Alternaria alternata fsp lycopersici and its toxin trigger production of h2o2 and ethylene in tomato

V. Prasad, R.S. Upadhyay
doi: 10.4454/jpp.v92i1.19
Alternaria alternata f.sp. lycopersici was isolated from a naturally infected tomato plant and characterized. The pure culture of this isolate produced typical necrotic lesions on the leaves of tomato (Lycopersicon esculentum cv. CO-3). The isolated pathogen also secreted a phytotoxic compound into the culture filtrate. This filtrate, when infiltrated into tomato leaves, produced necrotic lesions identical to those produced by pure cultures of the pathogen. Excised tomato leaves showed a dose-response effect to increasing concentrations of culture filtrate. Pathogen infection and culture filtrate infiltration triggered H2O2 production and ethylene evolution from tomato leaves within 6 h of treatment, followed by necrosis of the treated leaves. Application of the antioxidant L-ascorbic acid suppressed the production of H2O2. Ethylene evolution was also significantly lowered by application of aminoethoxy vinyl glycine. Application of both these compounds also reduced the necrosis induced by Alternaria alternata f.sp. lycopersici and its culture filtrate.