Placothyrium Bubák, Ber. dt. bot. Ges. 34: 302 (1916)
Facesoffungi number: FoF 07497
Ascomycota, genera incertae sedis
Saprobic on dead stems of Athyrium filix-femina (Athyriaceae). Sexual morph: undetermined. Asexual morph: Conidiomata dark brown, stromatic, pycnidial, solitary to gregarious or confluent, epidermal to subepidermal, immersed, globose to subglobose in section view, unilocular or occasionally multilocular, glabrous. Ostiole indistinct, dehiscence by irregular rupture of the apical wall. Conidiomatal wall composed of thick-walled, dark brown to hyaline cells of textura angularis. Conidiophores arising from the inner wall layer of conidiomata, hyaline, cylindrical to irregular, branched at the base and above, septate, smooth-walled, invested in mucus. Conidiogenous cells hyaline, holoblastic, cylindrical to lageniform or irregular, integrated, determinate, smooth-walled, terminal or lateral immediately below transverse septa. Conidia hyaline, filiform, tapered towards each end, 0–2-septate, smooth-walled (Sutton 1980).
Type species: Placothyrium athyrinum Bubák, Ber. dt. bot. Ges. 35(3): 302 (1917)
Notes: Placothyrium shows a similar conidial morphology with the asexual morph of Sphaerulina (such as S. oxyacanthae, S. rhabdoclinis), Pleurothyrium and Septoria as it has hyaline, filiform, septate conidia (Sutton 1980, Quaedvlieg et al. 2013). Placothyrium and Pleurothyrium have conidiophores, which are absent in the asexual morph of Sphaerulina and Septoria. Pleurothyrium differs from Placothyrium by its conidiophores without a gelatinous sheath covering and up to 8-septate, much longer conidia (Sutton 1980). Placothyrium is monotypic and no molecular data is available for this genus. Fresh collections are needed to place it in a natural group.
Distribution: Germany (Sutton 1980).
Placothyrium athyrinum (redrawn from Sutton 1980) a Vertical section of conidioma. b Conidiophores, conidiogenous cells and developing conidia. c Conidia.
Li WJ, McKenZie EHC, Liu JK, Bhat DJ, Dai DQ, Caporesi E, Tian Q, Maharachcikumbura SSN, Luo ZL, Shang QJ, Zhang JF, Tangthirasunun N, Karunarathna SC, Xu JC, Hyde KD (2020) Taxonomy and phylogeny of hyaline-spored coelomycetes. Fungal Diversity 100: pages279–801.