Gloeodiscus Dennis, Kew Bull.

Ariyawansa, Hiran A., Kang, Ji-Chuan, Alias, Siti A., Chukeatirote, Ekachai & Hyde, Kevin D., 2013, Towards a natural classification of Dothideomycetes: The genera Dermatodothella, Dothideopsella, Grandigallia, Hysteropeltella and Gloeodiscus (Dothideomycetes incertae sedis), Phytotaxa 147 (2), pp. 35-47 : 44-45

Gloeodiscus Dennis, Kew Bull. 15(2): 319, 1961.

MycoBank: MB 2080

Parasitic on leaves in terrestrial habitats. Ascomata solitary or scattered, semi-immersed or superficial, globose to subglobose, wall dark brown to black, coriaceous and spores release via a slit. Peridium comprising two layers, outer layer consisting of small, heavily pigmented, pseudoparenchymatous, dark brown cells, inner layer composed of wide, light brown cells of textura angularis. Hamathecium composed of cellular pseudoparaphyses, anastomosing between asci. Asci 8-spored, fissitunicate, ovoid to sub-cylindrical, with a short, broad pedicel, apically thickened and rounded with an ocular chamber. Ascospores cylindrical with narrowly rounded ends, hyaline, 4-septate, but breaking in to part spores, smooth-walled. Asexual state: unknown.

Type species: Gloeodiscus nigrorufus (Berk.) Dennis [as 'nigro-rufus'], Kew Bull. 15(2): 319. 1961. FIG. 5 A–M MycoBank: MB 331385

≡ Excipula nigrorufa Berk. , in Hooker, Bot. Antarc. Voy. Erebus Terror 1839–1843, Fl. nov.-zel.: 202. 1855.

≡ Scleroderris nigrorufa (Berk.) Sacc., Syll. fung. (Abellini) 8: 598. 1889.

≡ Durella nigrorufa (Berk.) Sacc., Syll. fung. (Abellini) 8: 794. 1889.

Parasitic on leaves in terrestrial habitats. Ascomata 170–190× 120–140 µm (x = 180× 125 µm, n = 10), solitary or scattered, semi-immersed or superficial, globose to subglobose, wall dark brown to black, coriaceous and spores released via a slit. Peridium 12–20 µm (x = 15 µm, n = 10) wide, comprising two layers, outer layer consisting of small, heavily pigmented, pseudoparenchymatous, dark brown cells, inner layer composed of wide, light brown cells of textura angularis. Hamathecium composed of dense, 2–4 µm diam (x = 3 µm, n = 10), hyaline, broad, cellular, septate pseudoparaphyses, anastomosing between asci. Asci 70–78× 15–25 µm (x = 75× 20 µm, n = 20), 8-spored, bitunicate, fissitunicate, ovoid to sub-cylindrical, with a short, broad pedicel, apically thickened and rounded with an ocular chamber. Ascospores 15–20× 5–9 µm (x = 16× 8 µm, n = 40) 2–3 overlapping seriate, cylindrical with narrowly rounded ends, hyaline, 4-septate, but breaking in to part spores, smooth-walled, thick-walled, without a sheath. Asexual state: unknown.

Notes: Berkeley (1855) introduced Excipula nigrorufa (basionym of Gloeodiscus nigrorufus ) in the order Helotiales , and Dennis (1961) referred the genus to Dothideomycetes , genera incertae sedis and typified the genus with Gloeodiscus nigrorufus . This classification was followed by Lumbsch and Huhndorf (2010) Gloeodiscus is characterized by cellular pseudoparaphyses and asci with a furcate pedicel and 4-septate ascospores that easily break into part spores. The ascomata are single with a thick peridium of heavily pigmented, pseudoparenchymatous, dark brown cells. This combination of characters does not fit well in any Dothideomycete families and therefore we retain this genus in Dothideomycetes , genera incertae sedis. Morphology coupled with molecular data is essential to show the correct placement of this unusual genus.

Material examined: New Zealand, on leaf of Pittosporum sp. , M.J. Berkeley ( K 174632 , holotype)

Figures

FIGURE 5. Gloeodiscus nigrorufus (holotype). A. Herbarium material. B. Ascomata on host substrate. C. Close up of ascoma. D. Section of ascoma. E. Close up of the peridium. F–G Asci bearing 8 ascospores stained in Melzer’s reagent. H. Apical part of asci. I. Short, broad pedicel of asci. J. Cellular, septate pseudoparaphyses. K. Ascospore stained in Congo red. L–M. Ascospores with narrowly rounded edges. Scale Bars: D = 130 µm, E = 25 µm, F–G = 30 µm, H–I = 10 µm, J = 75 µm, K–L = 5 µm