Dacryobolus caesius Q. Z. Zhu, Yuan Yuan & S. H. He sp. nov.

Fig. 2

Type.

China • Sichuan Province, Yanyuan County, Lugu Lake Scenic Area, on fallen branches of Pinus yunnanensis, 21 Jul 2024, Yuan Yuan, Yuan 1546 (BJFC 053959, holotype).

Etymology.

Refers to the bluish-gray basidiomes when fresh.

Fruiting body.

Basidiomes annual, resupinate, effused, closely adnate to the substrate, slightly ceraceous when fresh, becoming coriaceous to horny after dry, forming irregular patches or narrow strips extending along the longitudinal axis of the wood, confluent up to 7 cm long, 1 cm wide. Hymenophore odontoid, grayish white, pale bluish white to light gray when fresh, slightly glossy when moist, becoming grayish white to pale grayish yellow when dry, unchanged in KOH, not cracked; aculei conical to cylindrical, unbranched, solitary, rather uniform under the naked eyes, 2–3 per mm, up to 0.5 mm long, 0.4 mm wide at base; margin thinning out, determined, closely adnate, indistinct, concolorous with hymenophore surface.

Microscopic structures.

Subiculum thin and tightly adnate to the substrate. Hyphal system monomitic; generative hyphae with clamp connections and secondary simple septa, IKI –, CB –; subicular hyphae colorless, slightly thick- to thick-walled, smooth, moderately branched, interwoven, 3.5–5 μm in diam., occasionally with short tubular lateral branches perpendicular to the main hyphae; tramal hyphae colorless, thin- to slightly thick-walled, smooth, occasionally branched, 1.5–4.5 μm in diam., more or less parallel arranged. Cystidia absent. Basidia narrowly clavate, colorless, thin-walled, smooth, with a basal clamp connection and four sterigmata, 27–35 × 3–3.5 μm; basidioles similar in shape but slightly smaller. Basidiospores allantoid, colorless, thin-walled, smooth, IKI –, CB –, 5.5–7 × 1–1.5 μm; L = 6 μm, W = 1.14 μm, Q = 5.26 (n = 30 / 1).

Notes.

Dacryobolus caesius is characterized by resupinate, odontoid, bluish-gray basidiomes with short, evenly distributed aculei, a monomitic hyphal system with clamped generative hyphae, the absence of cystidia, relatively long, narrow, allantoid basidiospores, and a habitat on Pinus yunnanensis. In the phylogenetic tree, D. caesius was nested within the D. sudans subclade, which included three known species with odontoid hymenophores: D. sudans, D. gracilis H. S. Yuan, and D. montanus X. Z. Wan & H. S. Yuan (Fig. 1). Morphologically, D. sudans and D. gracilis differ from D. caesius by the presence of cystidia, whereas D. montanus differs in having longer aculei (up to 1.5 mm) and growing on angiosperm trees (Yuan et al. 2016).