Dendryphion nanum (Nees) S. Hughes
Index Fungorum number: IF296539; Facesoffungi number: FoF 01745
≡ Helminthosporium nanum Nees [as ‘Helmisporium’], Syst. Pilze (Würzburg): 67 (1816) [1816–17]
Sexual morph: Undetermined. Asexual morph: Colonies on the substratum superficial, effuse, scattered, hairy, dark brown. Mycelium immersed, composed of septate, branched, thin-walled, smooth, pale brown hyphae. Conidiophores mononematous, macronematous, sometimes caespitose, septate, erect, straight to slightly flexuous, smooth, rounded or subobtuse at the apex, wider at the base, dark brown, paler towards the apex, cylindrical, 3–5-septate, 52–64 μm (x̄ = 58 μm, SD = 6, n = 10) long, 6.5–8.5 μm (x̄ = 7.5 μm, SD = 1, n = 10) wide. Conidiogenous cells polytretic, discrete, terminal and later becoming intercalary, pale brown or subhyaline, solitary or clusteredat the tip, cylindrical, truncate. Conidia acropleurogenous, solitary or catenate, dry, pale olivaceous to dark brown, with paler end cells, obclavate, rounded at the apex, attenuate and narrowly truncate at the base, 3–11-septate, thick-walled, smooth, 56.5–74.5 μm (x̄ =66 μm, SD = 9.5, n = 30) long, 10–12 μm (x̄ = 11 μm, SD = 1, n = 30) wide. Conidial secession schizolytic.
Material examined: CHINA, Yunnan Province, Dali, WanHua stream, saprobic on submerged decaying wood, May 2014, Hong-Yan Su, S-125, (HKAS 84012, reference specimen designated here), living culture, MFLUCC 15–0425, KUMCC; ibid. (DLU-065); Yunnan Province, Dali, Yongping County, saprobic on submerged decaying wood, June 2014, Zhuo Li, S-117, (HKAS 84010), living culture, MFLUCC 15–0426, KUMCC; ibid. (DLU-117).
Notes: Dendryphion nanum fits well into the generic concept of Dendryphion but differs from other taxa in the genus in having conidiophores with a series of short cylindrical cells, while other species have single or few cells. Furthermore, D. nanum has unbranched conidiophores, discrete conidiogenous cells at the tip and obclavate conidia with a truncate base and lighter end cells, which is a clear deviation from other species of the genus. This species was initially introduced as Helminthosporium nanum and later transferred to Dendryphion by Hughes (1958). Dendryphion nanum was originally described from Europe, whereas our specimen is from decaying wood, China. Therefore, even though the conidiophores, conidiogenous cells and conidia are typical of D. nanum (Hughes 1958; Matsushima 1975) it would be unwise to epitypify this species with the China collection as they are from different continents. We therefore designate our collection as a reference specimen of D. nanum so that further work on this taxon can be carried out. However, until this taxon is recollected from Europe, this interpretation should be treated with caution.