Fungi Occurrence in Ready-to-Eat Hazelnuts (Corylus avellana) From Different Boreal Hemisphere Areas

Abstract

The present study evaluated the fungal contamination of ready-to-eat dried hazelnuts considering for the first time the application of the same condition drying process of several hazelnut cultivars from different boreal hemisphere areas. Fifty lots of hazelnuts (Corylus avellana), belonging to eight cultivars from seven regions in four countries, were analyzed for fungal microbiota, describing both load levels and species diversity. For this purpose, a polyphasic approach consisting of morphological examination (optical and scanning electron microscope observation) and molecular characterization [PCR-DGGE analysis and sequence analyses of the internal transcribed spacer (ITS)] was performed. The results show that different fungal populations occur in dried hazelnuts regardless of their geographical area of production. Although some varieties appear to be relatively less susceptible, species related to Aspergillus, such as A. commune and A. ochraceus, Penicillium, including P. commune, P. solitum, and P. expansum, and Rhizopus, for instance, R. stolonifer and R. oryzae, have generally been found. A related character “hazelnut cultivar—fungi” was found for species related to the genera Trichoderma and Fusarium, including F. oxyxporum, F. solani, and F. falciforme. All 14 species found are known to host pathogenic strains. Therefore, their presence in a ready-to-eat product, such as dried hazelnuts, can pose a real danger to the consumer. Based on these considerations, the development of new protective strategies seems highly desirable. The species-level description of the contaminating fungal community acquired through this study is the starting point for the development of tailor-made protective biotechnologies.

Damages on hazelnut kernels caused by Penicillium spp.

“…A light microscope Leica DM500 was used for microscopic analysis in the laboratory of Agricultural University Plovdiv. In agreement with the description of Lombardi (Lombardi et al, 2022) the septate conidiophores, broom-like branched at the upper end were observed under the microscope. A chain of conidia forms on the branches.…”

“…Al, 2019. A comprehensive analysis on 134 isolates from hazelnut kernels revealed that the most widespread Penicillium species were P. commune (69 isolates), P. solitum (36 isolates) and P. expansum (29 isolates) (Lombardi et. al, 2022).…”

Pathogenic fungi shape the fungal community, network complexity, and pathogenesis in kiwifruit

“…Our analysis revealed that the largest number of co-occurring species occurred in ND samples and the highest number of species were common to the co-occurring species in other sample groups. Similarly, a previous study reported on the cooccurrence of different filamentous fungi, including Aspergillus and Penicillium, in hazelnuts (Corylus avellana) (Lombardi et al, 2022) and another study reported that Pseudopithomyces chartarum, Cladosporium allicinum, and Alternaria sect co-occurred together with Botrytis spp., P. digitatum, and P. glabrum in the indoor environment of homes in Denmark depending on moisture conditions (Andersen al., 2021). The newly identified in our study play a key role in the process of fruit decay in kiwifruit through their interactions.…”