Genetic Diversity and Characterization of Plant Growth-Promoting Effects of Bacteria Isolated from Rhizospheric Soils

Plant growth-promoting rhizobacteria (PGPR) have the potential to make a significant contribution to the development of sustainable agricultural systems. Generally, PGPRs function in three different ways, summarized as the synthesis of certain compounds for plants, facilitating the uptake of certain nutrients from the soil and protecting plants from diseases. This study aims to isolate plant growth-promoting bacteria from different plant rhizospheres from Ankara province, to reveal their genetic diversity, and to determine their plant growth-promoting properties. The identification of the 69 isolates was made according to the 16S rDNA sequence results and ARDRA analyses were also performed using Alu I, Hea III, and Msp I enzymes. Nitrogen fixation, phosphate dissolving, IAA (indole-3-acetic acid) and siderophore production capacities of the 69 bacterial strains including 12 different genera (30 Pseudomonas , 13 Arthrobacter , 7 Bacillus , 4 Phyllobacter , 4 Variovorax , 3 Olivibacter , 3 Enterobacter , 2 Paenarthrobacter , 1 Stenotrophomonas , 1 Flavobacterium , 1 Caulobacter , 1 Paenibacillus ) were evaluated in in vitro conditions. Nitrogen fixation capacities of 55 isolates varied between 2.29 and 46.11 µg mL −1 according to micro-kjeldahl method. Among the strains studied, nifH gene was detected only in Paenibacillus polymyxa H8/2 strain. The highest Phosphorus dissolving and IAA production capacity (in tryptophan-added medium) of isolates were 186.52 µg mL −1 , and 50.05 μg mL−1 respectively, and 31 of 69 isolates were able to produce siderophore. Regarding antifungal activities, results showed that 31 bacterial isolates had antagonistic activities against at least one of the tested pathogens. Nitrogen fixation and phosphate solubilizing potential of the promising bacterial strains were determined through two-independent pot experiments with wheat and it has been found that they have positive effects on the yield parameters of wheat.