Synergistic Effects of the Inoculation with Plant Growth-Promoting Rhizobacteria and an Arbuscular Mycorrhizal Fungus on the Performance of Wheat

The synergistic effects of plant growth-promoting rhizobacteria and an arbuscular mycorrhizal (AM) fungus (Glomus fasciculatum) on plant growth, yield, and nutrient uptake of wheat plants were determined in field conditions. The triple inoculation of Azotobacter chroococcum with Bacillus and Glomus fasciculatum significantly increased the dry matter by 2.6-fold above the control. Grain yield of plants inoculated with A. chroococcum together with Bacillus sp. and G. fasciculatum was 2-fold higher than that of non-inoculated plants, at 135 days after sowing (DAS). The maximum increase in grain protein (255.2 mg g-1) was observed in plants inoculated with A. chroococcum with Bacillus sp., G. fasciculatum, and Penicillium variabile, while the minimum grain protein (113.7 mg g-1) was with a single inoculation of G. fasciculatum. The higher N content (33.6 mg plant-1) and P content (67.8 mg plant-1) in wheat plants were observed with the co-inoculation of A. chroococcum with Bacillus sp. and G. fasciculatum. The N and P contents of the soil at 135 DAS differed among treatments. Addition of P. variabile to single or double inoculation treatments negatively affected the measured parameters. Populations of A. chroococcum, phosphate solubilizing microorganisms, percentage root infection, and spore density of the AM fungus in some treatments increased at 80 DAS. The findings show that the multiple inoculations with plant growth promoting rhizobacteria consistently increased the growth and yield, N and P concentrations, and quality of wheat grains.