Russula minirosea Y.Song, 2024

Song, Yu, Wang, Yu-Yu, Yu, Jin-Ling, Yuan, Rui & Li, Fang, 2024, Phylogenetic and morphological evidence for four new species of Russula (Russulaceae, Basidiomycota) from northwestern China, European Journal of Taxonomy 958, pp. 48-76 : 63-67

Russula minirosea Y.Song sp. nov.

MycoBank: MB847690

Figs 1–2 , 7–8 , 11C–D

Diagnosis

Russula minirosea sp. nov. can be separated from other morphologically and phylogenetically related species by a unique combination of characteristics: very small basidiocarps with thin context, peach pink to rosy pileus less than 3.3 cm in diam., basidiospores with low ornamentation and fine reticulum, septate pileocystidia and sequence data.

Etymology

The species name refers to its small basidiocarp often with rosy pileus.

Type material

Holotype

CHINA • Shaanxi Province, Hanzhong City, Micangshan Biosphere Reserve ; 32°37′66″ N, 107°25′49″ E; 1010 m a.s.l.; 21 Sep. 2022; Y. Song, K22092145; gregarious on the ground in mixed coniferous and broad-leaf forest, mainly with Quercus variabilis Bl. , Q. aliena Bl. , Q. acutissima Carruth. and Pinus massoniana Lamb. ; GenBank nos: OP828699 (ITS), OP828720 (LSU), OP831171 (rpb2), OP857224 (tef1); SERC [ SERC2205 ].

Additional material examined

CHINA • Shaanxi Province, Hanzhong City, Liancheng Mountain ; 33°12′25″ N, 106°57′39″ E; 593 m a.s.l.; 6 Sep. 2021; Y. Song, K21090617; gregarious on the ground in mixed coniferous and broad-leaf forest; GenBank nos: OP828698 (ITS), OP828719 (LSU), OP831170 (rpb2), OP857223 (tef1); SERC [ SERC2206 ] • Shaanxi Province, Hanzhong City, Han Mountain; 5 Oct. 2022; Y. Song, K22100508; gregarious on the ground in mixed coniferous and broad-leaf forest; GenBank nos: OP828700 (ITS), OP828721 (LSU), OP831172 (rpb2), OP857225 (tef1); SERC [ SERC2207 ] • same data as for preceding; 5 Oct. 2022; Y. Song, K22100509; GenBank nos: OP828701 (ITS), OP828722 (LSU), OP831173 (rpb2), OP857226 (tef1); SERC [ SERC2208 ] • Hanzhong City, Nan-zheng District, Qing-shu Town ; 30 Sep. 2023; Y. Song, J.L. Yu, 23093003; gregarious on the ground in mixed coniferous and broad-leaf forest; GenBank no.: PP062887 (ITS); SERC [ SERC2302 ] .

Description

Basidiomata very small sized. Pileus 1.8–3.3 cm in diam., hemispherical to convex when young, turning applanate with depressed center at maturity; surface viscid, easy to peel off ⅔ radius when mature, dark blood red (#DE3C37) to deep rosea (#EC7063) when young, becoming peach pink (#F97D8E) at margin, fuchsia pink to rosy (#C85868, #DF828F) at center; margin smooth and entire at first, turning striate with age. Lamellae adnate, interveined, sometimes forked near stipe, white when young, turning yellowish cream (#FCF3CF, #FEF9E7) at maturity; edge concolorous, smooth; lamellulae rare, irregularly dispersed. Stipe central, fleshy, fragile, smooth, cylindrical, often tapering upwards, solid at first, turning hollow to multi-chambered with age, 2.5–3.9 × 0.5–1.3 cm, chalky white to white (#FCF3CF, #FBFCFC). Context white (#FCF3CF), unchanging when bruised. Taste mild. Odor indistinct. Spore print not observed.

Basidiospores subglobose to ellipsoid, (80/4/4) (6.5–)7–7.5–8(–8.3) × (5.5–)5.7–6.2–6.8 µm, [Q = 1.14– 1.21–1.30(–1.45)], hyaline in 5% KOH; ornamentation amyloid, less than 0.8 µm in height, moderately distant to dense ((5–7(–8) in a 3 µm circle), forming a complete reticulum; suprahilar spot amyloid. Basidia (26.5–)28–33–39(–41) × 10–12–13.5(–15) µm, clavate, 4-spored, thin-walled, with oil dorplets; sterigmata 3.7–5.9–8.5 × 1.4–2.0–2.6 µm. Pleurocystidia subcylindrical to fusiform, (38.5–)41–49–60.5 (–66) × 7.5–9.5–11(–13.5) µm, with obtuse, papillate or mucronate apices, thin-walled, with irregular refractive contents, projecting up to 30 µm, unchanging in SV. Cheilocystidia similar to pleurocystidia in shape, but relatively smaller, measuring (31–)38–40–46(–56) × 6–8–12 µm. Lamellar trama composed of numerous sphaerocytes surrounded by connective hyphae, sphaerocytes measuring 30–62 × 23–42 µm. Subhymenium pseudoparenchymatous. Pileipellis orthochromatic in cresyl blue, thin, 100–150 µm thick, gelatinized, vaguely divided into two layers: suprapellis 80–120 µm thick, composed of ascending to erect hyphae and pileocystidia; subpellis thin, 20–50 µm deep, composed of more horizontal hyphae and pileocystidia; hyphae 2.5–5 µm in diam. Acidoresistant incrustations not observed. Hyphal terminations near the pileus margin often branched, thin-walled, sometimes narrowed; terminal cells measuring (16–)18.5–27–43 × 2.5–3.5–5 µm, subcylindrical, with obtuse apices; subterminal cells usually equally wide. Hyphal terminations near the pileus centre of similar structure; terminal cells measuring (13.5–)16– 21–27 × 2–3–5 µm, cylindrical or slightly narrowed towards apex, apically obtuse-rounded; subterminal cells usually equally wide. Pileocystidia near the pileus margin (31–)42–68–119(–138) × 4–6–8 µm, abundant, 1- to 4-celled, thin-walled, cylindrical to subclavate, flexuous, with obtuse apices, with refractive contents, weakly becoming pinkish in SV. Pileocystidia near the pileus center of similar shape, 1- to 4-celled, abundant, measuring (26–)37–54–97(–112) × 3–5–7.5 µm, with refractive contents, weakly SV+. Cystidioid hyphae in subpellis and context with heteromorphous granulose contents. Oleiferous hyphae in the subpellis. Clamp connections absent in all tissues.

