Xenoroussoella triseptata Mapook & K.D. Hyde, sp. nov.

MycoBank number: MB 557368; Index Fungorum number: IF 557368; Facesoffungi number: FoF 07823; Fig. 82

Etymology: The specific epithet “triseptata” is based on the 3-septate ascospores

Holotype: MFLU 20-0382

Saprobic on dead stems of Chromolaena odorata. Sexual morph: Ascomata (155–)170–220 µm high × 185–235 µm diam. ( x̄ = 185 × 210 µm, n = 5), immersed, solitary or scattered, appearing as orange spots, coriaceous, globose to subglobose, brown to dark brown. Ostiolar neck protruding. Peridium 10–15 µm wide, comprising 2–4 layers of hyaline to brown cells of textura angularis. Hamathecium comprising 1.9–3 µm wide, oblong to cylindrical, septate, branching pseudoparaphyses. Asci 55–70 × 10.5–15 µm ( x̄ = 65 × 12 µm, n = 20), 8-spored, bitunicate, cylindric-clavate to clavate, straight or slightly curved, apically rounded, short pedicellate. Ascospores 13.5–17 × 5–7.5 µm ( x̄ = 15 × 6.5 µm, n = 30), bi-seriate, initially hyaline, 1-septate when immature, becoming pale brown to dark brown at maturity, ellipsoid to obovoid, 3-septate, with irregular longitudinal striations, constricted at the central septum, straight or slightly curved, without gelati- nous sheath. Asexual morph: Undetermined.

Culture characteristics: Ascospores germinating on MEA within 24 h. at room temperature and germ tubes produced from both ends. Colonies on MEA circular, mycelium slightly raised, undulate, cultures white, pale grayish brown from the centre of the colony with olivaceous to olivaceous- brown at margin on surface, creamy-white in reverse, olivaceous-brown to brown from the centre of the colony with olivaceous to olivaceous-brown at margin (Fig. 83).

Pre-screening for antimicrobial activity: Xenoroussoella triseptata (MFLUCC 17-1438) showed no inhibition of E. coli, B. subtilis and M. plumbeus.

Material examined: THAILAND, Chiang Rai Province, Doi Pui, on dead stems of Chromolaena odorata, 5 August 2015, A. Mapook (DP22, MFLU 20-0382, holotype); ex- type culture MFLUCC 17-1438.

GenBank numbers: LSU: MT214437, ITS: MT214343, SSU: MT214391, TEF1: MT235767, RPB2: MT235804

Notes: In a BLASTn search of NCBI GenBank, the closest match of the ITS, LSU, TEF1 and RPB2 sequences of Xenoroussoella triseptata (MFLUCC 17-1438, ex-holotype) with 99.65% (LT796887), 99.88% (LN907477), 99.38% (LT797127) and 97.80% (LT797047) similarity, respectively, was Arthopyrenia sp. strain UTHSC: DI16-334, while the closest match of the SSU sequence with 93.39% similarity was Roussoella intermedia (strain KT 2303, AB524483). In the present phylogenetic analysis, Xe. triseptata (MFLUCC 17-1438) is closely related to Arthopyrenia sp. UTHSC: DI16-334 (Fig. 76). However, we could not compare the morphological characteristics of both strains as the morphology of Arthopyrenia sp. (UTHSC: DI16-334) has not been reported. Therefore, we introduce a new species based on phylogeny and their distinct morphology in having 3-septate ascospores, with irregular longitudinal striations.

Fig. 76 Phylogram generated from maximum likelihood anal- ysis based on combined dataset of LSU, ITS, TEF1, RPB2 and SSU sequence data. Eighty- four strains are included in the combined sequence analysis, which comprise 4416 charac- ters with gaps. Tree topology of the ML analysis was similar to the BYPP. The best scoring RAxML tree with a final likeli- hood value of − 35074.673502 is presented. The matrix had 1690 distinct alignment pat- terns, with 39.45% of unde- termined characters or gaps. Estimated base frequencies were as follows: A = 0.246392, C = 0.254324, G = 0.268438, T = 0.230846; substitution rates: AC = 1.657341, AG = 4.989387, AT = 2.205689, CG = 1.285998, CT = 10.615734, GT = 1.000000; gamma distribution shape parameter α = 0.486933. Bootstrap sup- port values for ML equal to or greater than 60% and BYPP equal to or greater than 0.90 are given above or below the nodes. Newly generated sequences and new combination are in dark red bold and type species are in bold. Occultibambusa bambusae (MFLUCC 11-0394) and O. bambusae (MFLUCC 13-0855) are used as outgroup taxa

Fig. 82 Xenoroussoella trisep- tata (holotype) a, b Appear- ance of immersed ascomata on substrate. c Section through ascoma. d Ostiole. e Peridium. f Pseudoparaphyses. g–j Asci. k–p Ascospores. Scale bars: a = 200 µm, b = 100 µm, c = 50 µm, d, g–j = 20 µm, e = 10 µm, f, k–p = 5 µm

Fig. 83 Culture characteristic on MEA: Xenoroussoella triseptata (MFLUCC 17-1438)