Bryothele
Bryothele Döbbeler, Nova Hedwigia 66(3-4): 337 (1998).
Index Fungorum number: IF 27881; Facesoffungi number: FoF 12143, 2 morphological species (Species Fungorum 2022), no molecular data available.
Biotrophic parasite on host. Sexual morph: Ascomata superficially on or between the leaves, (sub)globose, ovoid or conical, black, carbonaceous, without setae. Ostiole small, irregularly bordered, not visible as a light spot under light microscope. Excipulum without recognizable cells when seen from the outside; composed of thick-walled cells with small, tangentially extended, rounded lumina and merging walls, outer cells with very strong black thickenings. Interascal filaments with ramifications and anastomoses, connected to the inner excipular wall. Asci elongated ellipsoidal to claviform, thick-walled, 2- or 3-spored; degenerating spores not recognizable; discharged asci cylindrical, two separating wall layers not discernible. Iodine (LUG) negative. Ascospores ellipsoidal, 2-celled, at the septum sometimes slightly constricted, cells usually asymmetrical, brown, becoming darker in KOH, wall at both ends with a light, transverse, thin-walled ring in subterminal position; epispore smooth; 1(2) spores often oriented with the thicker cell towards the ascus foot. Hyphae colorless, with walls up to 2 μm thick, superficial, preferring the anticlinal host cell walls. Haustoria intracellular, corkscrew-like, with up to 8 coils, rich in plasmatic content, connected to the hypha of origin by a delicate about 1 µm wide hypha that perforates the host cell wall. Appressoria missing. Asexual morph: not observed (adapted from Döbbeler 2016).
Type species: Bryothele mira Döbbeler & Melnik
Notes: Bryothele is characterised by ovoid or conical, black, carbonaceous ascomata lacking setae, elongated ellipsoidal to claviform, 2- or 3-spored asci and ellipsoidal, two-celled brown ascospores becoming darker in KOH. Döbbeler (1998) placed Bryothele in Dothideomycetes, genera incertae sedis due to lack of molecular data. Bryothele resembles Meliolina in having similar ascomata, asci and interascal tissues, and light circular transverse bands within the brown spore walls. Bryothele differs from Meliolina in that the latter has three-septate ascospores with up to eight bands, the mycelium comprises superficial, brown hyphae at times forming mats and appressoria to penetrate the host stomatopodia. Meliolina also has pale intercellular hyphae and intracellular haustoria are unknown while Bryothele has intracellular haustoria (Döbbeler 2016). Bryothele lacks sequence data hence its systematic position within Dothideomycetes is not clear. Fresh collections with DNA sequence data are needed to confirm the generic placement of Bryothele.
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