Isolation and characterization of plant growth promotion of efficient endophytic diazotrophs from Oryza officinalis wall in Cenxi

Abstract:

[Objective] To screen efficient nitrogen fixation and plant growth promoting endophytes from Oryza officinalis wall in Cenxi, Guangxi. [Methods] The nitrogen-fixation ability of the isolates was tested by acetylene reduction assay. The SDS-PAGE patterns of the whole-cell protein electrophoresis and IS-PCR DNA finger-printings were used to group these isolates. Phylogenetic analysis based on 16S rRNA gene and nifH gene was performed. The ability of indole acetic acid secretion and the production of siderophore were tested by the Salkowski colorimetric method and the blue plate assay, separately, and the ability of phosphate solubilization also was detected. The property of plant growth promoting rice was tested by plate and potting. [Results] A total of 35 endophytic diazotrophs were isolated and classified into 6 groups, in which CX24 belonging to the Klebsiella variicola showed the highest nitrogenase activity. The nitrogenase activity (298.64 nmol/(mL·h)) was 9 times as much as the reference strain DSM15968. Besides the secreting siderophore, indole acetic acid and ability of solubilize phosphorus, the strain CX24 could also effectively promote the germination and growth of rice. [Conclusion] The strain CX24 belonging to Klebsiella variicola, was an efficient endophytic diazotroph and had a very good application prospect.