Lactarius tangerinus H.T. Le & De Crop, 2015

Wisitrassameewong, Komsit, Nuytinck, Jorinde, Le, Huyen Thanh, Crop, Eske De, Hampe, Felix & Verbeken, Annemieke, 2015, Lactarius subgenus Russularia (Russulaceae) in South-East Asia: 3. new diversity in Thailand and Vietnam, Phytotaxa 207 (3), pp. 215-241 : 235-236

Lactarius tangerinus H.T. Le & De Crop , sp. nov. (Figure 10, 11e and 11f)

MycoBank number: MB811748; Facesoffungi number: FoF00641

Diagnosis: a small to medium sized species with reddish brown to reddish orange cap and a paler margin, watery latex, incompletely to almost completely reticulate basidiospores, pleuromacrocystidia present and pileipellis a trichoderm.

Etymology: —‘tangerinus’ refers to the reddish orange color on cap.

Typus: — 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!).

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 FeSO 4.

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.

FIGRUE 10. L. tangerinus : a. basidiospore, b. pleuromacrocystidia, c. cheilocystidia, d. marginal cell, e. basidia, f. pseudocystidia , g. pileipellis (a− g: LTH203, holotype) (scale bar = 10 μm).

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!) .

Comments: 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 .