Unveiling the potential of native Blueberry-derived yeasts as biocontrol agents against Botrytis cinerea and Alternaria alternata

Blueberry production in Argentina faces economic losses caused mainly by fungal pathogens such as Botrytis cinerea and Alternaria alternata. Synthetic fungicides are expected to be discontinued in favor of a more sustainable agriculture, making indigenous yeast, which protects the plants, a promising alternative. This study explored the cultivable portion of blueberry fruits and flowers epiphytic yeast community to identify yeasts capable of protecting fruits against the major phytopathogens affecting this crop. Native yeasts were isolated and identified based on the PCR-amplified and sequenced D1/D2 domains of the 26S rRNA gene. Members of the genera: Rhodotorula, Hanseniaspora, Naganishia, Moesziomyces, Rhizosphaera, Metschnikowia, Clavispora, Pallidophorina, Hannaella, Aureobasidium, Sporobolomyces, Filobasidium, and Cystobasidium were identified. Subsequently, antagonism against B. cinerea and A. alternata was assessed in vitro and in vivo. Finally, potential modes of action such as killer phenotype, siderophore production and formation of volatile organic compounds (VOCs) were also evaluated. Among 38 yeast strains identified, the strain Aureobasidium leucospermi LAF2 stood out in vitro and in vivo with respect to protect blueberry fruits against B. cinerea by 58.33 % and A. alternata by 67.78 % of biocontrol efficiency at 25 °C. It also proved the ability to produce hydroxamate-type siderophores and VOCs capable of inhibiting B. cinerea growth by 48.19 %. These results suggest that fruits and flowers epiphytic microbial communities are a reservoir of potential biological control agents. A. leucospermi LAF2 is a strong candidate for a sustainable alternative to synthetic fungicides in blueberry production.