Compostos bioativos de Ganoderma lucidum na indução de resistência a oídio em soja e a toxicidade a organismos não-alvo

Abstract

The Ganoderma lucidum is a medicinal fungi widely used in Eastern countries and currently worldwide. Its fruiting body and mycelium are composed of polysaccharides, triterpenes and more than 200 secondary metabolites. These compounds exhibit a range of bioactivities, such as anti-inflammatory, antitumorigenic, antibacterial and antifungal action. Multiple scientific publications demonstrate the potential and performance of the compounds of G. lucidum in the control of diseases in animals and humans. However, the information about the effect of these secondary metabolites on plant pathogens control still scarce, either in direct form or by activating plant defense mechanisms. In the research of new molecules that have induction activity and/or direct toxicity against fitopathogenic fungi, the aim of this work was to evaluate the bioactive compounds produced by G. lucidum through liquid culture under elicitation, to control powdery mildew (Erysiphe diffusa) in soybean plants. The activation of plant defense mechanisms, and toxicity to non-target organisms were evaluated. The compounds tested were: C01- control (distilled water); C02- Copper oxychloride (1,0 L ha-1); C03- Azoxystrobin + Ciproconazole (1,0 L ha-1), FC01- filtered mycelial growth broth of G. lucidum without elicitation, FC02- elicitation filtrate with lignin standard (5%); FC03- filtered from the culture elicited with 2 mM salicylic acid (SA). The data were all analyzed using the R® software. The Ganoderma filtrate associated with SA showed fungicidal action on powdery mildew (Erysiphe diffusa) in vitro, with a minimum inhibitory concentration of 5 mg mL-1. The Ganoderma filtrates demonstrated the potential of induction of resistance in soybean plants by the activation of phytoalexins, activation of the enzyme phenylalanine ammonialyase, increase of phenolic compounds, peroxidases and chitinase enzyme activity. Such activity has specificity in relation to time and association with elicitors. The MGF (mycelial growth filtrate) have fungicidal potential when applied to soybean plants infected by powdery mildew, reducing disease severity. The MGF had been proved to be non-toxic to non-target organisms. New researches should be considered, seeking to identify and isolate the active principles present in the MGF, as well as in other pathosystems of agricultural interest.