Commercial essential oils with antifungal effect against the maize phytopathogen fungus Fusarium verticillioides

ACHIMÓN F; ARENA J.S; PIZZOLITTO R.; BRITO V.; MERLO C.; KRAPACHER C.; ZYGADLO J.A

Córdoba

Jornada; XXII Jornadas Científicas, Sociedad Biología de Córdoba.; 2020

Fusarium verticillioides (Sacc.) is a fungal pathogen of maize, and the major causal agent of stalk and ear rot worldwide. The application of synthetic fungicides is the most commonly used strategy to control food deterioration by fungi. However, these chemical substances proved to be toxic for the environment and organisms. In this context, there is an increasing public demand for the development of natural and safer antifungal agents, such as plant essential oils (EOs). Essential oils are hydrophobic substances of complex mixtures of volatile organic compounds. The aims of the present work were to study the chemical composition, antifungal and anti-conidiation activities of Curcuma longa, Pimentadioica, Rosmarinus officinalis, and Syzygiumaromaticum EOs using a multivariate approach (Principal Component Analysis; PCA). The chemical composition of the EOs was analyzed by GC/MS. The antifungal and anti-conidiation activity was evaluated by the agar diffusion method. Different aliquots of each EO were diluted in Czapek Dox Agar (CDA) culture medium to achieve the following concentrations: 1000 ppm, 500 ppm, 250 ppm and 125 ppm.Data were analyzed by one-way analysis of variance (ANOVA) followed by a Multiple Comparison test.Syzygiumaromaticum EO reported the highest antifungal effect, followed by P. dioicaand to a lesser extent C. longa. The major compounds of these EOs were eugenol (88.7 % in S. aromaticumand 16.7 % in P. dioica), methyleugenol (53.09 % in P. dioica), α-turmerone (44.7 %), β-turmerone (20.67 %), and Ar-turmerone (17.27 %) in C. longa. The bioactivity of eugenol is attributable to the free-OH group that act as the hydrophilic portion increasing its solubility in the plasma membrane and forming hydrogen bonds with the active sites of different enzymes. On the other hand, turmerones are ketoneswith an extra double bond between the alpha and beta carbons. Theseα,β-unsaturations increase the polarizability of the molecule, allowing them to bind with amino acids and nucleic acids and affecting different fungal metabolic pathways. Rosmarinus officinalis poorly inhibited fungal growth, but was the only EO that inhibited conidial production, being its major components 1,8-cineole (53.48 %), α-pinene (15.65 %), and (-)-camphor (9.57 %).Our results showed that some compounds are capable of decreasing mycelial growth without affecting sporulation, and vice versa. However, not all the compounds of an EO are responsible for its bioactivity. In the present work, we were able to identify different major compounds or mix of major compounds that were responsible of antifungal and anti-sporulation effects. Further experiments combining these pure components are necessary in order to achieve a highly bioactive plant-based formulation against the phytopathogen fungus F. verticillioides.