The functional roles of endophytic Bacillus and Pseudomonas bacteria to improve tomato and bean plants’ growth under induced-drought stress conditions

Abstract

Drought is a major constraint to crop productivity, highlighting the need for sustainable approaches to improve plant resilience. In this study, three endophytic bacteria, Bacillus subtilis BS-114 and BS-116, and Pseudomonas wadenswilerensis PPW-26, previously selected based on their plant growth-promoting traits and genomic potential, were evaluated for their ability to enhance drought resilience in common bean and tomato. Their effects were investigated through in vitro screening under polyethylene glycol (PEG)-induced drought, greenhouse drought validation, and open-field evaluation. Bacterial inoculation improved seed germination, seedling vigor, and plant water status under PEG-induced stress, with strain-dependent responses observed between crops, with the most pronounced effects observed in bean. Under greenhouse drought, inoculated bean plants exhibited improved photosynthetic performance and relative water content, together with reduced oxidative damage and proline accumulation, suggesting enhanced physiological adjustment to water deficit. These responses were associated with changes in the expression of drought-responsive genes involved in abscisic acid signaling, antioxidant defense, and osmoprotection, and were accompanied by a 52% increase in yield compared with non-inoculated drought-stressed plants. Based on greenhouse performance, a consortium containing BS-114 and two additional Bacillus strains was further evaluated under field conditions, where crop productivity was comparable to conventional NPK fertilization and a commercial algae-based biostimulant. Overall, these findings highlight the potential of beneficial endophytic bacteria isolated from medicinal plants to improve drought resilience, accompanied by changes in plant water status, hormonal signaling, and oxidative stress responses.