Lactarius aff. wenquanensis
Lactarius aff. wenquanensis Y. Wang & Z.X. Xie
Pileus 35–76 mm diam., convex to plano-convex, infundibuliform in age; surface viscid, zonate (with about 7 distinct zones especially in outer half), pale yellow (3A3–4), but slightly darker in the center and in the glutinous hairs; margin decurved, very hairy and tomentose when young (with hairs up to 5 mm long), later with hairs forming glutinous triangles on top of the zonate outer part. Lamellae decurrent, rather dense (12–14 L+l/cm), with abundant lamellulae (at least 3 between 2 lamellae), 5 mm broad, yellowish white (3A2); edge entire, concolourous. Stipe 35–55 × 8–13 mm, cylindrical, curved, scrobiculate, concolourous with lamellae, yellowish white (3A2–3), darker in the scrobicules, with whitish zone at the top. Context rather firm in the pileus, hollow in the stipe, cream-coloured, unchanging; smell sweet, apple-like; taste very acrid. Latex rather abundant, white, drying cream, changing to bright yellow with KOH. Spore deposit unknown. Basidiospores 5.8–7.3–8.6 × 5.3–5.9–6.5 μm, (n = 20, Q = 1.1–1.23– 1.4), broadly ellipsoid, sometimes subglobose or ellipsoid; ornamentation up to 0.5(–0.8) μm high, composed of ridges forming an incomplete reticulum with some isolated irregular warts present; plage inamyloid. Basidia 35–45 × 9–10 μm, with sterigmata 5–7 × 1.2–1.5 μm, thin-walled, 4-spored, subclavate to cylindrical, with guttate contents. Pleuromacrocystidia 54–76 × 9.5–12 μm, emergent, abundant, subclavate to subfusiform with tapering, sometime moliniform, sometimes rather round apex, thin-walled; needle-like to granular contents. Pleuropseudocystidia 4–5.5 μm diam., abundant, emergent up to 20–35 μm, with lactiferous contents, thin-walled, tortuous to cylindrical. Lamellar edge sterile, composed of marginal cells that are cylindrical, 15–33 × 3–4.5 μm, thin-walled, hyaline. Hymenophoral trama composed of interwoven, filamentous hyphae; lactifers abundant. Pileipellis an ixocutis, 60–130 μm thick, composed of hyaline, thin-walled hyphae 2–5 μm diam.; underlying layer composed of filamentous hyphae and sphaerocytes mixed, abundant pleuropseudocystidia and lactifers. Stipitipellis an ixocutis, 40–60 μm thick. Clamp connections absent.
Habitat and distribution: gregarious on the soil, among leaf litter; probably only known from Thailand, possibly conspecific with L. wenquanensis known from China.
Material examined: THAILAND, Chiang Mai Prov., Doi Inthanon Natl. Park, junction of Highway 1009 and road to Mae Chem, N19°31.58' E 98°29.64', 1700 m alt., humid montane rainforest with Quercus, Castanopsis, Lithocarpus echinops etc., 25 June 2004, leg. A. Verbeken & R. Walleyn 04/100 (GENT), leg. Huyen T. Le 143 (CMU, SFSU).
Notes: The species is characterized by the firm basidiomes with pale yellow, viscid and zonate pileus with very long hairs at the margin that form glutinous triangles and with a distinctly scrobiculate stipe. The latex is white and unchanging and the taste is very acrid. L. wenquanensis is the phonetically most similar species to the Thai taxon, but we do not have access to type material of L. wenquanensis so our determination is only provisional. Most Asian look-a-likes have bright yellow latex (e.g. L. abbotanus K. Das & J.R. Sharma). A similar species with unchanging, white latex is L. changbainensis Y. Wang & Z.X. Xie, but the latter species differs in the subcinnamon colour of the pileus and the smooth margin. The molecular data (Fig. 13) suggest a close relationship with L. torminosus, suggesting that L. aff. wenquanensis belongs to L. sect. Piperites, a section that is characterized by a sticky pileus with tomentose, hairy margin and white, unchanging latex. The Thai species also shows some features that are typical for L. sect. Zonarii (e.g. the sweet apple-like smell, strongly zonate cap, scrobiculate stipe), but as mentioned before the sections within L. subgenus Piperites are not yet clearly delimited and traditional European and American classification systems of this subgenus are not confirmed by the molecular data.
Fig. 1 Lactarius aff. Wenquanensis. a. Basidiocarp. b. Spores. c. Pleuromacrocystidia. d. Marginal cells. e. Basidia. f. Pleuropseudocystidia. g. pileipellis. Scale bars = 10 mm (basidiocarp) and 10 μm.
Le HT, Nuytinck J, Verbeken A, Lumyong S, Desjardin DE. 2007 – Lactarius in Northern Thailand: 1. Lactarius subgenus Piperites. Fungal Diversity, 24(1), pp.173-224.
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