Prospecção de óleos essenciais com atividade antifúngica para alternativa no controle de Botrytis cinerea (PERS) e Colletotrichum acutatum (SIMMONDS) em videira

Abstract

The Brazilian viticulture is presented as one of the most important activities socially and economically within the national fruit production. The Serra Gaúcha is the main producing region of grapes and wine in Brazil. However, it has unfavorable climatic conditions for cultivation due to high rainfall and high relative humidity. Thus, the wine industry in the area becomes possible only with a rigorous preventive and curative control system of fungal diseases. Among the many diseases that affect the growing of vines, there are Botrytis cinerea and Colletotrichum acutatum, causing botrytis rot and ripe rot grapes, respectively. These fungi attack mainly berries, which reduces the quality and productivity, resulting in high economic losses. Control measures for these diseases generally consist in applying synthetic fungicides, but this method can have undesirable consequences, both for the human health and for the environment. Thus, it is necessary to search for new methods of low environmental impact control, which are economically viable and can be integrated into plant disease control programs. Many essential oils have fungicidal properties and research in this area to confirm this activity, according to scientific protocols, become increasingly necessary. In this situation, the aim of this study was to evaluate the antifungal activity of essential oils of Eucalyptus staigeriana, Eucalyptus globulus, Foeniculum vulgare, Baccharis trimera and Baccharis dracunculifolia on in vitro and in vivo growth control of Botrytis cinerea and Colletotrichum acutatum on vines (Vitis spp. and Vitis vinifera). In vitro tests were performed to evaluate the fungicidal action of essential oils on the germination of conidia and mycelial growth of fungi (contact phase and volatile) and from the results it was defined the essential oils to be used in vivo. In vivo tests were performed in order to evaluate the antifungal activity of essential oils in the control of diseases caused by B. cinerea and C. acutatum on grape variety “Isabela” (Vitis spp.) in the postharvest and vines varieties “Isabela” (Vitis spp.) and “Tannat” (V. vinifera) in the field. The grapes from the treatments performed on the vines iv were vinificated and the wine analyzed for their chemical properties and their volatile compounds. In vitro results show that E. staigeriana, E. globulus, B. trimera and F. vulgare essential oils have fungicidal action, inhibiting both fungi in small concentrations ranging from 50 to 600 ppm according to the essential oil and fungus tested. In postharvest tests it was used E. staigeriana, F. vulgare and B. trimera esssential oils. All of them reduced the incidence and severity of diseases, on both preventive and curative treatment. The curative treatment was more effective, inhibiting completely the symptoms of the diseases in concentrations ranging from 100 to 600 ppm according to the essential oil and fungus tested. For the in vivo treatment of vines, we used the essential oil of E. staigeriana at Concentrations of 100 and 500 ppm, which has promising results, reducing incidence and severity of disease on both varieties of vines. The chemical analysis of wines demonstrates that the essential oil does not interfere in the characteristic of the wine. In the analysis of volatile compounds of wines, it was identified low concentrations of 1.8-cineole compound in both wines and the compound citral in wine made from the grapes Vitis spp. cv. ‘Isabela”, but that does not interfere with the sensory characteristics of the wine. Thus, we can conclude that the essential oils presents potencial use as biofungicides in control of B. cinerea and C. acutatum on vines.