Pholiota betulicola Tolgor Bau & Enjing Tian sp. nov.
Index Fungorum number: IF 559944; Mycobank number: MB 559944; Facesoffungi number: FoF 12906; Figs. 1, 2
Etymology – The epithet betulicola refers to the tree which this species grows on.
Holotype – HMJAU37328.
Diagnosis – Differs from other Pholiota species by yellowish pileus with light brown minute fibrillose spots, distinct spicy-aromatic content, whitish stipe with brownish longitudinal stripes and basal yellowish tomenta, plerocystidia buried in hymenium, sometimes sub-rectangle basidiospores, as well as growing on living birch.
Pileus 11 cm in diam, convex; surface slightly viscid, with appressed light brown (6D6) minute fibrillose spots; brownish yellow (5C8) at center, becoming yellowish white (1A2) to white towards the margin; the margin irregularly undulate. Context thick, firm, yellowish white (2A2), odor distinct spicy-aromatic. Lamellae adnexed, broad, close, L=60–65 mm, I=3–7 mm, dark blonde (5D4), the edges even. Stipe 5 cm long, 1.9 cm thick, central or eccentric, slightly enlarged at the base, hard, solid, smooth and white above the annulus, ground color whitish and with brownish longitudinal stripes and brown fibrillose squamules below the annulus, with yellowish white (1A2) tomenta near the base. Partial veil leaving an annular zone. Spore print cinnamon brown (6D6).
Basidiospores (6.5–)7.5–10 × (3.7–)4.5–5 μm, Q =(1.25–)1.5–2, in face view elliptic, oblong to sub-rectangle, rarely broadly elliptic, in side view elliptic, somewhat inequilateral to slightly reniform, wall smooth and thick, germ pore minute, pale rusty, yellow-brownish to pale brown in KOH, slightly paler in Melzer’s reagent. Basidia 22–28 × 5–7.5 μm, 4-spored, clavate, hyaline in KOH. Pleurocystidia 15–27×4.5–5 μm, buried in the hymenium, clavate to subfusiform, sometimes with refractive and amorphous-granular content, wall thin, smooth, pale tawny to dark yellow brown in KOH. Cheilocystidia 17–25×5–8 μm, clavate, clavate-irregular to utriform or lageniform to versiform, rarely branched, thin-walled, smooth, content homogeneous, hyaline to pale yellow brown in KOH. Caulocystidia not observed. Gill trama of parallel hyphae hyaline to yellowish in KOH, walls smooth, thin to thick, 3.5–10 μm in diam. Pileus cutis of yellowish brown to cinnamon hyphae 2.5–5 μm in diam, thin-walled, smooth. Content hyphae hyaline to yellowish in KOH, cells inflated, smooth, thin-walled, interwoven. Clamp connections present in all tissues.
Habitat – Solitary at the base of living birch in mixed broadleaf-conifer forest in late summer.
Materials examined – China, Jilin Province, Jiaohe, Hongye Valley, elev. 520 m, solitary at the base of living birch in mixed broadleaf-conifer forest, 27 August 2016, Tolgor Bau, HMJAU37328 (holotype); Jiaohe, Shansongling, 1 September 2020, Yuhou Zhai, HMJAU37369.
Genbank numbers – HMJAU37328: ITS= OP244886, LSU=MN251156, RPB2=MN329729, TEF1-α=MN311972; HMJAU37369: ITS=OP244887, LSU=OP223414.
Notes – This species is readily recognized due to its yellowish pileus with light brown minute fibrillose spots, thick content with distinct spicy-aromatic odor reminding of Tricholoma matsutake, whitish stipe with brownish longitudinal stripes and yellowish tomenta at the base, as well as numerous plerocystidia buried in hymenium and sometimes sub-rectangle basidiospores. Growing on living trees and the large and robust basidiomes of this species remind one of Pholiota populnea. However, the pileus of the latter has no yellow tone and covers with conspicuous floccose or patches scales, and the lack of the pleurocystidia and cylindric-capitate cheilocystidia also makes it different from P. betulicola. In the phylogenetic analysis (Fig. 3), the samples of Pholiota betulicola occupied an isolated phylogenetic position apart from the other species of Pholiota. Furthermore, in the multiple alignment, this species has a unique insertion of 181 bp.
Figure 1 – Basidiome of Pholiota betulicola (HMJAU37328, holotype). Photo by T. Bau
Figure 2 – Pholiota betulicola. A Pleurocystidia. B Cheilocystidia. C Basidia. D Basidiospores. Scale bars: 10 μm. Drawings by E. Tian
Figure 3 – BI phylogram of Pholiota based on data set (ITS+28S). PPs>0.95 and bootstrap values>70% are shown. The new species in this study are in bold and blue. The tree is rooted with the two species of Stropharia