Amphisphaeria micheliae

Amphisphaeria micheliae M.C. Samar., Jian K. Liu & K.D. Hyde, in Samarakoon, Maharachchikumbura, Liu, Hyde, Promputtha & Stadler, J. Fungi 6(3): 16 (2020)

Index Fungorum number: IF 836112 Facesoffungi number: FoF 08752

            Saprobic on decaying branch of Micromelum integerrimum (Roxb. ex DC.) Wight & Arn. ex Voigt. (Rutaceae). Sexual morph: Ascomata 200–310 µm high × 320–410 µm wide (x̄ = 260 × 370 µm, n = 8), immersed, appearing as a tiny dark spot surrounded by a light-coloured area, solitary, scattered, subglobose to oblate, loosely aggregated on the host surface, papillate ostiole. Ostiole 70– 80 µm high × 50–60 µm wide, centric. Periphyses short, hyaline, 1–2 µm wide (x̄ = 1.5 µm, n = 15). Peridium two-layered; outer layer 6–12 µm (x̄= 8.5 µm, n = 6), dense, brown to black cells of textura angularis, thick-walled, inner layer 4–8.5 µm (x̄ = 6 µm, n = 6), loosely arranged, hyaline cells of textura angularis, thin-walled. Hamathecium comprising 3–5.5 µm wide, cellular, hyaline, septate, guttulate paraphyses. Asci 90–135 µm × 6.5–9.5 µm (x̄= 118 × 8.5 µm, n = 25), 8-spored, unitunicate, cylindrical, short or elongated pedicel, apically rounded with J+, discoid ring. Ascospores 15–21 µm × 6–7.5 µm (x̄ = 18 × 6.5 µm, n = 30), 2.8 length/width ratio, uniseriate, oblong or narrowly fusiform, hyaline at first, turning pale yellow to yellowish brown at maturity, slightly overlapping, uniseptate, guttulate, with a slight constriction at the septum, straight or slightly curved, smooth-walled. Asexual morph: Undetermined.

 Culture characteristics: Colonies on PDA, reaching 70–75 mm diam. after two weeks (at 25 ± 5 ˚C), colonies flat, dense, with a smooth and velvety surface, lobate margin, white to light brown; reverse view: yellow to brown concentric rings, pale brown to whitish mycelium at the margin.

Material examined: Thailand: Chiang Rai Province, Doi Tung forest, on a decaying branch of Micromelum integerrimum (Rutaceae), 08 March 2024, L.S. Pathirana (MFLU 25-0078), living culture (MFLUCC 24-0324).

Notes: Based on the multigene phylogenetic analysis using ITS, LSU, and rpb2 sequence dataset, our isolate (MFLUCC 24-0324) clustered within Amphisphaeria micheliae clade (UESTCC 23.0123, UESTCC 23.0124, UESTCC 23.0125, MFLU 20-0172, HKAS107012, and MFLU 21- 0207), sister to UESTCC 23.0123 with 85 % ML value and 0.65 PP support (Figure 1). Base pair similarity between the ITS, LSU, and rpb2 sequences of our isolate (MFLUCC 24-0324) and the A. micheliae clade (Table 3), confirms its genetic affinity with the clade and reinforces its classification as a member of this group. The topology of our phylogenetic tree was similar to previously published phylograms of Amphisphaeria. Our isolate (MFLUCC 24-0324) is similar to Amphisphaeria by having solitary, scattered, aggregated, immersed, and ostiolate ascomata that appear as dark spots. It also resembles the generic description of Amphisphaeria by having ostiole with periphyses, peridium with two layers, unitunicate asci with a discoid, J+, apical ring, and brown ascospores (Cesati et al. 1863, Samarakoon et al. 2020, Samarakoon 2023, Li et al. 2024). Our new collection (MFLU 24-0324) has similar morphological characteristics to the holotype of A. micheliae (HKAS107012), in having uniseptate, oblong or narrowly fusiform ascospores and subglobose to oblate ascomata (Samarakoon et al. 2020). Thus, we identify our isolate as A. micheliae based on morphology and molecular evidence. 

Figure 1.   Phylogram generated from maximum likelihood analysis using concatenated ITS-LSU-rpb2 sequence datasets. The tree is rooted with Beltraniella endiandrae (CBS 137976), Beltrania rhombica (CBS 123.58), and Beltraniopsis longiconidiophora (MFLUCC 17-2139). Bootstrap support values for ML equal to or greater than 80% and PP values equal to or greater than 0.90 are reported at the nodes (ML/PP). The new isolate is in blue and the type species are in bold.