Anastomitrabeculia chiangraiensis Gomdola, Z. L. Tun & Yong Wang bis 2026, sp. nov.

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Anastomitrabeculia chiangraiensis Gomdola, Z. L. Tun & Yong Wang bis sp. nov. Fig. 2 Holotype. MFLU 26-0002. Etymology. Referring to Chiang Rai Province, where the species was collected. Diagnosis. Ascospores without longitudinal striations. Description. Saprobic on stems of an unidentified host. Sexual morph: Ascomata 350–450 μm diam. (x ̄ = 405 μm, n = 5), 375–500 μm high (x ̄ = 445 μm, n = 5), semi-immersed or immersed, solitary, aggregated or scattered, globose to subglobose, black, ostiolate. Ostiole 50–75 μm diam. (x ̄ = 61.9 μm, n = 5), 45–80 μm high (x ̄ = 72 μm, n = 5), central. Peridium 5.5–10 μm thick (x ̄ = 7.4 μm, n = 5), composed of 4–6 layers of pale brown to brown textura angularis cells, with hyaline inner layers. Hamathecium consisting of dense, filiform, filamentous, trabeculate pseudoparaphyses. Pseudoparaphyses 0.5–2 μm wide (x ̄ = 1.6 μm, n = 30), branched or unbranched, septate, hyaline. Asci (89 –) 128–197 × 15–21 μm (x ̄ = 173 × 18.6 μm, n = 20), bitunicate, fissitunicate, 8 - spored, cylindrical to clavate, straight or slightly curved, broadly rounded at the apex with an ocular chamber and mostly with a short pedicel [8–15 (– 19) μm long (x ̄ = 11.1 μm, n = 20)]. Ascospores 25–30 × 7–8.5 µm (x ̄ = 28.1 × 7.8 µm; n = 20), overlapping uni- to biseriate, hyaline, broadly fusiform or subcylindrical, broader at the center and tapering towards the ends, mostly straight, smooth-walled, 1 - median-septate, constricted at the septum, containing two large guttules in each cell and surrounded by a mucilaginous sheath of nearly equal thickness [0.7–1.8 μm long (x ̄ = 1.2 μm, n = 20)]. Asexual morph: Not observed. Material examined. Thailand. • Chiang Rai Province: Mae Fah Luang University premises, on dead stems of an unidentified host, 15 June 2024, Zaw Lin Tun, P 21 (MFLU 26-0002, holotype). Same details, P 21 - B (MFLU 26-0003). GenBank numbers. MFLU 26-0002: ITS = PX 940740, 28 S = PX 956940, rpb 2 = PZ 097584; MFLU 26-0003: ITS = PX 940741, 28 S = PX 956941. Notes. Our strains (MFLU 26-0002 and MFLU 26-0003) conform to the morphological species concept of Anastomitrabeculia, which is characterised by bitunicate, fissitunicate and cylindrical to clavate asci with an ocular chamber, and hyaline, 1 - septate, broadly fusiform ascospores that taper towards the ends and are surrounded by a mucilaginous sheath (Bhunjun et al. 2021). Our strains clustered together with maximum support (100 % ML, 1.00 PP) and formed a sister lineage to the clade comprising isolates of A. didymospora (MFLUCC 16-0412; ex-type, MFLUCC 16-0417, MFLUCC 11-0197 and MFLUCC 11-0200), with 89 % ML bootstrap support (Fig. 1). Excluding gaps, significant interspecies genetic distances were observed: 19.1 % in ITS (92 / 482 bp) between our strains and A. didymospora (MFLUCC 11-0197 and MFLUCC 11-0200), 4.6 % in 28 S (38 / 827 bp) between our strains and the ex-type of A. didymospora (MFLUCC 16-0412) and 15.4 % in rpb 2 between our strain (MFLU 26-0002) and A. didymospora (MFLUCC 11-0200). Morphologically, the most distinguishable feature separating our strains from A. didymospora is the presence of longitudinal striations in the ascospores, a character not observed in our strains (Bhunjun et al. 2021; Phookamsak et al. 2022). Morphological data and multigene phylogenetic analyses support the establishment MFLU 26-0002 and MFLU 26-0003 as a new species, Anastomitrabeculia chiangraiensis, saprobic on stems of an unidentified host in Thailand. This represents the third species in the genus.

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