Extreme environments are a largely unexplored reservoir of microbial diversity, with a remarkable potential to be exploited in agriculture. One hundred and seventeen yeast isolates,
derived from different ecosystems in Italy, Sweden, Algeria, and France, were molecularly
identified, and the most represented genus was Aureobasidium (57%). A phylogenetic
analysis based on a multi-locus sequence typing (ITS, ELO, EF-1alpha) was conducted to
characterize the black yeasts’ population. To investigate A. pullulans extremophilic and
extremotolerant behaviour, different temperatures and pH, together with the enzymatic
production, were evaluated. The strains were tested by in vitro and in vivo assays against
the postharvest fungal pathogen Monilinia fructicola as potential biocontrol agents (BCAs).
Results displayed a great ecological variability concerning strains’ growth and cell production depending on different culture conditions. However, a remarkable thermotolerance
aptitude was detected in almost all the strains. In particular, the strains belonging to Group
2 (Algerian Desert) and 3 (Alto Adige Region) showed, respectively, higher thermotolerance
and biocontrol ability. These findings showed how some extreme environments could
represent a promising source for new potential BCAs. However, further studies are needed
to investigate the mechanisms of action of these putative BCAs for application during the
postharvest phase.
