Identification of the Rhizosphere Bacterial Communities Associated with Native Desert Plants in the Hajiabad Desert Region

Desert ecosystems are vulnerable due to the lack of soil moisture, sunlight intensity, sudden temperature fluctuations, poor humus, soil salinity, water and wind-induced erosion. The rhizosphere biological community of desert plants can play an essential role in overcoming these harsh environmental conditions due to the production of plant growth regulators and secondary metabolites. Bacterial strains were isolated from the rhizosphere of Haloxylon ammodendron , Capparis Spinosa , and Nitraia schoberi , dominant and native plants in the Hajiabad desert region, Semnan, Iran. After physiological and phylogenetic identification of isolates, some plant growth-promoting traits, such as auxin production, phosphate solubilization, nitrogen fixation, salinity, and drought tolerance, were investigated. The results showed that Gram-positive spore-forming bacilli were dominant in the rhizosphere bacterial community of desert plants in the Hajiabad region. The predominance of these bacterial species indicates the prevalence of drought and salinity in the rhizosphere of studied plants. Assessing plant growth-promoting traits of the rhizosphere bacterial community revealed that 58.0% of the isolates were able to dissolve in-soluble phosphate, and isolates Microbacterium oxydans CaK2 and Bacillus subtilis NiGh2 were able to fix atmospheric nitrogen. Also, Bacillus subtilis HaTa2, isolated and screened from the rhizosphere of Haloxylon ammodendron , had the highest auxin production (34.2 µg IAA. mL −1 ) in 120 min among the isolates. Bio-priming of Nitraria schoberi seeds with native isolates of Bacillus subtilis NiGh5, Bacillus subtilis NiGh4, and Bacillus tequilensis NiGh7 increased the germination index by 11.0, 18.0, and 38.0%, respectively, compared to the control. Graphical abstract