Pseudochaetosphaeronema puerensis R.F. Xu, K.D. Hyde & Tibpromma, sp. nov.

Index Fungorum number: IF 901412; Mycobank number: MB 901412; Facesoffungi number: FoF 15836 Fig. 1

Etymology – The name refers to the location from which species was collected, Pu’er, Yunnan, China.

Holotype – MHZU 22-0153

Saprobic on a dead branch of Hevea brasiliensis. Sexual morph Ascomata 120–350 μm high, 160–340 diam., (x̅=233×300 μm, n=10), solitary, scattered, immersed, erumpent on host, uni-loculate, black, globose to subglobose. Peridium 15–30 μm wide, thin-walled, composed of several layers of, brown to pale brown cells of textura angularis. Hamathecium comprises numerous, 1–2 μm wide, cellular, unbranched, pseudoparaphyses, septate, without constrictions at the septa. Asci 80–115×15–25 μm (x̅=98×21 μm, n=20), 8-spores, cylindric-clavate obovoid, short pedicel with rounded bitunicate, end, apex rounded with a minute ocular chamber. Ascospores 20–30×8–10 μm (x̅=27×10 μm, n=20), overlapping, 2–3-seriate, fusiform, with pointed ends, hyaline, 1-septate at the center (become 3-septate when germinated), constricted at the septa, containing up to four guttulate, thick-walled, surrounded by a mucilaginous sheath. Asexual morph Not observed.

Culture characteristics – culture on PDA, colonies slow growing, umbonate, smooth, edges brown, fat or efuse, from above, brown, dark brown in reverse side.

Material examined – China, Yunnan Province on dead branch of Hevea brasiliensis, 16 September 2021, Ruifang Xu, XPER-24 (MHZU 22–0153, holotype); ex-type ZHKUCC 22–0288; ibid. (ZHKUCC 22–0289, ex-isotype).

GenBank numbers – ZHKUCC 22-0288: ITS=OR807846, LSU=OR807850, SSU=OR807848, tef1-α=OR966288; ZHKUCC 22–0289: ITS= OR807847, LSU = OR807851, SSU=OR807849, tef1-α=OR966289.

Notes – In the multigene phylogeny, Pseudochaetosphaeronema puerensis (ZHKUCC 22–0288 and ZHKUCC 22-0289) clustered as a sister taxon to P. xishuangbannaensis (ZHKUCC 23-0804, ZHKUCC 23-0805) with 100% ML, 1.00 BYPP statistical support (Fig. 2). Pairwise nucleotide comparison of ITS showed that Pseudochaetosphaeronema puerensis differs from P. xishuangbannaensis in 15/559 bp (2.68%, 1 gap) (Jeewon and Hyde 2016). Moreover, Pseudochaetosphaeronema puerensis shares similar morphologies with P. xishuangbannaensis, but can be differentiated by having the peridium with the cells of textura angularis, smaller ascomata (120–354×166–340 μm vs. 270–410 × 370–480 μm), smaller (22–30 × 8–11 μm vs. 30–50×10–20 μm) and 1–3-septate ascospores with a mucilaginous sheath. Therefore, we introduce Pseudochaetosphaeronema puerensis as a new species.

Figure 1 – Pseudochaetosphaeronema puerensis (ZHKU 22–0153, holotype). a, b Appearance of ascomata on host substrate. c Section of ascoma. d Peridium. e Pseudoparaphyses. f–j Asci. k–q Ascospores. s Germinated ascospore. s Ascospore stained with Indian ink. t, u Colonies on PDA. Scale bars: c=100 μm, d–f=20 μm, g–j, s=30 μm, q–r=10 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU, ITS and tef1-α sequence data. Related sequences are taken from Xu et al. (2024) and additions according to the BLAST searches in NCBI. Sixty-one strains are included in the combined analyses which comprised 3382 characters (860 characters for LSU, 1033 characters for SSU, 573 characters for ITS, and 916 characters for tef1-α) after alignment. Leptosphaeria doliolum (CBS 505.75) was used as the outgroup taxa. The best-scoring RAxML tree with a final likelihood value of − 22,870.768793 is presented. The matrix had 1295 distinct alignment patterns, with 26.98% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.239877, C=0.248600, G=0.271623, T=0.239900; substitution rates: AC=1.424996, AG=2.985437, AT=1.629409, CG=1.504009, CT=7.211381, GT=1.000000; gamma distribution shape parameter α=0.189842. Bootstrap support values for ML equal to or greater than 60% are given above the nodes. Bayesian posterior probabilities (BYPP) equal to or greater than 0.90 are given above the nodes. Ex-type strains are in bold and newly generated sequence is in blue bold