Abiomyces laojunshanensis 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-

Abiomyces laojunshanensis Lan Zhuo & C. L. Hou sp. nov.

Figs 2 , 3

Etymology.

Referring to the host genus Abies .

Diagnosis.

This new species is similar to Coccomyces mertensianae Sherwood , but Abiomyces laojunshanensis has longer, fili-fusiform ascospores.

Type.

CHINA, Yunnan Province, Lijiang, Laojunshan , 26.6310°N, 99.7227°E, alt. ca. 3930 m, on twigs of Abies georgei Orr ( Pinaceae ), 17 Aug 2023, C. L. Hou, L. Zhuo, and S. Y. Zhao, HOU 2070 ( BJTC 2023200 , holotype) .

Sexual morph.

Ascomata on twigs, scattered, not associated with pale areas. In surface view, ascomata subround or slightly irregular, 500–1250 × 750–1500 µm, black (# 000000), erumpent from the bark, opening by radial splits to expose a yellow (# ffd 400) to pale orange (# ffa 500) hymenium. Lips absent. In median vertical section, ascomata intracortical. Covering stroma 30–50 μm thick near center of ascomata, not extending to the basal Covering stroma, consisting of an outer layer of remains of the host cortex and an inner layer of carbonized, angular to globose cells. Basal Covering stroma poorly developed, consisting of carbonized, angular to globose cells. Internal matrix of Covering stroma 375–470 µm thick, consisting of hyaline, thin-walled, angular cells with some irregular crystalloids and short hyphae. Subhymenium 40–60 µm thick, consisting of small, hyaline cells. Paraphyses aseptate, filiform, not branched, not swollen at tips, 130–150 × ca. 1 µm, covered by a thin gelatinous sheath. Asci ripening sequentially, clavate, apex truncate, 80–90 × 8–10 µm, stalked, thin-walled, J –, 8 - spored. Ascospores aseptate, filiform to fusiform, 50–65 × 3 μm, hyaline, without a gelatinous sheath.

Asexual morph.

Conidiomata and zone lines not seen.

Additional specimens examined.

CHINA, Yunnan Province, Lijiang, Laojunshan , 26.6314°N, 99.7235°E, alt. ca. 3880 m, on twigs of Abies georgei , 17 Aug. 2023, C. L. Hou, L. Zhuo, and S. Y. Zhao, HOU 2064 ( BJTC 2023194 ) ; CHINA, Yunnan Province, Dali Bai Autonomous Prefecture, Mount Cangshan , 25.6644°N, 100.1024°E, alt. ca. 3830 m, on twigs of Abies delavayi Franch. ( Pinaceae ), 18 Aug. 2023, C. L. Hou, L. Zhuo, and S. Y. Zhao, HOU 2113 ( BJTC 2023244 ) .

Distribution.

Known only from Yunnan Province, China.

Notes.

Morphologically, A. laojunshanensis resembles Coccomyces mertensianae growing on twigs of Tsuga mertensiana (Bong.) Carrière , however, Coccomyces mertensianae has septate paraphyses and shorter (19–25 × 2.5–3.0 µm), narrowly clavate ascospores. The multi-locus gene analysis indicates that the molecular sequences of A. laojunshanensis form an independent clade with high support (MLB = 100 %, MPB = 100 %, PP = 1.00). These sequences do not cluster with any species of Coccomyces , especially the type Co. tumidus (Fr.) De Not. Therefore , A. laojunshanensis is considered as a species new to science.

Figures

Figure 2. Abiomyces laojunshanensis (HOU 2070 / BJTC 2023200, holotype) a ascomata on a twig of Abies georgei b, c mature ascomata. Scale bars: 3 mm (a); 500 μm (b, c).

Figure 3. Abiomyces laojunshanensis on Abies georgei (HOU 2070 / BJTC 2023200, holotype) a part of an ascoma in vertical section, the internal matrix of Covering stroma filled with numerous crystals b paraphyses, mature asci with ascospores, and immature ascus. c Liberated ascospores. Scale bars: 50 μm (a); 10 μm (b, c).