Genetic identification, pathogenicity and patulin production of Penicillium species from apple blue mold in China

Blue mold is a common postharvest disease that leads to serious rot and patulin contamination in fruits, which is a key factor endangering the storage and quality of apple products. However, the Penicillium species from apple blue mold in China and their pathogenicity and patulin (PAT) production ability have not been well studied. In this study, 62 strains of pathogenic Penicillium species were isolated from blue mold apples collected from different Chinese regions. The ITS, BenA and CaM genes were sequenced for molecular identification. Penicillium strains were identified as three species with 57 P. expansum, 3 P. crustosum, and 2 P. polonicum. Twelve variants of the ITS sequence, 61 variants of BenA and 67 variants of CaM genes were identified between Penicillium species. Fungal morphology was observed on PDA. After 10 d of cultivation, P. expansum cultures were detected with PAT concentrations ranging from 457.98 to 1333.85 mg/kg, and two P. polonicum strains were 6.02 and 6.30 mg/kg. Three P. crustosum strains could not produce PAT on PDA. In apple inoculation, P. expansum strains showed significantly faster infection rates than P. crustosum and P. polonicum strains. All P. expansum strains can produce PAT during infection, and the concentrations in the rot apple tissues were 2.31 to 88.67 mg/kg. The P. crustosum and P. polonicum strains could not produce PAT during infection. This study provided data and information regarding the morphology, virulence and PAT production of Penicillium pathogens that will improve the understanding of apple blue mold and postharvest disease control.