Boletales » Boletaceae » Pulveroboletus

Pulveroboletus fragrans

Pulveroboletus fragrans Raspé & Vadthanarat

MycoBank number: MB814679; Faces of Fungi number: FoF 01917


Basidiomata medium-sized, entirely covered by a general veil when young; Pileus obtusely convex to hemispherical with inflexed margin at first, becoming convex to plano-convex with straight to slightly deflexed, appendiculate margin (1–2 mm), (4.5)5.0–8.5 cm in diameter; at first entirely covered by a viscid, mostly yellow (1–2 A 3–7) veil, with pinkish tinges (11A4) in places, later becoming scaly-squamulose, yellow with brownish to reddish stains. Pileus context 5–8 mm halfway to the margin, yellow at first, later pale yellow, at first cyanescent, then reddish brown in cuts and bruises; the space between hymenium and stipe invaded by cortina-like, white hyphae during expansion of immature basidiomata; Stipe irregularly cylindrical, (4.1)4.8–5.6 × 0.8–1.2 cm, at first entirely covered by a viscid, mostly yellow (1–2 A 3–7) veil, with pinkish to reddish tinges in places and tiny brown (7 E/F 5) scales near the base of the stipe, later developing a slightly narrowing base and an ill-defined annular zone at ca. two-thirds of height; uppermost part of the stipe showing a purplish (13A4) to violaceous (15A4) zone, with remnants of the cortina-like tissue, lower part dirty yellow, irregularly scaly-scurfy, near the base often beset with brownish gray fibrils; basal mycelium thick, yellowish white (2A2) to yellow (3A5), grasping soil particles, forming abundant rhizomorphs; stipe context slightly marmorate, usually yellowish at the top, then red at least at the level of the violaceous-purplish zone on stipe surface, then yellow again or reddish brown, sulfur yellow at the base, cyanescent only at the top; Hymenophore tubulate, adnate with very short decurrent teeth, sometimes slightly depressed around stipe, subventricose; tubes easily separable, 8–9 mm long, rarely compound; pores 0.4–1.1 mm wide at mid-radius, mostly angular, elongated near the stipe, roundish near the margin, distinctly yellow (2A5) when young, becoming grayish yellow (2B3) with spores, quickly cyanescent when cut or bruised; Odor aromatic, strong, especially in young basidiomata; Taste mild, not distinctive; Spore print olivaceous brown. Macrochemical reactions: KOH, orange on context of cap and stipe, hymenium, and top of the stipe; null on the general veil; NH4OH, yellowish on top of the stipe; null or subnull elsewhere.

Spores (7–)6.9–7.9–8.9(–9.4) × (4.7–)4.7–5.2–5.7(–5.8) μm, Q= (1.33–)1.33–1.51–1.69(–1.71), N = 65 (OR673), (7.7–)7.6–8.1–8.6(–8.9) × (4.8)5–5.4–5.8(–6) μm, Q=(1.38–)1.37–1.5–1.63(–1.66), N= 65 (OR1121), ovoid to broadly ellipsoid, smooth under light microscope and subsmooth under SEM, yellowish to yellowish-brown in 5 % KOH and Melzer’s reagent, thin-walled, inamyloid. Basidia 4-spored, (20–)21.1–24.9–28.6(– 27.5) × (8–)8.1–9.1–10.1(–10) μm, clavate, hyaline, yellowish to yellowish-brown in 5 % KOH, sterigmata up to 3 μm long, without clamp connections. Cheilocystidia of two types, 1) subglobose, (13–)10.4–16.3–22.1(–24) × (7–)6.7–8.9–11(–11) μm, thin-walled, hyaline, yellowish to yellowish-brown in 5 % KOH, and 2) fusiform, (18–)8.9–38.8–68.6(–66) × (7–)6.9–9–11.1(–11) μm, thin-walled, yellowish to yellowish-brown in 5 % KOH. Pleurocystidia similar to type 2 cheilocystidia, not abundant. Hymenophoral trama divergent, with regular, gelatinized mediostratum. Pileus surface composed of two more or less differentiated tissues (at least when immature), an upper ixocutis ca.10–20 μm thick, composed of cylindrical, gelatinized, thin-walled, 14–42 × 2–5.5 μm elements, hyaline in 5 % KOH, but densely covered with refractive pigment incrustations when observed in water, and a lower tomentum, 40–90 μm thick, composed of moderately interwoven hyphae, cylindrical, thin-walled, hyaline 22–53 × 3–6.5 μm elements; Stipe surface similar to pileus surface; Stipe cortex under the veil sterile, a rectocutis, composed of parallel, densely packed, and anastomosing hyphae, the latter 3–5 μm wide and occasionally forming isolated and more or less anticlinally protruding, elongate elements (Fig. 3); Stipe trama composed of branching, non-anastomosing, 5–11 μm wide hyphae. Cortina-like tissue composed of cylindrical, 3–6 μm wide, thin-walled, smooth and hyaline (both in water and 5 % KOH) hyphae; Clamp connections not seen in any tissue.


Ecology: On soil, in hill forest dominated by Castanopsis spp. and Lithocarpus spp., and regularly subject to fire. Ectomycorrhizal host probably Castanopsis. Basidiomata never observed at the beginning of the rainy season.

Known distribution: Found only in the type locality in Chiang Mai Province, Northern Thailand.

Additional collections examined: Thailand. Chiang Mai Province, Mae Taeng District, Baan Pha Deng, N19°07 25.7- E98°43 55.9, 950 m asl, 28/07/2014, O. Raspé 849 (MFLU, BR). –ibid., N19°07 26.6 - E98°43 54.6, 950 m asl, 08/08/2015, O. Raspé 1121 (CMU, BR).

Fig. 1 Maximum likelihood phylogenetic tree inferred from the three-gene dataset (atp6, rpb2, tef1), including Pulveroboletus fragrans sp. nov. and selected Boletaceae. The three Chalciporus species were used as outgroup taxa. Bootstrap frequencies >50 % are shown above supported branches. The prefix BGB^ before voucher numbers indicates that sequences were retrieved from GenBank.


Fig. 2 a Photograph of basidiomata of Pulveroboletus fragrans sp. nov. b Detailed photograph of a sectioned immature basidioma of P. fragrans showing the white, cortina-like hyphae invading the space between the hymenium and stipe. c SEM micrograph of a basidiospore of P. fragrans. All pictures from the type (OR673). Scale bars: a, b = 1 cm; c=1 μm.

Fig. 3 Micromorphological characters of Pulveroboletus fragrans. a Basidiospores. b Basidia. c First type of cheilocystidia. d Second type of cheilocystidia. e Transversal cut of pileus surface of an immature basidioma, composed of an upper ixocutis and a lower tomentum. f Stipe cortex. Scales bars: a–c=10 μm; d–f=50 μm. All drawings were made from the type (OR673.



Raspé O, Vadthanarat S, De Kesel A, Degreef J, Hyde KD, Lumyong S. 2016 Pulveroboletus fragrans, a new Boletaceae species from Northern Thailand, with a remarkable aromatic odor. Mycological Progress, 15(4), p.38.


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