Abstract
Tomato bacterial spot caused by Xanthomonas vesicatoria is an important disease in many tomato production areas in the world. The potentiality of salicylic acid (SA) to suppressing bacterial spot of tomato (Lycopersicon esculentum L. var.) under artificial inoculation conditions was investigated in the current work. Tomato plants cv. Super Strain B were sprayed with SA (10 mM) and inoculated with a virulent X. vesicatoria strain for four days post spraying. SA significantly reduced bacterial leaf spot severity, number of lesions per leaf and spot diameter in tomato plants pre-treated with SA compared with the untreated control plants. Changes in the activities of peroxidase, catalaze and polyphenol oxidase in tomato plants after application by SA and inoculation with X. vesicatoria were studied. In SA-treated leaves (plants), an increase in enzymes activities was observed five days after challenge inoculation with X. vesicatoria. The expression of resistance induced by SA was evidenced by the increase in peroxidase (POX) and polyphenol oxidase (PPO) activities, starting from the first day after spraying. These results indicated that the future integrated disease management programs against tomato bacterial spot may be enhanced by including foliar spray of SA.