Pleurothecium guttulatum H. Yang, K.D. Hyde & H. Zhang, 2021

Shi, Lin, Yang, Hao, Hyde, Kevin D., Wijayawardene, Nalin N., Wang, Gen-Nuo, Yu, Xian- Dong & Zhang, Huang, 2021, Freshwater Sordariomycetes: new species and new records in Pleurotheciaceae, Pleurotheciales, Phytotaxa 518 (2), pp. 143-166 : 149-151

Pleurothecium guttulatum H. Yang, K.D. Hyde & H. Zhang , sp. nov.

Index Fungorum number: IF557784, Facesoffungi number: FoF 08709

Etymology: Referring to the guttulate conidia.

Holotype: IFRD 9203 , ex-type strain KMUCC 20-0152 .

FIGURE 2

Description: Saprobic on submerged wood. Sexual morph: Undetermined. Asexual morph: Colonies effuse, superficial, solitary, hairy, grayish to dark brown with visible whitish to grayish conidia. Mycelium mostly immersed. Conidiophores macronematous, mononematous, straight or slightly flexuous, 1-septate, smooth, pale brown, becoming subhyaline towards the apex, 50–60 μm (x = 55 μm, n = 10) long, 3.5–4.5 μm (x = 3.8 μm, n = 10) wide. Conidiogenous cells polyblastic, terminal, integrated, cylindrical to tapered, sympodial, denticulate at the apex, pale brown to subhyaline, 30–39 × 2–5.5 μm, with 3–10 denticles 1.5–3 × 0.6–1.3 μm. Conidia clavate, straight or slightly curved, rounded at the apex, tapering towards the base, 3–4-septate occasionally 1-septate, hyaline, often with conspicuous guttulae, smooth-walled, 22–28 × 5–6 μm (x = 25.5 × 5.7 μm, n = 15).

Cultural characteristics: Conidia germinated on PDA within 24 hours. Germ-tubes produced from both ends. Colonies on PDA reaching 17–22 diameters in 60 days at 25°C, with concavo-convex, humid, atrovirens to dark brown mycelium on the surface, in reverse dark brown to black, with irregular margin.

Material examined: CHINA. Yunnan Province, Qiubei City, a small river in Puzhehei scenic area, on dead submerged decaying wood of unidentified plants, 25 June 2019, Hao Yang, P 23 ( IFRD 9203 , holotype), ex-type living culture KUMCC 20-0152 .

Notes: Pleurothecium guttulatum clustered in Pleurothecium with strong support (98%/0.99, MLBS / MBPP, Figure 1 ). Morphologically, it fits well the generic concept of Pleurothecium in having brown conidiophores, polyblastic, sympodially conidiogenous cells with cylindrical to tapered denticles and hyaline, clavate conidia ( Réblová et al. 2012, Luo et al. 2018). Among the 11 species epithets of Pleurothecium ( Index Fungorum 2021) , five species can be distinct from P. guttulatum by molecular data ( Figure 1 ). In addition, the hyaline conidia in P. guttulatum are distinguished from the pigmented conidia in P. bicoloratum , P. clavatum and P. leptospermi ( Wu & Zhang 2009) . Pleurothecium guttulatum differs from P. malayense by hyaline, clavate conidia with a tapering base, while the latter has hyaline to pale brown, cylindrical conidia without a tapering base ( Matsushima & Matsushima 1996). Pleurothecium guttulatum is different from P. magnum in having smaller conidia (22–28 × 5–6 μm vs. 27–31 × 9–11 μm) ( Subramanian & Bhat 1989).

Pleurothecium guttulatum is phylogenetically close to P. aquaticum . However, P. guttulatum differs in having 3–4-septate and larger conidia (22–28 × 5–6 μm vs. 19–21 × 4.5–5.5 μm), while the latter possesses 0–3-septate conidia ( Luo et al. 2018). Based on the sequence divergence in the ITS gene region, they differ in 16 nucleotides (3%, including 5 gaps), which follows the generally accepted norm that more than 1.5% of nucleotide differences in the ITS region is likely to be a new species ( Jeewon & Hyde 2016).

Pleurotheciella species

Figures

FIGURE 1. Backbone tree for Pleurotheciales generated from RAxML analyses based on a dataset of combined LSU, SSU, ITS and RPB2 sequence data. Bootstrap support values for maximum likelihood (the first value) equal to or greater than 70% and Bayesian posterior probabilities (the second value) equal to or greater than 0.95 are given above the nodes. The strain numbers are noted after the species names. Newly generated sequences are indicated in blue, new species are in red, and ex-type isolates are in bold. The tree is rooted with Conioscypha tenebrosa and C. minutispora. Strains known from freshwater habitats are marked as “ ”.

FIGURE 2. Pleurothecium guttulatum (IFRD 9203, holotype) a, b Colonies on wood. c, d Conidiophores. e, f Conidiogenous cells bearing conidia. g–j Conidia. k Germinating conidium. l, m Colony on PDA from above and reverse. Scale bars: a, b = 100 μm, c–d = 15 μm, e–j = 10 μm, k = 20 μm.