Nigrograna thailandica Samarak. & K.D. Hyde, sp. nov.

Index Fungorum number: IF 556462; MycoBank number: MB 556462; Facesoffungi number: FoF 06105; Fig. 1

Etymology – The specific epithet reflects the name of Thailand, where the species was collected

Saprobic on dead branches of an unidentified plant. Sexual morph: Ascomata 250–380 μm high×390–440 μm diam., perithecioid, single or gregarious, immersed in bark, sometimes erumpent, subglobose or ellipsoidal, black, with an ostiole, cylindrical neck. Ostiole mostly central, brittle. Peridium 3–4-layered, composed of textura angularis cells, outer layer, dark brown, thick-walled, large cells, often surrounded by an olivaceous to dark brown subiculum of 1.5–2.4 μm wide brown hyphae, middle and inner layers, pale brown, thin-walled small cells. Hamathecium composed of 1.4–2 μm (x=1.7 μm, n=25) wide, numerous, distally tapering, rarely trabeculate pseudoparaphyses. Asci 50–95 μm×8.5–11 μm (x=80×10 μm, n=20), 8-spored, bitunicate, fissitunicate, clavate to cylindricclavate, short pedicellate, apically rounded, sometimes with an ocular chamber. Ascospores 13.8–16×4.2–5.6 μm (x = 14.8 × 4.9 μm, n = 30), biseriate, fusoid to clavate, yellowish-brown to dark brown, 3-septate, apical cell often acute, second cell usually slightly widened, constricted at the medium, only slightly at other septa, straight or curved, terminal cells often slightly longer than mid cells. Asexual morph: Undetermined.

Culture characteristics – Ascospore germinating within 12 h on PDA at 25 °C, germ tube from four cells. Colonies on PDA reaching 23.5 mm diam. after 16 days at 25 °C, dull, white to light brown, circular, flat, slightly woolly, smooth margin; reverse dark brown centre and light brown marginal area.

Material examined – Thailand, Lampang Province, Wang Nuea, on dead branches of an unidentified plant, 18 August 2017, M.C. Samarakoon, SAMC009 (MFLU 18-0851, holotype; HKAS 102335, isotype), ex-type culture, MFLUCC 17-2663.

GenBank numbers – ITS: MK762709, LSU: MK762716, SSU: MK762704

Notes – Our collection (MFLU 18-0851) is morphologically similar to other taxa in Nigrograna in having globose to subglobose ascomata, periphysate ostioles, pseudoparenchymatous peridium, clavate asci, and asymmetric, fusoid to narrowly ellipsoid ascospores. Our collection is in a cluster with N. yasuniana with ML=100%, BI=1.00 statistical support. The base pair comparison of ITS shows 98% similarity (452/461, 3/461 gaps) of N. thailandica to N. jinghongensis (HKAS 115776). However, N. yasuniana was described as an endophyte from South and Central America. Since there is an incomplete morphological comparison, our combined phylogeny (LSU-SSU-tef1-α-rpb2) reveals that our strain forms a distinct clade in Nigrograna (Ahmed et al. 2018; Kolařík 2018), as we introduce this collection as Nigrograna thailandica (Fig. 2).

Figure 1 – Nigrograna thailandica (MFLU 18-0851, holotype). a–d Ascomata on the substrate. e, i Cross sections of ascomata. f Section of the peridium. g Subicular hyphae. h Pseudoaraphyses. j–m Asci. n–r Ascospores. s Germinating ascospore. t Upper view of the colony. u Reverse view of the colony. Scale bars: a, b=1 cm, d=500 μm, c, e=200 μm, i=100 μm, f, j–m=20 μm, g, n–s=10 μm, h=5 μm

Figure 2 – Phylogram generated from ML analysis based on combined LSU-SSU-tef1-α-rpb2 sequence data of the genus Nigrograna. Thirty-six strains are included in the combined analyses which comprised 3799 characters (833 characters for LSU, 1023 characters for SSU, 933 characters for tef1-α, 1010 characters for rpb2). The tree topology of the maximum likelihood analysis is similar to the Bayesian analysis. The best RaxML tree with a final likelihood value of − 14,937.288660 is presented. The matrix had 951 distinct alignment patterns, with 25.69% of undetermined characters or gaps. Evolutionary models applied for all genes are GTR+G+I, respectively. Bootstrap support for ML greater than 50% and Bayesian posterior probabilities greater than 0.95 are given at nodes, respectively. The tree was rooted with Occultibambusa chiangraiensis (MFLUCC 16-0380), O. maolanensis (GZCC 16-0116), Parathyridaria ramulicola (CBS 141479) and Thyridaria broussonetiae (WU36864). Ex-type strains are in bold. The newly generated sequences are indicated in blue bold