Stigmatodiscus labiatus – Sociedad Ibérica de Micología

Stigmatodiscus labiatus Voglmayr & Pintos, Mycol. Progress 17(10): 1192. 2018.

MycoBank MB827487

AUTHORS: Pintos A. & Voglmayr H.

Taxonomic classification

phy Ascomycota

sbp Pezizomycotina

cls Dothideomycetes

sbc

ord Stigmatodiscales

fam Stigmatodiscaceae

gen Stigmatodiscus

sp Stigmatodiscus labiatus

Description

Ascomata hysteriform, scattered, rarely gregarious or confluent, corticolous, erumpent through the periderm, in face view (275–)380–1000(–1610) μm long, (145–)200–350(–570) μm wide ( n=51), with sides consisting of usually two, rarely three black lips (peridium), (45–)90–170(–200) μm wide (n=50), with a narrow central slit, usually closed when dry and not exposing the blackish elongated disc. Bark tissues not visibly altered, no black line visible in bark or wood. Peridium coriaceous, pseudoparenchymatous, black, up to 130 μm thick at the apex, 17–31μm thick at the sides, almost absent to 10 μm thick at the base, composed of small angular to rounded, dark brown, thick-walled cells 4–8 μm diam. Hamathecium composed of hyaline, septate, filiform branched paraphyses 1.7–3 μm wide, embedded in a tough hymenial gel, simple, not anastomosing, 82–130 μm long, longer than asci, swollen at their apices up to 4 μm and incrusted with dark brown granules forming an epithecium, neither staining blue in Lugol nor in Melzer’s reagent after pre-treatment with 3% KOH. Asci (67–)78–103(– 108)×(41–)43–59(–71) μm( n=18), bitunicate, broadly ellipsoid to globose, almost sessile, with a distinct apical chamber, thick-walled, typically containing 8 irregularly bi- to triseriate ascospores, very stable, fissitunicate dehiscence not observed. Ascospores (34.5–)38–43(–47.5)×(13.8–)15.5– 17.5(–19.3) μm, l/w=(2.2–)2.3–2.6(–2.8) (n=84), brown, asymmetric, broadly fusiform, straight, 1-septate, strongly constricted at the septum, each hemispore surrounded by a separate gelatinous sheath quickly dissolving in water, upper cell slightly broader, with broadly rounded ends and distinctly constricted in the middle with a ring-like thickening inside; wall finely verruculose, brown, the contents granular, usually with a large and several smaller guttules per cell.

Conidiomata on the natural substrate associated with ascomata, visible as minute black dots 80–160 μm in diam, immersed, peridermal, pycnidial, unilocular, of circular shape, opening with a central ostiole, 100–200 μm diam, marginal wall thin, ca. 10 μm, composed of subhyaline to light brown cells, wall around ostiole ca. 22–50 μm thick, composed of dark brown cells. Conidiophores short, branched up to three times. Condiogenous cells phialidic, cylindrical, (8.5–)9.0– 12.3(–15.5)×(1.5–)1.7–2.3(–2.7) μm( n = 50). Conidia (14–)17–20(–22)×(0.9–)1.1–1.4(–1.7) μm( n=36), hyaline, falcate to semicircular, aseptate. Cultures slow-growing, with uneven lobed margins, colony on CMD reaching 42 mm diam after 42 day sat 16°C, first whitish,turning medium to dark red brown,with sparse lighter brown aerial mycelium in the centre, reverse zonate, dark brown in the centre, with medium and dark red brown concentric zones towards the margins, entire culture black after 6 months. No conidiomata seen in pure culture.