The potential of cadmium ion-immobilized Rhizobium pusense KG2 to prevent soybean root from absorbing cadmium in cadmium-contaminated soil.

AIMS

Because the effect of Cd -immobilized microbe on Cd uptake of plants in Cd-contaminated soil remains underexplored, this study focuses on the effect of Cd -immobilized rhizobia on Cd uptake of soybean.

METHODS AND RESULTS

Strain KG2 from soybean nodule was identified as Rhizobium pusense KG2 by phylogenetic analysis. Rhizobium pusense KG2 showed the 120 mg l of minimal lethal concentration for Cd . In 50 and 100 mg l of Cd liquid, approximately 2 × 10 cells removed 56·71 and 22·11% of Cd , respectively. In pot soil containing 50 and 100 mg kg of Cd , strain KG2 caused a 45·9 and 35·3% decrease in soybean root Cd content, respectively. Meanwhile, KG2 improved the root and shoot length, nitrogen content and biomass of soybean plants and superoxide dismutase activity.

CONCLUSIONS

The Cd -immobilized rhizobia could inhibit soybean plants to absorb Cd from soil, promote plant growth and improve plant's tolerance against Cd. This study is the first time to report that R. pusense is an effective nodulating rhizobium of legume.

SIGNIFICANCE AND IMPACT OF THE STUDY

Some Cd -immobilized microbe lowering Cd uptake of plant and promoting plant growth should be considered as an effective strategy for producing safety crops in the Cd-contaminated agricultural soil.