Atividade antifúngica de óleos essenciais de espécies florestais

Abstract

Forest crops are highly affected by fungal diseases, however the market lacks alternatives to chemicals products to control these pathogens. In this sense, the objective of this work was to evaluate the antifungal activity of different essential oils and their effects on the morphological characteristics of fungi. The tests were conducted in the laboratory with the essential oils extracted from leaves of Nectandra grandiflora, Nectandra megapotamica and Piper gaudichaudianum, and had the chemical constituents identified through gas chromatographic analysis. The fungi of the genus Fusarium, Cladosporium, Pestalotiopsis, Colletotrichum and Lasiodiplodia were cultivated in Potato Dextrose Agar(PDA) medium, enriched with 1μL mL-1 of oil previously diluted in ethanol. The negative control consisted of PDA combined with ethanol, and the positive control consisted of the supplementation of medium with the fungicide Propiconazole, the plates were incubated in controlled conditions at 25 ° C, with photoperiod of 12h. The growth of the colonies was evaluated daily, and after 10 days, was characterized the sporulation, the colony coloration, the spore size and the mode of action of the oils. The variables analyzed were mycelial growth, mycelial growth rate and inhibition of mycelial growth, in a completely randomized design with six replicates. The N. grandiflora essential oil (EO) was composed mainly by (+) - Dehydrofukinone (26%), Dehydrofukinone epoxide (12.81%), those of N. megapotamica EO by α-Pinene (23,19%), β-Pinene (17,13%), Spathulenol (11,68), and for P. gaudichaudianum EO the phenylpropanoid Dilapiol (66,26%) was the major constituent. All EOs presented antifungal activity against fungi under study, however each EO acts differently in each fungal species. The P. gaudichaudianum EO showed the highest antifungal activity, being able to provide the lowest values of mycelial growth and the highest inhibition values for all fungi. In addition, it completely prevented the growth of Pestalotiopsis spp. and the formation of spores, which suggests a promising fungicidal action, since it has a high percentage of Dilapiol in its composition. Subsequently, the EO of N. grandiflora showed a behavior similar to the previous one, however with smaller percentages of inhibition. The lowest antifungal activity was identified for the N. megapotamica EO. The sporulation variable was highly affected by EOs, and the reduction of sporulation occurred proportionally to inhibition of mycelial growth. Based on the above, the potential of EOs to be used in disease control is emphasized, especially EO of P. gaudichaudianum because it presented a fungicidal effect.