Abstract: Little is known regarding the nature and composition of the endophytic communities in Pennisetum sp.,we explored the diversity of endophytic bacteria community in Pennisetum sp. in different habitats. In this study,Pennisetum sp. from five different habitats were chosen to make phylogenetic analysis for the genetic diversity of the endophytic bacteria associated with Pennisetum sp. using 16S rDNA gene sequence analysis. Characteristics including the ability of solubilize phosphorus,fix nitrogen,produce IAA,iron-producing carrier capacity,and inhibition of pathogenic bacteria were used to evaluate the growth-promoting activities of the selected strains. In this research,a total of 187 strains were isolated from the Pennisetum sp. of five different habitats,of which:86 strains had the ability to secrete IAA,accounting for 46% of all strains,and the strain XJ-4 had the highest ability with an IAA yield of 30.13 mg·L^-1;47 strains,accounting for 25% of all,had the ability to solubilize phosphorus,strains FJ-23 and FJ-15 had the highest ability with phosphorus content of 7.10 mg·L^-1 and 7.35 mg·L^-1,respectively. In addition,there were 128 strains,of all the 187,could grow normally in Ashby nitrogen-free medium,indicating that 64% of the endophytic bacteria had potential nitrogen fixation ability,34 strains endogenous bacteria were pink in color in the CAS assay medium,indicating that 18% of the endophytic bacteria had the ability to produce iron-producing vectors. More than 80% of the endophytic bacteria had inhibitory effects on one or more indicator bacteria,of which strains SX-21,SX-30,SX-1,NY-10 showed broad-spectrum antibacterial activity against three indicator bacteria. The strain SX-30 had the best antibacterial activity Exserohilum turcicum,whose inhibition zone could reach 30 mm. Moreover,twenty-three genotypes were tested from all the 187 strains. 16S rDNA sequencing revealed that these strains belonged to the following genera:Bacillus,Rhizobium,Stenotrophomonas,Pseudomonas,Acinetobacter,Enterobacter. Our results demonstrated that the endophytic bacteria of Pennisetum sp. have rich diversity,the finding might be useful for providing good germplasm resource for the further construction of promoting bacterial flora in Pennisetum sp.

Key words: Pennisetum sp., Genetic diversity, Endophytic bacteria, Growth promoting activities

摘要： 为探究不同生境巨菌草（Pennisetum sp.）内生细菌群落组成多样性，明确促生菌株的促生特性，本试验采用菌株16S rDNA全序列分析法，对5个不同生境的巨菌草中内生细菌的遗传多样性进行系统发育分析，并以溶磷、固氮、产吲哚乙酸（Indoleacetic Acid，IAA）、产铁载体和抑菌活性等为筛选标准，对初筛菌株进行多项促生活性测定。本研究中，从巨菌草植株中共分离得到187株内生菌株，其中86株具有分泌IAA的能力，占全部菌株的46%，菌株XJ-4产IAA的能力最强，分泌的IAA浓度为30.13 mg·L^-1；47株具有溶磷能力，占全部菌株的25%，菌株FJ-23，FJ-15溶磷能力最高，分别为7.10 mg·L^-1和7.35 mg·L^-1；128株可以在Ashby无氮培养基中正常生长，表明64%的巨菌草内生细菌都具有潜在的固氮能力；34株可以在产铁载体的培养基中正常生长，表明18%的菌株产铁载体；试验中，80%以上的内生细菌对1种或者多种指示菌具有抑制作用，其中菌株SX-21，SX-30，SX-1，NY-10表现出对3种指示菌的广谱性抑菌活性，菌株SX-30对玉米大斑病菌的抑制效果最好，抑菌圈达到30 mm。供试菌株共产生了23种遗传图谱类型，通过对每种图谱类型的代表性菌株进行16S rDNA全序列分析，23株菌株分别归属于芽孢杆菌属（Bacillus）、根瘤菌属（Rhizobium）、寡养单胞菌属（Stenotrophomonas）、假单胞菌属（Pseudomonas）、不动杆菌属（Acinetobacter）和肠杆菌属（Enterobacter）。巨菌草中具促生特性的内生细菌表现出丰富的多样性，可为进一步构建巨菌草促生菌菌群提供良好的种质资源。

关键词: 巨菌草, 内生菌, 遗传多样性, 促生特性