Suillus aenoplacidus R. Zhang, X. F. Shi, G. M. Mueller and 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 aenoplacidus R. Zhang, X. F. Shi, G. M. Mueller and P. G. Liu sp. nov.

Figs 4 , 5

Etymology.

“ aeno -” indicates the bronze color of the sticky layer of the cap. “- placidus ” refers to its sister species S. placidus .

Diagnosis.

Suillus aenoplacidus has the bronze glue covering on the cap when young and a white stipe covered with whitish to reddish brown glandular dots. Suillus aenoplacidus are associated with two-to-three needle pines.

Typification.

China: • Yunnan Province, Dali City, Jian Chuan town, Qian Shi Mountain (26°32'17.81"N, 99°53'20.18"E, alt. 2385 m), 07 September 2009, Xiaofei Shi, Shi 272 (holotype, HKAS 71785 ) .

GenBank.

ITS = KU 721265 ; LSU = KU 721386 ; TEFα- 1 = KU 721566

Morphology.

Pileus develops from convex to plane, margin incurved when young, wavy at maturity, 2–10 cm diameter, surface viscid to glutinous, glabrous, cap covered with pallid grey (6 B 2) to bronze brown (5 B 4, 5 B 5, 5 C 5) glue over the white background, cap background color becoming yellow (4 A 4) at maturity. Hymenophore adnate to subdecurrent, pale buff (6 B 2) when young, beaded with pinkish buff (6 B 3) droplets, turning yellowish (4 A 5) at maturity. Does not change color when bruised. Pores 1 to 2 per mm, angular, compound. Pore surface covered with glandular dots. Tubes shallow, 2–5 mm, whitish yellow (4 A 2) when young, becoming yellow (4 A 6) with age. Stipe 5.0–10.0 × 0.8–1.5 cm, equal to slightly bulbous at base, solid, no veil, stipe cuticle white, covered with glandular dots, dots are whitish when young becoming brownish red (6 C 6, 6 C 7, 6 D 7), big and dense, almost connected to form streaks. Mycelia white. Context in pileus white to yellowish, 5–15 mm, stipe context concolorous, unchanging. Spore print light cinnamon brown (6 C 2, 6 C 3). Odor and taste indistinctive.

Basidiospores [40 / 2 / 2] (6.5) 7–8.5 × 3.0–4.0 μm, Q = (2.00) 2.14–2.50, Q sd = 2.31 ± 0.14, smooth, oblong in face view, narrowly inequilateral with a hilar appendage in profile view, hyaline yellow or brown in KOH, tawny ochraceous in Melzer’s. Basidia 4 - spored, clavate, bulbous, 15.0–28.0 × 5.5–8.0 μm, brown in KOH, tawny ochraceous in Melzer’s regent. Hymenophoral trama divergent, wrinkled, thin-walled, hyaline and mostly 2–7 μm, up to 11 μm. Pleuro- and cheilocystidia in fascicles, abundant, clavate, up to 100 μm long, content brown or hyaline, surrounded by brown amorphous material in KOH. Pileipellis densely encrusted by ochraceous granules, hyphae densely distributed as if interwoven, mostly 3–10 μm, up to 15 μm wide. Stipitipellis covered by patches of brown amorphous pigments, composed of interwoven hyphae about 3–15 μm, up to 23 μm wide. Caulocystidia abundant, covering the stipe, morphologically similar with pleuro- and cheilocystidia, basal part surrounded by brown pigments, up to 100 μm. Context trama hyaline, smooth, thin-walled, interwoven, similar in pileus and stipe, mostly 3–30 μm, up to 40 μm wide at the stipe base. Clamp connections absent.

Habitat.

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

Known distribution.

Currently known from southwestern and northeastern China and Japan.

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 08201204 ( HKAS 91431 ) ; China: • Tibetan Autonomous Prefecture, Deqin town, valley of Bai Ma Snow Mountain (28°29'42.05"N, 99°02'19.67"E, alt. 4198 m), 12 October 2011, Xiaofei Shi, Shi 1026 ( HKAS 71999 ) ; China: • Guizhou Province, Bijie, Hezhang town, Shui Tang plantation , 18 September 2008, Xiaofei Shi, Shi 193 ( HKAS 71752 ) ; China: • Guizhou Province, Bijie, Rhododendron forest in Bai Mu , 10 August 2009, Xiaofei Shi, Shi 195 ( HKAS 63319 ) ; China: • Heilongjiang Province, Yichun City, Wuying National Forest Park (48°14'08.64"N, 129°12'39.22"E, alt. 350 m), 17 August 2010, Xiaofei Shi, Shi 555 ( HKAS 63151 ) ; China: • Tibetan Autonomous Prefecture, Lin Zhi, 25 km away from the military base (29°45.566"N, 94°44.050"E, alt. 3150 m), 26 June 2009, A. W. Wilson Aww 471 .

Notes.

This species is morphologically similar to North American Suillus weaverae and S. placidus . Geographical ranges and hosts are the keys to distinguish these three species. This species has often been morphologically confused with the Suillus granulatus complex. But Suillus aenoplacidus is distinguished by association with five-needle pines ( Pinus subg. Strobus ), whereas S. flavopunctipes , S. granulatus , and S. longiflavopunctipes are associated with two-to-three needle pines ( Pinus subg. Pinus ). In addition, even though morphological features of the caps are similar, stipe features are very distinct. Suillus aenoplacidus has a white stipe covered with whitish to reddish brown glandular dots; S. flavopunctipes and S. longiflavopunctipes have yellowish stipes, especially close to apex, and their glandular dots develop from yellow to brown. A potential new species, sister to S. aenoplacidus , from Japan has been identified in the ITS phylogeny (Suppl. material 1: fig. S 2).

Figures

Figure 4. Basidiomata of Suillus aenoplacidus (holotype, HKAS 71785). Scale bar: 5 cm.

Figure 5. Suillus aenoplacidus (holotype, HKAS 71785). a Basidiospores; b Cheilocystidia; c Hymenium with basidia; d Pileipellis (mature specimens). Scale bars: 5 μm (a); 20 μm (b – d).