Annulohypoxylon chiangraiense
Annulohypoxylon chiangraiense Rathnay., K.D. Hyde & Chethana, in Rathnayaka, Chethana, Manowong, Bhagya, Win, Tun, Mapook & Hyde, MycoKeys 120: 56 (2025)
Index Fungorum number: IF 903883 Facesoffungi number: FoF 17288
Saprobic on the dead branch of Tamarindus indica. Sexual morph: Ascostromata 0.4–0.6 × 0.8–1.5 mm (x̄ = 0.5 × 1.2 mm, n = 10), semi-immersed to superficial, with the base immersed, pulvinate to hemispherical, solitary or clustered, spherical surface black, carbonaceous. Ascomata immersed in stroma, globose to subglobose, black. Peridium 18–30 μm wide, composed of several layers of hyaline to dark brown cells of textura angularis. Paraphyses 3–6 μm wide, hyaline, abundant, persistent, unbranched, septate. Asci 90–145 × 8–5 μm (x̄ = 124 × 7 μm, n = 20), 8-spored, unitunicate, cylindrical, short pedicellate, with an apical ring not bluing in the Melzer’s reagent (without KOH pretreatment). Ascospores 10–12 × 4–7 μm (x̄ = 11 × 5 μm, n = 30), uniseriate, one-celled, inequilaterally ellipsoidal, with narrowly rounded ends, hyaline at immature stages, dark brown when mature, guttulate. Asexual morph: Undetermined.
Culture characters: Ascospores germinated on the PDA within 24 hours at 25 °C. Germ tubes are produced from one side of the ascospore. Colonies on the PDA reaching 1.0–2.0 cm diam. after five days at 25 °C, circular in shape, white at first, cottony, slightly thinning towards the edge, with white color in the middle and pale yellow color in the margin of the front view, and pale yellow in the reverse view.
Material examined: Thailand near Nang Lae waterfall, Chiang Rai, on decaying wood of Tamarindusindica (Fabaceae), 18 March 2024, Achala Rathnayaka, AA11 (MFLU 24-0524, holotype); ex-type living culture, MFLUCC 24-0606.
Notes: Annulohypoxylon is a speciose genus with more than 60 species; however, the present study shows the genus to be more diverse as predicted by Bhunjun et al. (2024). Based on the multi-gene phylogeny (ITS, LSU, β-tub, and rpb2), Annulohypoxylonchiangraiense (MFLUCC 24-0606) formed a distant lineage sister to A.archeri (SGNLB 5) and A.microdiscum (HMAS 285320) with 100% ML bootstrap and 1.00 PP support. Annulohypoxylon chiangraiense fits within the generic concept of Annulohypoxylon by having spherical, carbonaceous ascostromata; 8-spored, cylindrical asci; and ellipsoid, light- to dark-brown ascospores (Li et al. 2016). Annulohypoxylonchiangraiense differs from both A.archeri and A.microdiscum by having smaller ascostromata (0.4–0.6 × 0.8–1.5 mm vs. 8–20 × 5–10 mm and 0.5–4 × 0.3–2 cm) (Raei et al. 2012; Cruz et al. 2020). The asci of A. chiangraiense are shorter and wider (90–145 × 8–5 μm) than A. microdiscum (130–187 × 5–6.5 μm). However, asci were not observed in A. archeri (Cruz et al. 2020). In A .chiangraiense, the apical ring does not turn blue in Melzer’s iodine reagent, whereas in A. microdiscum, the apical ring turns blue in Melzer’s iodine reagent (Raei et al. 2012). While ascospores of both A.archeri and A.microdiscum have a straight germ slit, such a character was not observed in the ascospores of A. chiangraiense (Raei et al. 2012; Cruz et al. 2020). When comparing the ITS base pair differences of A. chiangraiense with A. archeri and A. microdiscum, it shows 1.6% (8/564) and 1.9% (10/533) differences (without gaps), respectively. Based on the distinct morphology and phylogenetic evidence, we established Annulohypoxylon chiangraiense as a new species.
Figure 1. Phylogram generated from ML analysis based on the combined dataset of ITS, LSU, β-tub, and rpb2. The tree is rooted to Biscogniauxiapetrensis (HKAS102388). Bootstrap support values for ML ≥ 70% and Bayesian posterior probabilities (PP) ≥ 0.90 are noted at the nodes. Strain numbers are noted after the species names. Strains isolated in this study are represented in blue, and type strains are in bold.
Figure 2. Annulohypoxylon chiangraiense on a dead branch of Tamarindusindica (MFLU 24-0524, Holotype). a. Sustrate; b, c. Stromata on the host; d. Cross section of the stroma; e. Peridium; f. Paraphyses; g–j. Asci; k. Ascal apical apparatus (not staining in Melzer’s reagent); l–o. Ascospores; p, q. Colony on the PDA (p upper, q lower). Scale bars: 5 mm (b); 1 mm (c); 500 μm (d); 20 μm (e–k); 10 μm (l–o).
- Rathnayaka AR, Chenthana KWT, Manowong A, Bhagya T, Win H, et al. (2025) Taxonomy, phylogeny, and bioactive potential of Xylariales (Sordariomycetes, Ascomycota) from Thailand: novel species discovery, new host and geographical records, and antibacterial properties. MycoKeys 120, 35-117.
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