Effect of Serendipita indica and Sinorhizobium meliloti on alfalfa plant growth (Medicago sativa L.) in a calcareous soil contaminated with zinc

Heavy metal accumulation in soils has been become one of the most dangerous environmental issues in human societies. The use of a cheap and safe technology such as phytoremediation with a proper symbiosis between plants and plant growth-promoting microorganisms, can be an effective step in phytoremediation technology. In the present study, the effects of individual and combined inoculation of Serendipita indica and Sinorhizobium meliloti on alfalfa grown in a contaminated soil with different concentrations of zinc (0, 400 and 800 mg kg−1 soil) were investigated. The results showed that the highest level of zinc contamination led to a significant decrease of 53.3%, 71%, 25.2% and 60.2 of shoot and root dry weight, Phosphorus concentration, and plant catalase enzyme respectively, it was also associated with an increase of 174.5, 56.6, 60.2 and 36.6% in the amount of hydrogen peroxide, malondialdehyde, peroxidase and superoxide desmutase enzymes. The combined inoculation of fungi and bacteria increased phosphorus absorption in the plant. In addition, this treatment reduced the transfer of zinc from the roots to the shoots and stimulated the system of plant oxidative enzymes such as catalase and reduced the amount of hydrogen peroxide and malondialdehyde, which increased the growth characteristics of the plant. Therefore, the combined inoculation of fungi and bacteria has an important role in alfalfa plant nutrition by reducing the pH of the rhizosphere soil and increasing the Zn absorption and increasing the Zn stabilization in alfalfa roots.