Pseudochaetosphaeronema xishuangbannaense
Pseudochaetosphaeronema xishuangbannaense R.F. Xu & Tibpromma [as 'xishuangbannaensis'], in Xu, Karunarathna, Phukhamsakda, Dai, Elgorban, Suwannarach, Kumla, Wang & Tibpromma, Index Fungorum 103: 83 (2024)
Index Fungorum number: IF 663538
Saprobic on a dead branch of Hevea brasiliensis. Sexual morph: Ascomata 270–410 μm high, 370–480 μm diam., (
= 350 × 420 μm, n = 5), solitary, scattered, immersed, globose to subglobose, uni-loculate, black. Peridium 40–90 μm wide, thin-walled, composed of several layers of small, brown to pale brown cells of textura intricata. Hamathecium comprises 2–3 μm wide, numerous, dense, filiform, unbranched, hyaline, cellular pseudoparaphyses. Asci 130–180 × 25–35 μm ( = 155 × 32 μm, n = 20), 8-spored, bitunicate, obovoid, short distinct pedicel with conical end, apex rounded with a minute ocular chamber. Ascospores 30–50 × 10–20 μm ( = 42 × 13 μm, n = 30), hyaline, fusiform, with pointed ends, 3–5-septate, larger upper third cell, constricted at the septa, guttulate, thick-walled, with mucilaginous sheath, the sheath constricted at the middle. Asexual morph: Undetermined.
Culture characteristics: Colony on PDA, colonies slow growing on 28 °C, umbonate, filiform, smooth, edges brown, from above, brown, dark brown on reverse side.
Material examined: China, Yunnan Province, Xishuangbanna on a dead branch of Hevea brasiliensis, 12 September, 2021, Rui-Fang Xu, XSBNR–41 (ZHKU 23–0107, holotype); ex-type ZHKUCC 23–0804, ZHKUCC 23–0805.
GenBank numbers: ZHKUCC 23–0804 = ITS: OR853097, LSU: OR922338, SSU: OR922344, tef1-α: OR966286; ZHKUCC 23–0805 = ITS: OR853098, LSU: OR922339, SSU: OR922345, tef1-α: OR966287.
Notes: In the phylogenetic analyses, Pseudochaetosphaeronema xishuangbannaensis clusters with P. lincangensis with 99% ML and 1.00 PP support. Morphologically, P. xishuangbannaensis differs from P. lincangensis in having longer asci (130–180 μm vs. 90–145 μm), 3–5-septate ascospores with sheath constricted at the central septum and brown to dark brown colonies, while P. lincangensis has ascospores with a normal sheath in a circle, 1-septate ascospores with obtuse ends and colonies off-white from the forward edge, orange in reverse. Pseudochaetosphaeronema xishuangbannaensis shares similar morphologies with P. chiangraiense, but can be differentiated by having the peridium with the cells of textura intricate, larger ascomata (270–410 × 370–480 μm vs. 190–255 × 190–200 μm), longer asci (130–180 μm vs. 50–110 μm), larger (30–50 × 10–20 μm vs. 20–45 × 15–30 μm) and 3–5 septate ascospores with a sheath constricted at the central septum and brown to dark brown colonies. Pseudochaetosphaeronema chiangraiense has textura angularis peridium, ascospores surrounded by a normal sheath in a circle, 1-septum, obtuse ends, from above, greenish-grey in the middle and pale brown at the margin, yellowish-brown on the reverse side (Boonmee et al. 2021). In addition, P. xishuangbannaensis formed a different lineage with P. chiangraiense . Therefore, P. xishuangbannaensis is described as a new species, based on phylogenetic analyses and morphological comparison.
Figure 1. Phylogram generated from Maximum Likelihood analysis based on combined LSU, ITS, SSU, tef1-α and rpb2 sequence data of 119 taxa, which comprised 4399 base pairs (LSU = 908 bp, ITS = 512 bp, SSU = 1000 bp, tef1-α = 925 bp, rpb2 = 1054 bp). The best scoring RAxML tree with a final likelihood value of -38918.764563 is presented. The matrix had 2023 distinct alignment patterns, with 39.00% of undetermined characters or gaps. Estimated base frequencies were as follows: A = 0.245191, C = 0.247520, G = 0.268228, T = 0.239061; substitution rates: AC = 1.533778, AG = 3.877174, AT = 1.672983, CG = 1.254032, CT = 8.838860, GT = 1.000000; gamma distribution shape parameter α = 0.208600. Bootstrap support values for ML equal to or greater than 60% and Bayesian Inference analysis values equal to or greater than 0.90 PP are labelled at each node. The tree is rooted with Seriascoma didymospora (MFLUCC 11–0179) and S. didymospora (MFLUCC 11–0194).
Figure 2. Pseudochaetosphaeronema xishuangbannaensis (ZHKU 23–0107, holotype) a–c appearance of ascomata on host substrate d section of an ascoma e peridium f pesudoparaphyses g–j asci m–t ascospores u ascospore stained with Indian ink k, l colonies on PDA (k-front and l-reverse view). Scale bars: 200 µm (d); 100 µm (e); 50 µm (f–j); 10 µm (m–t); 20 µm (u)
- Xu R-F, karunaratha SC, Phukhamsakda C, Dai D-Q, et al. (2024) Four new species of Dothideomycetes (Ascomycota) from Pará Rubber (Hevea brasiliensis) in Yunnan Province, China. MycoKeys 103, 71–95.
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