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

Fig. 7

Etymology.

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

Holotype.

MFLU 25-0073 .

Description.

Saprobic on recently dead branches of Pterocarpus sp. Sexual morph. Ascomata 225–237 μm high, 355–373 µm wide, (xˉ = 231 × 360 µm, n = 5), immersed, visible as black spots, host tissue becoming reddish around the apical pores, solitary to aggregated, scattered, globose to sub-globose, brown. Ostiole central, 70–60 wide, comprising a short papilla. Peridium 12–16 µm wide (xˉ = 14 µm, n = 5), two-layered; outer layer wide, dark brown, thick-walled cells of textura angularis, inner layer comprising one layer of hyaline cells of textura angularis, thin-walled. Paraphyses 4–6 µm wide (xˉ = 4.8 µm, n = 5), hyaline, septate, guttulate, embedded in a gelatinous matrix. Asci 95–116 × 9–14 µm (xˉ = 106 × 11 µm, n = 20), 8 - spored, unitunicate, cylindrical, deliquescing, with short pedicel, apically rounded, with a J +, wedge-shaped, apical ring. Ascospores 19–21 × 5–7 µm (xˉ = 20 × 6 µm, n = 20), ellipsoidal, hyaline when immature, turning yellow to yellowish-brown when mature, 3 - septate, guttulate, smooth-walled, surrounded by a mucilaginous sheath. Asexual morph: Not observed.

Culture characteristics.

Colonies on MEA reaching 4 cm diam. after 15 days at 27 ° C, from above white, dense, irregular, flattened with smooth surface, with lobate margin; reverse yellow red in the middle, yellow at the margin.

Material examined.

Thailand • Chiang Rai Province, Mae Fah Luang University premises ( 20°02′42″N, 99°53′41″E), on recently dead branches of Pterocarpus rotundifolius ( Fabaceae ), 06 November 2023, Zaw Lin Tun H 62 ( holotype MFLU 25-0073 ), ex-type culture MFLUCC 25-0195 .

Additional specimens examined.

Thailand • Chiang Rai Province, Mae Fah Luang University premises ( 20°02′42″N, 99°53′41″E), on dead branches of Pterocarpus rotundifolius ( Fabaceae ), 06 November 2023, Zaw Lin Tun 2 H 62 ( MFLU 25-0072 ) .

Notes.

Based on our phylogenetic analyses, A. pterocarpi formed a separate lineage, sister to A. curvaticonidia ( MFLUCC 18-0620 , HKAS 102288), with 100 % ML and 1.00 PP bootstrap support (Fig. 1 ). Amphisphaeria pterocarpi can be distinguished from A. curvaticonidia by its smaller ascomata (225–237 × 355–373 µm vs. 320–390 × 360–410 µm), asci (95–116 × 9–14 µm vs. 121–162 × 10.5–17.5 µm), and ascospores (19–21 × 5–7 µm vs. 17–23 × 6–9 µm) ( Samarakoon et al. 2020). Additionally, the ascospores of A. pterocarpi are ellipsoidal, whereas A. curvaticonidia have oblong or narrowly fusiform ascospores. The asexual morph of A. curvaticonidia has been documented as coelomycetous in culture, while the asexual morph of A. pterocarpi has yet to be observed in culture ( Samarakoon et al. 2020). When considering the base pair differences (without gaps) between A. pterocarpi and A. curvaticonidia ( MFLUCC 18-0620 , HKAS 102288), 2.5 % base pair differences (without gaps) were revealed in LSU (27 / 1040 bp) and 3.30 % base pair differences (without gaps) in ITS (18 / 545 bp). Due to the distinct morphology and phylogenetic evidence, along with the species delineation guidelines provided by Chethana et al. (2021), we introduce A. pterocarpi 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 7. Amphisphaeria pterocarpi (MFLU 25-0073, holotype). A. Dead branches; B. Appearance of ascomata on host (arrows indicate ascomata as spots on host surface); C, D. Vertical sections through ascomata; E. Vertical section of peridium; F. Paraphyses; G, H. Asci; I. J + apical ring; J – L. Ascospores; M. Germinated ascospore; N. Upper view of culture; O. Reverse view of culture. Scale bars: 100 μm (C, D); 10 μm (E); 5 μm (F, G); 50 μm (H, I); 20 μm (J – M).