Abstract
ABSTRACT Secondary compounds of medicinal plants can activate defense mechanisms in plants against pathogens. The aqueous extract (AE) of Corymbia citriodora has shown that activity, but there is scarce information about the involved mechanisms of action. Therefore, this study aimed to evaluate the effect of AE on the induction of defense enzymes and protection of cucumber from Colletotrichum lagenarium. Thus, the AE, autoclaved or not, was evaluated for its capability of protecting and inducing peroxidases, polyphenoloxidases, chitinases and β-1.3-glucanases, and phenylalanine ammonia-lyase. Distilled water and acibenzolar-S-methyl (50 mg a.i. L-1) were used as controls. The effect of AE at the concentrations of 1, 5, 10, 15 and 20% was also evaluated, as well as its local and systemic effect, and the effect of one or two applications. Pathogen inoculation or sample collection for determination of enzyme activity was performed at 72 hours after treatments. The AE reduced the severity of C. lagenarium and induced peroxidases and β-1.3-glucanases by 37.6, 67.2 and 122.7%, respectively. There was a reduction in the disease severity and an increase in peroxidases from the concentration of 5% AE. The latter showed only local effect and greater reduction in severity when two applications were performed. These results suggest the effect of AE in inducing resistance in cucumber and inducing peroxidases and β-1.3-glucanases.
Highlights
Secondary compounds of medicinal plants can activate defense mechanisms in plants against pathogens
Resistance induction in plants consists in activating latent defense mechanisms by means of localized infection by pathogens or as a response to treatment with different biotic agents or abiotic factors [18, 19, 20]
The leaves of C. citriodora were obtained from the garden of medicinal plants at “Universidade Estadual de Maringá”/Paraná State, and the aqueous crude extract with 20% plant material was obtained according to Bonaldo et al [3]
Summary
Secondary compounds of medicinal plants can activate defense mechanisms in plants against pathogens. There was a reduction in the disease severity and an increase in peroxidases from the concentration of 5% AE The latter showed only local effect and greater reduction in severity when two applications were performed. These results suggest the effect of AE in inducing resistance in cucumber and inducing peroxidases and β-1.3-glucanases. Sustainability, food security and environmental protection become a necessity, as well as guidelines for agricultural production In this context, alternative control of plant diseases have been studied [5, 24]. Resistance induction in plants consists in activating latent defense mechanisms by means of localized infection by pathogens or as a response to treatment with different biotic agents (such as viable or inactivated micro-organisms) or abiotic factors [18, 19, 20]
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