Helicoma fagacearum Boonmee & K.D. Hyde, sp. nov.,MycoBank: MB 804557.

Etymology: in reference to its occurrence on Fagus.

Holotype: MFLU11–0138

Saprobic on dead wood. Sexual state:Ascomata 256–300(-324) µm high × 235–258(-265)µm diam. (= 282 × 251 µm), superficial,solitary, scattered, with a subiculum composed of dark brown hyphae,withblack stalk, globose to subglobose, broadly ellipsoid-ovate, yellowish or brownish, pale brown, ostiolate, collapsing, brown when dry.Peridium 43–51 µm wide, comprising several layers of angular and prismatic cells, with inner cells pale brown, with outer cells reddish-brown to brown. Hamathecium with numerous,ca. 1.5 µm wide,filiform, septate, branched,hyaline pseudoparaphyses. Asci (121-)134–160(-179) × 10–14 µm ( = 144 × 12 µm, n = 20), 8-spored, bitunicate, elongate-cylindrical, apically thickened when young, pedicellate, rounded at apex. Ascospores (63-)71–86.5 × 4–6.5 µm ( = 78 × 5 µm, n = 20), overlapping 2–3-seriate, cylindric-fusiform, tapering towards rounded ends, straight to slightly curved, 9–12(-13)-septate, not constricted at septum, hyaline, pale brown at maturity, guttulate when young, smooth-walled. Asexual state: Unknown.

Cultural characteristics: Ascospores germinating on MEA within 12 h and germ tubes produced at both ends. Colonies growing on MEA slowly, reaching less than 5 mm in 7 days at 28C, slightly convex on surface, with undulating margin, white or pale brown to dark brown, turning dark with age, asexual spores not formed within 60 days.

Material examined: THAILAND, Chiang Rai, Muang, Doi Pui, elev. ca. 403–936 msl., on dead wood of Fagaceae,10 May 2011, Saranyaphat Boonmee, DP-04 (MFLU11–0138 holotype; PDD 104456 isotype); ex-type living culture = MFLUCC11–0379 = BCC 52030 = ICMP 20071.

Notes: Helicoma fagacearum was found on wood of Fagaceae in northern Thailand. Morphologically, this species is similar to Helicoma miscanthiin its coloured ascomata with yellowish white surface, brown peridium and pale brown ascospores. An asexual morph did not develop in culture. Our phylogenetic study showsthat Helicoma fagacearum groups with Helicomasensu stricto (Clade A, Fig. 2) with a good support (89% BS and 0.99 PP).

Fig. 1 Helicoma fagacearum (MFLU11–0138, holotype). a Ascomata on substrate. b L.S. of ascoma. c Peridium. d Pseudoparaphyses. e-g Asci. h-j Ascospores. k Germinating ascospore. l, m Colonies on MEAfrom surface and reverse. Asexual state not produced. Scale bars: a-b=100µm, c=40µm, d=5µm, e-g=50µm, h-k=20µm, l-m=10mm