Bacillus subtilis HG‐15, a Halotolerant Rhizoplane Bacterium, Promotes Growth and Salinity Tolerance in Wheat (Triticum aestivum)

Certain plant growth‐promoting bacteria (PGPB) reduce salt stress damage in plants. Bacillus subtilis HG‐15 is a halotolerant bacterium (able to withstand NaCl concentrations as high as 30%) isolated from the wheat rhizoplane in the Yellow River delta. A qualitative and quantitative investigation of the plant growth‐promoting characteristics of this strain confirmed nitrogen fixation, potassium dissolution, ammonia, plant hormone, ACC deaminase, and proline production abilities. B. subtilis HG‐15 colonization of wheat roots, stems, and leaves was examined via scanning electron microscopy, rep‐PCR, and double antibiotic screening. After inoculation with the B. subtilis HG‐15 strain, the pH (1.08–2.69%), electrical conductivity (3.17–11.48%), and Na + (12.98–15.55%) concentrations of rhizosphere soil significantly decreased ( p < 0.05). Under no‐salt stress (0.15% NaCl), low‐salt stress (0.25% NaCl), and high‐salt stress (0.35% NaCl) conditions, this strain also significantly increased ( p < 0.05) the dry weight (17.76%, 24.46%, and 9.31%), fresh weight (12.80%, 20.48%, and 7.43%), plant height (7.79%, 5.86%, and 13.13%), and root length (10.28%, 17.87%, and 48.95%). Our results indicated that B. subtilis HG‐15 can effectively improve the growth of wheat and elicit induced systemic tolerance in these plants, thus showing its potential as a microbial inoculant that can protect wheat under salt stress conditions.