Pseudothyridariella fagacearum W. X. Su, R. Xu & X. Li, 2025

Pseudothyridariella fagacearum W. X. Su, R. Xu & X. Li sp. nov.

Fig. 4 View Figure 4

Etymology.

Refers to the host family, Fagaceae .

Description.

Saprobic on dead stems of Fagaceae . Sexual morph: Ascomata 110–254 × 145–320 µm (x ̄ = 171 × 213 µm, n = 5), solitary or scattered, immersed, bulge on the branches, visible as black spots, coriaceous, globose to subglobose, brown, ostiolate. Peridium 27.8–32.3 µm wide, thick, multi-layered, composed of 4–6 layers of brown to pale brown cells of textura angularis. Hamathecium comprising 1.9–3.27 µm wide, dense, filiform, branched, transversely septate, hyaline, cellular pseudoparaphyses, embedded in a gelatinous matrix. Asci 88–138 × 24–36 µm (x ̄ = 113 × 30 µm, n = 15), 8 - spored, cylindric, bitunicate, fissitunicate, straight or slightly curved, with a short pedicellate. Ascospores 47–66 × 13–23 µm (x ̄ = 58 × 19 µm, n = 30), hyaline, 1–2 - seriate, partially overlapping, straight or slightly curved, ellipsoid to broadly fusiform, smooth-walled, tapering towards both ends, 8 - septate, constricted at the central septum, the septum breaks from the middle and the contents overflow when mature, with a hyaline gelatinous sheath. Asexual morph: Undetermined.

Culture characteristics.

Ascospores germinate on PDA within 24 h at 25 ° C in the dark. Colonies on PDA, reaching 46–52 mm after 2 weeks at 25 ° C. Culture from above, circular, asperulate, dense, mycelium slightly raised, tangerine in the center, pale orange radiating outward, margin was undulate to petaloid, zonate, with concentric rings; reverse dark orange, pale yellow at margin. Yellow pigmentation diffused into the media.

Material examined.

China, • Jiangxi Province, Anfu , from the branches of Fagaceae , 14 June 2023, Wenxin Su, AF 01 ( HMJAU 70074 , holotype); ex-type living culture, EMFCC 0043 ; ex-isotype living culture, EMFCC 0047 .

GenBank accession number.

EMFCC 0043 : ITS = PQ 557514, SSU = PQ 557516, LSU = PQ 530968, rpb 2 = PQ 736597, tef 1 - α = PQ 683825. EMFCC 0047 : ITS = PV 463747, SSU = PV 490596, LSU = PV 490599, and rpb 2 = PV 670039.

Notes.

In a BLASTn search, the ITS sequence of Pseudothyridariella fagacearum ( EMFCC 0043 ) was 96.21 % similar to P. chromolaenae (MFLUCC 17-1472). The LSU and SSU regions showed 98.73 % and 98.97 % similarity with those of P. aquilariae (ZHKUCC 23–0044). The rpb 2 sequence of P. fagacearum showed 86.87 % similarity with Pseudothyridariella sp. JM- 2024 a, while the tef 1 - α sequence displayed 96.49 % similarity with Pseudothyridariella sp. (RL- 2023 a). In the phylogenetic analyses, our isolates of P. fagacearum ( EMFCC 0043 and EMFCC 0047 ) formed a well-separated lineage distinct in Pseudothyridariella with high statistical support (83 % ML / 0.99 BPP).

The genus Pseudothyridariella currently comprises two asexual species, P. aquilariae and P. idesiae ( Li et al. 2023; Tian et al. 2024), and two sexual morph species, P. chromolaenae and P. mahakoshae ( Devadatha et al. 2018; Mapook et al. 2020). Pseudothyridariella fagacearum can be distinguished from P. chromolaenae and P. mahakoshae by larger asci (70–220 × 10–20 µm vs. 88–138 × 24–36 µm vs. 80–135 × 14–22 µm) and larger ascospores (47–66 × 13–23 µm vs. 23–28 × 9–12.5 µm vs. 17–27 × 5–12 µm). Additionally, the ascospores of P. fagacearum are hyaline, 8 - septate, and lacking a longitudinal septum. In contrast, the ascospores of P. chromolaenae are brown, olivaceous brown to dark brown at maturity, with 5–8 transverse septa and 1 longitudinal septum ( Mapook et al. 2020), while those of P. mahakoshae are hyaline, with 3–6 transverse septa and 1 longitudinal septum ( Devadatha et al. 2018). Therefore, based on both phylogenetic and morphological evidence, P. fagacearum was described herein as a new species.