Preliminary trials on the use of volatile organic compounds for the postharvest control of grey mold on grape.

Several plant species, including grapevine, are rich in a wide range of volatile organic compounds such as terpenes and their derivatives (caryophyllene, linalool, nerolidol etc.) that can act as defence against herbivores and pathogens. Botrytis cinerea Pers. is also able to produce a variety of terpenes including botrydial, which is the primary phytotoxic compound of the fungus but can also have a limiting effect on its growth. Botrydial biosynthetic intermediates appear to be cyclization products of caryophyllene. Terpenes are already present in the food chain and do not display significant human toxicity, thus their use for the postharvest control of fruit and vegetable diseases could be interesting. However, only few studies deal with the effect of pure terpenes against phytopathogenic fungi. For this reason, we investigated the effectiveness of caryophyllene, linalool, nerolidol and ±-pinene against B. cinera. Nerolidol and linalool reduced significantly fungal growth in vitro when used at concentrations ranging from 1000 to 2500 μl/l and from 1500 to 2500 μl/l, respectively. In particular, linalool completely inhibited the fungal growth at the highest concentration. In vivo, linalool (2500 μl/l) reduced significantly infection percentage when applied by dipping the berries in a solution, while it was not effective when applied by evaporation. Nerolidol (2500 μl/l) was not effective in both cases. Unfortunately, the two compounds exerted a strong phytotoxic activity when applied by dipping, causing browning of the berries. In further investigations, other terpenes and other strategies of application will be tested.