Molecular characterization of the two postharvest biological control agents Aureobasidium pullulans L1 and L8

L1 and L8 are Aureobasidium pullulans strains previously shown to effectively act as biocontrol agents (BCA) against fruit postharvest pathogens. Here, L1 and L8 strains were tested in vivo against Monilinia laxa of peaches showing the ability to reduce the brown rot incidence by 95% and by 80% respectively. To develop future bioformulation and allow commercial use of these biocontrol agents (BCAs) it is necessary to develop specific identification tools. Since A. pullulans strains share very similar morphological features and are not distinguishable by visual analysis, the RAPD (Random Amplified Polymorphic DNA) technique was applied to genomic DNA of L1 and L8 and of other 40 different A. pullulans strains, and SCAR markers were developed from a L1 and L8 specific RAPD fragment of 984 bp. These primers amplify a fragment of 137 bp exclusively in L1 and L8, and can be used to distinguish the two yeasts strains from other A. pullulans strains with high specificity. The droplet digital PCR, used to determine the precise limit of detection (LOD), showed that these markers allow to detect up to 43 and 215 cells of L1 and L8 respectively.