Pleurotheciella dimorphospora H.B. Jiang, Phookamsak & K.D. Hyde, sp. nov.

Index Fungorum number: IF 558191; MycoBank number: MB 558191; Facesoffungi number: FoF 09762; Fig. 1

Etymology – The specific epithet “dimorphospora” refers to the fungus forming two types of conidia.

Holotype – MFLU 20-0138

Saprobic on dead branches of Malus sp. Sexual morph Undetermined. Asexual morph Natural substrate visible as small, black, shiny dots on host substrate. Mycelium immersed to partly immersed, sparse, brown, composed of septate, branched hyphae. Conidiophores 9–15(–21)×2–4 μm (x̅=10.5×2 μm, n=30), difficult to distinguish on host, macronematous, mononematous, subhyaline to brown, septate, unbranched to branched, erect on host surface. Conidiogenous cells holoblastic, terminal, integrated. Conidia (16.5–)20–27(–32)×(15–)20–25(–28) μm (x̅=23×20.5 μm, n=30), dark brown to black, muriform, variedly shaped, ellipsoidal, subglobose, or irregular in shape, sectored, inconspicuously septate. In vitro: Dimorphic, with two types of conidial morphology. Type I: Conidiophores 4.5–6 × 2.5–4 μm (x̅=5–3 μm, n=20), semi-macronematous or macronematous, mononematous, straight or flexuous, hyaline to brown, cylindrical, septate, unbranched. Conidiogenous cells holoblastic, terminal or intercalary, integrated, brown. Conidia 20–29×14–19 μm wide (x̅=24.5×17 μm, n=30), brown, muriform, varied in shape, subglobose to cordiform, or irregular in shape, with a protuberant hilum. Type II: Conidiophores reduced to conidiogenous cells. Conidiogenous cells 6–8 μm long (x̅=8 μm, n=20), 2–3 μm wide (x̅=2 μm, n=20), holoblastic, terminal, hyaline, ellipsoidal, aseptate, unbranched. Conidia 8.5–10.8 μm long (x̅=9.7 μm, n=20), 4–5 μm wide (x̅=4 μm, n=20), hyaline, ellipsoidal, 0–1-septate, 2-guttulate, smooth-walled.

Culture characteristics – Conidia germinating on WA within 24 h and germ tubes produced in all directions. Colonies on PDA, reaching 20–25 mm diam. after 14 days at room temperature, with subglobose, dense, humid, dark brown mycelium on the frontage, convex at the entre, dark brown to black in reverse. Mycelium 1.5–3 μm (x̅=2 μm, n=20) wide, superficial to immersed in media, with dark brown, composed of septate, branched, smooth hyphae.

Material examined – CHINA, Yunnan Province, Kunming City, Kunming Institute of Botany Kunming Institute of Botany (102°44′19″ E 25°8′27″ N; 1951 msl±3 msl), on dead branch of Malus sp. (Rosaceae), 18 August 2018, R. Phookamsak, KIB049 (MFLU 20-0138, holotype), ex-type living culture, KUMCC 20-0185.

GenBank Numbers – ITS =MW981446, MW981447, LSU =MW981444, MW981445, SSU = MW981454, MW981455, TEF1-α = MZ509663, MZ509664, RPB2=MZ509665, MZ509666.

Notes – In this study, we observed a terrestrial fungus occurring on dead branches of Malus sp. in Kunming, Yunnan, China. The species forms dark brown to black, shiny conidia on the host tissue in nature. We obtained a pure culture of this fungus by single conidia isolation from these dark brown to black conidia and the species formed black conidial masses and hyaline conidial masses on PDA after 1 month. We re-isolated hyaline and brown conidia, and obtained DNA sequence data for both hyaline and brown conidia. Based on DNA sequence data analyses, the sample forming hyaline conidia (KUMCC 20-0185H) are supported to be conspecific to the sample forming brown conidia (KUMCC 20-0185).

Figure 1 – Pleurotheciella dimorphospora (MFLU 20-0138, holotype; KUMCC 20-0185, ex-type). a Appearance of black, shiny conidia on host substrate. b Squash mount showing mycelia partly immersed in host substrate. c, d Conidiophores erect on host surface. e Black, muriform conidia on natural substrate. f Germinated conidium on WA. g Colony on PDA after 4 weeks. h Conidial masses induced on culture growing on PDA after 4 weeks. i, m–o Dark brown, muriform conidia on PDA. j–l Conidiogenous cells with attached conidia. p Hyaline, didymosporous conidia associated with dark brown, muriform conidia. q, r Conidiogenesis of hyaline conidia. s–w Hyaline conidia. x, y Lateral and intercalary conidia. Scale bars: b, f, i, x=50 μm, c, l–n, q, y=30 μm, d, e, k, o, p=20 μm, j, r–w=10 μm