Pseudochaetosphaeronema chiangraiense Wijesinghe, Boonmee & K.D. Hyde, sp. nov.

Index Fungorum number: IF 558549; MycoBank number: MB 558549; Facesofungi number: FoF 09950; Fig. 1

Etymology – The name reflects the location from which species was collected, Chiang Rai, Thailand.

Holotype – MFLU 21-0083

Saprobic on dead terrestrial branch of Tamarindus sp. Sexual morph Ascomata 190–255 μm high, 190–200 μm diam., (x̅= 223 × 197 μm, n = 10), solitary, scattered, immersed, erumpent on host, uni-loculate, black, globose to subglobose. Peridium 13–17 μm wide, thin-walled, composed of several layers of small, brown to pale brown cells of textura angularis. Hamathecium comprising numerous, 2–4.5 μm wide, cellular, unbranched, pseudoparaphyses that are septate, without constrictions at the septa. Asci 50–110×15–30 μm (x̅=80×18 μm, n=30), 8-spored, bitunicate, fissitunicate, with obovoid, short distinct pedicel with rounded end, apex rounded with a minute ocular chamber. Ascospores 20–45×7–8 μm (x̅=34×7.5 μm, n=30), overlapping, 2–3-seriate, hyaline, fusiform, with pointed ends, 1-septate at the center, constricted at the septa, guttulate, thick and smooth-walled. Asexual morph Undetermined.

Culture characteristics – Ascospores germinating on PDA within 24 h. Germ tubes produced both sides of ascospore. Colonies on PDA reaching 1–2 cm diam. after 5 days in day light at 25 °C, colonies medium dense, flat or effuse, from above, greenish gray in middle and pale brown at the margin, yellowish brown in reverse side.

Material examined – THAILAND, Chiang Rai Province, Nang Lae Village, on the dam of the pond near Lake Hill Resort, dead branch of Tamarindus sp. (Fabaceae),10 May 2020, S.N. Wijesinghe, N2 (MFLU 21-0083, holotype), extype living culture, MFLUCC 21-0070.

GenBank numbers – ITS=MZ457923, LSU=MZ457922, TEF1-α=MZ476770.

Notes – In our DNA sequence analysis, all reported members of Pseudochaetosphaeronema and closest Camarographium strains are grouped together in Clade A in Macrodiplodiopsidaceae (Fig. 52). Pseudochaetosphaeronema chiangraiense is only known from its sexual morph (Fig. 51) and therefore, we cannot compare it with the existing species in this genus with respect to their asexual characteristics (Punithalingam 1979; Ahmed et al. 2015; Zhang et al. 2016b; Tibpromma et al. 2018; Jayasiri et al. 2019; Hyde et al. 2020b). The BLAST searches of ITS and LSU sequence data for our new isolate indicates high similarity to Camarographium koreanum (CBS 117,159) and TEF1-α sequence data indicates high similarity to Camarographium sp. (1 NV-2015). Therefore, we include these strains in our final multigene phylogenetic analysis and our novel isolate forms a distinct lineage with an unidentified Camarographium sp. (B45, B46) with 88% MLBS support (Clade A; Fig. 52). According to the guidelines of Jeewon and Hyde (2016) we have analysed nucleotide differences within the rRNA gene region for further clarification. When comparing the ITS (ITS1-5.8S-ITS2) region between our isolate with the B45 and B46 strains, there were 48 and 43 bp (11.11% and 9.95%) difference respectively from 432 nucleotides in ITS. Also, in comparison of the LSU gene region of our strain with B45 and B46 strains, we have revealed (13/774) bp (1.67%) difference and 16/785 bp (2.03%) difference respectively. According to these phylogenetic results we conclude our isolate is a new species of Pseudochaetosphaeronema. We introduce the species as Pseudochaetosphaeronema chiangraiense collected from Thailand.

Figure 1 – Pseudochaetosphaeronema chiangraiense (MFLU 21-0083, holotype). a, b Appearance of ascostromata on host substrate. c Longitudinal section of ascomata. d Peridium e Pseudoparaphyses. f–i Asci. j–l Ascospores. m Germinated ascospore. n, o Cultures on PDA from surface and reverse. Scale bars: a=500 μm, b=200 μm, c=100 μm, m=50 μm, e–k=20 μm, d, l=10 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU, ITS and TEF1-α sequence data representing suborder Massarineae in Pleosporales. Related sequences are taken from Hyde et al. (2020b) and additions according to the BLAST searches in NCBI. Fifty-eight strains are included in the combined analyses which comprised 3070 characters (798 characters for LSU, 961 characters for SSU, 469 characters for ITS, 842 characters for TEF1-α) after alignment. Alternaria alternata (CBS 916.96) and Leptosphaeria doliolum (CBS 505.75) in Pleosporaceae and Leptosphaeriaceae respectively (Pleosporales) were used as the outgroup taxa. The best scoring RAxML tree with a final likelihood value of − 18300.642497 is presented. The matrix had 1007 distinct alignment patterns, with 36.82% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.240587, C=0.242773, G=0.272823, T=0.243817; substitution rates: AC=1.614921, AG=3.258874, AT=1.951323, CG=1.249772, CT=8.508461, GT=1.000000; gamma distribution shape parameter α=0.183977. Bootstrap support values for ML equal to or greater than 75% are given above the nodes (left side). Bayesian posterior probabilities (BYPP) equal to or greater than 0.95 are given above the nodes (right side). Ex-type strains are in bold and newly generated sequence is in blue bold