Induction of defense mechanisms from filtrates of saprophytic fungi against early blight disease in tomato

The induction of defense enzymes presents efficient plant disease management when triggered by metabolic products of microorganisms. The aim of the present study is to select filtered saprobes fungi used for the management of early blight of tomato by inducing pathogenesis related to tomato plant. Filtrates of the fungi Curvularia eragrostidis, Curvularia inaequalis, Memnoniella echinata and Pseudobotrytis terrestris were cultured in potato and dextrose (PD) media and maintained in a growth chamber at 25 ± 2°C, with a photoperiod of 12 h light. After 20 days, the mycelial mass was removed through filtration. Concentrations (0, 5, 10, 15 and 20%) of filtrates and Acibenzolar-S-Methyl were applied in the 3rd tomato leaf 3 days before inoculation with Alternaria solani. Then the disease severity was analyzed calculating the area under the disease progress curve. The activity of the enzymes, catalase, guaiacol peroxidase and phenylalanine ammonia-lyase (locally and systemically) at plant control (72 h before inoculation) and 0, 24, 48, 72 and 96 h after inoculation with A. solani was analyzed. C. eragrostidis, C. inaequalis, M. echinata and P. terrestris filtrates reduced the AUDPC, both locally and systemically. Greater activity of phenylalanine ammonia-lyase was observed in plants treated with C. eragrostidis (local and systemic) and C. inaequalis filtrates (local). The filtrate of P. terrestris promoted greater catalase activity, either locally or systemically. The filtrate of M. echinata increased peroxidase activity locally and systemically. The filtrates tested are resistance inducers used for the management of tomato early blight, although further testing is necessary to identify elicitors present in filtrates.