Tryblidiopsis melanostroma Lan Zhuo & C. L. Hou, 2025

Zhuo, Lan, Wang, Hai-Qi, Zhang, Peng, Sui, Xiao-Nan, Guo, Mei-Jun, Wang, Shi-Juan & Hou, Cheng-Lin, 2025, New genera and species of coniferous twig-inhabiting Rhytismatales from China, IMA Fungus 16, pp. e 138790-e 138790 : e138790-

Tryblidiopsis melanostroma Lan Zhuo & C. L. Hou sp. nov.

Figs 36 , 37

Etymology.

Melano- (Greek), referring to the melanized basal Covering stroma between the subhymenium and the internal matrix of the Covering stroma.

Diagnosis.

This new species is similar to Tryblidiopsis sichuanensis , but differs by a melanized basal Covering stroma between the subhymenium and an internal matrix of the Covering stroma, and an internal matrix filled with crystals.

Type.

CHINA, Yunnan Province, Lijiang, Laojunshan , 26.6452°N, 99.7838°E, alt. ca. 3290 m, on twigs of Picea likiangensis (Franch.) E. Pritz. ( Pinaceae ), 17 Aug. 2023, C. L. Hou, L. Zhuo, and S. Y. Zhao, HOU 2105 ( BJTC 2023235 , holotype) .

Sexual morph.

Ascomata on twigs, erumpent from the bark, scattered or aggregated in groups of three to five ascomata, not associated with pale areas. In surface view, ascomata round to elliptical, 1000–1150 × 800–1000 µm, as seen from the side 900–1200 µm high, black (# 000000), opening by irregular splits to expose a yellow (# ffe 562) hymenium. Lips absent. In median vertical section, covering stroma 50–110 μm thick near the center of ascomata, consisting of an outer layer of carbonized, angular to globose cells and an inner layer of hyaline, angular to globose cells. Basal Covering stroma 15–25 µm thick, located between the subhymenium and the internal matrix of the Covering stroma, consisting of brown to dark brown, globose cells. Internal matrix of the Covering stroma well-developed, consisting of hyaline, thin-walled, gelatinous cells and hyaline hyphae, filled with irregular crystals. Subhymenium 10–20 µm thick, consisting of hyaline, angular to globose cells. Paraphyses aseptate, filiform, not branched, slightly swollen at tips, 135–165 × 1 µm. Asci ripening sequentially, clavate, apex obtuse, 120–150 × 15–18 µm, thin-walled, J –, 8 - spored. Ascospores 1 - septate, fusiform, 20–25 × 3–4 μm, hyaline, covered by a ca. 2 µm thick gelatinous sheath.

Asexual morph.

Conidiomata and zone lines not seen.

Additional specimens examined.

CHINA, Yunnan Province, Lijiang, Laojunshan , 26.6452°N, 99.7838°E, alt. ca. 3290 m, on twigs of Picea likiangensis ( Pinaceae ), 26 Jul. 2024, C. L. Hou, L. Zhuo, and X. N. Sui, HOU 2307 ( BJTC 2024157 ) .

Distribution.

Known only from Yunnan Province, China.

Notes.

The multi-locus gene analysis indicates that the sequences of Tryblidiopsis melanostroma form a well-supported clade sister to the sequences of Try. sichuanensis . Tryblidiopsis melanostroma is morphologically similar to Try. sichuanensis , but the latter has an internal matrix of Covering stroma without crystals and lacks a melanized basal Covering stroma between the subhymenium and the internal matrix of the Covering stroma. Interestingly, a similar melanization phenomenon has been observed in Try. magnesii , where the inner wall of the covering stroma is melanized (Magnes 1997; Tanney and Seifert 2019). The taxonomic relevance of this feature remains uncertain and requires further study. Therefore, Try. melanostroma is considered to be a distinct species.

Figures

Figure 36. Tryblidiopsis melanostroma (HOU 2105 / BJTC 2023235, holotype) a ascomata on a twig of Picea likiangensis b, c mature ascomata. Scale bars: 2 mm (a); 1 mm (b); 500 μm (c).

Figure 37. Tryblidiopsis melanostroma on Picea likiangensis (HOU 2105 / BJTC 2023235, holotype) a part of an ascoma in vertical section, having a melanized basal Covering stroma between the subhymenium and an internal matrix of the Covering stroma b paraphyses, mature asci with ascospores, and immature ascus c liberated ascospores. Scale bars: 100 μm (a); 15 μm (b); 10 μm (c).