Diaporthales » Cytosporaceae » Cytospora

Cytospora pubescentis

Cytospora pubescentis Q.J. Shang, E. Camporesi & K.D. Hyde, in Shang, Hyde, Camporesi, Maharachchikumbura, Norphanphoun, Brooks & Liu, Mycosphere 11(1): 213 (2020)

Index Fungorum number: IF 555505; Facesofungi number: FoF 05102

Etymology – Names reflect the host, of which the fungus was isolated from “Quercus pubescens”.

Holotype – MFLU 17-0727

Saprobic on the bark. Sexual morph: Stromata 943–1461 µm wide, with the poorly developed interior, solitary to gregarious, immersed, becoming raised to erumpent the bark by the ostiolar canal, dark brown to black, glabrous, circular to irregular in shape, arranged with conspicuous, clustered, roundish to cylindrical prominent ostioles. Ascomata (excluding necks) 183–333 μm high, 158–259 µm diam. (x̄ = 258 ×209 μm, n = 18), perithecial, immersed in a stroma, brown to dark brown, globose to subglobose, glabrous, individual ostiole with the neck. Ostiolar canal 300–460 μm high, 65–103 μm diam. (x = 382 × 84 μm, n = 15), cylindrical, sulcate, periphysate. Peridium 22–38 μm wide, composed of two section layers, outer section comprising 2–3 layers, brown to dark brown, thick–walled cells, arranged in textura angularis, inner part comprising 3–4 layers of hyaline cells of textura angularis. Hamathecium comprising only asci. Asci (28–)32–37(–40) × (4–)5–6(–6.8) μm (x̄ = 34 × 5.5 μm, n = 80), 8-spored, unitunicate, cylindrical to clavate, sessile, apically rounded to truncate, with a J- apical ring. Ascospores (5.7–)6.8–8.7(–10.3) × (1.5–)1.9–2.7(–3.4) μm (x̄ = 7.8 × 2.3 μm, n = 110), overlapping 1–2-seriate, hyaline, allantoid, aseptate, smooth-walled. Asexual morph: Coelomycetous. Conidiomata pycnidial, with 2–4-loculate, appearing as brown to black, watery, rounded, conidial masses, superficial, solitary or aggregated, globose, with beige-white to brown mycelium covering the surface. Pycnidial walls 60–83 μm wide, comprising several layers of brown, compressed hyphae, arranged in a textura intricata. Conidiogenous cells (7.5–) 9–22 (–28.5) × (2.0–)2.2–4.5(–6) (x̄ = 15.5× 3.3 μm, n = 10), clavate to ampulliform, holoblastic, straight. Conidia (2.7–)5.8–7.5(–8.5) × (1–)1.3–1.6(–1.8) (x̄ = 7.4 × 1.5 μm, n = 85), hyaline, allantoid, unicellular, smooth-walled.

Culture characteristics: Ascospores germinating on PDA within 24 hrs. Germ tubes produced from all sides. Colonies on PDA reaching 5–5.5 cm diam. after 15 days at room temperature, colonies circular to irregular, medium dense, flat or effuse, slightly raised, with edge fimbriate, fluffy to fairy fluffy, white to gray from above, light yellow to brown from below; After 20 days, gray to brown from above, dark brown from below; not producing pigments in agar.

Material examined: Italy, Monte Mirabello, Predappio (Province of Forlì-Cesena [FC]), on a dead land branch of Quercus pubescens (Fagaceae), 28 February 2017, E. Camporesi, IT 3265 (MFLU 17- 0727, holotype; KUN-HKAS 100910, isotype), ex-type living culture, MFLUCC 18-1201.

Notes: Cytospora pubescentis can be distinguished from Cytospora quercicola by its smaller asci and ascospores. It differs from Cytospora junipericola by its shorter ascomata, more slender asci and larger ascospores (Senanayake et al. 2017). Cytospora pubescentis differs from C. fraxinigena and C. rosae by having larger asci, ascospores and ostioles (Senanayake et al. 2017). Moreover, the phylogenetic analysis by Shang et al. (20200 shows that the strain of C. pubescentis (MFLUCC 18-1201) forms a distinct lineage and shares a sister relationship to C. fraxinigena (MFLUCC 14-0868, BBH42442), C. junipericola (MFLUCC 17-0882, BBH42444), C. quercicola (MFLUCC 14-0867, BBH42443) and C. rosae (MFLUCC 14-0845, MFLUCC 17-1664) with moderate support (89% ML and 86% MP). Therefore, Shang et al. (2020) identify the specimen as the new taxon C. pubescentis and provide the holomorph description for the species.