Obliquifusoideum guttulatum W. Dong, Doilom and K.D. Hyde sp. nov. (Figure 6)

MycoBank number: MB 558199; Index Fungorum number: IF 558199; Facesoffungi number: FoF 09876;

Etymology: in reference to the guttulate ascospores of the fungus

Holotype: MFLU 18-1575

Saprobic on decaying wood submerged in freshwater. Sexual morph: Ascomata 100–120 µm high, 155–170 µm diam., scattered, superficial, ellipsoidal, black, coriaceous, ostiolate, with a lateral neck, ejecting asci and ascospores soon during incubation and becoming empty. Necks 160–180 µm long, 17–30 µm wide, hyaline to black, subcylindrical, oblique or horizontal to the host substrate. Peridium thin, 8–20 µm thick, soft, comprising several layers of pale brown, thin-walled cells of textura angularis, dark brown outwards. Pa- raphyses 3.5–5 µm wide, tapering towards the apex, dense, hypha-like, septate, unbranched, hyaline, embedded in a gelatinous matrix. Asci 97–110  x  7.3–7.7 µm (x = 105  x   7.5 µm, n = 10), 8-spored, unitunicate, cylindrical, slightly narrower and truncate at the apex, short pedicellate, with a small, distinct, refractive, barrel- or jar-shaped, apical ring, 2 2.7 µm, persistent. Ascospores 14–17.5 x 4.3–5 µm (x = 15.5 x 4.6 µm, n = 10), overlapping uniseriate, fusoid, straight or slightly curved, one median septate, with two additional obscure septate at two sides, guttulate, hyaline, thin and smooth-walled, without a gelatinous sheath. Asexual morph: undetermined.

Culture characteristics: on PDA, colony circular, reaching 8 mm diam. in 48 days at room temperature (25–30 C), surface rough, with dense mycelia, dry, rigid, umbonate from the side view, edge entire; from above, creamy at the margin, dark grey to dark brown at the middle, brown at the center; dark brown from below; not producing pigmentation in culture.

Material examined: THAILAND, Songkhla Province, Rattaphum District, Khao Phra Sub-District (70003” N 1000833” E), on decaying wood submerged in a stream originated from Borriphat Waterfall, 10 May 2018, W. Dong, hat138 (MFLU 18-1575, holotype), ex-type living culture MFLUCC 18-1233; ibid., HKAS 105007, isotype, ex-isotype living culture KUMCC 19-0023.

Habitat and distribution: stream is located in tropical rainforest in Southern Thailand with hot and humid climate conditions, shallow and clear, flowing slowly from the Borriphat Waterfall, surrounded by angiosperms.

Figure 6. Obliquifusoideum guttulatum (MFLU 18-1575, holotype). (a,b) ascomata lying on submerged wood; (c) section of ascoma; (d) peridium; (e) section of neck; (f) paraphyses; (g,h) unitunicate asci; (i,j) apical rings; (km) ascospoers (m ascospore in Indian Ink); (n,o) colony on PDA (up-front, down-reverse). Scale bars, (c) 50 µm; (d,f) 20 µm; (e) 30 µm; (g,h) 15 µm; (i,j) 5 µm; (km) 10 µm.