Exploring Wild and Local Fruits as Sources of Promising Biocontrol Agents against Alternaria spp. in Apples

Biological control agents (BCAs) are a promising option for managing postharvest diseases. Their environmentally friendly nature makes them valuable for sustainable and eco-friendly postharvest disease management. This study evaluated the antagonistic potential of epiphytic yeasts isolated from a local apple genotype known as “Niğde Elması” and a range of wild fruits: rosehip, hawthorn, and wild pear. There were 375 yeast isolates obtained and screened in vitro and in vivo. Initially selected were 32 isolates able to inhibit the growth of Alternaria alternata mycelia in the in vitro experiments and identified using molecular methods as candidate BCAs. These isolates were identified as Aureobasidium pullulans using sequence analysis of the internal transcribed spacer (ITS) and the translation elongation factor EF-1α gene (EF1α). Based on two rounds of in vivo screening, four isolates were subsequently selected for their capability to control the infection of apple fruits under high inoculum pressure. Finally, their volatile and non-volatile antimicrobial activity was tested against Alternaria spp. These findings showed how wild fruits and a local apple genotype could represent a promising source for new BCA isolation. However, further studies are needed to reveal the mechanisms of action of these putative BCAs for application during the postharvest processing and storage of apples.