Nitric oxide-induced modulation of physiological and molecular responses in tomato (<i>Solanum lycopersicum</i> L.) plants infected with <i>Xanthomonas perforans</i>

Abstract

Bacterial spot, caused by Xanthomonas perforans, significantly threatens global tomato production. Traditional control methods have proven inadequate, necessitating innovative approaches. This study assessed nitric oxide (NO) pretreatment at 0.5, 1, and, 2 mM concentrations to induce abiotic resistance against X. perforans in greenhouse-grown tomatoes. Results indicated that NO pretreatment enhanced plant growth, biomass, and defense mechanisms under both normal and pathogen-stressed conditions. Specifically, NO regulated physiological processes such as lipid peroxidation, chlorophyll content, and fluorescence parameters. It also modulated key enzymes like NADPH oxidase and phenylalanine ammonia lyase (PAL), bolstering antioxidant defenses by scavenging reactive oxygen species, thereby reducing oxidative damage and improving stress tolerance. Additionally, No induced sugar accumulation, increasing energy reserves during stress, and elevated amino acid content, facilitating defense protein synthesis. Notably, NO pretreatment significantly reduced disease severity by upregulating defense-related genes, including non-expressor of pathogenesis-related genes (NPR), PAL, and peroxidase (POD). Overall, NO pretreatment improved plant health, decreased pathogen proliferation, and increased biomass, highlighting its potential as an environmentally friendly strategy for managing bacterial diseases and activating specific resistance responses in tomato plants.