Lactifluus luteolamellatus H. Lee & Y.W. Lim

Index Fungorum number: IF553808 Facesoffungi number: FoF 03645

Etymology: ‘luteolamellatus’ refers to the yellowish lamellae.

Holotype: SFC 20150818-39

Pileus 45–75 mm diameter, convex with central depression to infundibuliform; margin incurved rugulose when young; edge even, sometimes rather irregular; surface smooth but rugulose when young, pruinose, pale orange (6A3) to peach (7A4), unicolourous. Lamellae adnate to subdecurrent, distant, pale yellow, very broad; edge entire and concolourous. Stipe 40–65 × 15–20 mm, stuffed, cylindrical, sometimes tapering downwards, centrally attached to pileus; surface dry, pruinose, concolourous with pileus, sometimes more yellowish upwards. Context solid, whitish-yellow, unchanging; fishy smell when old. Latex abundant, white, slowly brownish discoloration. Basidiospores subglobose to broadly ellipsoid, 7.6–8.6–9.8 × 6.6–7.2–7.6 μm (n = 20, Q = 1.11–1.19–1.25); ornamentation amyloid, forming an almost complete reticulum, composed of low warts connected by fine ridges, up to 0.3 μm high; plage inamyloid. Basidia 4-spored, 50–70.5 × 9.5–11.5 μm, subclavate to clavate; content guttate to granular. True cystidia absent. Pleuropseudocystidia scarce, 4–6 μm, cylindrical; content granular. Pileipellis a lampropalisade; elements of the suprapellis 30–125 × 4–5 μm, cylindrical, obtuse, thick-walled; subpellis 150–175 μm thick, sphaerical cells 8–25 μm diameter, with thickened wall.

Material examined: KOREA, Incheon-si, Ganghwa-gun, Mt. Mani, N37°36′42″ E126°25′48″, alt. 192 m, on soil in deciduous forest, with Quercus spp., 18 August 2015, Y.W. Lim (SFC20150818-39, holotype); KOREA, Chuncheongnam-do, Cheongyang-gun, Mt. chilgap, N36°23′56″ E126°53′28″, alt. 190 m, on soil in mixed forest, with Pinus densiflora, Populus davidiana and Quercus serrata., 29 July 2004, S. J. Seok (ASIS12249, paratype) GenBank numbers SFC20150818-39 ITS:MF611655; LSU:MF611680; RPB2:MF617782. ASIS12249 ITS:MF611654; LSU:MF611679; RPB2:MF617781.

Notes: Lactifluus luteolamellatus can be recognized by its yellow lamellae and brownish discoloration of latex, absence of true cystidia, subreticulate basidiospores and long pileipellis hairs up to 125 μm. In the multiple-locus phylogeny, this new species has an isolate position where is sister to L. sect. Lactifluus and is closely related to L. subg. Lactifluus sect. Tenuicystidiati. All species treated in sect. Lactifluus have pleurolamprocystidia and all members in sect. Tenuicystidiati have pleuromacrocystidia (De Crop et al. 2017).

Phylogram generated from maximum likelihood (RAxML) analysis based on combined ITS, LSU, RPB2 sequence data of Lactifluus. ML bootstrap support values greater than 70% are indicated above or below the nodes and the new species are in bold. The tree is rooted with species in other Russulaceae genera. Superscript T after specimen number represents as a type specimen

Lactifluus luteolamellatus (SFC20150818-39, holotype). a, b Fruiting bodies in the field. c Basidia. d Basidiospores. e Pleuropseudocystidia. f Pileipellis