Bioactivity of volatile organic compounds byAureobasidiumspecies against gray mold of tomato and table grape

Aureobasidiumstrains isolated from diverse unconventional environments belonging to the speciesA. pullulans,A. melanogenum, andA. subglacialewere evaluated for Volatile Organic Compounds (VOCs) production as a part of their modes of action againstBotrytis cinereaof tomato and table grape. By in vitro assay, VOCs generated by the antagonists belonging to the speciesA. subglacialeshowed the highest inhibition percentage of the pathogen mycelial growth (65.4%). In vivo tests were conducted with tomatoes and grapes artificially inoculated withB. cinereaconidial suspension, and exposed to VOCs emitted by the most efficient antagonists of each species (AP1, AM10, AS14) showing that VOCs of AP1 (A. pullulans) reduced the incidence by 67%, partially confirmed 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% byA. pullulans; < 30.5% byA. melanogenum, andA. subglaciale). Solid-phase microextraction (SPME) and subsequent gas chromatography coupled to mass spectrometry identified ethanol, 3-methyl-1-butanol, 2-methyl-1-propanol as the most produced VOCs. However, there were differences in the amounts of produced VOCs as well as in their repertoire. The EC(50)values of VOCs for reduction of mycelial growth ofB. cinereauncovered 3-methyl-1-butanol as the most effective compound. The study demonstrated that the production and the efficacy of VOCs byAureobasidiumcould be directly related to the specific species and pathosystem and uncovers new possibilities for searching more efficient VOCs producing strains in unconventional habitats other than plants.