高效解磷菌筛选优化及其对弱碱土小麦促生效应OA

[Objective]To address the severe phosphorus(P)immobilization and low plant availability in slightly alkaline soils,this study aimed to screen high-efficiency and stress-tolerant phosphate-solubilizing bacteria(PSB),optimize their culture conditions,clarify the P-solubilizing mechanism,and verify their effects on soil P activation and wheat growth promotion.[Method]A total of 26 candidate strains from 7 genera were used as test materials.High-efficiency PSB were isolated via primary screening by the plate transparent zone method(using inorganic P selective medium,with phosphorus-solubilizing index as the evaluation criterion)and secondary screening by the liquid culture method(soluble P content determined by molybdenum antimony anti-spectrophotometry).Single-factor experiments and response surface methodology(RSM)were conducted to optimize the cluture conditions.High-performance liquid chromatography(HPLC)was used to identify organic acid components,and Pearson correlation analysis was performed to reveal the relationship between organic acid profiles and P-solubilizing efficiency.Wheat pot experiments were carried out to evaluate soil application effects.[Result]An efficient PSB strain was identified as Enterobacter asburiae N4129-2AT.This strain maintained stable P-solubilizing capacity under low temperature(15℃)and high alkalinity(pH 10).After RSM optimization,the optimal culture conditions were confirmed to be 35℃,initial pH 6,and an inoculum size of 7.2%.Under these conditions,the soluble P content in fermentation broth reached 823.471 mg/L within 72 h,which was 23.7%higher than that before optimization,and the culture cycle was shortened by 96 h.E.asburiae N4129-2AT stably secreted six types of small-molecule organic acids.The core P-solubilizing mechanism was acidification mediated by organic acids,and the key factor improving P-solubilizing efficiency was organic acids strongly associated with P solubilization rather than their content proportion;total organic acid content only played an auxiliary role.In wheat pot experiments,all PSB treatments significantly increased soil available P content and wheat growth parameters compared with the control.The medium-dose optimized whole bacterial broth treatment showed the best performance:soil available P content increased by 376.76%,wheat the root dry weight increased by 157.4%,and root-shoot ratio decreased by 22.69%.A highly significant positive correlation was observed between soil available P and wheat growth parameters.[Conclusion]E.asburiae N4129-2AT possesses excellent stress tolerance(low temperature and high alkalinity)and high P-solubilizing efficiency.Its P-solubilizing mechanism,dominated by strongly associated organic acids through targeted optimization of organic acid profiles,breaks the traditional cognition that total organic acid content determines P-solubilizing capacity,providing a theoretical reference for the improvement of similar strains.This strain and its optimized culture conditions offer reliable technical support for P activation in slightly alkaline soils and high-yield wheat production.