Screening of phosphorus-solubilizing strains with stress tolerance in the permafrost region of the Qinghai-Xizang Plateau

Abstract:

[Objective] To isolate efficient phosphorus-solubilizing strains from soils in the permafrost region of the Qinghai-Xizang Plateau and provide strain resources for the activation of unavailable phosphorus in the soil of the Plateau. [Methods] The selective media with organic and inorganic phosphorus were used to isolate phosphorus-solubilizing strains from the soil samples collected in the permafrost region around the Tanggula Pass of the Qinghai-Xizang Plateau by the plate streaking method. The phylogenetic tree was built based on the 16S rRNA gene sequences to identify the strains, and then the phosphorus-solubilizing abilities and stress tolerance of the strains were determined. [Results] Five strains belonging to Pseudomonas were isolated, including three inorganic phosphorus-solubilizing strains (i5, i6, and i9L) and two organic phosphorus-solubilizing strains (Qb and Qo). After 7 days of incubation in shake flasks at 30 ℃, the content of available phosphorus in the supernatants of Qb and Qo was 534.8 mg/L and 723.7 mg/L, respectively, which was significantly higher than that (166.9–210.5 mg/L) in the supernatants of i5, i6, and i9L. The available phosphorus content in the supernatant of Qo was the highest (519.7–683.0 mg/L) among the five isolates under different concentrations of PEG6000. The phosphorus-solubilizing abilities of Qb and Qo were stronger than those of the other strains at 5 ℃ and 10 ℃. [Conclusion] Qo outperformed the other strains in terms of tolerance to low temperature and drought stress, serving the development of microbial fertilizers and vegetation restoration in alpine regions such as the Qinghai-Xizang Plateau.