Role of Bacillus subtilis W1L in Mitigating Oxidative and Osmotic Stress in Lettuce under Drought and Salt Conditions

Abiotic stresses, such as drought and high salinity, threaten global food security by severely limiting crop yields. Among diverse agricultural practices, the usage of plant growth-promoting rhizobacteria has been expanding to enhance plant resilience against environmental stresses. In this study, we examined the effects of Bacillus subtilis W1-like strain (BsW1L) on increasing plant tolerance in lettuce plants (Lactuca sativa) grown under drought and high-salt stresses. BsW1L-treated plants exhibited improved tolerance to both stresses, as indicated by increased shoot and root growth, leaf area, and chlorophyll content. Application of the BsW1L strain enhanced the mRNA expression and activity of key antioxidant enzymes, catalase and ascorbate peroxidase. This facilitated the detoxification of reactive oxygen species, leading to decreased hydrogen peroxide levels, reduced malondialdehyde accumulation, and increased total soluble sugars. Notably, treatment with the BsW1L strain elevated proline levels in the leaves of lettuce plants grown under drought stress but reduced them in plants exposed to salt stress. Taken together, these findings suggest that BsW1L can serve as an ecofriendly biostimulant for improving plant tolerance to abiotic stresses, contributing to sustainable agricultural practices.