Identification and Characterization of Phosphate-solubilizing Endophytes in Coix lacryma-jobi L.

  Objective  Screening bacteria with phosphate-solubilizing ability in Coix were identified and provide excellent strain resource for bio-fertilization agent.

  Methods  Endophytic bacteria were isolated and purified from specimens the roots, stems, and leaves of 25-d-old seedlings of Coix lacryma-jobi L. Abilities of the isolates in dissolving organophosphate and inorganic phosphate as well as in secreting phosphatase were determined. In a pot experiment, effects of two selected isolates on the growth of Coix seedlings were examined.

  Results  Eight strains of bacteria capable of dissolving organophosphate and 5 of degrading inorganic phosphate were isolated. In the 5-d culture supernatants, the highest concentration of phosphorous converted from organophosphate at 37.20 mg·L⁻¹ was reached by R24, and that from inorganic phosphate at 62.93 mg·L⁻¹ by L21. The enhancing effects on plant height, stem girth, and tillering number of the potted Coix seedlings by each and mixture in equal proportion of the two supernatants ranked in the order of L21＞R24＞mixed bacterial liquid V （R24）∶ V （L21）=1∶1. The 16S rDNA sequence phylogenetic analysis identified R24 as Bacillus pumilus and L21 as B. velezensis.

  Conclusion  The phosphobacteria L21 and R24 displayed a significant effect in promoting the growth of Coix seedlings.