Isolation and characterization of phosphate-solubilizing bacteria from rhizosphere of poplar on road verge and their antagonistic potential against various phytopathogens.

Background: Phosphate-solubilizing bacteria (PSB) can solubilize insoluble phosphate compounds and improve phosphate availability in soil. Road verges are important in urban landscaping, but the population structure of PSB and their ecological functions in the road verge soil is still unclear.

Results: Twenty-one mineral PSB strains and 14 organic PSB strains were isolated from the rhizosphere of poplar on urban road verge. All the mineral PSB strains showed better solubilization to Ca(PO) than FePO or AlPO. Among them, 7 strains showed high phosphate-solubilizing (PS) activities to Ca(PO) (150-453 mg/L). All the organic PSB strains displayed weak solubilization to lecithin. 16S rRNA gene-based phylogenetic analysis showed good species diversity of the PSB strains, which belongs to 12 genera: Bacillus, Cedecea, Cellulosimicrobium, Delftia, Ensifer, Paenibacillus, Pantoea, Phyllobacterium, Pseudomonas, Rhizobium, Sinorhizobium and Staphylococcus. Moreover, 8 PSB strains showed various degrees of growth inhibition against 4 plant pathogenic fungi, Fusarium oxysporum S1, F. oxysporum S2, Pythium deliense Meurs Z4, Phomopsis sp. AC1 and a plant pathogenic bacterium, Pectobacterium carotovorum TP1.

Conclusions: The results indicated that these PSB strains could perform multiple ecological functions on road verge. The development and application of bio-agents based on the strains would provide a new strategy for maintaining and improving the ecosystem stability of road verges.