Lactarius chichuensis W.F. Chiu
Basidiocarps small to medium-sized. Pileus 5−37 mm diam., broadly convex to convex initially with umbo, becoming infundibuliform with age; surface dry, smooth to wrinkled, color generally varying from brown (6E4−7E6) to reddish brown (8D8, 9D−E8), with paler shade near margin, brownish orange (6C4−6) to light brown (6D7−8), in some specimens brownish (7C7) to light brown (7D4−5) to grayish brown (7E3) to brown (7E4) with cream-colored margin, sometimes with a fine whitish powder covering the surface; margin not striate, involute initially and becoming incurved to straight in age. Lamellae subdecurrent to decurrent, crowded, 0.5−3 mm broad, grayish orange (5B4) to brownish orange (5C4), light brown (7D4) to brown (7E4) when older, with 2−3 series of lamellulae. Stipe 8−24 × 2−6.5 mm, cylindrical, central to eccentric; surface dry, smooth, light brown (7D6) to brown (6−7E6). Context 1−3 mm broad in pileus, hollow in stipe, pale orange (5A3) to grayish orange (5B3−B4); odor strong, like L. quietus or Pentatomidae bugs; taste mild. Latex abundant, watery white to white, unchanging on exposure, unchanging with 10 % KOH, pale yellow on white tissue paper and unchanging on white cotton handkerchief. Macrochemical reaction on context: olive brown (4D6) to light brown (5D6) with 10 % KOH, brown (6E7) with FeSO4. Basidiospores globose to broadly ellipsoid, 6.1−6.7−7.3−8.1(−8.3) × 5.5−6.0−6.4−7.2(−7.3) μm; Q = 1.02−1.10−1.16−1.28; ornamentation amyloid; ridges up to 1 μm high forming a zebroid ornamentation composed of parallel irregular, short and long ridges, never reticulate; plage inamyloid. Basidia 50−57 × 13−18 μm, 4-spored, subclavate, with fine granules. Pleuromacrocystidia rare to abundant, 45−71 × 10−15 μm, protruding up to 30 μm, subfusiform, bent to straight with mucronate to moniliform apex, typically with refractive contents at apex. Pseudocystidia 3−6 μm diam., slightly protruding, cylindrical, tortuous to straight, with fine granulate content. Lamellar edge heterogeneous, consisting of basidia, marginal cells and cheilocystidia; marginal cells 12−28 × 7−15 μm, subcylindrical to clavate; cheilocystidia abundant 31−45 × 10−19 μm, protruding up to 15 μm, subfusiform to subclavate, rarely clavate, with refractive contents at apex. Lamellar trama consisting of globose cells, septate hyphae and lactiferous hyphae. Pileipellis a hyphoepithelium, with a dense upper layer of repent hyphae and an underlying layer of globose cells, suprapellis composed of cylindrical hyphae about 20−40 μm thick; subpellis consisting of globose cells about up to 20 μm diam.
Habitat: gregarious on ground in montane mixed forest with Fagaceae and Pinus kesiya.
Distribution: reported from China (Chiu 1945, Wang & Liu 2002), Thailand.
Collections examined: THAILAND, Chiang Rai province, Mae Fah Luang district, Doi Mae Salong Nok sub-district, Doi Mae Salong, alt. 1269 m., N20º16.90 E99º62.30, 13/07/2012, KW352 (GENT!, MFLU!);−ibid., 27/07/2012, KW372 (GENT!, MFLU!);−ibid., 08/08/2012, KW388 (GENT!, MFLU!);−ibid., 16/09/2012, KW403 (GENT!, MFLU!);−ibid., 28/08/2013, KW465 (GENT!, MFLU!);−ibid., 10/09/2013, KW467 (GENT!, MFLU!); Chiang Mai province, Mae Teang district, Pa Pae sub-district, Bahn Pha Deng village, mushroom research center, N19º17.12 E98º44.00, alt. 900 m, 13/05/2011, KW012 (GENT!, MFLU!); Chiang Mai province, Mae Teang district, Pa Pae sub-district, Bahn Pha Deng village,Pathummikaram Temple, forest trail, alt. 1050 m, 07/06/2012, KW271 (GENT!, MFLU!);−ibid., 07/06/2012, KW272 (GENT!, MFLU!).
Notes: Lactarius chichuensis is a distinctive species in the subgenus because of its zebroid basidiospore ornamentation. The species has small, reddish brown basidiocarps and a strong L. quietus-like or Pentatomidae bug odor. The species was discovered by Chiu (1945). The holotype is in poor condition and only the spore ornamentation was studied by Chiu. Later the species was described in more detail and distinguished from a look-alike species, L. hirtipes J.Z. Ying by Wang & Liu (2002) on account of its different basidiospore ornamentation. Morphological characters of our specimens are consistent with the documentation of Wang & Liu (2002). In our collections we sometimes observed the pileus to be whitish pruinose. Wang & Liu (2002) stated that the species is found in forests with Fagaceae, whereas we found the species in mixed forest.
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.