Pseudochaetosphaeronema xishuangbannaensis R.F. Xu & Tibpromma, 2024

Xu, Rui-Fang, Karunarathna, Samantha C., Phukhamsakda, Chayanard, Dai, Dong-Qin, Elgorban, Abdallah M., Suwannarach, Nakarin, Kumla, Jaturong, Wang, Xiao-Yan & Tibpromma, Saowaluck, 2024, Four new species of Dothideomycetes (Ascomycota) from Para Rubber (Hevea brasiliensis) in Yunnan Province, China, MycoKeys 103, pp. 71-95 : 71

Pseudochaetosphaeronema xishuangbannaensis R.F. Xu & Tibpromma sp. nov.

Fig. 6

Etymology.

The name refers to the location "Xishuangbanna, Yunnan, China", where the holotype was collected.

Holotype.

ZHKU 23-0107.

Description.

Saprobic on a dead branch of Hevea brasiliensis . Sexual morph: Ascomata 270-410 μm high, 370-480 μm diam., (x‾ = 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 (x‾ = 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 (x‾ = 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, tef 1-α: OR966286; ZHKUCC 23-0805 = ITS: OR853098, LSU: OR922339, SSU: OR922345, tef 1-α: OR966287.

Notes.

In the phylogenetic analyses, Pseudochaetosphaeronema xishuangbannaensis clusters with P. lincangensis with 99% ML and 1.00 PP support (Fig. 3 ). 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 (Fig. 3 ). Therefore, P. xishuangbannaensis is described as a new species, based on phylogenetic analyses and morphological comparison.

Figures

Figure 3. Phylogram generated from Maximum Likelihood analysis based on combined LSU, ITS, SSU, tef 1 - α and rpb 2 sequence data of 119 taxa, which comprised 4399 base pairs (LSU = 908 bp, ITS = 512 bp, SSU = 1000 bp, tef 1 - α = 925 bp, rpb 2 = 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). Related sequences were obtained from De Silva et al. (2022), Lu et al. (2022) and Li et al. (2023). The new isolates are indicated in red and the ex-type strains are in bold.

Figure 6. 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).