Isolation and identification of new beneficial bacterial strains from rhizosphere of Citrus sinensis orchards

The rhizosphere is the area around the root of a plant occupied by a unique population of useful bacteria known as plant growth promoting rhizobacteria (PGPR). In this study, the isolation and identification of rhizobacteria from orange (Citrus sinensis) orchards using 16S rRNA gene, as well as biological and biochemical assays is reported. Analysis of 16S rRNA gene was confirmed by biological and biochemical assays and showed that the isolated bacteria belong to the genera Bacilli, Enterobacter and Pseudomonas. Accordingly, Enterobacterkobei MR-R2, Pseudomonas putida MRR5, Bacillus cereus MR-R, Bacillus thuringiensis MR-R1 and Bacillus mycoides MR-R4 were identified and registered in GenBank. The results of phosphate solubilization testing revealed that the maximum rate of phosphate solubilization was observed for B. thuringiensis, and E. kobei; however, B. cereus, B. mycoides, and P. putida indicated the least activity. It can be concluded that the isolated strains (especially B. thuringiensis) are newly identified phosphate solubilizing bacterial strains, among which B. thuringiensis can be used for growth promotion of orange trees.