Russula luteocarpa G.J. Li & Chun Y. Deng, sp. nov.
Index Fungorum number: IF 570738; Fungal Names Number: FN 570738; Facesoffungi number: FoF 14526; Figs. 1c, d, 2d, 3
Etymology – Referring to the yellowish pileus of basidiomes.
Holotype – HGAS-MF 013966.
Basidiomes medium sized. Pileus 37–48 mm in diam, first plano-hemisphere to convex, turning applanate to slightly depressed at center when mature, ocherous tinged, brownish yellow (947563, B0876D) to dark yellow (BC9C69, D1A14A), faded to a pale yellow tinge (F1DE9C, F9E397) towards the margin, smooth, glabrous, somewhat sticky when wet; margin not striate to slightly striate, seldom cracked, peeling 1/3–1/2 from the edge. Lamellae adnate, 3–4 mm in height, 14–18 pieces per centimeter at edge, often forked near the stipes, interveined, white (FFFFFF) when young, cream (F1DDCF, F0D8C3) when mature, unchanging when bruised, lamellulae not observed. Stipes 42–56×10–14 mm, central to subcentral, cylindrical, rugulose longitudinally, white (FFFFFF), slowly turning pale ocher (B88E4D, B48834) when bruised, smooth, dull, not viscid when wet, slightly attenuate downward the base, first stuffed, hollow when old, annulus absent. Context 2–3 mm thick at pileus center, slightly turning white (FFFFFF), pale ocher (BD7B27, D5A372) when injured, taste mild, smell indistinct. Spore print cream (Romagnesi IIc–IId).
Basidiospores [150/3/3] (4.8–)5.1–7.1 (–7.4) × (4.1–) 4.4–6.6 (–7.1) μm, Q=1.02–1.31 (1.36), Q=1.18±0.07), hyaline, subglobose to broad ellipsoid, rarely globose and ellipsoid, ornamentations amyloid, up to 0.5 μm in height, composed of long ridges interconnected as nearly complete reticulum, often intermixed with rare isolated warts, suprahilar area plage indistinct and inamyloid. Basidia 32–44×7–10 μm, cylindrical, subcylindrical to subclavate,
rarely clavate four-spored, projecting 10–20 μm beyond hymenium, hyaline, sterigmata 4–6 μm long. Hymenial cystidia 61–76×11–14 μm, fusiform to cylindrical, sometimes subclavate, contents granulate, sparse, weakly greyish in SV, apex lanceolate, sometimes subacute. Pileipellis two layered, indistinctly delimited from the spherocytes in context; epipellis a trichoderm, ca. 100–150 μm thick, hyphae erect to ascending, rarely branched, cylindrical, hyaline, 2–4 μm wide, rarely septate, some hyphae inflated to 5–7 μm, multi-septate; terminal cells attenuated towards the apex; pileocystidia rare, 6–8 μm wide, cylindrical to clavate, often with an obtuse apex, contents dense, granulate, blackish in SV; subpellis composed of somewhat gelatinized, densely interlaced, rarely branched and septate, hyaline hyphae 3–6 μm wide.
Habitat – Single or scattered in coniferous and broadleaved intermixed forest.
Material examined – China, Guizhou Province, Weining County, Caohai Nature Reserve, in coniferous and broadleaved intermixed forest, 4 August 2016, Chun-Ying Deng CH2016080404 (HGAS-MF 013966, holotype).
GenBank number – ITS=MT505889.
Notes – Topologically, Russula luteocarpa lies in the clade of Russula subsect. Heterophyllae, but the phylogenetic position of this new species in this subsection is still not clear (Fig. 2). Future multi-gene phylogenetic analyses are needed to clarify the concrete relationships between R. luteocarpa and the other species of this subsection. The viscid yellowish, not furfuraceous or areolate pileus of R. luteocarpa is unique in R. subsect. Heterophyllae, but is reminiscent of R. section Ingratae. However, members of that section are different from R. luteocarpa, because they often have strongly striate pileus margin and acrid context taste.
Figure 1 – Basidiomes of new Russula species (holotypes). a, b Russula chlorina. c, d R. luteocarpa. Scale bars: a–d=10 mm
Figure 2 – Basidiospores of new Russula species (holotypes). a Russula chlorina. b R. chrysea. c R. cruenta. d R. luteocarpa. Scale bars: a–d=10 μm
Figure 3 – Microscopic structures of Russula luteocarpa (HGASMF 013966, holotype). a Basidia. b Hymenial cystidia. c Suprapellis of pileipellis. Scale bars: a–c=10 μm