Drought priming and plant growth‐promoting rhizobacteria enhance Solanum lycopersicum metabolites under drought stress

BACKGROUND Drought stress is an important factor that consistently decreases plant productivity. Bio‐stimulants such as plant growth‐promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) have been shown to modulate stress‐related pathways. The aim of this study was to enhance the metabolic memory of tomato under different drought stress conditions using these bio‐stimulants. Two weeks after planting, air‐dried sieved soil mixed with 150 g of Glomus deserticola and 1 mL of 10 10 CFU mL −1 Enterobacter ludwigii was applied to the root zone. Drought treatments included control, drought stress, and drought priming. RESULTS Drought priming increased the accumulation of proline, phenolics, and anthocyanins compared with drought stress (DS). Compared with control plants under drought priming, combining PGPR with drought priming enhanced ATPase by 81%, proline by 137%, soluble sugar by 296%, and phenylalanine ammonia‐lyase by 12%. Phenylalanine ammonia‐lyase is actively involved in the biosynthesis of secondary metabolites like flavonoids, which increased by 60%, and anthocyanins, which increased by 75%. An increase in biomass, a 100% survival rate, and low malondialdehyde content were observed. Combining AMF and drought priming significantly increased proline (108%), soluble sugar (240%), flavonoids, antioxidant enzymes, and phenylalanine ammonia‐lyase, resulting in a survival rate of 66.67%. Plant growth‐promoting rhizobacteria and AMF also enhanced the accumulation of NO, which is necessary for antioxidant enzyme accumulation. CONCLUSION Integrating PGPR with drought priming constitutes an effective strategy for enhancing immediate stress resilience and strengthening metabolic responses. Further research using epigenetic approaches is recommended to uncover drought stress memory under drought priming, with a focus on PGPR.