Bioactivity of volatile organic compounds by Aureobasidium species against gray mold of tomato and table grape

Aureobasidium strains isolated from diverse unconventional environments belonging to the species A. pullulans, A. melanogenum, and A. subglaciale were evaluated for Volatile Organic Compounds (VOCs) production as a part of their modes of action against Botrytis cinerea of tomato and table grape. By in vitro assay, VOCs generated by the antagonists belonging to the species A. subglaciale showed the highest inhibition percentage of the pathogen mycelial growth (65.4%). In vivo tests were conducted with tomatoes and grapes artifcially inoculated with B. cinerea conidial suspension, and exposed to VOCs emitted by the most efcient antagonists of each species (AP1, AM10, AS14) showing that VOCs of AP1 (A. pullulans) reduced the incidence by 67%, partially confrmed by the in vitro results. Conversely, on table grape, VOCs produced by all the strains did not control the fungal incidence but were only reducing the infection severity (<44.4% by A. pullulans;<30.5% by A. melanogenum, and A. subglaciale). Solid-phase microextraction (SPME) and subsequent gas chromatography coupled to mass spectrometry identifed ethanol, 3-methyl-1-butanol, 2-methyl-1-propanol as the most produced VOCs. However, there were diferences in the amounts of produced VOCs as well as in their repertoire. The EC50 values of VOCs for reduction of mycelial growth of B. cinerea uncovered 3-methyl-1-butanol as the most efective compound. The study demonstrated that the production and the efcacy of VOCs by Aureobasidium could be directly related to the specifc species and pathosystem and uncovers new possibilities for searching more efcient VOCs producing strains in unconventional habitats other than plants.