Yeasts From Xerophilic Environments Reveal Antimicrobial Action Against Fruit Pathogenic Molds

In the present study, we investigated the occurrence of yeast flora in a xerophilic environment, the desert region of Namibia, with the aim to isolate the yeast strains with antimicrobial activity toward plant pathogen molds. Using traditional culture-dependent methods, a total of 44 yeast strains belonging to 6 genera and 12 species were isolated. The yeast isolated from red berry samples revealed the widest biodiversity, while only Cryptococcus albidus strains were isolated from desert melon and leaf samples. A wide antimicrobial activity toward pathogenic molds was observed in vitro tests for the yeasts belonging to Aureobasidium pullulans (strains F32 and F60), C. albidus (S14) and Saccharomyces cerevisiae (RB24). This behavior was confirmed in vivo tests, where A. pullulans F32 and F60 completely counteracted Penicillium digitatum decay in lemon and orange, respectively, while C. albidus S14 showed a similar strong antimicrobial effect in both fruits. S. cerevisiae strain RB24 exhibited a widespread inhibitory activity against Monilinia fructicola on cherries.