Durotheca macrostroma Srikitik., Wongkanoun & Luangsa-ard, sp. nov.
Index Fungorum number: IF 551628, Facesoffungi number: FoF 02033, Fig. 1
Etymology – based on the large stroma when compare with other Durotheca species.
Holotype – BBH39917

Saprobic on bark of dead Castanopsis acuminatissima (Blume) A.DC. Sexual morph Stromata superficial, solitary, subglobose 1 cm thick × 2.3 – 2.4 cm diam., stromata surface smooth, chalky white, creamy, owing to the presence of a thin pruina, when mature surface greyish green (28C3), crust and tissue highly carbonaceous, with beveled margin. Perithecia completely immersed, usually monostichous, globose-ovoid, 1.8 – 2 mm high × 0.8 – 1 mm diam. Ostioles umbilicate/lower than stromatal surface. Paraphyses not observed. Asci 8-spored, deliquescing, mature asci not observed, young asci 77 – 93.5 × 11 – 13 μm, cylindrical, and long stalked, apical apparatus lacking, and no reaction with Melzer’s reagent. Ascospores light brown, unicellular, oblong to allantoid in side view, smoothwalled, (13–) 14 – 16 (–17.5) × (5–) 6 – 7 (–8) μm (x̄ = 15.03 × 6.67 μm, n = 54), germ slit lacking; perispore nondehiscent in 10 % KOH. Asexual morph Undetermined.

Culture characteristics – Colony on PDA reaching 49 – 51 mm diam. in 10 days, the culture produced botryose structures from the type and paratypes after 4 weeks. Mycelia initially white and fluffy, turning to yellow brown after 2 weeks.

Material examined – THAILAND, Chaiyaphum, Phu Khiao Wildlife Sanctuary, 12 August 2015, on Castanopsis acuminatissima wood (Fagaceae), P. Srikitikulchai & S. Wongkanoun (BBH39917, holotype); ex-type living culture, BCC78380.

Distribution – Only known from a single site in Phu Khiao Wildlife Sanctuary in northeastern Thailand.

Notes – Molecular phylogenetic analyses of combined β- tubulin and α-actin gene datasets based on maximum parsimony and Bayesian analysis has placed D. macrostroma in Durotheca. Durotheca macrostroma differs from other Durotheca species in having a large stroma; the shape of D.macrostroma is subglobose, 10 mm thick, while other species are widely effused-pulvinate and are not over than 2.5 mm thick. The ascospores of D. macrostroma are smaller than other Durotheca species. In addition, the phylogenetic tree supported the position of D. macrostroma as closely related to D. rogersii with 100 % bootstrap support. They differ in the shape of stromata and ascospore shape and size. Durotheca rogersii has a widely effused-pulvinate 2.5 mm thick stroma (Ju et al. 2007), while that of D. macrostroma is very thick (10 mm) and subglobose. Ascospores of D. rogersii have very thick walls (3 – 4.5 μm) and are larger (25 – 36 × 19 – 24 μm) than D.macrostroma, but all lack a germ slit.

Fig. 1 Durotheca macrostroma (holotype) a Stroma on bark b Stroma surface and ostiole, arrow: ostioles c Ascospore release on apex of ostioles, arrow: black spore mass d Young asci e Perithecium f Botryose structures produced in culture g – i Ascospores j Colony on PDA plate after 2 weeks. Scale bars: d = 5 μm, e = 0.25 mm, g – i = 5 μm, f = 10 μm, j = 1 cm.