In vivo evaluation of Aggressiveness, pathogenicity and patulin accumulation by three Penicillium expansum strains isolated from Algerian apples

Among the postharvest pathogens of apple fruit, Penicillium expansum (P.expansum) is considered to be one of the most common fungal pathogens worldwide. It is the causal agent of blue mold decay; the main serious economically disease of apple fruits, and the main producer of patulin (PAT). The principal objective of this work was to evaluate the aggressiveness and the PAT production of three isolated strains from apples produced in the East of Algeria. These strains were isolated then screened for their inhibitory activity against Escherichia coli and Bacillus subtilis (18 mm and 18 mm for S7; 10 mm and 11mm for S3), as well as their ability to cause blue rot (S4). The three strains S7, S3, and S4 (MN904448, MT023795 and MN904449, respectively) were identified as P. expansum by ITS1, ITS4, and β-tubulin gene sequences analysis. The in vitro ability to produce PAT was confirmed by Gas chromatography-mass spectrometry of strains’ crude extracts cul-tured on YES (Yeast-Extract-Sucrose) medium. Indeed, these strains exhibited a great capacity to cause blue mold decay for all tested apples (26 to 52 mm lesion diameter), after nine days of incubation at 25°C. Apples rotten area analysis that was performed by UPLC analysis revealed that these three strains were able to produce PAT at different concentrations ranging from 0.57 to 469 μg/mL. Thus, these strains constitute a risk to consumer health because these amounts exceed the permissive level of PAT.