Caracterização parcial de indutores de resistência em pepino e feijão a partir do extrato aquoso de eucalipto citriodora

Abstract

Secondary compounds of medicinal plants can activate defense mechanisms against plants pathogens. The aqueous extract (AE) of Corymbia citriodora have shown activity, but there is little information about the action mechanism and the characteristic of the fractions with activity. Thus, the aim of this work was evaluate the effect of AE on defense mechanisms in bean and cucumber, and the protection against Colletotrichum lagenarium and Xanthomonas axonopodis pv. phaseoli, respectively, and to characterize the fractions with biological activity. For this, the AE was evaluated with the ability respect to the abilits of induction of peroxidase, ß-1.3 glucanase, phenylalanine ammonia-lyase, polyphenol oxidase and chitinase in bean and cucumber, and bean phaseolin. Distilled water and acibenzolar-S-methyl (50 mg a. i. L-1) were used as controls. Precipitation with ammonium sulfate and gel filtration and ion change chromatography (ICC) were conducted to separate elicitors fractions. Fractions with activity were evaluated to autoclaving or treatment with proteínase. In cucumber, AE reduced the severity of C. lagenarium and induced peroxidase and ß-1.3-glucanases. In the bean, AE induced phaseolin and peroxidases. Three fractions with activity were obtained by ICC. Fraction I containing carbohydrates and protein activity was reduced by the action of proteínase, suggesting a glycoprotein nature. The heat treatment did not reduce the activity of the fractions indicating the presence of heat-resistant compounds. The achievement of different fractions with effect below of the AE, suggests the synergistic activity between compounds in the resistance induction by of C. citriodora AE.