Effects of Inorganic Phosphorus-Solubilizing Bacteria on Rhizosphere Phosphorus Forms and Steroid Saponin Content of Paris polyphylla var. yunnanensis.

Abstract

To improve the phosphorus utilization efficiency and medicinal quality of the traditional Chinese medicinal herb Paris polyphylla var. yunnanensis, three inorganic phosphorus-solubilizing bacteria strains (Bacillus cereus Y1-1, Bacillus aryabhattai Z6-1, and Bacillus aryabhattai Z3-4) were inoculated individually and in combination into the rhizosphere soil of Paris polyphylla var. yunnanensis in a greenhouse pot experiment. At the late growth stage, the contents of total and inorganic phosphorus in the rhizosphere soils, as well as the total phosphorus and six steroidal saponins in the plants, were measured. The proportion of inorganic phosphorus in rhizosphere soils of treatment groups increased by 9.83~30.43%. The content of effective phosphorus form Ca₂-P in the rhizosphere soils of treatment groups increased by 50.81~328.37%. Inoculation with B. aryabhattai (S2, S3, and S6) significantly increased total steroidal saponin content in plants by 9.14%, 10.64%, and 16.58%, respectively. An antagonistic effect was observed when multiple bacterial strains were inoculated together. Thus, mixed inoculation was less effective than single-strain inoculation in improving rhizosphere soil phosphorus structure. In conclusion, inoculation with inorganic phosphorus-solubilizing bacteria could enhance phosphorus availability in rhizosphere soil and improve medicinal quality of Paris polyphylla var. yunnanensis. These findings provide a basis for efficient phosphorus resource utilization and sustainable cultivation to enhance medicinal plant quality.