Dyfrolomyces distoseptatus M. Niranjan & V.V. Sarma, in Hongsanan et al., Fungal Diversity 105:73 (2020)

Index Fungorum number: IF 556726; MycoBank number: MB 559726; Facesoffungi number: FoF 06625; Fig. 1

Saprobic on submerged decaying wood in a freshwater habitat. Sexual morph Ascomata 600–800×350–530 μm (x̅=682×433 μm, n=10), perithecial, immersed in periderm, erumpent neck with pseudoparaphyses, clypeate, ostiolate, papillate. Peridium 30–40 μm, with two strata, outer thick, carbonaceous and inner brown and hyaline cells of textura angularis. Peridium comprising of dark pigmented cells of textura angularis. Hamathecium pseudoparaphyses, filamentous, septate, unbranched, 2–4 μm wide, long, dense, longer than asci. Asci thin walled and quickly evanescent, unable to observed. Ascospores 17–26×3.5–6 μm (x̅=23×5 μm, n=30), uniseriate, hyaline, 1–2-distoseptate in early stages, usually 3-distoseptate, with a large guttules at each cell, fusoid, acute ends, apical ends slightly bent. Asexual morph Undetermined.

Culture characteristics – Conidia germinating on malt extract agar (MEA) within 24 h. Germ tubes produced from the basal and apical cell of conidia. Colonies growing on MEA, reaching 25–30 mm in 2 weeks at 25 °C, colony circular, entire to filiform edge, dry, surface rough, with dense mycelium, grayish brown in top view, reverse dark brown.

Material examined – THAILAND, Tak Province, Tha Sing Yang, Ban Mae Ja Wang on submerged decaying wood in a freshwater river, 17 October 2019, N. Padaruth, CC51 (MFLU 21-0121, new geographical record), living culture, MFLUCC 21-0102.

GenBank numbers – ITS=MT864349, LSU=MT860427.

Notes – Dyfrolomyces distoseptatus was introduced by Hongsanan et al. (2020b) isolated from an unidentified decaying twig in India. Our new isolate, Dyfrolomyces distoseptatus MFLUCC 21-0102 clustered with D. distoseptatus strain NFCCI: 4377 with 95% MPBS, 96% MLBS, 1.00 BYPP (Fig. 2). Dyfrolomyces distoseptatus clustered with D. sinensis and D. phetchaburiensis, however, D. distoseptatus differs having 2–3 septate ascospores with acute ends, while D. sinensis and D. phetchaburiensis have 6–7 septate and 1–10 septate ascospores, respectively (Hyde et al. 2017, 2018a). Unlike other species (viz. D. aquatica, D. mangrovei, D. marinosporus, D. rhizophorae and D. thailandicus), D. distoseptatus lacks a gelatinous sheath around the ascospores (Hyde 1992; Tsui et al. 1998; Pang et al. 2013; Hongsanan et al. 2020b). In addition, Dyfrolomyces distoseptatusis strains (MFLUCC 21-0102 and NFCCI: 4377) clustered with D. thamplaensis, however, D. distoseptatusis differs in having longer ascospores (17–26.5×3.5–6.5 μm) whereas D. thamplaensis has shorter ascospores (9.5–23.5×5–6.5 μm) (Fig. 1). A comparison of the ITS nucleotides indicates that our strain of D. distoseptatus is largely similar to strain NFCCI: 4377 based on DNA sequence (Jeewon and Hyde 2016). Therefore, we identify our new collection as D. distoseptatus which is the new record from a freshwater habitat in Thailand. Since the ascal morphology was not included in the observed substrates, recollection of the specimen is recommended.

Figure 1 – Dyfrolomyces distoseptatus (MFLU 21-0121, new geographical record). a Vertical section of ascoma. b Peridium. c Pseudoparaphyses. d–h Ascospores (Note: Asci thin walled and quickly evanescent, unable to observe). i Germinated ascospore. j, k Culture on MEA from surface and reverse. Scale bars: a=200 μm, b=100 μm, c=20 μm, d–i=10 μm

Figure 2 – Phylogram generated from maximum likelihood analysis based on combined LSU, SSU and ITS sequence data representing the species of Dyfrolomycetales and Acrospermales. Related sequences are taken from Hongsanan et al. (2020b). Kirschsteiniothelia lignicola (MFLUCC 10-0036) and K. atra (AFTOL-ID 273) are used as the outgroup taxa. Twenty-one taxa are included in the combined analyses which comprised 3532 characters (1359 characters for LSU, 1669 characters for SSU, 504 characters for ITS) after alignment. The best scoring RAxML tree with a final likelihood value of − 10567.325091 is presented. The matrix had 700 distinct alignment patterns, with 44.47% of undetermined characters or gaps. Estimated base frequencies were as follows: A=0.242587, C=0.243215, G=0.300854, T=0.213344; substitution rates: AC=1.335920, AG=2.320033, AT=0.575696, CG=1.101975, CT=5.314102, GT=1.000000; gamma distribution shape parameter α=0.248862. The MP analysis resulted a single most parsimonious tree (TL=1145, CI=0.851, RI=0.803, RC=0.683, HI=0.149). Bootstrap support values for ML and MP equal to or greater than 70% and BYPP equal to or greater than 0.95 are given above the nodes. The newly generated sequence is in blue