The purpose of the present research was to study the diversity of bacterial endophytes inhabiting the halophytic plant black saxaul (Haloxylon aphyllum Minkw.). A total of 20 bacterial isolates were isolated from tissues of black saxaul and identified based on their 16S rRNA genes analysis and comparison with the closest relatives registered in GenBank nucleotide data bank from the National Centre for Biotechnology Information. The endophytes were checked for plant growth-promoting activity toward cucumber plants and the strains Bacillus amyloliquefaciens HAPH2, Priestia endophytica HAPH5, Bacillus subtilis HAPH7, Bacillus toyonensis HAPH8, Halomonas sulfidaeris HAPH11, Isoptericola halotolerans HAPH12, Planomicrobium soli HAPH15, and Pseudomonas kilonensis HAPH16 demonstrated high plant growth-promoting activity of cucumber in four soil salinity levels (0, 25, 50, and 100 mM) after seeds inoculation. These bacterial endophytes were able to fix nitrogen, solubilize phosphates, and produce indole-3-acetic acid, 1-aminocyclopropane-1-carboxylate deaminase, and siderophores which are considered as the main plant growth-promoting traits. After field experiments, the best plant growth-promoters can be used as bioinoculants for plants growth improvement in salinity conditions.
Key words: Black saxaul, endophytic bacteria, diversity, plant growth-promotion, salinity, cucumber
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