Soil application of manganese sulfate effectively reduces Cd bioavailability in Cd-contaminated soil and Cd translocation and accumulation in wheat

Cadmium (Cd) pollution in wheat fields has caused serious food safety issues in China. Manganese (Mn)-containing materials have been widely used in paddy fields to reduce Cd accumulation in rice. However, the remediation effects of MnSO4 in wheat fields have not been well studied and the underlying mechanisms are poorly understood. Our field experiment showed that the application of 0.1% and 0.2% MnSO4 in soil reduced Cd concentrations significantly in wheat root, stem, leaf, and grain by 26.67-30.76%, 15.78-29.30%, 22.03-30.66%, and 30.57-50.55%, respectively, while increasing Mn concentrations significantly in these wheat tissues. MnSO4 application significantly increased soil available Mn content by 3.78-6.19 times, the free Mn oxides and amorphous Mn oxides by 1.72-10.38 times, and Mn oxides bound Cd contents by 10.23-39.55%, resulting in a reduction of Cd availability by 30.11-40.78%. Simultaneously, MnSO4 treatment altered the chemical forms of Cd and Mn, promoted the soluble protein concentration, and decreased the malondialdehyde (MDA) content in wheat roots. Additionally, soil application of MnSO4 down-regulated the expression of TaNramp5, TaHMA2, and TaLCT1 in wheat roots, mediating the reduction of wheat root Cd concentration, and increased the sequestration of Cd into vacuoles by up-regulating the expression of TaHMA3. These findings add to the current knowledge of how MnSO4 affects Cd mobilization and absorption via different mechanisms occurring both in the soil medium and at the plant level. This research indicates that soil application of MnSO4 has great potential to remediate Cd-contaminated wheat fields.