Volatile organic compounds of Clavispora lusitaniae AgL21 restrain citrus postharvest pathogens

Microbial agents exert their biocontrol effects through different mechanisms of action. Clavispora lusitaniae AgL21, a yeast capable of controlling postharvest diseases in lemon, produces volatile organic compounds (VOCs) impairing phytopathogenic fungi. Here we elucidate the nature of such compounds and check individual effects on mycelial growth of citrus fungal pathogens: Penicillium digitatum, Penicillium italicum, and Geotrichum citri-aurantii. VOCs characterization was carried out deploying solid-phase microextraction/gas chromatography-mass spectrum techniques. Among the compounds produced by C. lusitaniae AgL21, ethyl acetate, isoamyl acetate, 3-methyl butanol, and phenethyl alcohol displayed the highest relative abundance. Synthetic ethyl acetate, tested in vitro on P. digitatum, had no discernable effect on mycelial growth, whereas isoamyl acetate and both of the above alcohols exhibited fungistatic and fungicidal effects, respectively. The data provided in this study prove for the first time, that VOCs released by C. lusitaniae AgL21 are able to take part in antagonistic activities against citrus postharvest fungal pathogens.