A novel method to alleviate arsenic toxicity in alfalfa plants using a deletion mutant strain of Sinorhizobium meliloti

Reduction in crop yield and contamination of food crops are major problems in many areas due to high soil arsenic content. In this study an aquaglyceroporin (AqpS) disrupted Sinorhizobium meliloti smk956 strain was found to accumulate 70.5% more arsenic than its parental strain S. meliloti Rm1021 under free living condition. This strain was inoculated onto alfalfa host plants under different arsenic concentrations (0, 1 and 5 mg/L) and its ability to alleviate arsenic toxicity in the host plant was investigated. At 1 and 5 mg/L arsenic concentrations the average arsenic contents in the shoots of the plants inoculated with the strain S. meliloti smk956 were 45.5 and 27.5% less than those of the plants inoculated with S. meliloti Rm1021, respectively. Under arsenic stress conditions the strain S. meliloti smk956 showed increased symbiotic efficiency than its parental strain. These results demonstrate a novel method to alleviate arsenic toxicity in alfalfa plants.