Lactarius tangerinus

Lactarius tangerinus H.T. Le & De Crop

MycoBank number: MB811748; Facesoffungi number: FoF00641

Basidiocarps small to medium sized. Pileus 8−36 mm diam., plane to slightly infundibuliform with a central depression; surface rugulose, typically darker in center, reddish brown (8E8−F8) to dark brown (7F8), reddish blond (6C6), to beige, paler towards the margin, orange-yellow (4A3−5), light yellow (4A5) at the margin; margin striate at maturity. Lamellae 1.5−4 mm broad, decurrent with tooth, crowded, with 3−4 series of lamellulae, yellowish white (4A1−2) to light yellow (4A4) to grayish orange (5B5). Stipe 10−36 × 2−6 mm, cylindrical to tapering downwards, central to eccentric; surface dry, smooth, rugose when old, with paler color at apex, grayish orange (6B4) to pale orange (5A3) at apex, brownish orange (6C4), light brown (6D4), light brown (7D7−8), whitish pruinose at the base solid to hollow. Context 1−2 mm broad in the pileus, pale pinkish cream (5A3) to gray cream (5A−B3); odor like L. quietus or Pentatomidae bugs; taste mild. Latex transparent, abundant, unchanging on exposure, unchanging with 10 % KOH; taste mild. Macrochemical reaction on context: becoming pale grayish green with 10 % KOH, light grayish blue with FeSO4. Basidiospores subglobose to broadly ellipsoid, (5.8−)6.1−6.6−7.2−7.9 × 5.4−6.1−6.3−7.0 (−7.2) μm; Q = 1.02−1.09−1.13−1.25 (n=40); ornamentation amyloid, up to 1.8 μm high, composed of blunt to subacute, thick irregular ridges, forming an incomplete to almost complete reticulum; short ridges interconnected by fine lines; plage inamyloid to slightly amyloid. Basidia 30−65 × 9−18 μm, 4-spored, mostly subclavate, rarely subcylindrical, with fine granules and guttate contents. Pleuromacrocystidia not abundant, 35−77 × 10−18 μm, subcylindrical to subclavate, with mucronate apex, protruding up to 10 μm. Pleuropseudocystidia 2−4 μm broad, not protruding, tortuous to straight, cylindrical, with fine granules. Lamellar edge heterogeneous, consisting of basidia, subcylindrical to subclavate to obovoid marginal cells 15−30 × 4−15 μm, and a few cheilocystidia 39−49 × 11−15 μm, not protruding, subclavate, with mucronate apex. Lamellar trama composed of cylindrical hyphae, lactiferous hyphae and sphaerocysts. Pileipellis a trichoderm, about 35−50 μm thick, consisting of erect cylindrical hyphae, subpellis mainly with small globose cells, around 10−20 μm diam., intermixed with hyphae.

Habitat: solitary or gregarious on soil among leaf litter, near Lithocarpus thomsonii and L. elegon stands.

Collections examined: THAILAND, Chiang Mai province, Mae Teang district, Pa Pae sub-district, Bahn Pha Deng village, mushroom research center, N19º17.12 E98º44.00, alt. 900 m, 28/07/2004, LTH 203 (holotype GENT!, isotype, CMU!, isotype, SFSU!);—ibid., 13/08/2004, LTH217 (GENT!, CMU!, SFSU!);−ibid., 01/07/2011, KW091 (GENT!, MFLU!);—ibid., 28/07/2014, EDC14-475 (GENT!, MFLU!).

Notes: Immature basidiocarps of this species might be mistaken for L. fuscomaculatus or L. inconspicuus. However, L. fuscomaculatus has watery white latex and develops dark brown spots on the cap in mature specimens. The latex also separates L. tangerinus from L. inconspicuus. The latter species has watery white latex that slowly turns yellowish white or pale yellow. For the microscopic differences between both species, see under L. inconspicuus.

Fig. 1 The obtained ML phylogeny based on ITS sequences. Names in boldface are new species. Names in blue are obtained from public databases. Bootstrap values and posterior probabilities are indicated if they exceed 50% and 0.85, respectively. The bar scale represents the expected number of nucleotide changes per site.