[Genotypic analysis and plant growth-promoting ability of four plant growth-promoting bacteria from mangrove].

Objective: We identified four strains of plant growth-promoting bacteria (PGPB) and their plant growth-promoting ability.

Methods: Four PGPB strains were genetically analyzed by PCR detection of nifH and 16S rRNA gene. Phosphate-solubilizing and nitrogen-fixation capacity were examined by spectrophotometric quantification and acetylene reduction assay, respectively. Effect of strain inoculation on plant growth was also evaluated.

Results: Phylogenetic analysis based on nifH and 16S rRNA gene sequences indicated that strain HN011 was mostly related to Vibrio natriegens, and SZ7-1 and SZ7-2 resembled Klebsiella oxytoca. Although similarity of 16S rRNA sequence showed that SZ002 belongs to Paenibacillus sp., nifH gene of SZ002 had high sequence similarity with Klebsiella genus. Phosphate solubilization showed that insoluble phosphate was well solubilized in the liquid medium by all four strains of PGPB, which also had high nitrogen-fixation capacity. Plant dry weight, total N and total P were higher in some inoculated than in the non-inoculated plants (P < 0.05).

Conclusion: Our results showed that all four strains of PGPB isolated from mangrove had both phosphate solubilization and nitrogen fixation ability, resulting in beneficial effects on growth.