Antifungal activity of lemon, eucalyptus, thyme, oregano, sage and lavender essential oils against Aspergillus niger and Aspergillus tubingensis isolated from grapes

Today, it is very important to find out the protection of products of natural origin as an alternative to synthetic fungicides. The promising alternative is the use of the essential oils (EOs). Essential oils from plants have great potential as a new source of fungicide to control the pathogenic fungi.The main objective of this study was evaluation of the antifungal activity of lemon (Citrus lemon L.), eucalyptus (Eucalyptus globulus LABILL.), thyme (Thymus vulgaris L.), oregano (Origanum vulgare L.) sage (Salvia officinalis L.) and lavender (Lavandula angustifolia MILLER.) EOs against Aspergillus niger and Aspergillus tubingensis isolated from grapes and their ability to affect the growth. It was tested by using the vapor contact with them. At first both tested isolates were identified by using PCR method. Sequence data of 18S rRNA supported the assignment of these isolates to the genus Aspergillus and species A. niger (ITS region: KT824061; RPB2: KT824060) and A. tubingensis (ITS region: KT824062; RPB2: KT824059). Second, EO antifungal activity was evaluated. The effect of the EO volatile phase was confirmed to inhibit growth of A. niger and A tubingensis. EOs were diluted in DMSO (dimethyl sulfoxide) final volume of 100 μL. Only 50 μL this solution was distributed on a round sterile filter paper (1 x 1 cm) by micropipette, and the paper was placed in the center of the lid of Petri dishes. Dishes were kept in an inverted position. The essential oils with the most significant activity were determined by method of graded concentration of oils - minimum inhibitory doses (MIDs). The most effective tested EOs were oregano and thyme oils, which totally inhibited growth of tested isolates for all days of incubation at 0.625 μL.cm-3 (in air) with MFDs 0.125 μL.cm-3 (in air). Lavender EO was less active aginst tested strains (MIDs 0.313 μL.cm-3). The results showed that the tested EOs had antifungal activity, except lemon and eucalyptus. Sage EO was the only one which decelerated the radial growth of colony of both tested strains after all days of cultivation in comparison with a control sets. Our study provides the support that essential oils can be used to control plant pathogens such as A. niger and A. tubingensis.