地锦草内生细菌多样性、拮抗及促生特性测定

【背景】植物内生细菌既能抑制病原菌对植物的侵染,也具有促生作用。分离具有拮抗和促生活性的内生细菌可为开发微生物菌肥提供理论依据。【目的】筛选内生细菌中的优势拮抗、促生菌种资源。【方法】以地锦草为材料,采用4种分离培养基分离该植物内生细菌,通过形态特征以及16S r RNA基因序列分析,鉴定内生细菌的分类归属。采用平板对峙法,测定内生细菌对棉花立枯丝核菌(Rhizoctonia solani)、小麦赤霉病菌(Fusarium graminearum)、玉米小斑病菌(Bipolaris maydis)的拮抗活性。通过固氮、解磷、产吲哚乙酸(Indole Acetic Acid,IAA)、产铁载体能力等指标初步检测地锦草内生细菌的促生活性。【结果】共分离到133株内生细菌,分属于4门5纲8目13科25属,其中变形菌门(Proteobacteria)为优势门(52.63%),优势属为芽孢杆菌属(Bacillus),占15.79%。发现有8株菌相似性小于98.65%,可能为潜在新物种。拮抗活性结果表明,22株菌有不同程度的抑菌作用,其中菌株DHL56、DHN17、DHP3、DHP8对这3种病原菌都有抑制作用,均为芽孢杆菌属。菌株DHP8抑制作用最强,对棉花立枯丝核菌、小麦赤霉病菌抑制率分别为73.80%、71.25%,对玉米小斑病菌抑制率为61.70%。促生潜力结果表明,76株菌具有固氮能力;19株菌具有解磷能力;37株菌能产吲哚乙酸,菌株DHL55产吲哚乙酸的量达到105.67mg/L;7株菌能合成铁载体。其中有9株菌同时有固氮、解磷、产吲哚乙酸能力;菌株DHP8具有固氮、解磷、合成铁载体能力。DHP8不仅具有一定促生潜力,还对棉花立枯丝核菌、小麦赤霉病菌、玉米小斑病菌有明显的拮抗作用,需进一步研究。【结论】地锦草内生细菌种类丰富,获得多株具有优良拮抗和促生活性的菌株,为进一步开发微生物农药及菌肥资源提供新的菌株材料。

Endophytic bacteria from Euphorbia humifusa: diversity, antagonism and growth-promoting activities

Background] Plant endophytic bacteria not only inhibit the infection of pathogens on plants, but also promote plant growth. Screening the antagonistic and growth-promoting endophytic bacteria can provide a theoretical basis for the development of microbial fertilizers. Objective] Screen superior antagonistic and growth-promoting bacteria resource from plant endophytic bacteria. Methods] Four kinds of isolation media were used to isolate endophytic bacteria from Euphorbia humifusa, colony morphological characteristics were combined with 16S rRNA gene sequence analysis to identify the classification of endophytic bacteria. The antagonistic activity of endophytic bacteria on three pathogenic fungi, Rhizoctonia solani, Fusarium graminearum, Bipolaris maydis, was tested by plate confrontation method. Through nitrogen fixation, phosphate solubilization, production of indole acetic acid (IAA) and synthesize siderophore capacity to evaluate the growth-promoting potential of endophytic bacteria in Euphorbia humifusa. Results] A total of 133 endophytic bacteria were isolated, which belonged to 4 phyla, 5 classes, 8 orders, 13 families, and 25 genera. Proteobacteria was dominant phylum (52.63%), Bacillus was dominant genus (15.79%). eight strains are found to be similar less than 98.65%, may be potential new species. The result of antagonistic activity showed that 22 endophytic bacteria had different antagonistic activity. Among them, strains DHL56, DHN17, DHP3 and DHP8 against to both of these three kinds of pathogenic fungi, they are different species of Bacillus genus. Strain DHP8 had the strongest antagonistic activity, with the inhibitory rates of F. graminearum, R. solani being 73.80% and 71.25% respectively, and the inhibitory rates of B. maydis being 61.70%. The results of growth-promoting experiments showed that 76 strains shave the ability of nitrogen-fixing; Nineteen strains showed phosphate solubilization ability; Thirty-seven strains showed IAA-producing activity, and strain DHL55 produced 105.67 mg/L of IAA; Seven strains had the ability to synthesize siderophore. Nine strains showed the ability of fix nitrogen, phosphorus, and produce IAA. Strain DHP8 has the ability to fix nitrogen, phosphorus, and synthesize iron. In addition, the strain DHP8 not only displays significant role in plant growth, but also has a remarkable antagonistic activity against pathogenic fungi we used. So that, need further study. Conclusion] The species of endophytic bacteria are abundant, and many strains have excellent antagonistic and growth-promoting activities, which provides some new sources for the further studies.