Astrocystis bambusae
Astrocystis bambusae (Henn.) Læssøe & Spooner, Kew Bull. 49(1): 13 (1994) [1993]
Index Fungorum number: IF361739 Facesoffungi number: FoF17292
Saprobic on dead culms of Bambusa vulgaris. Sexual morph: Stromata 1.2–0.9 mm diam., 0.8–1 mm high, scattered, solitary, superficial, black, appear as black raised spots on the host surface, hexagonal prism-shaped, containing one ascoma, with a circle of black tissue at the bottom. Perithecia 0.5–0.7 mm diam., 0.4–0.5 mm high, comprising black, fragile, carbonaceous tissue. Peridium 15–45 μm wide, 5–8 layers, brown to dark brown cells of textura angularis. Hamathecium comprising 2–8 μm wide, oblong to cylindrical, septate, unbranched, cellular, paraphyses. Asci 55–90 × 5–6.5 µm (
= 75 × 6.2 µm, n = 30), 8- or 6-spored, unitunicate, cylindrical, short pedicellate, persistent, apically rounded, with amyloid, cuboid, apical apparatus, staining blue in Melzer’s reagent, 2–3 µm high × 1.4–2.44 μm wide ( = 2.6 × 1.9 μm). Ascospores 10–13.5 × 4–6 µm ( = 12 × 5 μm, n = 30), uniseriate, unicellular, hyaline when immature, dark brown at maturity, aseptate, equilateral ellipsoid, with rounded ends, smooth, guttulate, with a straight germ slit nearly full-length, surrounded by a sheath. Asexual morph: undetermined.
Culture characteristics: Ascospores germinated on the PDA within 24 hours at 25 °C. Germ tubes are produced from one side of the ascospore. Colonies on PDA reaching 2–2.5 cm diam. after 5 days at 25 °C, circular in shape, white at first, cottony, slightly thinning towards the edge, white color in the front view, and light brown in the reverse view.
Material examined: Thailand Chiang Rai, Mae Chan, Mae Chan District, on dead culms of Bambusa vulgaris (Poaceae), 18 March 2024, Hsan Win (MFLU 24-0522), living culture MFLUCC 25-0022.
Notes: Morphologically, our collection (MFLUCC 25-0022) exhibits characteristics similar to the holotype of A. bambusae (basionym: Rosellinia bambusae) (Merrill 5030) and other isolates of A. bambusae (GMB0700). These similarities include scattered, solitary, superficial, black stromata containing one ascomata, with a circle of black tissue at the bottom and unitunicate, cylindrical, short pedicellate asci, with an apical apparatus that stains blue in Melzer’s reagent (Li et al. 2024). The ascospores have a straight germ slit nearly full-length and are surrounded by a sheath (Ju and Rogers 1990; Li et al. 2024). However, the asci and ascospores in our collection (MFLUCC 25-0022, 55–90 μm and 10–13.5 μm, respectively) are smaller than the holotype (100–130 μm and 10.5–15(–16) μm) (Ju and Rogers 1990). Based on multi-gene phylogenetic analyses (ITS, β-tub, and rpb2), our strain (MFLUCC 25-0022) clustered with other authentic strains (HAST 89021904 and GMB0700) in a well-supported clade (89% ML, 0.95 BYPP). Astrocystis bambusae has previously been recorded on Bambusa sp. in China, India, the Philippines, and Thailand (Ju and Rogers 1990; Læssøe and Spooner 1993; Li et al. 2024). In our study, we reported a new host record for A. bambusae on Bambusa vulgaris.
Figure 1. Phylogram generated from ML analysis based on the combined dataset of ITS, β-tub, and rpb2. The tree is rooted to Xylotumulus gibbisporus (ATCC MYA-4109), Xylaria glebulosa (GMB1053), and X. schweinitzii (HAST 92092023). Bootstrap support values for ML ≥ 70% and Bayesian posterior probabilities (PP) ≥ 0.90 are noted at the node. Strain numbers are noted after the species names. Strains isolated in this study are represented in blue, and type strains are in bold.
Figure 2. Astrocystis bambusae on a dead twig of Bambusa vulgaris (MFLU 24-0522, a new host record). a. Substrate; b, c. Appearance of stromata on the host; d. Cross section of the stroma; e. Peridium; f. Paraphyses; g–j. Asci; k. Ascus apical apparatus (stained in Melzer’s reagent); l–q. Ascospores; r. Ascospores with sheath; s, t. Colony on the PDA (s upper, t lower). Scale bars: 5 mm (b); 1 mm (c); 500 μm (d); 20 μm (f–j); 10 μm (e, k–r).
References
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