Russula cruenta G.J. Li & Chun Y. Deng, sp. nov.
Index Fungorum number: IF 570740; Fungal Names Number: FN 570740; Facesoffungi number: FoF 14522; Figs. 1c, 12c, d, 3
Etymology – Referring to the reddish tinge of pileus.
Holotype – HGAS-MF 013964.
Basidiomes small to medium sized. Pileus 29–38 mm in diam, hemispheric when young, then convex, expanded when old, a tinge of brightly red (D66467, CB3145), often faded to a paler orange reddish tinge (F4512C, E9693D) towards the margin, smooth, glabrous, slightly viscid when wet; margin not striate, rarely cracked, exfoliated in small patches, peeling 1/3–1/2 from the edge. Lamellae adnate, 3–4 mm in height, 13–16 pieces per centimeter at edge, not forked, interveined, white (FFFFFF), pale cream (F4EAE0) when mature, unchanging when bruised, lamellulae not observed. Stipes 29–48×10–13 mm, central to subcentral, cylindrical, rugulose longitudinally, white (FFFFFF), partly pale pink (F1ACB0, EEB0AE), unchanging when bruised, smooth, not viscid when wet, slightly ventricose downward the base, first stuffed, hollow when mature, annulus absent. Context 2 mm thick at pileus center, white (FFFFFF), unchanging when injured, taste mild to slightly acrid, smell indistinct to fruity. Spore print cream to pale ocher (Romagnesi IIc–IId).
Basidiospores [150/3/3] (6.6–) 7–5.9 (–10.3) × (5.4–) 5.9–8.5 (–9.1) μm, Q=1.00–1.34 (1.42), Q=1.17±0.07), hyaline, subglobose, broad ellipsoid to ellipsoid, rarely globose, ornamentations amyloid, up to 1.2 μm in height, composed of isolated warts rarely connected as short crests, not forming reticulum, suprahilar area plage distinct but inamyloid. Basidia 34–53×10–12 (–15) μm, cylindrical, subcylindrical to subclavate, rarely clavate four-spored, projecting 10–20 μm beyond hymenium, hyaline, sterigmata 4–6 μm long. Hymenial cystidia scarce, 60–70×8–10 μm, fusiform to subclavate, sometimes subfusiform or clavate, contents sparsely distributed, granulate, greyish in SV, apex obtuse to subacute. Pileipellis two layered, not clearly delimited from the spherocytes in context; epipellis trichoderm, ca. 30–60 μm deep, erect to ascending, rarely horizontal; terminal cells hyaline, sometimes inflated, 5–10 μm wide; primordial hyphae abundant, 5–8 μm wide, septate, surface with
acido-resistant incrustations; pileocystidia absent; subpellis composed of somewhat gelatinized, densely interlaced, rarely branched and septate, hyaline hyphae 3–6 μm wide. Stipitipellis a cutis, composed of parallel hyaline hyphae 3–5 μm wide.
Habitat – Single or scattered in coniferous and broadleaved intermixed forest.
Material examined – China, Guizhou Province, Songtao County, in coniferous and broad-leaved intermixed forest, 20 October 2017, HGAS-MF 013964 (holotype).
GenBank number – ITS=MT505893.
Notes – The new species Russula cruenta clusters with an unknown Russula sample from Japan (Fig. 4). The Cruenta clade loosely groups with another clade which is composed of two North American species R. ballouii and R. burlinghamiae (Fig. 4). These two species can be distinguished from R. cruenta by their yellowish tinged pileus with fractured pigment patches. Russula ballouii also differs in basidiospore ornametations forming incomplete reticulum (Peck 1913; Buyck et al. 2003). Russula cruenta is also morpholoically similar to two reddish-capped species: one is the newly described Asian R. clavatohyphata from India, and the other is the North American species R. luteobasis. Russula clavatohyphata differs in having rare lamellulae at pileus margin, pink to pale red stipe, and appendages up to 30 µm long at the hymenial cystidium apex (Wang et al. 2019b). Russula luteobasis can be differentiated in its yellowish turning pileus, low basidiospore ornamentations 0.1–0.3 μm without isolated warts, and hymenial cystidium apex mainly with 4–10 μm long appendage (Adamčík et al. 2018).
Figure 1 – 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 2 – Basidiomes of new Russula species (holotypes). a, b Russula chrysea. c, d R. cruenta. Scale bars: a–d=10 mm
Figure 3 – Microscopic structures of Russula cruenta (HGAS-MF 013964, holotype). a Basidia. b Hymenial cystidia. c Suprapellis of pileipellis. Scale bars: a–c=10 μm
Figure 4 – Maximum likelihood tree illustrating the phylogeny of Russula chrysea and R. cruenta (holotypes) with related species in “crown clades” as illustrated in Looney et al. (2016) based on ITS sequences. Branches are labeled with maximum likelihood bootstrap higher than 50%, and Bayesian posterior probabilities more than 0.9 respectively. Sequences of R. sect. Auratinae were used as outgroup to root trees. The new isolates are in bold