Avaliação da atividade antifúngica do óleo essencial de capim-limão (Cymbopogon flexuosus) contra fungos fitopatogênicos

Abstract

The fungi kingdom, characterized by a large diversity of species, plays an important role in natural ecosystems. However, some fungal species have phytopathogenic effects, making studies to control diseases, particularly, in agriculture challenging. With the prevalence of synthetic fungicide uses and their adverse effects, it is imperative to explore sustainable alternatives, such as the use of natural products, including essential oils many of which with fungicidal potential. In this context, this study aimed to evaluate the antifungal efficacy of Cymbopogon flexuosus essential oil against the fungal species Colletotrichum musae, Fusarium pallidoroseum, and Lasiodiplodia caatinguensis. The biological assays were carried out in triplicate, with each repetition consisting of 4 Petri dishes. The fungi were inoculated on potato dextrose agar (PDA) medium in the presence of four concentrations of the essential oil (0.125; 0.25; 0.5 and 1 mL/L), with the positive control thiabendazole-based fungicide (Tecto®SC) in a concentration of 0.125 mL/L, and as negative control the fungus inoculated only in the culture medium (PDA). Every 24 hours, assessments of the fungal growth halo were made. To calculate the percentage of inhibition, the Edington formula was applied. Concentrations of 1 mL/L for the phytopathogens C. musae and F. pallidoroseum completely inhibited their mycelia in all replicates, whereas for the phytopathogen L. caatinguensis, full inhibition was observed in two of the replicates, but approximately 97% in the other repetition. Based on the chemical composition of lemongrass essential oil, the antifungal activity was associated with the citral, a monoterpene mixture consisting of two isomeric aldehydes, which present antifungal activity against several species of fungi. Furthermore, based on the literature, possible forms in which citral acts concerning its antifungal properties were discussed. It is worth noting that no study was found on the antifungal activity of this compound against L. caatinguensis.