Byssosphaeria vaginata Y.X. Yu and Y.H Lu, 2025

Yu, Yong-Xiu, Lu, Yu-Hang, Tian, Qing & Dissanayake, Asha J., 2025, Byssosphaeria vaginata, a new species of Melanommataceae from Magnolia officinalis in Sichuan Province, China, Phytotaxa 705 (1), pp. 35-49 : 42

Byssosphaeria vaginata Y.X. Yu and Y.H Lu sp. nov. FIGURE 2

MycoBank: MB 851925

Etymology: —Name reflects the sheath of its ascospores.

Holotype: —HKAS 131318

Saprobic on dead stems of Magnolia officinalis in terrestrial habitat. Sexual morph: Ascomata 510–645 × 460–565 µm (x = 582 × 517 µm, n = 10), perithecial, solitary or gregarious, immersed, semi-immersed to erumpent, globose to depressed-globose, pale brown to dark brown, coriaceous, rough-walled, ostiolate. Ostioles 90–272 µm wide (x = 206 µm, n = 15), central, neck terete, papillate, opening by a pore, filled with periphyses, with pale yellow pigment around the pore. Peridium 30–45 µm thick, wider at the apex, multi-layered, outer layer composed of heavily pigmented, brown cells of textura angularis, inner layer composed of thin and hyaline cells of textura angularis. Hamathecium comprises 1.6–3 µm wide (x = 2.2 µm, n = 15), numerous, dense, filiform, branched, anastomosing, septate, and cellular pseudoparaphyses. Asci 155–205 × 25–40 µm (x = 170 × 33 µm, n = 30), 8-spored, bitunicate, fissitunicate, cylindrical to clavate, short pedicellate with a furcated base, apically rounded, with an ocular chamber. Ascospores 45– 65 × 9–16 µm (x = 55 × 15 µm, n = 30), bi-seriate, partially overlapping, broadly fusiform, sometimes inequilateral, usually widest in the middle, straight, with acute ends, hyaline, 5–7-euseptate, constricted at the septa, cell above the median septum enlarged, with guttules in each cell, rough-walled, with a clear mucilaginous sheath. Asexual morph: Undetermined.

Culture characteristics: —Ascospores germinated on PDA within 72 h, and germ tubes were produced from basal cells. Colonies on PDA reaching 60 mm in diam. after one month at 25℃. Above cream without pigment in the middle, with a white edge, medium dense, flattened, umbonate, floccose; reverse: cream, thin, flat, circular.

Known distribution —Southern China

Material examined: — CHINA, Sichuan Province, Dujiangyan City, Longxi-Hongkou National Nature Reserve, 103°69′05′′E, 31°13′66′′N, elevation 1050m, on dead branches of a medicinal plant Magnolia officinalis ( Magnoliaceae ), 20 March 2023, HK 27 ( HKAS 131318, holotype); ex-type living culture CGMCC 3.25590; ibid., HUEST 23.0224, isotype, ex-isotype living culture UESTCC 23.0224. Additional genes sequenced: tub 2 PP800890.

Notes: — Cooke and Plowright (1879) established Byssosphaeria to accommodate B. keithii as the type species. Byssosphaeria species have superficial ascomata with bright yellow, orange or red flat apices around the ostiole, with dependent hyphal appendages that merge with the subiculum below, and with hyaline ascospores ( Tian et al. 2015; Tennakoon et al. 2018). Byssosphaeria vaginata is established as a new species in Byssosphaeria within Melanommataceae based on its immersed ascomata, central papilla filled with periphyses, cellular pseudoparaphyses, and fusiform and hyaline ascospores.

In the BLASTn searches of GenBank, the ITS sequences alignment of B. vaginata strain indicated that it has the closest similarity to B. phoenicis ( ZHKUCC 21-0122, identities = 412/476 (87%), 6 gaps (1%)); LSU sequences alignment indicated that it has the closest similarity to B. clematidis ( MFLUCC 17-0794, identities = 831/832 (99%), 0 gaps); SSU sequences alignment indicated that it has the closest similarity to Muriformistrickeria rosae ( MFLU 16- 0227, identities = 1,005 / 1,027 (98%), 0 gaps); and they belong to the family Melanommataceae . The combined gene analyses of LSU, SSU, ITS, and tef 1-α ( Figure 1 ) showed that our two isolates formed a distinct clade that is sister to B. clematidis ( MFLUCC 17-0794) with ML/BYPP = 100%/1.00 support. Comparison of the DNA sequence of LSU and SSU loci of B. vaginata , with B. clematidis revealed the base pair differences of 1/832, and 7/252 respectively. Morphologically, B. vaginata can be distinguished from B. clematidis in having paler, larger ascomata (510–645 × 460–565 µm vs. 525–550 × 500–520 µm) with yellow pigment, wider and shorter asci and ascospores (155–205 × 25–40 µm vs. 160–210 × 20–30 µm; 45–65 × 9–16 µm vs. 55–75 × 8–14 µm), and with a clear mucilaginous sheath ( Phukhamsakda et al. 2020). Besides, B. vaginata differs from B. clematidis by its culture with orange in the middle, lacking pigment in the middle of the culture. Our isolates failed to produce an asexual morph in culture and therefore it is not possible to compare the asexual characteristics with other species in Melanommataceae . Therefore, the new species, B. vaginata is introduced in Byssosphaeria based on the sexual morphology and multi-gene phylogeny.

Figures

FIGURE 1. Phylogenetic tree generated from ML analyses based on a combined sequence dataset of LSU, SSU, ITS, and tef1-α of Melanommataceae. Bootstrap values for ML (first set) equal to or greater than 70% are placed above the branches, and Bayesian posterior probabilities (BYPP) equal to or greater than 0.95 are indicated in bold branches. Ex-type strains are indicated in bold, and newly generated sequences are in red. The tree is rooted with Cyclothiyriella rubronotata (CBS 121892, CBS 141486).

FIGURE 2. Byssosphaeria vaginata (HKAS 131318, holotype). a Habitat of the host Magnolia officinalis. b, c Ascomata immersed in the host surface. d Vertical section through an ascoma. e Ostiole. f Vertical section of the peridium. g–j Asci. k Pseudoparaphyses. l–o Ascospores. p Ascospore stained in Indian ink showing the mucilaginous sheath. q A germinating ascospore. r, s Colony on PDA above (r) and below (s). Scale bars: d, e = 100 µm, f = 50 µm, g–j =25 µm, k–q = 10 µm.