Polyplosphaeria nigrospora Kular., & K.D. Hyde, sp. nov.
Index Fungorum number: IF 900418; MycoBank number: MB 900418; Facesoffungi number: FoF 14173; Fig. 1
Etymology – based on the black conidia.
Saprobic on dead stem of unidentified plant. Sexual morph: Undetermined. Asexual morph: Hyphomycetous. Colonies on natural substrate solitary, scattered, as black spots. Hyphae superficially spreading over the substrate, dark brown. Conidiophores reduced to conidiogenous cells. Conidiogenous cells micronematous, monoblastic, forming directly on creeping hyphae, holoblastic, integrated, terminal, determinate, connected to base of conidia, with guttules, hyaline. Conidia 60–70×45–65 µm (x=68×57 µm, n=20), globose to subglobose, pyriform or irregular, solitary, black, verrucose at base, with unbranched, brown setose appendages at base and almost hyaline at apex, setose appendages on surface in two forms; long appendages 40–65×3–4 µm (x=55×3.6 µm, n=10), thick-walled, 4-septate, arising from apical part of conidia; short appendages 30–50 × 3.5–5 µm (x=40 × 4 µm, n=10), aseptate, thin-walled, arising eccentrically from conidial base.
Culture characteristics – Colonies on PDA reaching 4 cm diam. after 14 days in dark at 25 °C, irregular, flat, wavy margin and zonation with bluish brown, inner zone comprises white aerial, mycelial clots; outer zone comprises pale brown, filiform hyphae forming wings-like pattern; reverse black with brown margin, sporulate after 14 days.
Material examined – China, Guangdong Province, Guangzhou City, Nansha District, Huangshan Lu Forest Park (22° 78′ 74.2″ N 113° 58.4′ 21″ E), dead stem of unidentified plant, 18 July 2021, N.D. Kularathnage, NDK 13–2 (MHZU 22-0136, holotype), ex-type cultures ZHKUCC 22-0132, ZHKUCC 22-0134.
GenBank numbers – ITS: OR164935, OR164936; LSU: OR164963, OR164964.
Notes – The combined gene analyses of ITS, LSU, SSU, tef1-α and β-tubulin (Fig. 2) show that our isolates clustered with the type strain of Polyplosphaeria pandanicola forming a clade with ML/BI=100%/1.00 support. There are 4.08%, and 0.56% base pair differences in ITS and LSU. Our collection differs from P. pandanicola by its solitary, black, highly-melanized, setose conidia with thick-walled, 4-septate, long appendages (40–65 µm) and aseptate, thin-walled, short appendages (35–50 µm), while P. pandanicola has gregarious, brown to dark brown, less-melanized, setose conidia with 4–6-septate, long (60–105 µm) appendages and 0–2-septate, short (20–35 µm) appendages. Setae of our collection are equal in width, while long setae of P. pandanicola are wider at the apex and the short setae are wider at the base. Therefore, we introduce this collection as Polyplosphaeria nigrospora.
Figure 1 – Polyplosphaeria nigrospora (MHZU 22-0136, holotype). a Colonies on substrate. b–g Conidia. h Surface view of colony on PDA. i Reverse view of colony on PDA. Scale bars: b–e=50 µm
Figure 2 – Phylogram generated from maximum likelihood analyses based on combined ITS, LSU, SSU and tef1-α sequence data which comprised 3137 characters (ITS=539, LSU=879, SSU=764, tef1-α=306, β-tubulin=635). The best scoring RAxML tree with a final likelihood value of − 11,531.618251 is presented. The matrix had 782 distinct alignment patterns, with 22.63% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.229550, C=0.267919, G=0.242735, T=0.259795; substitution rates: AC=2.192656, AG=3.421541, AT=1.919197, CG=1.287792, CT=8.523851, GT=1.0; gamma distribution shape
parameter α=0.154399. Bootstrap support for maximum likelihood (ML) equal to or greater than 50% and clade credibility values greater than 0.90 (the rounding of values to 2 decimal proportions) from Bayesian inference analyses are labelled at each node. Ex-type strains are in bold, while the new isolate is indicated in blue bold. The tree is rooted to Muritestudina chiangraiensis (MFLUCC 17-2551)