一株达乌里胡枝子耐盐碱内生细菌的鉴定和促生特性

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

摘要:

【背景】达乌里胡枝子(Lespedeza daurica)是黄土高原地区退化盐碱草地修复和改良的重要乡土草，植物-内生细菌共生体在维持甚至提升植物抗逆性方面发挥重要作用。【目的】筛选优势达乌里胡枝子耐盐碱内生细菌，对其基本特性、耐盐碱能力和促生特性进行评价。【方法】从山西省人工栽培达乌里胡枝子根系中筛选出一株耐盐碱的内生细菌菌株DP20，通过形态学观察、生理生化测定和16S rRNA基因序列分析对该菌株进行鉴定；利用不同盐碱浓度(0、1%、3%、5%、7%)和不同pH值(7.0、8.0、9.0、10.0、11.0、12.0)的液体培养基测定其菌株密度；采用功能性培养基测定其促生特性，对促生产物进行定量测定；采用培养皿滤纸法验证该菌对达乌里胡枝子种子萌发及生长的影响，采用平板试验法分析该菌对拟南芥生长的影响。【结果】菌株DP20为路德维希肠杆菌(Enterobacter ludwigii)，其生长最适盐浓度为0-5%，最高耐受浓度达7%。菌株DP20具有产生长素吲哚乙酸(indole-3-acetic acid,IAA)能力，可达30.81mg/L；具有溶解有机磷能力，溶磷量为0.53mg/L；该菌株兼具分泌铁载体和有机酸能力，其中铁载体的相对表达量(SU值)达67.67%；并且可在无氮固体培养基上生长。菌株DP20显著提高了达乌里胡枝子种子发芽率，提高了达乌里胡枝子和拟南芥植株鲜重，促进了达乌里胡枝子和拟南芥根系发育。【结论】耐盐碱菌株DP20促生性能显著，这为后期应用于达乌里胡枝子改良晋北盐碱土地提供了高效促生、耐盐碱的内生细菌资源，同时有助于开发路德维希肠杆菌在微生物菌剂方面的潜能。

关键词:黄土高原;乡土植物;内生细菌;耐盐碱性;促生特性

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.

Key words:Loess Plateau;native plant;endophytes;saline-alkaline tolerance;growth-promoting property