Nowadays, exploiting the symbiosis between plants and beneficial microbes is a promising approach to increase plant tolerance to environmental stresses. In this study, the ability of Serendipita indica (S. indica), a root colonizing mycorrhiza like fungus, to ameliorate copper (Cu) stress was investigated in proso millet (Panicum miliaceum L.) plants under greenhouse conditions. Proso millet seedlings were subjected to 0, 50, 100, 150, and 200 mg Cu Kg-1 soil. All Cu concentrations applied to the soil significantly increased Cu content in the plants. In the presence of S. indica, the Cu accumulation enhanced in the roots while less Cu content was observed in the shoot tissues. A significant increase in root and shoot growth, chlorophyll content and photosynthetic activity was obtained in colonized plants as compared to controls. For example, at 200 mg Cu Kg-1 soil, inoculation of plants with S. indica, increased shoot and root dry matter, chlorophyll content and net photosynthesis by 41.9, 68.1, 25 and 29.3%, respectively. Excessive levels of Cu in the soil led to elevated antioxidant enzymes activity, such as superoxide dismutase (SOD), catalase (CAT), and specially peroxidase (POD). In inoculated stressed plants, the activity of antioxidant enzymes was higher and lipid peroxidation and hydrogen peroxide (H2O2) content reduced as compared to non inoculated stressed plants. These results indicated that colonized proso millet plants suffer from less oxidative damage under Cu toxicity and therefore utilization of the endophytic fungus S. indica can be a biological approach to combat Cu stress in contaminated soils.
