Poaceascoma taiwanense C.H. Kuo & K.D. Hyde, Mycosphere 9(2): 297 (2018)
Index Fungorum number: IF 554200; MycoBank number: MB 554200; Facesoffungi number: FoF 04084; Fig. 1
Saprobic on submerged wood. Sexual morph Ascomata 117–200 µm high, 198–209 µm diam., immersed to erumpent when mature, solitary, scattered or sometimes grouped beneath the host tissues, globose, dark brown to black, coriaceous, ostiolate, papillate. Peridium 22–31 μm wide, with thick walls, composed of several layers of pseudoparenchymatous cells, outer layer comprising several layers of dark brown cells, arranged in a textura angularis, inner layer comprising several layers of hyaline, flattened cells, arranged in a textura angularis to textura prismatica. Hamathecium composed of numerous, 1.5–2 μm wide, filamentous, broad, cellular pseudoparaphyses, with distinct septa, embedded in a mucilaginous matrix. Asci 63–77×8.5–10 μm (x̅=70×9.5 μm, n=10), 8-spored, bitunicate, cylindrical clavate, short pedicellate, apically rounded with minute ocular chamber. Ascospores 42–54×2.5–3 μm (x̅=49×3 μm, n=10), fasciculate, scolecosporous, hyaline, elongate, cylindrical filiform, tapering towards the rounded ends, slightly curved, 6–7-septate, slightly constricted at the septa, smooth-walled. Asexual morph Undetermined.
Culture characteristics – Ascospores germinating on PDA within 24 h and germ tubes arising from both ends. Colonies on MEA reaching 20 mm after 1 month at room temperature, slightly effuse, dense, radially with undulate edge, surface white with forming the water drops on the mycelium, with orangish pigmented at the surface, reverse dark purple at the middle, radiating dark pink to yellowish orange towards the edge.
Material examined – THAILAND, Phayao Province, Pong, on submerged wood in a small freshwater stream, 26 March 2019, S. Boonmee, PY1 (MFLU 21-0055, new record), living culture, MFLUCC 21-0078.
GenBank numbers – ITS=MZ538523, LSU=MZ538557, TEF1-α=MZ567099.
Notes – Multigene phylogenetic analysis indicates that our strain MFLUCC 21-0078 is sister to the type strain P. taiwanense (MFLU 18-0083) with high levels of support (100% MLBS, 1.00 BYPP (Fig. 2). A comparison of LSU and ITS nucleotide base pairs indicates that our strain is highly to P. taiwanense (3/842 bp differences (0.35%) in LSU and 5/564 bp differences (0.89%) in ITS). Therefore, we identify our strain MFLUCC 21-0078 as P. taiwanense (Fig. 1). Our strain shares similar characteristics of the ascomata, asci and ascospores to P. taiwanense (MFLU 18-0083). Although, our strain differs in having 8-spored in ascus and 6–7-septate ascospores, while P. taiwanense (MFLU 18-0083) having 4-spored in ascus and 15–17-septate. However, LSU and ITS sequences indicated that they are conspecific (Hyde et al. 2018a). Therefore, P. taiwanense is reported from submerged wood in a freshwater habitat for the first time in Thailand. If we used protein coding genes, they may however prove to be distinctive species, as showed by the morphological evidence.
Figure 1 – Poaceascoma taiwanense (MFLU 21-0055, new record). a Ascomata immersed, aggregated, erumpent on the dead wood. b Longitudinal sections of ascomata. c Peridium. d Pseudoparaphyses. e–h Asci. i–n Ascospores. o Germinated ascospore. p, q Culture on MEA from surface and reverse at 1 month. Scale bars: b=50 μm, c–n=20 μm, o=30 μm
Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, TEF1-α, SSU and ITS sequence data of Poaceascoma taxa and related genera in Lentitheciaceae. Massarina cisti CBS 266.62 and M. eburnea CBS 473.64 are selected as the outgroup taxa. Bootstrap support values for maximum likelihood (MLBS, left) equal to or greater than 70% is given above the nodes. Bayesian posterior probabilities (BYPP, right) equal to or greater than 0.95 are given above the nodes. Ex-type strains are in bold and newly generated sequence is in blue