Effect of the Plant Growth-Promoting Bacteria Strain Bacillus Mojavensis I4 on Potato Growth, Physiology, Tuber Yield, and Quality Under Salt Stress Conditions

Salinity is one of the major threats to potatoes. As the first vegetable crop, improving its production under salinity stress is of great interest. In previous work, Bacillus mojavensis I4 (BmI4) plant growth-promoting (PGP) bacterial strain was isolated from the soil. Since BmI4 showed a growth capacity under salt conditions (10% NaCl), we decided here to evaluate its PGP capacity on potato plants (Spunta and Claustar varieties) grown in the greenhouse in the presence of 100 mM NaCl. Stem elongation and diameter, leaf number, leaf area, and organ fresh weights were monitored during 40 days of culture as well as tuber yield, size, and composition. Our results showed that the inoculation of plantlet roots with BmI4 enhanced plant growth under salinity, particularly for Spunta variety. These beneficial effects were associated with an increase in auxin levels in plants, from both varieties. The assessment of H2O2 and malondialdehyde contents revealed that BmI4 inoculation led to reduced oxidation in plants exposed to salinity, via the increase of superoxide dismutase, catalase, and peroxidase activities. Moreover, the BmI4 treatment enhanced proline accumulation, especially in leaves of Spunta variety. BmI4 inoculated plants from Spunta variety exhibited an early induction of tuberization associated with an increase in tuber yield and size in addition to an improvement in tuber nutritional quality under both culture conditions. These findings suggest that inoculation of potatoes with BmI4 can be a promising strategy to improve plant growth in saline areas.