Identification and growth promotion analysis of a salt-alkali tolerant endophyte strain isolated from Lespedeza daurica

Abstract:

[Background] Lespedeza daurica is an important native grass for the restoration and improvement of degraded salt-alkali grassland in the Loess Plateau. Plant-endophyte symbiosis play an important role in maintaining and improving plant stress resistance. [Objective] To screen out the dominant endophyte with salt-alkali resistance and evaluate their basic characteristics, salt-alkali tolerance, and growth promoting properties. [Methods] A saline-alkali resistant endophyte strain DP20 was screened out from the root system of L. daurica artificially cultured in Shanxi Province. DP20 was identified by morphological observation, physiological and biochemical measurements, and 16S rRNA gene sequencing analysis. The liquid mediums with different salt-alkali concentration (salt concentration was 0, 1%, 3%, 5%, and 7%, and the pH was 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0) were used to measure their saline-alkali tolerance. The functional mediums were used to measure their growth-promoting function. Meanwhile, the catalyst was quantitatively determined. The petri dish filter paper method was used to verify the effects of this strain on the seed germination and growth of L. daurica. Plate test was used to explore the effects of this strain on the growth of Arabidopsis thaliana. [Results] The strain DP20 was Enterobacter ludwigii. The optimum salt concentration for its growth was 0-5%, and the highest tolerance concentration was 7%. It was found that strain DP20 had the ability to produce auxin (IAA), up to 30.81 mg/L, and the decomposition capacity of organophosphorus, reaching 0.53 mg/L. Furthermore, the strain had the ability to produce siderophores and secrete organic acids, and the concentration of siderophores reached 67.67%. Strain DP20 grew on the NFM solid medium. Strain DP20 significantly promoted the seed germination rate, plant fresh weight, and root development of L. daurica and A. thaliana. [Conclusion] The saline-alkali tolerant strain DP20 has significant growth promoting ability, which provides efficient and saline-alkali resistant endogenous resources for the later application of L. daurica in the improvement of saline-alkali soil in northern Shanxi, and is helpful to develop the potential of E. ludwigii as a microbial agent.