Combining the advantages of Rhizophagus intraradices and Serendipita indica to reduce the risk of Cd on soybean safety and environmental pollution

The discharge of industrial wastes and improper application of fertilizers have caused Cd pollution in farmland soil. Combined microbial and plant remediation is an environmentally friendly method for Cd pollution remediation, but single microbial colonization cannot meet the dual needs of safe production and remediation in Cd pollution. Therefore, we designed an 85 days pot experiment to investigate the effect of compound or single arbuscular mycorrhizal fungi (AMF: Rhizophagus intraradices, RI) and Serendipita indica (SI) with similar physiological and ecological functions, on the soybean physiological parameters, soil factors, and soil Cd fractions. Their effects were analyzed on the Cd accumulation and transport ability and the soil contamination degree/risk in different Cd stress. The results showed that under different concentrations of Cd stress, Both RI and SI could not only increase the chlorophyll content of soybean to promote photosynthesis, thereby increasing the stem length and biomass index to promote growth, but also reduce the malondialdehyde content and increase the proline content to reduce the Cd-mediated oxidative damage. In addition, they cannot only increase soil pH and available phosphorus, but also improve soil urease and catalase activities. Furthermore, compound inoculant can reduce the Cd content in soybean by 55.96% (aerial), 72.61% (underground), and convert the Cd acid-soluble fraction into a more stable chemical fraction to reduce the risk of soil Cd pollution. It was found that SI had a more positive impact on soybean physiology, while RI was on soil quality. In conclusion, the compound inoculant combining the advantages of the two fungi is suitable for farmland under different concentrations of Cd stress.