Rhexoacrodictys melanospora S.X. Bao, R.J. Xu & Q. Zhao, 2023

Bao, Shu-Xin, Xu, Rong-Ju, Zhu, Ying-An & Zhao, Qi, 2023, Rhexoacrodictys melanospora sp. nov. (Rhexoacrodictys, Pleurotheciales) from Yunnan, China, Phytotaxa 594 (3), pp. 213-222 : 217-219

Rhexoacrodictys melanospora S.X. Bao, R.J. Xu & Q. Zhao , sp. nov.

Index Fungorum Number: IF559983.

Facesoffungi Number: FoF 12898; Fig. 2 .

Etymology: The specific epithet ‘ melanospora ’ refers to the dark conidia of the fungus

Saprobic on decaying woods in terrestrial habitat. Sexual morph: Undetermined. Asexual morph: Conidiophores 19–60 × 3–5 μm (Q = 40 × 4 μm, n = 20), macronematous, mononematous, erect, straight or somewhat fexuous, pale brown to brown, cylindrical, thick-walled, smooth, 2–4 septate. Conidiogenous cells 2–6 × 3–4 μm (Q = 4 × 3.5 μm, n = 10), monoblastic, integrated, terminal, pale brown, cylindrical, with 1–3 pale brown percurrent extensions. Conidia 16–32 × 12–21 μm (Q = 23 × 16 μm, n = 40), solitary, acrogenous, ellipsoidal to obovoid or somewhat subglobose, muriform, with 2–5 transverse and several oblique septa, pale brown when immature, becoming dark brown at maturity, thick and smooth-walled.

Culture characteristics: Colonies on PDA, reaching 4 cm diam. after 15 days at room temperature (25 ˚C), colonies irregular, surface taupe, mycelium dense, and reverse blackish.

Material examined:— CHINA. Yunnan Province, Fugong County, decayed wood in terrestrial habitats, 13 May 2021, Song Wang , GLG41-1 (HKAS 124580, holotype), ex-type KUNCC 22-12406; China, Derung-Nu Autonomous County of Gongshan , 15 May 2021, Song Wang, GLG41-2 (HKAS 124581, paratype), ex-paratype KUNCC 22- 12411 .

Notes: Rhexoacrodictys melanospora is easily distinguished by its macronematous, conidiophores, and conidia ellipsoidal, 2–5 transverse, and several oblique septate. R. melanospora clustered with R. erect and R. fimicola with strong bootstrap support (100% ML/1.00 BI). However, R. melanospora has shorter conidiophores than R. fimicola (19–60 μm vs. up to 75 μm) ( Baker et al. 2002), R. erect has numerous irregular septa, and R. melanospora just has 2–5 transverse and several oblique septa ( Baker et al. 2002, Zhao et al. 2011).

Among the four species of Rhexoacrodictys ( Index Fungorum 2023) , R. broussonetiae and R. fuliginosa lack DNA sequences. Although their molecular data deficiency, R. melanospora clearly differs from R. broussonetiae and R. fuliginosa by its shorter conidiophores, 19–60 μm (vs. 70–90 μm in R. broussonetiae , and vs. up to 85 μm in R. fuliginosa ) and longer conidia, 16–32 μm (vs. 17–28μm in R. broussonetiae , and vs. 17–27 μm in R. fuliginosa ) ( Baker et al. 2002, Zhao et al. 2011, Xiao et al. 2018).

A morphological comparison of Rhexoacrodictys species is summarized in Table 2 and a photo plate of R. melanospora is in Fig. 2 .

Figures

FIGURE 2.Rhexoacrodictysmelanospora (HKAS 124580, holotype)a Colonieson naturalsubstrate.b–eConidiophores, conidiogenous cells and conidia. f–j Conidia k–l Colony on PDA (surface and reverse). Scale bars b–e = 20 μm, f–j = 10 μm.