Dothideomycetes families incertae sedis » Cookellaceae

Pycnoderma

Pycnoderma Syd. & P. Syd., Annls mycol. 12(6): 563 (1914).

Index Fungorum number: IF 4565; Facesoffungi number: FoF 07959, 2 morphological species (Species Fungorum 2022), no molecular data available.

Epiphytes on leaves. Sexual morph: Thyriothecia clustering together as rounded or irregular darkened regions, superficial, subglobose or irregular, surface rough, flattened, opening by fracture of the upper wall. Upper thyriothecial wall comprising radially arranged, angular or cuboid cells, with brown to dark brown walls. Hamathecium lacking pseudoparaphyses. Asci 8-spored, bitunicate, fissitunicate, oblong to subglobose, apedicellate, with narrow and wide ocular chamber, or ocular chamber lacking. Ascospores 2–3-seriate, ellipsoid, muriform with 3 transverse septa, and 1–2 longitudinal septa, slightly constricted at each septum, upper cells wider and shorter than lower cells, hyaline to pale brown, smooth-walled. Asexual morph: Unknown (adapted from Hongsanan et al. 2014).

 Type species: Pycnoderma bambusinum Syd. & P. Syd.

Notes: Pycnoderma is characterised by superficial, subglobose or irregular thyriothecia, oblong to subglobose, apedicellate asci and ellipsoid, muriform ascospores with 3 transverse septa and 1–2 longitudinal septa. Hyde et al. (2013) treated Pycnoderma in Brefeldiellaceae but also referred it to Cookellaceae in the same work. Hongsanan et al. (2014) re-examined the syntype specimen of P. bambusinum (S, F7745!) and agreed on its placement in Cookellaceae based on the grouped thyriothecia with rough, pigmented surface. Pycnoderma resembles Saccardinula in having muriform ascospores, but differs in having less well-developed thallus (Spegazzini 1885), while thyriothecia of Pycnoderma are grouped together with globose asci. Pycnoderma also resembles members of Elsinoe in having globose asci but differs in that Elsinoe have wart-like ascostromata, which are small, white to pale yellow or brown, soft, and multi-loculate (Hyde et al. 2013). Pycnoderma is a distinct genus in Cookellaceae. Fresh collections with DNA sequence data are needed to confirm this placement. Pycnoderma needs epitypification.

 

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