Inhibitory activity of essential oils components against the fungal plant pathogen Botrytis cinerea

Botrytis cinerea is the fungus responsible of the grey mould
disease of grape and other fruits. Chemical control is necessary
when environmental conditions are favorable to the disease.
In order to protect plants from disease the European Union by
directive 2009/128/EC gives priority to non-chemical methods
and encourages the use of natural non-toxic substances. Natural
compounds are used as an alternative to chemical fungicides
mostly to control post-harvest diseases. The major aim of this
work is to compare the fungicidal activity against B. cinerea of
11 natural compounds that are produced in plants through
the shikimate/phenylalanine pathway. In a spore germination
assay six compounds (eugenol, thymol, carvacrol, isoeugnol,
cinnamaldehyde and vanillin) completely inhibited the germination
of conidia. These natural products also reduced the viability of the
spores and inhibited the growth of B. cinerea mycelium (strain
PM10) even if with different efficiency. These compounds are the
major constituents of essential oils of many aromatic species.
Some chemical characteristics, like the high lipophilic and the low
value of polar surface area, are common among these compounds
indicating an high affinity for phospholipids compartment and
their difficult to overcome the external layer of the cell.