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

Fig. 5

Etymology.

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

Holotype.

ZHKU 23-0105.

Description.

Saprobic on a dead branch of Hevea brasiliensis . Sexual morph: Ascomata 140-245 μm high, 255-290 μm diam., (x‾ = 190 × 267 μm, n = 5), immersed, visible as dark-brown dots on the host surface, solitary, uni-loculate, ampulliform, without ostiole. Peridium 18-50 μm wide, several layers, comprising dark-brown to pale-brown cells of textura angularis. Hamathecium comprises 2-3 μm wide, numerous, hyaline, unbranched, pseudoparaphyses. Asci 90-145 × 15-30 μm (x‾ = 112 × 22 μm, n = 15), 8-spored, bitunicate, cylindrical to clavate, apically rounded, short pedicelate, with a small ocular chamber, thick-walled. Ascospores 25-40 × 8-15 μm (x‾ = 30 × 11 μm, n = 35), overlapping, 2-seriate, fusiform, 1-septum in the middle of cell, widest at the centre and tapering towards narrow ends, constricted at the septum, hyaline, guttulate, with ellipsoid mucilaginous sheath, thick and smooth-walled. Asexual morph: Undetermined.

Culture characteristics.

culture on PDA, colonies slow growing on 28 °C, low convex, entire, smooth, edge is off-white from above, dark brown, edge is orange on reverse side.

Material examined.

China, Yunnan Province, Lincang on a dead branch of Hevea brasiliensis , 28 July 2022, Rui-Fang Xu, LCR07 (ZHKU 23-0105, holotype); ex-type ZHKUCC 23-0800, ZHKUCC 23-0801 .

GenBank numbers.

ZHKUCC 23-0800 = ITS: OR853095, LSU: OR922336, SSU: OR922342, tef 1-α: OR966290; ZHKUCC 23-0801 = ITS: OR853096, LSU: OR922337, SSU: OR922343, tef 1-α: OR966291.

Notes.

In the phylogenetic analyses, Pseudochaetosphaeronema lincangensis clusters distinctly, sister to P. kunmingense , P. magnoliae and P. siamensis with 90% MP, 1.00 PP support (Fig. 3 ). The base pair differences in ITS, LSU, SSU and tef 1-α sequences of our new species are compared with P. kunmingense , P. magnoliae and P. siamensis (Table 3 ). However, we could not compare the morphological characteristics of the species above, as they were described, based on asexual morphs. Therefore, based on morphology and phylogeny, we introduce Pseudochaetosphaeronema lincangensis as a new species.

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 5. Pseudochaetosphaeronema lincangensis (ZHKU 23 - 0105, holotype) a, b appearance of ascomata on host substrate c vertical section of an ascoma d section of peridium e pseudoparaphyses f-i asci j a germinated ascospore l-q ascospores k ascospore stained with Indian ink r, s colonies on PDA (r-front and s-reverse views). Scale bars: 100 µm (c); 50 µm (d); 30 µm (e-j); 200 µm (g); 10 µm (k, l-q).