Roseodiscus sinicus H.D. Zheng & W.Y. Zhuang, 2013

ZHENG, HUAN-DI & ZHUANG, WEN-YING, 2013, A new species of Roseodiscus (Ascomycota, Fungi) from tropical China, Phytotaxa 105 (2), pp. 51-57 : 53

Roseodiscus sinicus H.D. Zheng & W.Y. Zhuang , sp. nov. ( Figs 1−3

MycoBank MB564249

Differs from Roseodiscus equisetinus in smaller asci and smaller ellipsoid ascospores, and from R. subcarneus in narrower asci and shorter ascospores of a different shape.

Type:— CHINA. Yunnan: Pingbian, Daweishan , 1600 m, 5 September 1999, on stems of an unidentified monocotyledon, W.Y. Zhuang & Z.H. Yu 3326-1 (holotype HMAS 188554 !) .

Apothecia stipitate, scattered, convex when fresh, drying flat, 1–2 mm in diam., stipe 1–2 mm long, dark at base; hymenium surface dirty white when fresh, drying light yellow to pale tan; receptacle surface drying wrinkled, cream to pallid. Outer covering layer composed of parallel to loosely interwoven hyphae, with thick-walled hyphal ends protruding at an acute angle to the surface, hyphae dextrinoid in Melzer’s reagent, 3.5–7 µm wide. Ectal excipulum of textura prismatica at and near margin, 12 20 µm thick, marginal cells pale brown, 6–15 3–5 µm; becoming large-celled textura prismatica and textura angularis at flank and near base, 25 55 µm thick, cells thin-walled, hyaline, 15–40 8–15 µm. Medullary excipulum of two layers, outer layer of textura porrecta, 10–55 µm thick, inner layer of textura intricata, 30 165 µm thick, hyphae hyaline, 3–5 µm wide. Subhymenium about 40 µm thick. Hymenium about 50 µm thick. Asci 40–52 3.3–5 µm, cylindricalclavate, 8-spored, stem being about 1/3 of the total ascus length, base attenuate, arising from simple septa, apex conical to round, apical thickening 1–1.5 µm, J+ in Melzer’s reagent with or without KOH pretreatment; apical ring strongly bluing as two lines extending to the very apex, 1–1.5 µm long, of Calycina - type. Ascospores 4.5–6.7 2.2–2.5 µm, aseptate, obliquely to irregularly uniseriate, ellipsoid, hyaline, eguttulate when young and multiguttulate in cotton blue at maturity, guttules indistinguishable in KOH. Paraphyses filiform, not exceeding the asci, 1–1.5 µm wide.

Etymology:— The specific epithet refers to the locality of the fungus.

Notes:— The taxonomic position of R. sinicus was further confirmed by the analysis of ITS rDNA sequences ( Fig. 4 ). The maximum parsimony tree indicated that it is closely related to the type species of the genus, R. rhodoleucus , with high bootstrap value (100%), rather than any other species of Hymenoscyphus .

Figures

FIGURE 1. Roseodiscus sinicus (holotype). Gross morphology of dried apothecia on nature substrate.

FIGURE 2. Roseodiscus sinicus (holotype). A, Structure of apothecium; B, Structure at and near apothecium margin; C, Structure at flank; D, Structure at flank near stipe; E, Structure of stipe outer layer; F–G, Asci with ascospores. Scale bars: A = 100 µm, B–E = 20 µm, F–G = 10 µm.

FIGURE 3. Roseodiscus sinicus (holotype). Asci with ascospores showing apical ring, simple septa at base, and ascospore arrangement in asci. Scale bar = 5 µm.

FIGURE 4. One of two maximum parsimony trees obtained from ITS rDNA sequences of Roseodiscus sinicus and allied fungi. Bootstrap support values are indicated at the nodes. CI = 0.7324, RI = 0.7480, HI = 0.2676.