Molecular characterization of Aureobasidium spp. strains isolated during the cold season. A preliminary efficacy evaluation as novel potential biocontrol agents against postharvest pathogens

Several Aureobasidium spp. strains isolated from wild environments during winter 2022 were characterized by sequence analysis of the internal transcribed spacer (ITS), the translation elongation factor EF-1α gene (EF1), and part of the elongase gene (ELO). The variability in the EF1 and ELO loci are higher than in the ITS. All strains but one (UC14), were identified as A. pullulans. To assess the effectiveness of the characterized strains as biocontrol agents (BCAs) of diseases occurring during postharvest storage, a selection of the strains was evaluated by in vitro and in vivo assays. On average, the reduction of Monilinia spp. colony growth was more marked for non-volatile metabolites than for volatile (VOCs). Strain UC14 provided the strongest mycelial growth reduction of Monilinia fructicola by VOCs (66%). According to the in vivo results, all strains were effective in controlling brown rot during cold storage and remarkably in restricting the growth of Monilinia polystroma. In particular, VB23 was the most effective in controlling brown rot incidence, by 80%, 60%, 100%, and severity, by 79.5%, 72.7% and 100%, for Monilinia laxa, M. fructicola, and M. polystroma, respectively.