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Scientia Silvae Sinicae ›› 2021, Vol. 57 ›› Issue (3): 90-97.doi: 10.11707/j.1001-7488.20210309

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Phosphate-Dissolving Mechanisms of Pseudomonas fluorescens and Its Colonizing Dynamics in the Mycorrhizosphere of Poplars

Hui Liu1,2,Xiaoqin Wu1,*,Jianren Ye1,Dan Chen1   

  1. 1. Co-Innovation Center for the Sustainable Forestry in Southern China College of Forestry, Nanjing Forestry University Nanjing 210037
    2. School of Ecology and Environment, Anhui Normal University Wuhu 241002
  • Received:2020-02-08 Online:2021-03-01 Published:2021-04-07
  • Contact: Xiaoqin Wu

Abstract:

Objective: This research aimed to explore the changes of phosphate-dissolving ability of Pseudomonas fluorescens at its strain JW-JS1 and the colonization dynamics in rhizosphere and mycorrhizosphere of poplars, to reveal the phosphate-dissolving mechanisms of this strain and further elucidate its interaction mechanisms with ectomycorrhizal fungi, so as to provide a theoretical basis for developing and exploiting the compound microbial fertilizer for poplar. Method: A liquid fermentation experiment was conducted to investigate the changes of soluble phosphorus contents, pH, and titratable acid contents in the broth of P. fluorescens JW-JS1. Kinds and concentrations of organic acids in the broth were also determined by HPLC. The stable marker of antibiotic rifampin was screened by using the rifampin-resistant mutant method, and the colonizing dynamics of mutant strain in rhizosphere and mycorrhizosphere of poplars were investigated by root irrigating method. Result: 1) The results showed that the soluble phosphorus contents in broth of JW-JS1 gradually increased with the time. Correlation analysis showed that the pH was negatively correlated with soluble phosphorus contents (r=-0.889**), while the titratable acid contents was positively correlated with soluble phosphorus contents (r=0.958**). 2) The total amounts of organic acid secreted by JW-JS1 (434.39 mg·L-1) was significantly higher than that of control (25.94 mg·L-1) (P < 0.05). Five kinds of organic acids were detected in the broth, including oxalic acid, tartaric acid, citric acid, maleic acid and fumaric acid. Among them, the amounts of oxalic acid (273.69 mg·L-1) was significantly higher than that of other kinds of organic acids, which was about 63.01% of the total organic acid concent. 3) A strain of with 30 μg·mL-1rifampicin resistance was selected. Compared with wild strain, there was no obvious change in colony morphology and phosphate-dissolving ability of JW-JS1Rif strain (P < 0.05). 4) The strain of JW-JS1Rif could effectively survive and maintain a certain colonizing population in the rhizosphere and mycorrhizosphere of poplar, and the colonizing population was a downward trend as the time of inoculation was prolonged, and the colonization dynamics were basically consistent. After 50 days of inoculation, the colonizing population was 5.2×104 cfu·g-1 and 4.5×104 cfu·g-1, respectively. Conclusion: The phosphate-dissolving ability of P. fluorescens JW-JS1 is closely related to the pH, titratable acid contents and organic acid in the culture medium, especially oxalic acid secreted by the strains may play an important role in the phosphate-dissolving process. P. fluorescens JW-JS1 can stably survive in the rhizosphere and mycorrhizosphere of poplar. The above results indicate that P. fluorescens JW-JS1 and Xerocomus chrysenteron are ideal materials for constructing functional compound microbial fertilizer for poplar.

Key words: Pseudomonas fluorescens, organic acid, oxalic acid, poplar, mycorrhizosphere, colonization

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