梭梭根际、内生细菌的促生作用及其复合菌群的构建

Evaluation of plant growth-promoting effects of rhizosphere and endophytic bacteria of Haloxylon ammodendron and construction of strain combinations

摘要:

背景 植物根际和内生菌凭借其促生、抗逆及定殖能力成为微生物肥料的主要菌种来源。梭梭作为荒漠抗逆先锋树种及肉苁蓉主要寄主，其根际与内生微生物的促生功能研究尚比较匮乏。目的 筛选梭梭根际及内生细菌中的促生菌株，为梭梭的可持续繁育提供微生物菌种资源。方法 从内蒙古磴口县乌兰布和沙漠采集梭梭根际土和植株样品，分离纯化梭梭根际和内生细菌，并探究其对梭梭幼苗的促生效果，对具有显著促生效果的菌株进行分子生物学鉴定和促生功能分析，选择不同种属间能力最强的菌株构建人工复合菌群，并检测复合菌群对梭梭的促生效果。结果 共分离得到97株梭梭根际细菌和68株内生细菌，5株根际细菌具有显著促生作用，其分属于4个属和4个种，假单胞菌属(Pseudomonas)为优势菌属，占比为40%；12株内生细菌具有显著促生作用，其分属于7个属和12个种，芽孢杆菌属(Bacillus)为优势菌属，占比为25%。这些促生菌株均有较高水平的固氮、解无机磷、解钾长石和产生物膜的能力；大多数菌株都具有解有机磷、解硅酸铝钾、产铁载体和产IAA的能力。人工复合菌群中，其中4个菌株组合的促生效果最好，其核心菌株为芽孢杆菌(Bacillus sp.) Ia-14、黄色假杜擀氏菌(Pseudoduganella flava) ASD1-2、假单胞菌(Pseudomonas sp.) SC1-7和水稻节杆菌(Arthrobacter oryzae) PaS-6-2。结论 梭梭根际及内生促生菌资源丰富，其主要通过固氮、解磷、解钾、产铁载体、产IAA和产生物膜来发挥对梭梭幼苗的促生作用。芽孢杆菌属(Bacillus)、黄色假杜擀氏菌(Pseudoduganella flava)、假单胞菌属(Pseudomonas)、水稻节杆菌(Arthrobacter oryzae)在促生人工复合菌群中起核心作用。

Abstract:

Background Rhizosphere and endophytic bacteria, with plant growth-promoting effects, stress tolerance, and colonization abilities, are the main sources of microbial fertilizers. As a desert stress-tolerant pioneer tree species and the main host of Cistanche deserticola, Haloxylon ammodendron has been rarely studied in terms of the plant growth-promoting effects of rhizosphere and endophytic microorganisms.Objective To screen plant growth-promoting strains from the rhizosphere and endophytic bacteria of H. ammodendron and provide microbial resources for the sustainable breeding of this plant.Methods Rhizosphere soil and plant samples of H. ammodendron were collected from the Ulan Buh Desert in Dengkou County, Inner Mongolia Autonomous Region. Rhizosphere and endophytic bacteria were isolated and purified, and their growth-promoting effects on H. ammodendron seedlings were investigated. Molecular biological identification and plant growth-promoting effect evaluation were conducted for the strains with significant plant growth-promoting effects. The most effective strains of different genera were selected to construct strain combinations, the growth-promoting effects of which on H. ammodendron were tested.Results A total of 97 bacterial strains from the rhizosphere of H. ammodendron and 68 endophytic bacterial strains were isolated. Five rhizosphere bacterial strains showed significant plant growth-promoting effects, belonging to 4 species of 4 genera, with Pseudomonas being the dominant genus, accounting for 40%. Twelve endophytic bacterial strains showed significant plant growth-promoting effects, belonging to 12 species of 7 genera, with Bacillus being the dominant genus, accounting for 25%. These strains all had high capabilities of nitrogen fixation, inorganic phosphorus solubilization, potassium feldspar solubilization, and biofilm formation. Most of the strains also had the abilities of organic phosphorus solubilization, potassium aluminosilicate solubilization, and siderophore and IAA production. Among the constructed strain combinations, four combinations had the best plant growth-promoting effects, of which the core strains were Bacillus sp. Ia-14, Pseudoduganella flava ASD1-2, Pseudomonas sp. SC1-7, and Arthrobacter oryzae PaS-6-2.Conclusion The plant growth-promoting microbial resources in the rhizosphere and endophytic bacteria of H. ammodendron are abundant. They mainly promote the growth of H. ammodendron seedlings through nitrogen fixation, phosphorus and potassium solubilization, siderophore production, IAA production, and biofilm formation. Bacillus sp., P. flava, Pseudomonas sp., and A. oryzae play a core role in the strain combinations with plant growth-promoting effects.