Role of volatile compounds from wounded oranges in induction of germination of Penicillium digitatum conidia.

Volatile compounds from exocarp-wounded oranges induced germination in about 50% of Penicillium digitatum conidia on water agar, compared to less than 5% on water agar alone. Limonene, α-pinene, sabinene, β-myrcene, acetaldehyde, ethanol, ethylene, and CO 2 were identified by gas chromatography as the major volatile compounds around wounded oranges. Conidial germination was not stimulated by exposure to any of these compounds alone. A mixture of limonene, acetaldehyde, ethanol, and CO 2 at concentrations measured in the atmosphere around wounded oranges stimulated spore germination on water agar and on silica gel medium to the same degree as the natural mixture of volatile compounds from the fruit. Ethylene alone or in combination with the synthetic mixture of volatile compounds did not increase germination