Seed biopriming with a novel endophytic Bacillus licheniformis strain RGS enhances drought tolerance and recovery in tomato.

Drought stress remains one of the most damaging abiotic factors affecting tomato (Solanum lycopersicum L.) cultivation, particularly in regions where water availability is unpredictable. The present study aims to investigate the potential of seed treatment with Bacillus licheniformis strain RGS to enhance drought tolerance in Solanum lycopersicum cv. Suvarna S22 under greenhouse conditions. Plant performance was assessed across three sequential phases comprising hydration, water deficit and recovery. Relative to uninoculated controls, primed plants showed improved vegetative growth, greater chlorophyll retention and higher leaf relative water content during water deficit, together with more rapid restoration of these traits following rehydration. Bioprimed plants also sustained lower electrolyte leakage and reduced malondialdehyde accumulation, indicating better membrane integrity, and displayed a more balanced antioxidant enzyme response under stress. In vitro, strain RGS produced indole-3-acetic acid and grew on nitrogen-free medium, traits consistent with plant growth-promoting behaviour. Collectively, these findings indicate that B. licheniformis strain RGS is a promising seed-applied bioinoculant for enhancing drought resilience and recovery in tomato grown under limited-moisture conditions.