Rosellinia chiangmaiensis Daranagama & K. D. Hyde, sp. nov.
Index Fungorum Number: IF 551728, Facesoffungi number: FoF 01638, Fig. 2b
Etymology – Referring to the province Chiang Mai, where the species was encountered.
Holotype – MFLU 15–3524

Saprobic on dead dicotyledonous wood. Sexual morph Stromata globose, with a pointed top, 1220 – 1400 × 800 – 1080μm (x̄ = 72.5 × 4.8 μm, n = 20), chestnut  brown, shiny, smooth, solitary, in small groups, uniperitheciate, surrounded by woolly to felty, pale yellow subiculum, confined to the stroma base, black entostroma, reduced at the base. Ostioles black, distinctively papillate, pointed. Ascomata globose, 400 – 500 × 500 – 600 μm (x̄ = 467 × 560 μm, n = 20). Peridium thick-walled, > 70 μm, carbonaceous. Hamathecium comprising long, dehiscent, filamentous, few paraphyses, 2 μm wide, longer than asci. Asci 150 – 200 × 4.5 – 6.4 μm (x̄ = 172 × 5.2 μm, n = 20), 8-spored, unitunicate, cylindrical, short pedicellate, apical narrowly rounded, with a J+, inverted hat-shaped, apical apparatus, upper width 4 – 6 μm, lower width 2 – 3 μm, with rounded bulge at upper rim. Ascospores 70 – 90 × 7 – 10 μm (x̄ = 84 × 9 μm, n = 20), overlapping uniseriate, dark brown, elongate fusiform, with acute ends, with thin mucilaginous sheath, germ slit and appendages absent.

Culture characteristics – Colonies on Difco OA plates at 25 – 28 °C reaching 5 cm edge of Petri-dish in 2 – 3 weeks, at first citrine, felty, azonate, with diffuse margins, reverse turning yellow.

Material examined – THAILAND, Chiang Mai Province, garden of Mushroom Research Center, on decorticated bark of a fallen log, 17 August 2014, Anupama Daranagama, AXL 342 (MFLU 15–3524, holotype, HKAS 92486, isotype), extype living culture, MFLUCC 15–0015, KIBCC.

Notes – Rosellinia chiangmaiensis is reminiscent to R. macrosperma Speg. and R. procera Syd. & P. Syd. because its large length: width ascospore ratio, lacking germ slits and generally large stromata more than 1 mm high (Petrini 2013). However the new species possess longer ascospores with thin mucilaginous sheath with acute ends and a white to pale yellow subiculum restricted to the stromatal base. These characters make this species unique from other known, morphologically similar species. According to the description by Petrini (2013) this new species belongs to the R. emergens group, which is a phylogenetically heterogeneous group. The reconstructed phylogenetic trees for the family Xylariaceae (Fig. 1) and the genus Rosellinia (Fig. 2a) confirmed the placement of Rosellinia chiangmaiensis with high bootstrap support.

Fig. 1 One of four MPTS inferred from combined β-tubulin and α- actin gene dataset generated with maximum parsimony and Bayesian analysis. Maximum parsimony bootstrap value greater than 50 % and Bayesian posterior probabilities greater than 0.95 are given above and below each clade, respectively. The internodes that are highly supported by bootstrap (100 %) and posterior probabilities (1.00) are shown as a thicker line. New taxa are in blue and ex-type strains in bold.

Fig. 2 a Phylogram generated from RAxML analysis based on ITS sequenced data of Rosellinia. Maximum Likelihood values equal or greater than 50 are indicated above or below the nodes and branches. The tree is rooted with Xylaria hypoxylon. Newly introduced taxa in this study are highlighted in blue and ex-type strains are in bold. b Rosellinia chiangmaiensis (holotype) a Ascomata in host surface b Papillate ostioles c Side view of ascomata d Cross section through stroma e Vertical section of stroma f, g Asci with J+, apical apparatus in Melzer’s reagent h, i Asci in water j, k Ascospores in water. Scale bars: a = 500 μm, b, c = 1000 μm, d, e = 200 μm, f,g = 10 μm, h, i = 50 μm, j, k = 30 μm.