Isolation and identification of plant growth-promoting bacteria (PGPB) from ramie (Boehmeria nivea L. Gaud) rhizosphere and their promoting growth effects

Abstract:

[Objective] We used roots and rhizosphere soils of ramie (Boehmeria nivea L. Gaud) to isolate plant growth promoting bacteria (PGPB), and then studied the mechanism why they promote growth of ramie in preliminarily. [Methods] Preliminary screening of PGPBs under the premises of bacteria have the abilities of phosphate-and potassium-solubilizing, moreover, the bacteria strains were screened by testing their abilities of siderophore, indole acetic acid (IAA) and ammonia production in vitro. Then, seeds germination and pot experiments were conducted to measure the promoting-growth effects on ramie of the isolates. Finally, PGPBs were classified and identified by combining physiological and biochemical tests and 16S rRNA gene sequences analysis. [Results] Thirteen strains were isolated based on the abilities of phosphate- and potassium-solubilizing, of which four strains (RA-2, RAM-2, RAM-5, and RAM-6) also exhibited plant growth promoting properties like siderophores, IAA and ammonia production. Seeds germination and pot experiments showed that four selected strains could promote growth of ramie, moreover, strain RA-2 and RAM-5 could significantly improve the germination rates, root lengths, plant heights, and root dry weights, both of isolates RA-2 and RAM-5 were identified as Burkholderia sp.. [Conclusion] PGPBs which were isolated from ramie rhizosphere will helpful for developing the specially PGPB microbial inoculants or bio-organic fertilizers of ramie.

Key words:Plant growth-promoting bacteria, Ramie, Growth and development, Burkholderia sp.