Abstract:[Background] Naked barley root rot caused by pathogenic fungus such as Fusarium avenaceum and Bipolaris sorokiniana are widely occurred, which poses a great threat to agricultural production and development in Tibetan areas. However, there is still a few research on its biocontrol by bacterial inoculant in China. [Objective] To screen strains with excellent disease-controlling and plant growth-promoting properties from the healthy naked barley rhizosphere. Furthermore, we explored the interaction effects among the bacteria to screen the excellent inoculant formulas, and the bacterial inoculants were made accordingly. After all, our ambition is to provide superior microbial inoculants which catering for the biocontrol of naked barley root rot, promoting the crop yield as well. [Methods] Firstly, we used the selective media to screen growth-promoting strains and plate confrontation method to screen the disease-controlling strains. After determining the pathogenicity of the bacteria by root irrigation and foliar inoculation, the nitrogen fixation capacities, phosphorus dissolution capacities, and IAA secretion capacities of them were determined by acetylene reduction method, molybdenum blue colorimetric method and high performance liquid chromatography, respectively. Additionally, the bacteria were identified by 16S rRNA gene sequence analysis. Finally, the biocontrol effects of the inoculants were measured by field test and evaluated by TOPSIS comprehensive analysis method. [Results] A total of 23 strains with nitrogen-fixing and phosphorus-solubilizing abilities were isolated in the initial screening, and 6 bacteria among them with eminent antagonistic ability, including 5 organophosphorus solubilizing strains, 3 inorganic phosphorus solubilizing strains and 3 nitrogen-fixing strains, all of which secreted IAA. Besides, the pathogenicity of the bacteria showed no pathogenicity to common crops in the sampling area, such as naked barley, oat, rapeseed and pea. According to the identification result, the bacteria isolates include 2 Bacillus subtilis, 1 Bacillus pumilus, 1 Bacillus cereus, 1 Pseudomonas fluorescens and 1 Acinetobacter sp. As a result, we firstly optimized 7 combinations (SC1−SC7) and then selected the best 4 (SC2, SC4, SC6, SC7) as inoculant formulas. Moreover, they were all made into liquid, powder and accumulative bacterial inoculant severally. Eventually, the field plot biocontrol determination showed SC7 (Bacillus pumilus Xpq-3, Bacillus cereus Xpq-15 and Acinetobacter sp. Xpq-21) had the best biocontrol and plant growth-promoting effects. [Conclusion] It’s clear that there are amount of biocontrol and growth-promoting strains in the naked barley rhizosphere soil. In addition, the microbial inoculant made by them have excellent biocontrol effects.
