Occultibambusa fusispora Phookamsak, D.Q. Dai & K.D. Hyde, sp. nov. Index Fungorum number: IF552017
Etymology: The epithet Bfusispora^ refers to the fusiform ascospores.
Holotype: MFLU 11–0163
Saprobic on dead bamboo culm. Sexual morph: Ascomata 135–185 μm high, 240–275 μm diam., scattered, gregarious, subpepidermal, semi-immersed to erumpent through host surface, raised, brown to dark brown, with black papillate dots, conical with wedged sides, uni-loculate, ostiole central with minute papilla. Peridium 7–60 μm wide, pseudostromatic, with thinto thick-walled cells of unequal thickness, slightly thick at the sides and towards apex, poorly developed at the base, composed of several layers of small, brown to dark brown, textura angularis to textura prismatica pseudoparenchymatous cells. Hamathecium composed of dense, broad, 1.8–2.7 μm wide, filamentous, distinctly septate, cellular pseudoparaphyses, not constricted at the septa, anastomosing at the apex, embedded in a gelatinous matrix. Asci (60–)65–90(−110) × (11–)12– 14(−15)(−16) μm (x = 75.6 × 13.2 μm, n = 30), 8-spored, bitunicate, fissitunicate, clavate to cylindric-clavate, short pedicellate, with furcate to obtuse ends, apically rounded with well-developed, ocular chamber. Ascospores (20–)22–25(−26) × 5–6(−6.5) μm (x = 23.9 × 5.7 μm, n = 30), overlapping, bi-seriate, fusiform, with acute ends, light brown, mostly 1-septate, rarely 2–3-septate, not constricted at the septum, slightly curved, smooth-walled. Asexual morph: Coeloemycetous, produced on bamboo pieces on WA after 12 weeks. Conidiomata 160–250 μm high (including beaks), 500–800 μm diam., eustromatic, subepidermal, solitary to gregarious, clustered, visible as raised, black, elongate spikes, covered by sparse hyphae on bamboo pieces, elongate irregular in shape, multi-loculate, glabrous, ostiolate with long beaked papilla. Locules 140–250 μm high (including neck), 110–230 μm diam., gregarious, clustered, immersed in cortex of host to erumpent through host surface by papilla, conical to ampulliform, or irregular-shaped. Neck 50–195 μm high 50–100 μm diam., in each locule, ostiole central, slightly oblique, with short to long beaks. Wall of conidiomata 10–45 μm wide, thin- to thick-walled, of unequal thickness, thick at the sides and base of pycnidia, composed of several layers of dark brown to black, textura angularis to textura prismatica pseudoparenchymatous cells, with host cells and fungal tissue. Conidiophores reduced to conidiogenous cells. Conidiogenous cells (6–)7–12(−15) × 2–4 μm (x = 10.2 × 2.7 μm, n = 30), enteroblastic, phialidic, determinate, discrete, cylindrical to ampulliform or lageniform, hyaline, aseptate, apically attenuated, with indistinct periclinal thickening, smooth-walled. Conidia (14–)15– 17(−19) × 4–5(−5.5) μm (x = 16.5 × 5.2 μm, n = 30), oblong to cylindrical, with rounded ends, hyaline, aseptate, smooth-walled, with large guttules.
Culture characters: Colonies on MEA fast growing, 55– 60 mm diam. after 4 weeks at 25–30 °C, under 12 h light/12 h dark, colonies irregular, dense, flat, slightly raised, dull to rough, with undulate edge, velvety, radiating, wrinkled and folded at the margin, green to brown greenish at the margin, dull green to white-grey at the centre from above, brown greenish at the margin, dark greenish to black at the centre from below, no pigments on PDA.
Material examined: THAILAND, Chiang Rai Province, Mae Fah Luang District, Doi Tung, on dead branch of bamboo, 29 June 2010, R. Phookamsak, RP0043 (MFLU 11– 0163, holotype), ex-type living cultures, MFLUCC 11– 0127, KUMCC.
Notes: Morphologically, Occultabambusa fusispora is similar to O. bambusae in having clavate asci and fusiform, brown ascospores. However, they differ in the size of asci and ascospores, ascospore septation, sheath surrounding the ascospores and asexual morph. Occultabambusa fusispora has longer asci (60–110 μm vs. 50–90 μm) and smaller ascospores (22–25 × 5–6 μm vs. 23.5–27.5 × 4.5–7 μm). In addition, O. fusispora has 1–3-septate ascospores, lacks a mucilaginous sheath. Occultabambusa bambusae has 1-septate ascospores with a mucilaginous sheath. Based on multi-gene phylogenetic analyses (Fig. 13), O. fusispora forms a robust clade which is distinct from O. bambusae (95 % MLBP, BYPP greater than 0.90). Therefore, we introduce a second species in the genus Occultabambusa.
FIG. Occultibambusa fusispora (MFLU 11–0163, holotype). a Appearance of ascostromata on host surface. b Vertical section through ascostroma. c Section through peridium. d Asci with pseudoparaphyses. e–h Asci. i–m Ascospores. n Pycnostroma produced on bamboo pieces on WA. o Section through pycnostroma. p Pycnidial wall. q–s Conidiogenous cells. t–x Conidia. Scale bars: o = 200 μm, b = 100 μm, c = 50 μm, d–h, p = 20 μm, i–m, q–s = 10 μm, t–x=5 μm