Lactifluus holophyllus H. Lee & Y.W. Lim

Index Fungorum number: IF553805 Facesoffungi number: FoF 03644

Etymology: ‘holophyllus’ refers to the ectomycorrhizal tree, Abies holophylla.

Holotype: SFC20150812-63

Pileus 75–160 mm diameter, convex with central depression to infundibuliform; margin slightly striate, involute and uplifted, even; edge undulate; surface dry, sometimes rugose, pruinose when young, orange white (6A2) to pale red (7A3), sometimes tawny spotted. Lamellae adnate to subdecurrent, rather distant, white to pale cream, pale tawny spotted in age, broad; edge entire and concolourous. Stipe 65–120 × 20–35 mm, stuffed, hollow in age, cylindrical, centrally attached to pileus; surface dry, pruinose, concolourous with pileus, sometimes deeper. Context solid, white, unchanging; smell not distinctive. Latex not very abundant, white, unchanging. Basidiospores broadly ellipsoid, 9–9.4–9.6 × 7.4–7.6–8.2 μm (n = 20, Q = 1.15–1.21–1.26); ornamentation amyloid, forming an incomplete reticulum, composed of elongated warts connected or aligned by fine ridges, up to 0.2 μm high; plage inamyloid. Basidia 4-spored, 52.3–60.2 × 9.4–11.2 μm, cylindric to subclavate; content granular, sometimes guttate. True cystidia absent. Pleuropseudocystidia scarce, 3–6 μm, cylindrical; content granular. Pileipellis a lampropalisade; elements of the suprapellis 25–63 × 3–5 μm, cylindrical, obtuse, thick-walled; subpellis 185–220 μm thick, sphaerical cells 6–22 μm diameter, with thickened wall.

Material examined: KOREA, Gangwon-do, Pyeongchang-gun, Mt. Odae, N37°43′32″ E128°35′47″, alt. 648 m, on soil in Abies holophylla forest, 12 August 2015, H. Lee & Y.W. Lim (SFC20150812-63, holotype); KOREA, Gangwon-do, Pyeongchang-gun, Mt. Odae, N37°47′09″ E128°33′51″, alt. 904 m, on soil in Abies holophylla forest, 26 July 2010, S. J. Seok (ASIS19960, paratype); KOREA, Gangwon-do, Pyeongchang-gun, Mt. Odae, N37°43′47″ E128°35′46″, alt. 663 m, on soil in mixed forest, Abies holophylla and Quercus spp., 22 July 2012, S. J. Seok (ASIS22632, paratype). GenBank numbers SFC20150812-63 ITS:MF611658; LSU:MF611683; RPB2:MF617785. ASIS19960 ITS:MF611659; LSU:MF611684; RPB2:MF617786. ASIS22632 ITS:MF611660, LSU:MF611685; RPB2:MF617787.

Notes: Lactifluus holophyllus belongs to L. subg. Pseudogymnocarpi sec. Pseudogymnocarpi and forms a clade with L. rugatus (Kühner & Romagn.) Verbeken from Europe, L. pseudoluteopus (X.H. Wang & Verbeken) X.H. Wang from China and L. hygrophoroides (Berk. & M.A. Curtis) Kuntze from North America. These three species can be distinguished from L. holophyllus as follows. Lactifluus rugatus has smaller basidiospores (7.5–9 × 6–7.5 μm) (Kühner and Romagnesi 1953) and warmer orange pileus. L. pseudoluteopus has longer pileipellis hairs (120–150 × 3–5 μm) (Wang & Verbeken 2006).

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 holophyllus (SFC20150812-63, holotype). a, b Fruiting bodies in the field. c Basidia. d Basidiospores. e Marginal cells. f Pileipellis. g Pleuropseudocystidia