Obba thailandica

Obba thailandica G.J. Ren & F. Wu

MycoBank MB 819393; Facesoffungi number FoF 02866.

Basidiocarps annual, resupinate, easily separated from substrate, soft and waxy when fresh, without

odour or taste, becoming bond hard when dry, up to 10 cm long, 6 cm wide and 1.2 mm thick at centre. Pore surface white when fresh, 7C2 pale mouse-grey to 19C2 ash-grey white when dry; sterile margin narrow, thinning out, up to0.5 mm; pores round, 5–7 per mm; dissepiments fairly thick, tomentose, entire to slightly lacerate. Subiculum white, cartilaginous when dry, extremely thin to almost lacking, less than 0.1 mm thick. Tubes paler than pore surface, resinous, up to 1.2 mm long. Hyphal system monomitic with generative hyphae bearing clamp connections, weakly dextrinoid, CB–, tissue unchanged in KOH. Subicular hyphae hyaline, thin-walled with a distinct lumen, frequently branched and bearing clamp connections, slightly agglutinated, sometimes covered with small crystals, loosely interwoven, 1.5–3 μm in diam. Tramal hyphae hyaline, thin-walled with a wide lumen, occasionally branched, frequently bearing clamp connections, slightly agglutinated, loosely interwoven, 2–3 μm diam. Cystidia absent, cystidioles frequently present, fusoid, spindle-shaped or fusiform, sometimes with a few small guttules; basidia broad clavate, with four sterigmata and a clamp connection at the base, 13–14 × 7–9 μm; basidioles in shape similar to basidia, but slightly smaller and sometimes with a few small guttules. Basidiospores subglobose to globose, hyaline, thin-walled, smooth, mostly with a large guttule, IKI–, CB–, (4.4–) 4.8–5.8(–6.5) × (3.9–)4.0–4.9(–5.1) μm, L = 5.16 μm, W = 4.22 μm, Q = 1.20–1.25 (n = 90/3).

Additional specimens examined (paratypes):Thailand. Chiang Rai Region, on charred wood of Pinus, 22 July 2016 Dai 16659 (BJFC022519, MFLU), Dai 16664 (BJFC022520, MFLU).