Dichostereum eburneum S.H. He & S.L. Liu

Liu, Shi-Liang & He, Shuang-Hui, 2018, Taxonomy and phylogeny of Dichostereum (Russulales), with descriptions of three new species from southern China, MycoKeys 40, pp. 111-126 : 119-120

Dichostereum eburneum S.H. He & S.L. Liu sp. nov. Figs 2c, 5, 6c

Typification.

CHINA. Fujian Province, Wuyishan County, Wuyishan Nature Reserve, on bark of living Castanopsis , 6 Apr 2018, He 5374 (holotype, BJFC, ITS GenBank accession number: MH538318; isotype in CFMR).

Etymology.

" eburneum " referring to the white colour of hymenophore.

Basidiomata.

Perennial, resupinate, effused, closely adnate, inseparable from substrate, coriaceous, at first as irregular small patches, later confluent up to 7 cm long, 2 cm wide, 200-500 µm thick. Hymenophore surface smooth, white (5A1), orange white (5A2) to greyish-orange [5B(3-4)], cracking with age; margin thinning out, concolorous with hymenophore.

Microscopic structures.

Hyphal system dimitic. Context thickening, compact, composed of generative hyphae, dichohyphae, embedded basidiospores and abundant crystals. Generative hyphae rare, with clamp connections, hyaline, thin- to slightly thick-walled, 2-3 µm in diam. Dichohyphae dominant, hyaline to yellow, distinctly thick-walled, dextriniod, frequently branched, aseptate, 1-2 µm in diam. Catahymenium composed of dichohyphae, gloeocystidia, basidia and basidioles. Dichohyphae in this layer abundant, hyaline to pale yellow, distinctly thick-walled, strongly dextriniod, dichotomously branched with acute terminal tips, 15-30 μm across, 2-4 µm wide at lowest part. Gloeocystidia abundant, fusiform to subclavate, hyaline, thin-walled, with solidified contents, 20-50 × 5-10 µm. Basidia subcylindrical with basal part slightly swollen, hyaline, thin-walled, with 4 sterigmata and a basal clamp connection, 30-45 × 6-9 µm; basidioles in shape similar to basidia, but slightly smaller. Basidiospores subglobose with a distinct apiculus, hyaline to pale yellowish-brown in KOH, thick-walled, strongly amyloid, 6-7 (-8) µm in diam.; walls ornamented with dense, large warts and crests.

Remarks.

Dichostereum eburneum is characterised by the pale basidiomata on bark of living tree, the presence of abundant crystals in context and basidiospores with dense and large ornamentations. Ecologically and macroscopically, D. eburneum resembles Dendrothele Höhn. & Litsch., but the microscopic features are largely different ( Nakasone and Burdsall 2011). Dichostereum kenyense Boidin & Lanq. is similar to D. eburneum by sharing the large ornamentations of basidiospores, but differs in having wider span of dichohyphae, slightly larger basidiospores (7-8 µm) and a distribution in Africa ( Boidin and Lanquetin 1980).

Key to 5 species of Dichostereum in China