Remarks

Russula minirosea sp. nov. is classified into subsect. Laricinae , which typically harbors small species of Russula with abundant dermatocystidia, short basidia and various colors of spore print. There are few species with reticulate-crested spores in Laricinae , most having isolated warts. Russula yadongensis S.H.Wang, R.L.Zhao & B.Cao , also a member of subsect. Laricinae reported from northwestern China, can be distinguished from R. minirosea by its medium-sized pileus (3.2–4.6 mm in diam.) with a purple coloration and spores with isolated ornamentations ( Wang et al. 2023). Two other members of subsect. Laricinae reported from China differ from R. minirosea : R. sichuanensis G.J.Li & H.A.Wen is characterized by its dirty white to pale tinged pileus and larger basidiospores [(8.8–)9.4–14.1(–15.5) × (7.6–)7.9–12.8(–13.1) µm] with cristulate to subreticulate ornamentations ( Li et al. 2013b), while R. vinosobrunneola G.J.Li & R.L.Zhao has a brown pileus and larger basidiospores [7.7–9.6 (–10.1) × 6.4–8 (–8.6) µm] ( Li et al. 2018a).

Russula minirosea sp. nov. shows a close relationship to the European species R. nauseosa and R. laricina . Russula nauseosa is variable in pileus color (reddish, purplish, brownish and whitish, but mostly with purplish tint) and size. Basidiospores of R. nauseosa are larger (7.8–10 × 6.6–7.8 µm) and often ornamented with isolated warts or spines never forming a reticulum ( Miller et al. 2012), distinguishing it from R. minirosea . Russula laricina is easily differentiated from R. minirosea by its purple pileus and reddish-tinged stipe.

In terms of very small basidiocarps and rosy pileus color, R. minirosea sp. nov. resembles R. minor Y.Song which belongs to subsect. Puellarinae . But the latter species has a pileus often with a white margin, much smaller basidiospores [(5.0–)5.3–5.8–6.1(–6.6) × (4.1–) 4.3–4.6–4.9(–5.2) µm] with isolated warts, very small basidia [(17–)17.5–21–27(–29.5) × 7–8.5–9.5(–10) µm] and non-septate pileocystidia ( Song et al. 2021).

In the phylogenetic analysis based on ITS, two unidentified sequences (KX441101, MW554359) and three sequences identified as R. cf. nauseosa (GU371293, KX655853, MT678891), all collected from China, clustered with R. minirosea sp. nov. ( Fig. 1 ), with sequence similarity more than 99% between each other. Consequently, these five sequences should also be reclassified as R. minirosea , which also indicates the relative abundance of the species in China.

Figures

Fig. 1. Maximum likelihood tree of subg. Russula crown clade based on ITS sequences, bootstrap (BS) values higher than 50% and posterior probability (PP) values higher than 0.9 are displayed around nodes. Newly generated sequences are shown in bold and clades with four new species are highlighted in green.

Fig. 2. Maximum likelihood tree of subgen. Russula crown clade based on 3-locus (nLSU-tef1-rpb2) combined sequences, bootstrap (BS) values higher than 50% and posterior probability (PP) values higher than 0.9 are presented around nodes. Newly generated sequences are shown in bold and four new species are highlighted in green.

Fig. 7. Russula minirosea Y.Song sp. nov. A–H. Fruiting bodies. A, D–E. Holotype (SERC2205) B. SERC2206. C. SERC2207. F–G. SERC2208. H. SERC2302. I. Basidiospores in Melzer’s reagent showing the amyloid ornamentations, holotype (SERC2205). Scale bars: A–H = 1 cm; I = 10 µm.

Fig. 8. Line drawings of Russula minirosea Y.Song sp. nov., holotype (SERC2205). A. Basidia. B. Cheilocystidia. C. Pleurocystidia. D. Pileocystidia near pileus margin. E. Hyphal terminations near pileus margin. Scale bar = 10 µm.

Fig. 11. Photograph of basidiospores under scanning electron microscope.A–B. Russula micangshanensis Y.Song sp. nov., holotype (SERC2201). C–D. R. minirosea Y.Song sp. nov., holotype (SERC2201). E–F. R. griseorosea Y.Song sp. nov., holotype (SERC2209). G–H. R. purpureomarginalis F.Li & Y.Song sp. nov., holotype (SERC2211). Scale bars = 1 µm.