Russula chrysea G.J. Li & Chun Y. Deng, sp. nov.
Index Fungorum number: IF 570739; Mycobank number: MB 570739; Fungal Names Number: FN 570739; Facesoffungi number: FoF 14521; Figs. 1b, 2a, b, 3
Etymology: Referring to the pale yellowish tinge of pileus.
Holotype: HBAU 15023.
Basidiomes small to medium sized. Pileus 26–35 mm in diam, hemisphere to plano-convex, rarely applanate, a tinge of pale greenish yellow (E2E3A7, E3ECA6), sometimes faded to slight yellow tinge (EFEFDF, F5EED3), smooth, glabrous, not viscid when wet; margin not striate, not cracked, peeling 1/5–1/4 from the edge. Lamellae adnate, 2–3 mm in height, 16–20 pieces per centimeter at edge, sometimes forked near the stipes, interveined, white (FFFFFF), pale cream (F4EAE0) when mature, unchanging when bruised, lamellulae not observed. Stipes 25–33×5–11 mm, central to subcentral, cylindrical, slightly ventricose downward the base, rugulose longitudinally, white (FFFFFF), unchanging or slightly turning pale ocher (B78B5F, B6855A) when injured, smooth, dull, not viscid when wet, stuffed when young, hollow after mature, annulus absent. Context 1–3 mm thick at pileus center, white (FFFFFF), unchanging or turning pale yellow (F0E1BF, ECD6A3) when bruised, taste mild, smell indistinct. Spore print cream to pale ocher (Romagnesi IIc–IId).
Basidiospores [150/3/3] 5.6–7.2 (–7.6)×(4.3–) 4.6–6 μm, Q =1.05–1.27 (1.36), Q =1.18±0.08), hyaline, subglobose to broad ellipsoid, rarely ellipsoid, ornamentations amyloid, up to 1 μm in height, composed of long ridges interconnected as complete reticulum, mixed up with a few isolated warts and short crests, suprahilar area plage distinct and amyloid. Basidia 34–52×9–12 μm, clavate to subclavate, rarely subcylindrical, four-spored, projecting 10–30 μm beyond hymenium, hyaline, sterigmata 4–7 μm long. Hymenial cystidia infrequent, 56–71×8–9 μm, fusiform to subclavate, sometimes clavate, contents granulate, sparse, unchanging or slightly grey in SV, apex obtuse, rarely subacute. Pileipellis two layered, not clearly distinguished from the context; epipellis a trichoderm, ca. 30–70 μm deep; terminal cells hyaline, cylindrical, rarely branched, often 3–5 μm wide, seldom up to 8 μm; primordial hyphae abundant, septate, 5–8 μm wide, surface with acido-resistant incrustations; pileocystidia absent; 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, Yinjiang County, Chanxi Township, Fengxiangping Nature Reserve, in broad-leaved forest, 31 July 2019, 16 June 2014, Guo-Jie Li, Lu-Yao Shi 20190155 (HBAU 15023, holotype).
GenBank number – ITS=MT505890.
Notes – Russula chrysea forms an independent clade with two unidentified samples from Japan in phylogenetic analyses (Fig. 4). This clade has a close relationship with members of Russula section Amethystinae. The yellowishcapped species of this section, R. helios, R. ochracea, R. postiana and R. risigallina are different from R. chrysea in follwing morphological characters: R. helios has larger basidiospores (8–9.5×6.3–7.8 μm) and narrower primordial hyphae 3–4 μm in diam; R. ochracea can be distinguished its thick and flashy pileus and larger basidiospores (7–9.2×5.3–7.2 μm) with isolated warts; R. postiana is differeciated in having greenish yellow tinged pileus, larger basidiospres (8–11×8.7 µm), and longer and wider hymenial cystidia (70–85×10–12 μm); R. risigallina differs in often reddish tinged pileus, context smell of old fruit, larger basidiospores (7–9×5.8–6.7 μm) with ornamentation composed of mostly isolated warts (Romagnesi 1985; Sarnari 2005).
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 chrysea (HBAU 15023, 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