Role of Beneficial Soil Microbes on Growth and Cd Uptake by Corn

Using the synergistic relations between plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) is a sustainable and economically significant management method for growing plants in soils with heavy metal contamination. A greenhouse experiment was carried out using corn plant in a factorial design with four Cd levels of zero، 10، 20، and 30 mg kg-1 and four microbial inoculation including control (C)، PGPR inoculation (B)، AMF inoculation (F) and PGPR+AMF (BF). PGPRs inoculant was a mixture of fluorescent Pseudomonads and the AMF isolate belonging to Glomus versiforme. After 98 days، plants were harvested and shoots and roots were separately weighed and dried. Growth parameters and Cd concentration and content (accumulation) were determined in different parts of the plants. Analysis of variances showed that different Cd levels and microbial inoculations significantly affected the measured indices. High concentration of Cd decreased shoot dry weight، and increased Cd concentration as well as Cd content compared to non-contaminated treatments by 1. 8 and 1. 4 fold، respectively. Accumulated Cd in plants of Cd0 treatment was 250 μg/pot and significantly increased in Cd30 treatment (966 μg/pot). Microbial inoculation of corn led to an increase in plant biomass compared to the control plants in the contaminated condition. The highest plant biomass (27. 5 g/pot) was achieved in PGPR inoculation which 3. 4 times higher than that of the control plants (8. 1 g/pot). Microbial inoculation increased significantly (2. 57 fold) Cd uptake in comparison with control condition. Among microbial treatments، PGPR inoculation showed the highest effect on shoot dry weight and Cd accumulation. Microbial inoculation reduced the concentration of shoot Cd، however، due to higher plant biomass، Cd accumulation increased in the whole plant. It is concluded that PGPR and AMF inoculations resulted in increasing phytoextraction and phytostabilization of Cd، respectively