Russula guangxiensis G. J.Li, H. A.Wen & R. L. Zhao

Index Fungorum number: IF551492 Facesoffungi number: FoF01007

Etymology: refers to the type locality

Holotype: CHINA. Guangxi Zhuang Autonomous Region, Wuzhou City, Tengxian County, Xiangqi Township, Xiangqi Village, 21 August 2013, Xin-Hua Chen 35 (HMAS267867). Basidiomata small to medium sized. Pileus 30–65 mm diam., first hemispheric to plano-convex, then expanding to applanate, finally slightly depressed in center to concave, smooth,viscid when wet, slightly glabrous when young,peeling 1/3–1/2 from the edge, sometimes desquamated in small patches, margin sometimes undulate, not striate, rarely cracked; pale pinkish red tinged with Begonia Rose (I1b) to Geranium Pink (I3d), intermixed with Strawberry Pink (I5d) in center, Hermosa Pink (I1f), Shrimp Pink (I5f), or even White (LIII) towards the margin. Lamellae adnate, equal to subequal,2–4 mm in height, 15–21 pieces per cm at the edge, rarely forked near the stipe and pileal edge, often interveined, White when fresh, slowly turning Orange Cinnamon (XXIX13″) to Mikado Brown (XXIX13″i) when injured, lamellulae absent. Stipe central, 6–9×0.8–1.5 cm, subcylindrical, surface dry, smooth, rarely rugulose longitudinally, dull, sometimes slightly attenuate upwards or downwards, white, a tinge of when injured and dry, first stuffed, becoming hollow at last. Context 2–4 mm at the center of the pileus, white, fragile, odour indistinct, taste mild. Spore print White (RomagnesiIa). Basidiospores [200/10/10] 5.9–6.9 (−7.2)×4.9– 6.1 μm, Q=(1.05–) 1.08 –1.23 (−1.26), (Q=1.16±0.05), hyaline, subglobose to broadly ellipsoid; ornamentation composed of amyloid conical warts that are mostly isolated or rarely linked, not forming network, warts 0.7–1 μm in height; suprahilar are distinct and amyloid. Basidia 38–47× 7–10 μm, mostly with four sterigmata 3–5 μm long, hyaline, sometimes yellowish in KOH, subclavate to clavate, rarely subcylindrical. Pleuroystidia scattered, 55–63×7–12 μm, projecting 10–20 μm beyond the basidia, subfusoid to subcylindrical, sometimes clavate to subclavate, apices round to subacute, often appendiculate to subcapitate, thin–walled, contents granular, crystal, refractive, weakly grey in SV. Cheilocystidia same as pleurocystidia. Subhymenium a cellular layer 15–30 μm thick composed of inflated cells 6–17 μm diam., hyaline, sometimes pale yellowish in KOH. Pileipellis orthochromatic in cresyl blue, composed of epipellis and subpellis; epipellis a dense, hymeniderm 50–60 μm thick, composed of thin-walled, cylindrical hyaline hyphae 3– 6 μm wide; terminal cells 15–30×5–10 μm, septate, clavate, apex mostly obviously inflated; subpellis less dense, a pseudoparenchymatic region, 40–60 μm thick, composed of irregular inflated sphaerocysts 20–30 μm diam., interweaved hyaline hyphae 2–6 μm wide; primordial hyphae cylindrical, septate, 3–6 μm diam., with heteromorphous-opalescent inclusions and acid-resistant incrustations, apex obtuse; pileocystidia not observed. Stipitipellis a cutis, composed of filamentous hyphae 3–6 μm diam., interweaved with inflated cells10–15μmdiam.,hyaline,somehyphaeyellowishtopale ochre in KOH; caulocystidia absent. Trama composed of sphaerocytes 30–90 μm diam.Clamp connections and lacticiferous hyphae absent from all tissues.

Habitat and distribution: Single or scattered in broadleaved forests (dominated by Lithocarpus spp.).

Additional specimens examined: CHINA, Guangxi Zhuang Autonomous Region, Wuzhou City, Tengxian County, Xiangqi Township, Xiangqi Village, 21 August 2013, XinHua Chen 57 (HMAS267863); ibid., Xin-Hua Chen 29 (HMAS267831); ibid., Xin-Hua Chen 19 (HMAS267869); ibid., Xin-Hua Chen 24 (HMAS267829); ibid., Xin-Hua Chen 41 (HMAS267833); ibid., Xin-Hua Chen 25 (HMAS267868); ibid., Xin-Hua Chen 28 (HMAS267832); ibid., Xin-Hua Chen 7 (HMAS267866); ibid., Xin-Hua Chen 14 (HMAS267836).

Notes: The combination of white spore print, mild taste, bright red pileus, pileipellis with primordial hyphae but without pileocystidia, pseudoparenchymatic subpellis, and the topology of phylogenetic analysis of ITS sequences clearly place R. guangxiensis within subgenus Incrustatula Romagn. Subsection Roseinae Singer ex Sarnari. Two new taxa, R. guangxiensis and R. hakkae, clustered together with strong support (BS 92%, PP 1.00) with most members of subsection between the two new taxa through a fairly good support (BS 80%, PP 1.00). The two Roseinae involvedin thisstudy. Our phylogenetic analysis also indicated a close relationship new taxa have context without distinctive odour, amyloid and distinct basidiospores uprahilar area, and habitat of Lithocarpus forest. However, R. hakkae has an acrid tasted context, larger basidiospores with dense ornamentation up to 1.2 μm in height, and a palisade epipellis. Other species of subsection Roseinae originally described from Europe can be distinguished from R. guangxiensis as follows. Russula lepidicolor Romagn. has a low basidiospore ornamentation composed of hemispherical warts up to 0.4 μm high which is often linked by fine lines as short to long ridges, and wider basidia (9–12 μm) (Romagnesi 1967; Sarnari 2005). Russula minutula Velen. has a small, velutinous pileus 17–30 mm, a context with a strong but short-lived odour of rosemary, and a quite rarely little amyloid basidiospores uprahilar area (Romagnesi 1967; Sarnari 2005). Russula velutipes Velen. has a pileus with copper brown or apricot orange shade, a bulbous stipe, and a low basidiospore ornamentation composed of hemispherical warts up to 0.4 μm high are which often linked by fine lines as short to long ridges. Type specimens of several members of subsection Roseinae which were described from America has been studied recently (Adamčík and Buyck 2012). Among good members of subsection Roseinae, R. albida Peck can be distinguished from R. guangxiensis by a white to slightly yellow tinged pileus which has a narrowly tuberculose-striatepileus margin, and a basidiospore ornamentation composed of spines which form an almost complete reticulum, connected by frequent line connections; R. nigrescentipes Peck differs in a stipe becoming blackish by handling or bruising, basidiospore ornamentation composed of warts connected by frequent line connections, and short basidia (22–30 μm); R. rimosa Murrill can be distinguished by shortly ellipsoid to ellipsoid basidispores which have dense, low ornamentations (0.2–0.5 μm) with numerous line connections, and pileipellis with pileocystidia SV-insensitive contents (Adamčík and Buyck 2012).

 Russula guangxiensis (holotype) a Basidiocarps b Basidiospores c Basidia d Pleurocystidia e Pileipellis

Russula guangxiensis (holotype) a Basidiocarps b Basidiospores c Basidia d Pleurocystidia e Pileipellis