Isolation of bacteria activating phosphorus and hydrolyzing complex organic matter from the rhizosphere soil of Carya cathayensis Sarg

Abstract:

[Objective]Multipurpose bioorganic fertilizers contribute to the sustainable development of the Carya cathayensis Sarg.industry.This work aims to explore the resources of phosphorus (P)-mobilizing bacteria (PMBs) with plant growth-promoting effects from the rhizosphere soil of C.cathayensisSarg.[Methods]PMBs were isolated with the dilution-plate coating method and identified based on 16S rRNA gene homology.Moreover,plate and liquid culture tests were conducted to determine their biological functions.[Results]A total of 34 strains of PMBs were isolated from the rhizosphere soil of C.cathayensisSarg.These PMBs belonged to 10 genera of four phyla:Bacillota,Proteobacteria,Actinobacteriota,and Gracilicutes.Among them,Bacillus(12 strains),Burkholderia(9 strains),and Pseudomonas(5 strains) were the dominant genera,with the strains accounting for 76.47% of the total isolated PMBs.After inoculation of PMBs,the content of soluble P produced by PMBs was 7.01–49.97,3.61–27.11,4.56–342.82,27.71–544.53,and 3.28–27.17 mg/L in the culture media with AlPO₄,FePO₄,Ca₃(PO₄)₂,sodium phytate,and lecithin as the sole P source,respectively.Twenty-three strains were capable of simultaneously mobilize insoluble inorganic and organic P components.Additionally,20,7,23,12,10,14,and 13 strains of PMBs could produce indole-3-acetic acid (IAA),siderophores,extracellular protease,β-1,3-glucanase,cellulase,phosphatase,and lipase,respectively,among which strains S3-6L and S3-22L exhibited five biological functions.[Conclusion] The PMBs identified in this study possess high P mobilization capability and multiple biological functions,enriching the resources of PMB strains and laying a foundation for the development of efficient,green,and composite microbial fertilizers for C.cathayensisSarg.

Key words:Carya cathayensis Sarg.;rhizosphere microorganisms;phosphorus-mobilizing bacteria;multipurpose