Amphisphaeria mesuae Z. L. Tun & K. D. Hyde, 2025

Tun, Zaw Lin, Bundhun, Digvijayini, Bhunjun, Chitrabhanu S., Maharachchikumbura, Sajeewa S. N., Thiyagaraja, Vinodhini, Al-Otibi, Fatimah & Hyde, Kevin D., 2025, The addition of six novel species and a new record of Amphisphaeria from northern Thailand, MycoKeys 125, pp. 1-31 : 1-31

Amphisphaeria mesuae Z. L. Tun & K. D. Hyde sp. nov.

Fig. 2

Etymology.

The epithet refers to the host genus, Mesua , from which the fungus was isolated.

Holotype.

MFLU 25-0069 .

Description.

Saprobic on decaying twigs of Mesua sp. Sexual morph: Ascomata 520–580 μm high, 260–290 µm wide (xˉ = 549 × 272 µm, n = 5), immersed, visible as black spots with tiny pores, flat, scattered or aggregated, globose to subglobose, ostiolate. Peridium 14–18 µm (xˉ = 15 µm, n = 5), two-layered; outer layer wide, comprising thick-walled, dark brown cells of textura angularis, inner layer thin, composed of hyaline textura angularis cells. Paraphyses 3–5 µm wide, hyaline, septate, longer than asci, narrow towards the apex. Asci 86–134 × 7–13 µm (xˉ = 115 × 9 µm, n = 20), 8 - spored, unitunicate, cylindrical, with short pedicel, apically rounded, with a J +, apical ring. Ascospores 14–18 × 5–6.8 µm (xˉ = 15 × 6 µm, n = 20), uniseriate, ellipsoidal, hyaline when immature, turning sub-hyaline to pale brown at maturity, 1 - septate, slightly constricted at the septum, guttulate, smooth-walled, lacking a sheath in Indian ink. Asexual morph: Not observed.

Culture characteristics.

Colonies on MEA, reaching 4 cm diam. after 15 days at 27 ° C, from above white to pale yellow radiating outwards, dense, circular to slightly irregular, flattened with smooth surface, with smooth margin; reverse pale brown in the middle, yellowish brown at the margin.

Material examined.

Thailand • Chiang Rai Province, Mae Fah Luang University ( 20°02′42″N, 99°53′41″E), on decaying dead twigs of Mesua sp. ( Calophyllaceae ), 02 October 2023, Zaw Lin Tun P 11 ( holotype MFLU 25-0069 ); ex-type culture MFLUCC 25-0197 .

Notes.

Phylogenetic analyses revealed that Amphisphaeria mesuae ( MFLUCC 25-0197 ) clustered with Amphisphaeria hibiscicola ( HKAS 136910) and Amphisphaeria umbrina ( PRA JV 24328 ) in (Fig. 1 ). The interspecies genetic distances between A. mesuae ( MFLU 25 - 0069 ) and A. hibiscicola ( HKAS 136910) showed the following base pair differences (without gaps): 5.7 % for LSU (49 / 935 bp) and 11.18 % for ITS (66 / 559 bp). Amphisphaeria mesuae ( MFLUCC 25-0197 ) and Amphisphaeria umbrina ( PRA JV 24328 ) showed the following base pair differences (without gaps): 3.3 % for LSU (28 / 844 bp) and 9.45 % for ITS (54 / 571 bp). Morphologically, A. mesuae differs from A. hibiscicola by having taller ascomata (520–580 μm) compared to those of A. hibiscicola (212–450 μm), whereas A. hibiscicola has broader ascomata (456–570 μm wide) than A. mesuae (260–290 μm) ( Sun et al. 2025). The asci of A. mesuae (86–134 × 7–13 µm) are smaller than those of A. hibiscicola (122–152 × 6–8 µm) ( Sun et al. 2025). The ascospores of A. mesuae (14–18 × 5–6.8 µm) are ellipsoidal, while the ascospores of A. hibiscicola (8–14 × 3.5–5 μm) are fusiform ( Sun et al. 2025). Amphisphaeria hibiscicola has a gelatinous sheath, whereas A. mesuae lacks a sheath ( Sun et al. 2025

Morphologically, A. mesuae differs from A. umbrina by having higher ascomata (520–580 μm vs. 400–480 μm) but narrower width (260–290 μm vs. 560–640 μm) ( Wang et al. 2004). The asci of A. mesuae (122–152 × 6–8 µm) are also smaller than those of A. umbrina (150–170 × 11–13 µm) ( Wang et al. 2004). Similarly, the ascospores of A. mesuae (14–18 × 11–12 µm) are smaller than those of A. umbrina (18–22 × 6–8 μm) ( Wang et al. 2004).

Based on the distinct morphology and phylogenetic evidence, along with the recommendations for species delineation proposed by Chethana et al. (2021) and Maharachchikumbura et al. (2021), we introduce A. mesuae as a new species.

Figures

Figure 1. Phylogram generated from ML analysis based on combined LSU, ITS sequence data. Bootstrap support values for ML ≥ 75 % and PP ≥ 0.90 are indicated near the corresponding nodes. The tree is rooted with Beltrania rhombica (CBS 123.58), Beltraniella endiandrae (CBS: 137976), and Beltraniopsis longiconidiophora (MFLUCC 17-2139). Type and reference strains are in bold, while the novel strains are in bold red.

Figure 2. Amphisphaeria mesuae (MFLU 25-0069, holotype). A. Decaying woody twig; B. Appearance of an ascoma on the host; C, D. Vertical section through an ascoma; E. Vertical section of peridium; F. Paraphyses; G. J + Apical ring; H, I. Asci; J – M. Ascospores; N. Upper view of culture; O. Reverse view of culture. Scale bars: 200 μm (B, C); 100 μm (D); 20 μm (E); 5 μm (F, G); 40 μm (H, I); 10 μm (J – M).