Vol. 9, Special Issue 12, Part M (2025)

Bacterial leaf spot of tomato, caused by Xanthomonas euvesicatoria, is associated with high genomic plasticity that enables rapid adaptation, virulence evolution, and the development of antibiotic resistance. These characteristics limit the effectiveness of conventional disease management strategies and underscore the need for sustainable alternatives to chemical control. This study evaluated the In vitro antibacterial activity of crude flagellin and exopolysaccharides (EPS) derived from Bacillus velezensis against Xanthomonas euvesicatoria. It investigated the molecular basis of flagellin recognition by the tomato FLAGELLIN-SENSING 2 (LeFLS2) receptor using computational methods. Antibacterial activity was measured using the poisoned food technique. Crude flagellin demonstrated the highest growth inhibition (31.11%), compared to EPS (15.56%) and Bacillus velezensis (16.67%). These results indicate that crude flagellin exhibits superior antibacterial activity. Sequence analysis of B. velezensis flagellin identified several conserved amino acid residues associated with flg22 epitope recognition, suggesting its ability to activate FLS2-mediated immune signaling in tomato. Molecular interaction analysis revealed a stable leFLS2-flagellin complex, supported by multiple hydrogen bonds and hydrophobic interactions, which facilitate adequate ligand accommodation within the receptor binding pocket. Docking analysis confirmed a strong and reliable interaction, with a docking score of −203.9 and a confidence score of 0.746. Collectively, these findings demonstrate the dual role of B. velezensis flagellin as both a direct antibacterial agent and an immune-eliciting molecule, highlighting its potential for eco-friendly disease management in tomato cultivation.