Abstract
We present the first major survey of regional diversity, distribution and host-association of Sepedonium. Whereas the rather scarce worldwide records of this mycoparasitic fungus suggested no specific distribution pattern of most species before, we provide new evidence of endemic and specific host-parasite guilds of Sepedonium in Southern South America, including the description of a new species. The corresponding inventory was performed in temperate central Chile. The regional landscape, a mosaic of exotic timber plantations and remnants of native Nothofagus forests, facilitates a unique combination of endemic and adventitious Boletales hosts. During a two-year survey, 35 Sepedonium strains were isolated and cultured from infected basidiomata of allochthonous Chalciporus piperatus, Paxillus involutus, Rhizopogon spp. and Suillus spp., as well as from the native Boletus loyita, B. loyo, B. putidus and Gastroboletus valdivianus. Taxonomic diagnosis included morphology of conidia and conidiophores, sequences of ITS, RPB2 and EF1 molecular markers and characteristics of in vitro cultures. Phylogenetic reconstructions were performed using Bayesian methods. Four Sepedonium species could be identified and characterized, viz.: S. ampullosporum, S. chrysospermum, S. laevigatum and the newly described species S. loyorum. The most frequent species on introduced Boletales was S. ampullosporum, followed by S. chrysospermum and S. laevigatum. S. loyorum sp. nov. was found exclusively on native boletacean hosts, separated from its closest relative S. chalcipori by micromorphological and molecular attributes. Species descriptions and identification keys are provided. Ecological and biogeographical aspects of endemic and allochthonous symbiotic units consisting of mycoparasite, ectomycorrhizal fungal host and respective mycorrhizal tree are discussed.
Highlights
Mycophilic fungi belonging to the anamorphic genus Sepedonium Link (Hypocreaceae, Ascomycota), teleomorph Hypomyces (Fr.) Tul. & C
Microorganisms 2021, 9, 2261 by Sepedonium spp., host structures are hardly ever visibly colonized by other parasitic microorganisms, not even by those known to be associated to Boletales [2]; this evident exclusion of competitors can be correlated with an arsenal of powerful antibiotic compounds like oligopeptides [3,4] and secondary metabolites [5], produced by the mycoparasite
The 35 Sepedonium strains sucessfully retrieved from different locations and hosts (Figure 1, Table S1), apart from molecular analysis, were characterized and identified based on diagnostic micromorphological attributes, viz.: phialoconidiophore branching, phialid length, size and shape of phialoconidia, size and ornamentation of aleurioconidia
Summary
Mycophilic fungi belonging to the anamorphic genus Sepedonium Link (Hypocreaceae, Ascomycota), teleomorph Hypomyces (Fr.) Tul. & C. Microorganisms 2021, 9, 2261 by Sepedonium spp., host structures are hardly ever visibly colonized by other parasitic microorganisms, not even by those known to be associated to Boletales [2]; this evident exclusion of competitors can be correlated with an arsenal of powerful antibiotic compounds like oligopeptides [3,4] and secondary metabolites [5], produced by the mycoparasite. The main diagnostic attributes have been shape, size and ornamentation of conidia, architecture of conidiophores and in vitro culture characteristics These morphological features are relatively few, not always discrete and most of them require the examination of live cultures, which may explain the low number of newly described species during most of the 20th century [6,7,8,9]. DNA-sequence-based phylogeny has proven a valuable tool to detect and separate new species like S. laevigatum [3,8,10]
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