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

Abstract

Abstract Background Phosphate-solubilizing bacteria can solubilize insoluble phosphate compounds and improve phosphate availability in soil. Road verges are important parts of urban landscaping, but the pupulation structure of phosphate-solubilizing bacteria and their ecological functions in the road verge soil is still unclear. Results We isolated and identified the phosphate-solubilizing bacteria from the rhizosphere of poplar in urban road verge to figure out the phosphate-solubilizing bacteria community and their functions in urban road verge soil. Their phosphate-solubilizing and antagonistic activities were evaluated. Twenty-one mineral phosphate-solubilizing bacteria and 14 organic phosphate-solubilizing bacteria were screened from the soil samples. All the mineral phosphate-solubilizing bacteria showed better solubilization to Ca3(PO4)2 than FePO4 or AlPO4. Among them, 7 strains showed high phosphate-solubilizing activities to Ca3(PO4)2 (150–453 mg/L). All the organic phosphate-solubilizing bacteria displayed weak solubilization to lecithin. 16S rRNA gene-based phylogenetic analysis showed good species diversity of the phosphate-solubilizing bacteria, which belongs to 12 genera: Bacillus, Cedecea, Cellulosimicrobium, Delftia, Ensifer, Paenibacillus, Pantoea, Phyllobacterium, Pseudomonas, Rhizobium, Sinorhizobium and Staphylococcus. Moreover, 8 strains showed various degrees of growth inhibition against the phytopathogens: Fusarium oxysporum S1, F. oxysporum S2、Pythium deliense Meurs Z4, Phomopsis sp. AC1 and Pectobacterium carotovorum TP1. The strain B. siamensis Mp4-Ha30 presented growth inhibition to all the five phytopathogens (FGI > 60%). Conclusions The results indicated that these PSB strains could perform multiple functions in maintaining ecosystems stability in road verge and provided potential microbial resources for the further research on biofertilizers and biocontrol agents.