荒漠银砂槐根际、非根际细菌促生特性及促萌发作用

Growth-promoting properties and germination-promoting effects of rhizosphere and nonrhizosphere bacteria of Ammodendron bifolium in deserts

摘要:

【背景】 荒漠土壤营养贫瘠、盐碱含量高，其植物根际微生物可帮助宿主抵抗逆境，对维持生态系统功能具有重要意义。【目的】 以银砂槐根际和非根际细菌为供试菌株，对其促生特性和促萌发作用进行研究，以期获得优良抗逆促生菌资源。【方法】 采用平板检测法测定了菌株固氮溶磷、产铁载体和产水解酶特性，结合比色法定量测定菌株溶磷、产水解酶和产生长素(indole-3-acetic acid, IAA)能力，通过菌株与银砂槐种子共培养检测了菌株促萌发作用，并观测了菌株对干旱和盐碱的抵抗能力。【结果】 35株供试菌株具有固氮活性，并且主要集中于根际变形菌门(Proteobacteria)和非根际厚壁菌门(Firmicutes)；菌株Ba-12、Ra-2、Rb-12和Rb-18具有较好的溶无机磷和有机磷能力，并且主要来源于根际；获得1株产铁载体菌株，即菌株Rb-12，来源于根际；发现6株菌具有明显的产生长素能力，其中产IAA量最高的菌株Rb-5和Rb-12来源于根际；同时产淀粉酶、蛋白酶和纤维素酶的8株菌主要来源于非根际，产2种酶的10株菌大部分来源于根际，产1种酶的13株菌主要来源于根际；获得一株具有显著促萌发作用的菌株，即菌株Bc-5，来源于非根际；大部分供试菌株能够耐受聚乙二醇6000 (PEG6000)浓度为30%，盐浓度为2%-4%，pH 11.5，并且抗逆性最强的菌株来源于根际。【结论】 具有优良促生特性的菌株Ba-12、Ra-2、Rb-5、Rb-12和Rb-18等菌株主要来源于根际，这表现出银砂槐具有明显的根际效应；而非根际菌株Bc-5的促萌发作用与促生特性并无相关关系，对此需进一步探讨。

Abstract:

[Background] Desert soil is barren and saline-alkaline, in which the rhizosphere microorganisms can help the host plants to tolerate stress, which is of great significance for maintaining the ecosystem function. [Objective] To evaluate the growth-promoting properties and germination-promoting effects of rhizosphere and nonrhizosphere bacteria of Ammodendron bifolium, and obtain elite bacterial resources with growth-promoting effects and stress tolerance. [Methods] We employed the plate culture method to examine the nitrogen-fixing, phosphorus-solubilizing, siderophore-secreting, and hydrolase-producing properties of the strains. The abilities of the strains to solubilize phosphorus and produce hydrolase and indole-3-acetic acid (IAA) were quantitatively measured by the colorimetric method. The germination-promoting effects of the strains were tested by strain-seed co-cultivation, and the tolerance of the strains to drought and saline-alkali stress was observed. [Results] Thirty-five strains showed nitrogen-fixing activity, mainly belonging to Proteobacteria in the rhizosphere and Firmicutes in the nonrhizosphere. Strains Ba-12, Ra-2, Rb-12, and Rb-18 had the abilities to solubilize inorganic and organic phosphorus, mainly originating from the rhizosphere. One strain (Rb-12) was capable of secreting siderophores, originating from the rhizosphere. Six strains had the ability of producing IAA, of which strains Rb-5 and Rb-12 with the highest levels of IAA came from the rhizosphere. Eight strains were capable of producing amylase, protease, and cellulase simultaneously, coming from the nonrhizosphere. The 10 strains producing two enzymes and the 13 strains producing one enzyme mainly came from the rhizosphere. One strain, i.e, Bc-5, showed a significant germination-promoting effect, originating from the nonrhizosphere. Most of the tested strains tolerated 30% PEG6000, 2%-4% NaCl, and pH 11.5, and the strain with the strongest stress tolerance came from the rhizosphere. [Conclusion] Strains Ba-12, Ra-2, Rb-5, Rb-12, and Rb-18 with excellent growth-promoting properties mainly originate from the rhizosphere, which indicates the significant rhizosphere effect of A. bifolium. However, the germination-promoting effect of the nonrhizosphere strain Bc-5 is not related to the growth-promoting properties, which requires further exploration.