Abstract
ABSTRACT This study aimed to evaluate the fungitoxic (antifungal) effect of seven essential oils on Plasmopara viticola, the causal agent of grapevine downy mildew. The cinnamon, eucalyptus globulus, marjoram, melaleuca, peppermint, oregano and white thyme essential oils were compared with the mancozeb + metalaxyl-M fungicide. Three experiments were conducted to evaluate the effect of essential oils on spore germination. The first experiment evaluated the effect of direct contact of essential oils on the pathogen; the second evaluated the effect of volatile compounds on the pathogen and the third assessed the behavior of essential oils, when applied to vine leaves in field conditions, on the pathogen. All essential oils inhibited the spores’ germination, but in varying degrees, in addition, presenting fungistatic activity. All the essential oils showed chemical instability when the incubation time or the interval between products application where increased, all oils decrease antifungal activity percentage. Noteworthy, the cinnamon and the eucalyptus globulus essential oils were the most fungitoxic (antifungal) on P. viticola.
Highlights
The grapevine (Vitis spp.) is economically one of the most important fruits cultivated in the world, because of the diverse uses of its fruits
In direct contact of the essential oils on the percentage of spore germination inhibition (PGI) of P. viticola spores and disregarding the concentrations, the cinnamon oil showed the highest percentage of germination inhibition (70%), followed by eucalyptus globulus and marjoram, while the lowest values of PGI were found for white thyme (43%) and oregano (Table 1)
The effect of the essential oils in direct contact with the pathogen varied over the long period of incubation, for inhibition of 50% of the spore germination (CL50)
Summary
The grapevine (Vitis spp.) is economically one of the most important fruits cultivated in the world, because of the diverse uses of its fruits. It is present in more than 90 countries and in Brazil it occupies the twelfth place in planted area (ha) among the fruits (Food and Agriculture Organization). The most important for the crop is downy mildew caused by Oomyceto Plasmopara viticola Due to its biotrophic characteristic, it can infect all the green tissues, reducing the photosynthetic area and blocking the translocation of assimilates, from its source of production to the growth areas and fruits, causing the plant death (AZIZ et al, 2006). When control measures are not applied, downy mildew can reduce fruit yield up to 70% (GARRIDO; ANGELOTTI, 2011)
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