Cd bioavailability. These results demonstrate that AMF and PSB synergistically improve growth and Cd phytoextraction in S. plumbizincicola , providing a feasible microbial strategy for enhancing phytoremediation of Cd-contaminated farmland soils.