Biological control of post-harvest diseases on apple by using plant essential oils and Trichoderma culture filtrates

Pure essential oils have been purified and chemically characterized from cinnamon, clove and black pepper. All these oils have antifungal properties and when applied to apple fruits in post harvest can efficiently control Botrytis cinerea, Alternaria alternata or Penicillium expansum. In addition, application of these compounds or Trichoderma culture filtrate can induce systemic resistance mechanisms in apple fruit. This has been confirmed through phytoalexins and proteomic analysis. The accumulation of the phytoalexins scopoletin, umbelliferone, and scoparone was induced by the three essential oils or Trichoderma CF. Proteomic analysis indicated many changes in protein production caused by the treatment with the oils, Trichoderma CF and the pathogens. The differential spots (TOTD) obtained were up to 166 in clove plus P. expansum treatment. Twenty nine of the most interesting differentially expressed proteins were further analysed by MALDI-TOF MS. The protein groups identified included: pathogenesis-related proteins belonging to the PR-10 sub-family, some antimicrobial proteins, enzymes involved in the biosynthesis of antimicrobial compounds pathway and ribosomal proteins. The most interesting essential oil was the one extracted from black pepper because it was not phytotoxic on tomato seedlings and apple fruits at all the tested concentrations and showed a good disease control activity. A new bio-formulate for post-harvest application, based on a combination of three different active ingredients (black pepper oil, Trichoderma CF and a natural ISR-inducing agent also used as emulsifier) was designed and successfully tested as a synergistic mixture.