Stress-Tolerant Viridibacillus arenosi Strain IHB B 7171 from Tea Rhizosphere as a Potential Broad-Spectrum Microbial Inoculant

Viridibacillus arenosi strain IHB B 7171 identified based on 16S rRNA gene sequence produced colony forming units (cfu/ml) ranging from 3.3 x 10(4) to 1.2 x 10(10) under pH 5-11, 2.2 x 10(2) to 1.4 x 10(10) for temperature 5-40 degrees C, 2.4 x 10(2) to 1.1 x 10(10) for PEG 6000 10-30%, 2.2 x 10(2) to 1.4 x 10(10) for 2.5-10% NaCl, 3.1 x 10(3) to 1.7 x 10(9) for 2.5-7.5 mM CaCl2, 2.2 x 10(2) to 1.4 x 10(7) for 2.5-7.5 mM AlCl3, and 3.2 x 10(2) to 1.2 x 10(7) for 2.5-7.5 mM FeCl3. The activities of plant growth-promoting attributes with the increasing acidity, desiccation and salinity ranged from 408 to 101, 20 to 8, 14 to 5 mu g/ml P-liberated from tri-calcium phosphate, aluminium phosphate and iron phosphate, 20-9% siderophore units, 14-4 mu g/ml IAA and 190-16 alpha-ketobutyrate h/mg protein ACC-deaminase activity. Plant height, leaf number, and leaf weight on treatment with bacterial inoculum showed an increment of 9.5, 17.6, 54.5 and 31.0% in tea seedlings, respectively. The bacterium also enhanced plant height and yield by 10 and 13% in pea and 2.8 and 13.9% in wheat. The results exhibited stress-tolerance and plant growth-promoting activities by the strain under stressed growth-conditions with potential as a broad-spectrum plant growth-promoting rhizobacterium.