Effect of Solanum nigrum L. combined microbial agent on Cd uptake and rhizosphere microbial community under Cd contaminated soil

Solanum nigrum L. and microbial agents are materials for the remediation of cadmium (Cd) contaminated soil. This study investigated the strengthening potential of Bacillus megaterium (BM) combined with citric acid (BM+CA), Glomus mosseae (BM+GM) and Piriforospora indica (BM+PI) to remediate Cd contaminated soil by Solanum nigrum L. by conducted greenhouse pot experiment. The results showed that the high concentration of Cd in BM and BM+CA inhibited the normal growth of Solanum nigrum L., while BM + PI and BM+GM made the normal growth of Solanum nigrum L. under the protection mechanism of them, and the protection of PI was weaker than that of GM. Therefore, BM and BM+CA reduced the cadmium accumulation of each pot of Solanum nigrum L., BM+PI increased the cadmium accumulation of each pot of Solanum nigrum L., they did not have significance difference with control. But BM+GM significantly increased the cadmium accumulation of each pot of Solanum nigrum L. by 104%. The microbe of rhizosphere was analyzed from multiple angles, it was found that the mechanism of GM improving Cd tolerance of Solanum nigrum L. may be related to bacteria Actinobacteria and fungi MortieRellomycot, and PI was mainly related to MortieRellomycot. Catalase (CAT), urease (UE) and alkaline phosphatase (ALP) were the main reason for Actinobacteria to promote the ability of plants to prevent diseases. And CAT was the main reason for MortieRellomycot to improve resistance and tolerance of plants. Overall, the results showed that BM+GM treatment was the strongest combination selected to remediate Cd pollution. It could promote the ability of Solanum nigrum L. to remediate Cd contaminated soil by regulating rhizosphere microbial community by affecting environmental factors such as pH, CAT, UE and ALP and so on.