Seiridium unicorne (Cooke & Ellis) B. Sutton

Seiridium unicorne (Cooke & Ellis) B. Sutton , Mycol. Pap. 138: 74 (1975)

Fig. 20 View Figure 20

Description.

Sexual morph: Not observed. Asexual morph: Fruiting bodies scattered on the surface of Platycladus orientalis branches, carbon-black to jet-black; Conidiomata acervular, immersed to erumpent through bark tissue, black, subglobose, scattered, unilocular; wall brownish, 65–255 µm diam. Conidiophores long-cylindrical, hyaline, thin-walled, septate, occasionally branched, 16.3–51.4 × 1.0–2.6 µm; Conidiogenous cells hyaline, thin-walled, smooth, cylindrical, solitary, 5.9–17.5 × 1.1–4.2 µm (av. ± S. D. = 10.8 ± 3.2 × 2.0 ± 0.6). Conidia falcate to lunate, hyaline when immature, becoming pale brown to yellowish-brown at maturity, 5 - septate, curved, with one hyaline apical appendage and one basal appendage, total conidial dimensions 19.4–29.8 × 6.2–11.9 µm (av. ± S. D. = 24.5 ± 0.4 × 9.6 ± 1.2), basal cell obconical, hyaline to pale brown, truncate, 2.5–7.1 µm long, the first cell from the basal cell upwards is 3.5–7.1 µm long, the second cell is 3.2–6.7 µm long, the third cell 3.1–6.0 µm long, the fourth cell 3.6–6.9 µm long, the apical cell conical, smooth, and hyaline, with a length of 1.6–5.7 µm. Appendages cylindrical, the apical appendages are mostly centric, 4.0–8.9 µm long, the basal appendages are mostly eccentric, 4.0–8.6 µm long.

Cultural characteristics.

On PDA medium, colonies exhibited appressed growth with a sparse, felt-like texture and slow expansion rates, reaching approximately 30 mm in diameter after 7 days of incubation. Aerial mycelium was poorly developed and diffuse. After 2 weeks, a pale yellow pigmentation became visible on the colony reverse.

Specimens examined.

China • Beijing City, Changping District, Ming Tombs Longshan Sub-farm , 40°14'21"N, 116°13'15"E, on the dead branches of Platycladus orientalis , 18 July 2024, Z. X. Bi & C. M. Tian. BJFC -S 2581 , living culture CFCC 72631 GoogleMaps .

Notes.

The genus Seiridium can be distinguished from other genera by its conidia with five septa ( Li et al. 2022). Seiridium unicorne has been documented to infect hosts across diverse plant families, including Anacardiaceae , Caprifoliaceae , Cornaceae , Cupressaceae , Hamamelidaceae , Rosaceae , and Vitaceae ( Guba 1961; Boesewinkel 1983; Cho and Shin 2004; Bonthond et al. 2018). Phylogenetic analysis revealed that the studied strains cluster within the same clade as reference strains of S. unicorne with a high support value of 100 / 1 ( ML / BI) (Fig. 7 View Figure 7 ). In terms of morphology, the maximum lengths of the basal cells (2.5–7.1 µm vs. 3–5.5 μm) and the first cell counted upwards from the basal cell (3.5–7.1 µm vs. 3.5–5.5 μm) in the conidia of the strains in this study are slightly larger than those of the reference species S. unicorne ( Bonthond et al. 2018) . However, the differences are not significant, and the remaining morphological characteristics are basically consistent with the previous descriptions of this species. Therefore, based on the above evidence, we identified this strain as S. unicorne .