Inhibitory effect of essential oils on the mycelial growth of penicillium digitatum (pers.) sacc. isolated from sweet orange (citrus sinensis osbeck)

The incidence of fungal diseases in post-harvest fruits, in storage, or both, is still a problem today due to the large losses caused to producers and merchandisers of these products. Therefore, the aim of this study was to evaluate in vitro and in vivo the inhibitory effect of essential oils of basil (Ocimum basilicum), cinnamon (Cinnamomum zeylanicum), clove (Syzygium aromaticum), soursop (Annona muricata), ginger (Zingiber officinale), mint (Mentha piperita), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis) and sage (Salvia officinalis) at different concentrations on a native strain of Penicillium digitatum as an organic alternative to the use of synthetic fungicides. In order to obtain the strain, fruits from localities producing sweet orange (Citrus sinensis Osbeck) in Puerto Rico were selected. Inhibition tests with essential oils were performed on a strain from the Guayanilla locality with morphological and molecular identification. Inhibition tests were performed in vitro and in vivo. The experimental design was completely randomized, and the means were compared with the Tukey test (p£0.05). Three in vitro inoculation methods were used with the essential oils in the culture medium at different concentrations. In addition, the fungus was treated in vivo in its natural environment with the oils that showed more than 90% inhibition in the in vitro methods. Cinnamon, clove and oregano leaf and bark oils inhibited 90 to 100% of P. digitatum development. Oils of basil, soursop, ginger, mint, rosemary, and sage inhibited little or not at all the fungal growth. There were some differences in vivo regarding in vitro methods, since only clove oil maintained similar levels to the in vivo and in vitro control as the treated fruits showed no contamination with P. digitatum at 7 and 14 days.