Characterisation of Aspergillus and Penicillium populations of pomegranate fruit by high resolution melting (HRM)

Because of its nutraceutical and cosmeceutical properties, the consumption of pomegranate fruit and its derivatives and consequently the cultivation of this crop in Europe are increasing. Postharvest fruit losses caused by fungal pathogens are one of the main issues, even because of the risk of contamination by mycotoxins of both fresh and processed products. Indeed, for example, within Penicillium and Aspergillus genera there are species producing mycotoxins as ochratoxin A (OTA) and fumonisins, hazardous to human health, so that the European Commission regulates the relative thresholds for food and feed. In this investigation, two collections, one of Penicillium and one of Aspergillus spp., from symptomatic pomegranate fruit of various cultivars were characterized. However, since their morphological identification at species level was not easy, particularly for Aspergillus species belonging to sect. nigri, and to avoid the misidentification between Talaromyces and Penicillium genera, a Talaromyces-specific PCR assay and two genus-specific and species-discriminating HRM assays were set up; moreover, the presence of OTA and fumonisin genes was evaluated. The 10% of the collection of Penicillium sensu lato proved to be made up of Penicillium sensu stricto strains. Furthermore, P. glabrum proved to be the most represented species. None of them seemed to produce OTA. Whereas within sect. nigri, A. tubingensis and A. welwitschiae were the most represented species, and several isolates of this last species seemed able to produce fumonisins