Abstract: 【Objective】 Isolation and identification of endophyte from the roots of Tetraena mongolica,screening for antibacterial activity,and analyzing their growth-promoting effects on seeds and plants of Tetraena mongolica. 【Methods】 The endophyte was isolated and purified from Tetraena mongolica roots using Gao's No.1 medium containing potassium dichromate. The strains were identified by physiological and biochemical characteristics and the construction of a phylogenetic tree of 16S rRNA gene sequence. A comparative test was used to detect the growth-promoting activity of the strain on Tetraena mongolica seeds and plants. Plate confrontation method was used to detect the antagonistic activity of the strain. 【Results】 The endophyte isolated from the root of Tetraena mongolica was an actinomycete strain named RE4. After identification,the strain RE4 was 100% similar to the model strain Streptomyces canus CSSP527^T,and the evolutionary distance was relatively close to the model strain,which was Streptomyces Streptomyces canus. RE4 could effectively promote the germination and seedling growth of Tetraena mongolica,the plant height,root length,rooting rate and germination rate of Tetraena mongolica seedlings treated with RE4 increased by 27.89%,197.09%,26 percentage points and 4 percentage points respectively compared with the control. RE4 could inhibit the growth of Verticillium dahliae,Fusarium oxysporum,Sclerotinia sclerotiorum and Phytophthora infestans,and the inhibition rates were 68.4%,63.8 %,53.8% and 38.6%. The inhibitory diameters of RE4 against Saccharomyces cerevisiae,Bacillus subtilis,Staphylococcus aureus and Escherichia coli were 17.04,12.45,11.39,11.35 mm,respectively. 【Conclusion】 The endophyte isolated from the roots of Tetraena mongolica were identified as Streptomyces Streptomyces canus,which could antagonize some pathogens and promote the germination of seeds and the growth of seedlings of Tetraena mongolica.

Key words: Tetraena mongolica, Endophytic actinomycete, Plant growth promotion, Antagonistic activity