Isolation and Identification of PGPR Strain and its Effect on Soybean Growth and Soil Bacterial Community Composition

Plant growth-promoting rhizobacteria (PGPR) are considered environmentally sound option to reduce chemical fertilizer inputs, improve soil quality and increase crop yields. The objective of this study was to isolate an effective PGPR strain and investigate its effects on soybean growth and soil bacterial community composition. A total of 163 bacterial isolates were obtained from rhizospheres of plants in four provinces of China. According to capacities for mineral potassium and phosphate solubilization, the best strain (designated 3016) was selected and identified as Paenibacillus mucilaginosus based on biochemical characterization and phylogenetic analysis. Moreover, strain 3016 showed a higher capacity for nitrogen fixation and phytohormone production than commercial strains. In a field experiment, P. mucilaginosus 3016 was used as an inoculant for seed dressing survived in the soybean rhizosphere as revealed by a species-specific PCR method. Inoculation significantly improved symbiotic nodulation, soybean growth parameters, nutrient contents and yields. The number of nodules was increased by 31.8% for the inoculation treatment compared with CK. Soybean height, pods and seeds per plant and dry weight of nodules were also significantly higher for the inoculation, as well as nutrient contents. Regarding yields, the highest of 3191.4 kg hm(-2) was obtained under inoculation regime. Moreover, numerous bacterial classes and genera, which were associated with symbiotic nitrogen-fixation, plant growth promotion, biological control and soil catalase activity improvement, were also overrepresented in the inoculation treatment Some taxa with negative impacts on soil quality decreased. In conclusion, inoculation with P. mucilaginosus 3016 had beneficial effects on both soybean growth and soil quality, and is a potential candidate for developing commercial inoculants of PGPR to be used as a bio-fertilizer. (C) 2018 Friends Science Publishers