Posidoniomyces Vohník & Réblová, in Vohník et al., MycoKeys 55: 72 (2019).
Index Fungorum number: IF 830267; Facesoffungi number: FoF 08151, 1 morphological species (Species Fungorum 2022), 1 species with molecular data.
Root mycobiont of the dominant and endemic Mediterranean seagrass Posidonia oceanica. Sexual morph: Unknown. Asexual morph: In vivo, hyphae brown, septate, forming intracellular microsclerotia in the hypodermis of the terminal fine roots and finger-like pseudoparenchymatous net on the surface of these roots, i.e. a colonization pattern resembling the DSE association ubiquitous in the roots of terrestrial plants. In vitro, two distinct colonial morphotypes termed compact and mycelial formed consistently. Colonies brown, mycelium composed of septate, hyaline, sub hyaline to pigmented hyphae with intercalary, terminal, rarely lateral, one-celled globose, subglobose to ellipsoidal swellings that are prominent especially on the surface of the compact colonies. (adapted from Vohnik et al. 2019).
Type species: Posidoniomyces atricolor Vohník & Réblová
Notes: Posidoniomyces is characterised by hyphal morphology mainly brown, septate hyphae in vivo forming intracellular microsclerotia in the hypodermis of the terminal fine roots and brown mycelium composed of septate, hyaline, subhyaline to pigmented hyphae in vitro. Posidoniomyces forms root-symbiotic relationship with saprobic lignicolous marine fungi from estuarine milieus inhabiting wood and roots of mangroves (Vohník et al. 2019). Posidoniomyces is morphologically and phylogenetically a distinct genus in Aigialaceae. Molecular markers available for Posidoniomyces are ITS, LSU, SSU and RPB2.