Identification and Growth-promoting Effects of Endophytic Pseudomonas sp. from Hippophae thibetana Root Nodules

  Objective  EndogenousPseudomonas sp. in the root nodules of Hippophae thibetana that displayed a biological activity were isolated for toxicological identification and growth-promoting effect determination for the development of a biological agent for crop fertilization.

  Methods   Strains of Pseudomonas sp. were isolated from the root nodules of H. thibetana by pure culture method. They were identified by morphology, physiological biochemistry, and 16S rDNA sequence, as well as examined for the growth-promoting effect on the host plant by artificial inoculation for evidence of phosphorus-dissolving and IAA-, iron- and cellulase-producing capacities.

  Results  Out of the isolated endophytic strains, 4 showed greater than 99% 16S rDNA alignment with the reference Pseudomonas. Among them, QY-X10 and QY-X22 produced 400 mg·L⁻¹ of solubilized phosphorus; QY-X4 yielded the highest IAA at 1.9 mg·L⁻¹; all 4 strains contained iron-generating carriers; except QY-X10, all could degrade cellulose; QY-X6 promoted seed germination; and QY-X6 and QY-X10 helped the host plant to grow significantly more leaves and longer seedlings, while QY-X10 and QY-X22 did significantly to make the maximum-length leaves longer than did control.

  Conclusion  There were 4 Pseudomonas sp. identified in this study that exhibited significant abilities to dissolve inorganic phosphorus and produce IAA and iron. Three of them could also degrade cellulose. By inoculating these strains on the host plants, the seed germination and seedling growth were effectively promoted. It appeared that they could be applied for crop fertilization.