Suillus subsibiricus R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu, 2025

Shi, Xiaofei, Zhang, Shiru, Mueller, Gregory M., Liu, Peigui, Yu, Fuqiang & Senanayake, Indunil C., 2025, A subgeneric revision of the genus Suillus (Suillaceae, Boletales) and novel taxa from Eastern Asia based on morphology and multigene phylogenies, IMA Fungus 16, pp. e 144260-e 144260 : e144260-

Suillus subsibiricus R. Zhang, X. F. Shi, G. M. Mueller & P. G. Liu sp. nov.

Figs 24 , 25

Etymology.

This species is related to Siberian Suillus sibiricus .

Diagnosis.

Suillus subsibiricus is in the S. americanus morphological complex. This species is in association with Pinus armandii and P. koraiensis in southwestern, northeastern and central China.

Typification.

China: • Sichuan Province, Huili Town, Da Qing Mountain (27°44'23.23"N, 102°20'24.20"E, alt. 2105 m), 29 July 2012, Rui Zhang, RZ 07291202 (holotype, HKAS 91415 ) .

GenBank.

ITS = KU 663189 ; LSU = KU 721520 ; TEFα- 1 = KU 663197 ; RPB 1 = KU 852259 ; RPB 2 = KU 852349 .

Morphology.

Pileus convex to flat or slightly umbonate, 2–9 cm diameter, surface viscid, glabrous, background color yellow (3 A 4, 3 A 5), covered mainly to the margin with pallid pink (6 A 2) appressed squamules. Appendiculated with whitish or pinkish (6 A 3) fibrillose partial veil, lost in age. Hymenophore subdecurrent to decurrent, yellow (4 A 4, 4 A 5), often beaded with pallid yellow (4 A 2) droplets when young, golden yellow (4 A 7, 4 A 8) in age, turning brownish or sometimes light blue when bruised. Pores 1–2 per mm, round to angular, radially arranged. Tubes 3–8 mm deep, concolorous with pores, turning brownish or sometimes light blue when cut. Stipe 3–6.5 × 0.4–1.2 cm, tapering towards apex or equal, solid; cuticle background color yellow (4 A 3). Glandular dots covering stipe, dense, large and often connected in streaks, yellowish (4 A 4) when young, becoming reddish brown (6 B 4, 6 B 5) or brown (5 F 6) with age. Veil forming appendiculate patches on pileus margin, yellowish white (4 A 2) and cottony, lost in age. Ephemeral annulus often covering some of the stipe below the annulus, turning pinkish when bruised. Mycelia white, turning pinkish (6 A 5, 6 A 6) when bruised. Context white to yellowish in pileus and stipe, turning brownish or slightly blue when exposed. Spore print brown (6 D 4). Odor and taste indistinctive.

Basidiospores [80 / 2 / 2] 8.5–11 (12) × 3–4 (4.5) μm, Q = 2.22–2.63 (2.75), Q sd = 2.48 ± 0.21, smooth, oblong in face view, narrowly inequilateral with hilar appendage in profile view, hyaline yellow to brown in KOH, tawny brown in Melzer’s. Basidia 4 - spored, clavate, bulbous, 24.0–35.0 × 5.0–7.0 μm, hyaline yellow in KOH, tawny yellow in Melzer’s. Hymenophoral trama divergent, thin-walled, smooth or wrinkled, sparsely encrusted with granules in KOH, usually 5–8 μm. Pleuro- and Cheilocystidia usually in fascicles, abundant, clavate or cylindrical, up to 70 μm long, contents brown or hyaline, surrounded by brown amorphous material in KOH. Pileipellis a layer of ochraceous and scattered gelatinous hyphae, encrusted with fine granules, mostly 4–7 (9) μm wide. Stipitipellis covered by amorphous pigment, most hyphae thin-walled, septate, 3–10 μm. Caulocystidia similar to pleuro- and cheilocystidia, embedded by in abundant brown amorphous material. Context trama hyaline, smooth, thin-walled, interwoven, similar for pileus and stipe, mostly 4–15 μm, up to 30 μm at stipe base. Clamp connections absent.

Habitat.

Solitary to scattered, in association with Pinus armandii and P. koraiensis .

Known distribution.

Currently known from southwestern, northeastern and central China.

Specimens examined.

China: • Yunnan Province, Dali City, Miaopu hill (25°34'7.32"N, 100°12'20.87"E, alt. 2208 m), 20 August 2012, Rui Zhang, RZ 08201203 ( HKAS 91430 ) ; China: • Yunnan Province, Dali City, Cang Mountain, on the way to the television tower (alt. 2700 m), 22 August 2009, Cai Qing, CaiQing 113 ( HKAS 58780 ) , China: • Heilongjiang Province, Harbin City, Mutan Xian, Dagui town, Friendship village, north side of Menggu Mountain (alt. 200 m), 11 August 2010, Xiaofei Shi, Shi 494 ( HKAS 63155 ) , China: • Heilongjiang Province, Yichun City, Liangshui National Nature Reserves (alt. 150 m), 14 August 2010, Xiaofei Shi, Shi 521 ( HKAS 63156 ) ; China: • Shaanxi Province, Baoji City, Mei Xian, Yingtou Town, Hao Ping Dali Village (alt. 1300 m), 12 September 2010, Xiaofei Shi, Shi 670 ( HKAS 63195 ) ; China: • Shaanxi Province, Ankang City, Langao town, Nangong Mountain (alt. 2000 m), 29 July 2011, Xiaofei Shi, Shi 761 ( HKAS 71891 ) .

Notes.

Suillus subsibiricus is morphologically identical to its sister species S. americanus . Geographic range and host associations are the keys to differentiate the two species. Suillus americanus was described from North America associated with Pinus subg. strobus and P. monticola . Another species, S. sibiricus , is not well documented in the literature and lacks holotype and following collections ( Singer 1945). Suillus sibiricus was described from Siberia and presumably is associated with five needle Pinus sibirica . Suillus himalayensis , growing with P. wallichiana in Himalayan region, is also in the S. americanus complex.

It seems that S. americanus and S. subsibiricus under current delimitations contain more cryptic species. At least S. subsibiricus collections associated with P. armandii in southwestern China are not the same as the ones from northeastern China associated with P. koraiensis , which is supported by the TEFα- 1, RPB 1, RPB 2, concatenated phylogenies and coalescent analysis (Wu et al. 2000; Mueller et al. 2001). Phylogenies based on the ribosomal regions and morphological characters are not effective in resolving the S. americanus complex.

Figures

Figure 24. Basidiomata of Suillus subsibiricus (holotype, HKAS 91415). Scale bar: 5 cm.

Figure 25. Suillus subsibiricus (paratype, HKAS 63155). a Basidiospores; b Cheilocystidia; c Hymenium with basidia. Scale bars: 5 μm (a); 20 μm (b – d).