Russula purpureomarginalis F.Li & 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 : 67-70

Russula purpureomarginalis F.Li & Y.Song sp. nov.

MycoBank: MB847718

Figs 1–2 , 9–10 , 11G–H

Diagnosis

Russula purpureomarginalis sp. nov. differs from the very similar R. xerampelinoides K.Das, I.Bera, A.Ghosh & Buyck from India in several aspects: it is not associated with Abies densa Griff. , it has larger basidia, unchanging pileocystidia in SV, and it has distinct ITS sequence data.

Etymology

The species name refers to the reddish purple margin of its pileus.

Type material

Holotype

CHINA • Xinjiang Uygur Autonomous Region, Burqin County, Hemu Village ; 2 Aug. 2022; F. Li, Hm23; solitary on the ground in mixed coniferous and broad-leaf forest; GenBank nos: OP828710 (ITS), OP828727 (LSU), OP831178 (rpb2), OP857230 (tef1); SERC [ SERC2211 ].

Additional material examined

CHINA • Shaanxi Province, Hanzhong City, Micangshan Biosphere Reserve ; 32°37′66″ N, 107°25′49″ E; 9 Se. 2021; Y. Song, K21090918; solitary on the ground in mixed coniferous and broad-leaf forest; GenBank no: OP828711 (ITS); SERC [ SERC2212 ] .

Description

Basidiomata medium to relatively large sized. Pileus 5–9 cm in diam., hemispherical when young, turning convex to applanate at maturity; surface dry, viscid when wet, not easy to peel off, pale pinkish purple (#D8BFD8) to reddish purple (#FDE9FB) at margin, yellow to brown (#FDFEE6) at center; margin smooth and entire at first, slightly striate with age. Lamellae adnate, interveined, white (#FEFEFE) to pale cream (#FFF8D1), up to 8 mm in diam.; edge concolorous, smooth. Stipe central, fleshy, cylindrical, often slightly tapering upwards, solid, 3.5–7 × 1–1.6 cm, white (#FCF3CF, #FBFCFC) with pinkish tinge (#FFF3FC). Context white (#FCF3CF), 9 mm thick in pileus, unchanging when bruised. Taste mild. Odor indistinct. Spore print not observed.

Basidiospores subglobose to ellipsoid, (40/2/2) (7.6–)7.9–9.0–9.6(–10) × (5.8–)6.3–7.0–7.7(–8.0) µm, [Q = (1.14–)1.21–1.28–1.40(–1.42)], hyaline in 5% KOH; ornamentation amyloid, conical to cylindircal warts less than 1.5 µm in height, moderately distant to dense (5–7(–8) in a 3 µm circle), often isolated, occasionally connected by line, line connections dispersed (0–1 in the circle); suprahilar spot amyloid. Basidia (46.5–)48–59–70(–74) × (8.5–)10.5–12.5–14 µm, long clavate, 4-spored, thin-walled, with irregular contents and oil dorplets; sterigmata 5.6–6.9–8.7 × 1.8–2.2–2.8 µm. Pleurocystidia cylindrical to fusiform, (48.5–)57–67.5.5–83(–87) × 6.5–10.5–14 µm, with obtuse, papillate or mucronate apices, thin-walled, with irregular refractive contents, projecting up to 20 µm, unchanging in SV. Cheilocystidia similar to pleurocystidia in shape, relatively smaller, measuring 46.5–57–66.5(–81) × 6.5–8.9–11 µm. Subhymenium pseudoparenchymatous. Lamellar trama composed of numerous sphaerocytes surrounded by connective hyphae, sphaerocytes measuring 14–31 × 11–27 µm. Pileipellis orthochromatic in cresyl blue, 120–200 µm thick, gelatinized, divided into two layers: suprapellis 60–90 µm thick, composed of ascending to erect hyphae; subpellis thin, 50–110 µm deep, composed of more horizontal hyphae; hyphae 2.5–6 µm in diam., some wider and strongly pigmented, up to 10 µm in diam. Acidoresistant incrustations rare. Hyphal terminations near the pileus margin thin-walled, often narrowed; terminal cells measuring 14–25.5–33(–40) × 2.5–4–5 µm, subcylindrical, with obtuse or sharp apices, rarely inflated, coracoid, up to 11 µm wide; subterminal cells usually equally wide. Hyphal terminations near the pileus centre of similar structure. Pileocystidia near the pileus margin (31–)53–82–108(–113) × 4–6–8.5 µm, abundant, 1- to 3-celled, thin-walled, cylindrical to subclavate, flexuous, with obtuse apices, with refractive contents, unchanging in SV. Pileocystidia near the pileus center of similar shape, 1- to 3-celled, abundant, measuring (36.5–)42–67.5–96.5(–106) × 3–6–7(8.5) µm, with refractive contents, unchanging in SV. Cystidioid hyphae in subpellis and context with granulose or crystalline contents. Oleiferous hyphae in the subpellis. Clamp connections absent in all tissues.

Remarks

Russula purpureomarginalis sp. nov. is classified into subsect. Xerampelinae , forming a distinct clade in both ITS and multi-locus phylogenetic trees. Russula paragraveolens S.H.Wang, G.J.Li, R.L.Zhao & B.Cao and R. pseudograveolens S.H.Wang, G.J.Li, R.L.Zhao & B.Cao reported from China also belong to this subsection ( Wang et al. 2023). Russula paragraveolens has a bright red pileus, much smaller basidiospores [(5.0–)5.5– 5.9–6.3(–6.6) × (4.0–)4.6–5.0–5.4(–5.6) µm] and basidia [(31–)31–36–41(– 50) × (10–)10–11–12(–14) µm]; R. pseudograveolens is diagnosed by its violet brown to brownish red pileus, much smaller basidiospores [(5.5–)6.0–6.3–6.6(–6.9) × (4.7–)5.0–5.2–5.5(–5.7) µm] and basidia [(27–)28–30–32(–35) × (8.5–)9–10(–11) µm], all can be distinguished. Russula xerampelinoides reported from India resembles R. purpureomarginalis in spore size and ornamentations, but the former species has smaller basidia (40–44–48(–50) × 9–10–11(–12) µm) and grey-black pileocystidia in SV. Moreover, R. xerampelinoides is distributed in subalpine forest and associated with Abies densa ( Buyck et al. 2021) , while R. purpureomarginalis inhabits mixed coniferous and broad-leaf forest mainly with Quercus and Pinus trees.

The European and American members of subsect. Xerampelinae , such as R. madrensis A.Kong & Buyck , R. sancti-pauli A.Kong & Buyck and R. xerampelina (Schaeff.) Fr. , show a bright red to dark red pileus color ( Adamčík et al. 2019). Russula flavobrunnescens A.Kong & Buyck and R. katarinae Adamčík & Buyck have a yellowish or brownish pileus, but not stained with purplish tint ( Adamčík et al. 2015). Russula purpureomarginalis sp. nov., characterized by its distinctly reddish purple tinged pileus, can be easily distinguished from these related species.

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. 9. Russula purpureomarginalis F.Li & Y.Song sp. nov., holotype (SERC2211). A–C. Fruiting bodies. D–E. Basidia. F. Pileocystidia near pileus margin. G. Basidiospores in Melzer’s reagent showing the amyloid ornamentations. Scale bars: A–C = 1 cm; D–G = 10 µm.

Fig. 10. Line drawings of Russula purpureomarginalis F.Li & Y.Song sp. nov., holotype (SERC2211). 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.