Hysteriales » Hysteriaceae » Rhytidhysteron

Rhytidhysteron thailandicum

Rhytidhysteron thailandicum Thambug. & K.D. Hyde, Cryptog. Mycol. 37(1): 110 (2016) Facesoffungi number: FoF 01841


Sexual morph: Ascomata 1300–1700 μm long × 380–790 μm high × 1160–1815 μm wide ( = 1500 × 585 × 1505 μm, n = 10), hysterothecial with a longitudinal slit, black, solitary to aggregated, semi-immersed to superficial, with irregular opening when wet, folded at the margin when dry, with striation, subiculum, coriaceous, yellow at the center, forming an elongate slit. Exciple 50–100 μm ( = 75 μm, n = 15), composed of textura angularis, comprising two cell layers, outer layer comprising black, thick-walled cells, inner layer comprising dark reddish to hyaline, thin-walled cells. Hamathecium comprising 1.–2.3 μm wide, dense, septate, filiform, cellular pseudoparaphyses, forming epithecium above the asci and enclosed in a gelatinous matrix. Asci 140–157 × 10–12 μm ( = 150 × 11 μm, n = 15), 8-spored, bitunicate, subcylindrical to cylindrical, with a short pedicel, apically rounded with an ocular chamber. Ascospores 21–25.5 × 7.5–9.6 μm ( = 23.5 × 8.7 μm, n = 20), uni-seriate, partially overlapping, hyaline to pale brown, becoming pale brown to dark brown, initially subglobose, 1-septate, slightly constricted at the central septum, becoming 3-septate, ellipsoidal to fusiform, slightly rounded or pointed at both ends, guttulate, without a mucilaginous sheath. Asexual morph: Undetermined (see Thambugala et al. 2016 for the type).

Culture characteristics: Ascospores germinating on PDA within 24 h and germ tubes produced from one or both ends or second or third cells. Colonies on PDA filamentous to irregular in shape, undulate edge, flat, initially white, becoming grey.

Host and habitat: on dead twigs of Afzelia xylocarpa (Hyde et al. 2020), on dead twigs (Thambugala et al. 2016), on dead twigs of an undetermined tree (Hyde et al. 2020), dead wood (Yacharoen et al. 2015).


Known distribution: Thailand, Chiang Rai Province (Thambugala et al. 2016, Hyde et al. 2020), Thailand, Phitsanulok Province (Yacharoen et al. 2015), China, Yunnan Province, Qujing City (Hyde et al. 2020).


Material examined: Thailand, Chiang Rai Province, Mae Suai District, on dead twigs of Afzelia xylocarpa (Leguminosae), 20 November 2012, M. Doilom (MFLU 19–2701, new host record), living culture (MFLUCC 13–0051).


GenBank Accession No: ITS: MN509433, LSU: MN509434, tef1: MN509435.


Notes: The holotype of Rhytidhysteron thailandicum has been reported from a dead twig in Thailand (Thambugala et al. 2016). Our collection has similar morphologies to the holotype (Thambugala et al. 2016) in its clavate to cylindrical asci, ellipsoidal to fusiform ascospores with 3 septa, but they are different with regards to the hysterothecia on host substrate along with their sizes. In combined analysis of sequence data of LSU, ITS and tef1of our strain (MFLUCC 13–0051) clusters with R. thailandicum (MFLUCC 14–0503, ex-type) and (MFLUCC 12–0530) with high bootstrap and Bayesian probabilities (100% ML/ 1.00 PP) (Hyde et al. 2020). Thus, we identify our collection as R. thailandicum. This is the first record of R. thailandicum on Afzelia xylocarpa.