Fungal biodiversity associated to alpine peatlands in northern Italy

Peatlands are waterlogged areas where the rate of organic matter (OM) accumulation is greater than the rate of OM decomposition, thus resulting in the formation of peat, a complex material that consists of partly fossilized plant residues. Peatlands can be found in the arctic, boreal, temperate and tropical zones, and support a unique biodiversity in terms of plants, animals and microorganisms (bacteria, filamentous fungi and yeasts). Fungi are the main responsible for the degradation of recalcitrant peat components; on the opposite, yeasts are involved in the utilization of simple carbon compounds and are generally considered secondary saprotrophs. However, their ecological roles in this ecosystem still need to be clarified (Thormann 2006, 2007; Rydim et al. 2013; Juan-Ovejero et al. 2020). The aim of this work was to isolate and identify the culturable fungal community (filamentous fungi and yeasts) from peat. Samples were collected from two alpine peatlands (Northen Italy) at different depths, diluted 1:10 and plated on YM agar, supplemented with sodium propionate to inhibit filamentous fungi growth, and PDA agar. The identification was carried out with single or multi-locus sequences (LSU, ITS, benA, RPB2, tef1, ACT, GPDH3, HSP60). A total of 26 filamentous fungi and 12 yeasts were isolated. The fungal taxa isolated from peatlands represent species that play fundamental roles in the OM decomposition. Some species rely on carbohydrates that leach out from plant tissues (e.g., Cladosporium, Aureobasidium), together with pioneer saprobes of OM derived from plant residues (e.g., Linnemannia, Mortierella, Mucor). Other taxa were identified as polymer degraders (e.g., Fusarium, Trichoderma). On the other hand, taxa associated with high activity in the degradation of recalcitrant polymers (e.g., lignin) were not detected; in fact, the isolates were mainly filamentous ascomycete fungi, whereas lignin degradation is primarily carried out by basidiomycetes. In addition, several plant pathogens were detected (Fusarium commune, Didymella pomorum, Cadopohora luteo-olivacea, Zymoseptoria sp.). Yeasts were also recovered, and most of them corresponded to taxa previously reported from peatland environments (e.g., Cyberlidneria, Rhodotorula). Notably, the occurrence of the species filamentous fungi and yeasts species (such as D. pomorum, Solicoccozyma aquatica, and Phaeotremella ovata) represents a new record for this ecosystem. Furthermore, phylogenetic analyses showed that seven filamentous fungal taxa (Chlamydocillium sp., Coniella sp., Myriosclerotinia sp., Cladosporium sp., Talaromyces sp., Coniochaeta sp., Zymoseptoria sp.) and two yeasts (Halobasidium sp. and Sterigmatospora sp.) could not be assigned to any recognized species. Overall, this study revealed the fungal biodiversity associated with alpine peatlands in Italy, with particular emphasis on the isolation of taxa not previously recovered from similar environments, as well as putative new species.