Entoloma caeruleoflavum Xiao Lan He & T.H. Li
MycoBank number: MB 563507
Pileus 3–6 cm latus, plano-convexus, haud hygrophanus, pallidus brunneo-fulvus cum viridibus. Lamellae sinuatae, moderate confertae, luteolae. Stipes 50–100 × 4–10 mm, lazulinus. Basidiosporae 6.5–7.5 × 6.3–7.3 μm, 5–7 angulatae. Acies lamellarum fertilis. Pileipellis cutis hyphis 27–63 × 11–16 μm latis e pigmentatis. Fibulae praesentes. Stature tricholomatoid. Pileus 3–6 cm broad, plano-convex, expanding with age, slightly umbonate, minutely scurfy, black-blue to almost black (20 F2) in the center, paler outwards and mixed with green, yellow, pink and somewhat brownish tinges (2B3–4A4), not hygrophanous, dry, slightly sulcate from margin to half-center, undulate at margin. Lamellae sinuate, ventricose, up to 8 mm broad, thin, very crowded, bright yellow (2A5–3A4), turning pink to pale reddish brown (6B3–9A2) when bruised, with wavy and concolorous edge, with three tiers of lamellulae. Stipe central, 50–100 mm in length, 4–10 mm in width, cylindrical, gradually broadening towards base, blue to dark blue (22 C5–22D5), longitudinally fibrillose-striate with innate fibrils, fragile, hollow, dry, with white tomentum at base. Context thin, whitish. Odor and taste not distinctive.
Basidiospores 6.5–7.5 × 6.3–7.3 μm (x = 6.9 ± 0.2 × 6.7 ± 0.3 μm), Q = 1.0–1.1 (Q = 1.0 ±0.04), isodiametric, 5–7-angled in side-view with weak angles, relatively thin-walled. Basidia clavate, sharply tapered at base, 30–48 × 9–12 μm, 4-spored, rarely 2-spored, clamped. Lamellar trama subparallel, consisting of cylindrical and inflated elements, 40–90× 8–22 μm. Lamellar edge fertile. Cheilocystidia and pleurocystidia absent. Pileipellis a cutis with a transition to a trichoderm of interwoven hyphae; terminal cells well differentiated, subclavate, cylindrical, bullet-shaped, sub-fusoid, somewhat inflated, 27–63 × 11–16 μm, with conspicuous pale brown intracellular pigment. Pileitrama regular, consisting of short, cylindrical and slightly inflated elements up to 23 μm broad, with very pale pinkish brown intracellular pigment or nearly hyaline. Clamp connections present in all tissues. Oleiferous hyphae scattered in lamellar trama and pileal trama.
Habitat. Scattered, on soil in mixed forest with Fagaceae, Theaceae and Pinus yunnanensis.
Notes: The combined characters of the blue stipe, the bright yellow gills with pink to reddish brown discoloration where bruised, the small isodiametric and weakly angled spores, the absence of cystidia, and the well differentiated pileipellis with conspicuous pale brown intracellular pigment are distinctive for Entoloma caeruleoflavum. Entoloma caeruleoflavum fits well into section Entoloma of subgenus Entoloma on account of its tricholomatoid habit, and small, weakly angled spores. Several species, i.e. Entoloma cerinum E. Horak from New Zealand, E. manganaense G.M. Gates & Noordel. and E. mathinnae G.M. Gates, B.M. Horton & Noordel. from Australia, and E. rugosostriatum Largent & T.W. Henkel from Guyana could be confused with this new species on account of their basidioma statures, yellowish gills and small weakly angled basidiospores. However, E. cerinum differs from E. caeruleoflavum in the dark brown pileus, the golden yellow or brass yellow stipe, and the clampless hyphae. E. manganaense differs in the brown (5 F6) pileus, stouter stipe (40 × 25 mm), the quite different yellow tinge (4A5) of the lamellae, and the much narrower terminal cells of the pileipellis [22–55(–70) × 3.5–7.5 μm]. E. mathinnae has a light yellow-brown (5D5) pileus, a white or pale brown stipe occasionally with a distinct gray-violet (16E3) hue, and a cutis-like pileipellis with 2–4 μm wide terminal cells. E. rugosostriatum can be distinguished by its dark grayish brown pileus and the presence of abundant cheilocystidia. Another four Entoloma s.l. species with yellowish gills, E. sinuatum (Bull.) P. Kumm., E. luridum Hesler, E. luteifolium Hesler and Trichopilus luteolamellatus Largent & Aime, are quite different from E. caeruleoflavum in the following characters: the European E. sinuatum can be easily differentiated by the paler pileus, larger and thick-walled spores (8–11 × 7–9.5 μm); E. luridum, described from North America, is distinguished by its almost white pileus and absence of clamp connections; E. luteifolium from Cuba is a small species with a squamulose pileus (2 cm broad) and clampless hyphae. T. luteolamellatus, reported from Guyana, has a coarser granulose-fibrillose stipe, cuboid spores and numerous cheilocystidia.
Fig. 1 Phylogeny of the relationship of the four new species with related species generated by Maximum Parsimony analysis based on ITS sequences. Values above or below the branches are parsimony boostrap (>50%).