Lactarius rubrobrunneus H. T. Le & Nuytinck 2015, sp. nov.
Creators: name: Wisitrassameewong, Komsit
name: Nuytinck, Jorinde
name: Le, Huyen Thanh
name: Crop, Eske De
name: Hampe, Felix
name: Verbeken, Annemieke
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Russulales
Russulaceae
Lactarius
Lactarius rubrobrunneus

description: Lactarius rubrobrunneus H.T. Le & Nuytinck, sp. nov. (Figure 8 and 11c)   
 MycoBank number: MB811746; Facesoffungi number: FoF00639   
 Diagnosis: a medium sized species with reddish brown cap, incompletely reticulate basidiospores, pleuromacrocystidia rare, pileipellis an epithelium to hyphoepithelium.   
 Etymology: —‘rubrobrunneus’ refers to the reddish brown color of the cap.   
 Typus: — THAILAND, Chiang Mai province, Mae-On district, Huaikaew sub-district, Bahn Mae Kampong, N18º51.43 E99º22.09, alt. 1450 m, 15/07/2012, KW356 (AV12-044) (holotype, GENT!, isotype, MFLU!).   
 Basidiocarps medium sized. Pileus 15−80 mm diam., convex to widely depressed or infundibuliform, papillate; surface dry, greasy, slightly rugulose, dark brown (8F5−6) in center, reddish orange (7A6−8) to light reddish brown to yellow-brown (6C6−7) to brown (6D7) at the margin. Lamellae 1−4 mm broad, decurrent, crowded, with 3−4 series of lamellulae, forked, cream to grayish orange (5B4−5), sometimes paler, discoloring with reddish brown spots in age. Stipe 50−105 × 2−8 mm, cylindrical to tapering upwards, central, dry, smooth, whitish to pale cream pruinose at apex, light brown (6D4) to brown (6E7) to dark brown (6F6), fistulose, hairy at base. Context 1−3 mm thick in pileus, cream to brownish cream (5B4−5), odor strong, reminiscent of L. quietus or Pentatomidae bugs; taste mild. Latex watery white to white, abundant, unchanging on exposure, unchanging on white tissue paper and on a white cotton handkerchief and with 10 % KOH, taste mild. Macrochemical reaction no reaction on context with 10% KOH, or with FeSO 4.   
 Basidiospores subglobose to broadly ellipsoid, 6.1− 6.6−6.9 −7.4(−7.5) × 5.6− 6.0−6.3 −6.9(−7.0) μm, Q = 1.05− 1.10−1.11 −1.23 (n = 40); ornamentation amyloid, an incomplete reticulum up to 1 μm high,, consisting of blunt and irregular ridges, connected by thinner ridges, isolated warts common; plage inamyloid to distally amyloid. Basidia 41−57 × 12−16 μm, 4-spored, some 2-spored, subclavate, with guttate contents. Pleuromacrocystidia rare, 38−50 × 10−14 μm, not protruding, with guttate contents. Pleuropseudocystidia abundant, slightly protruding, 3−7 μm diam., with fine granules, irregular to tortuous, sometimes with broadened apex. Lamellar edge heterogeneous, consisting of basidia and marginal cells without cheilocystidia, marginal cells abundant, 15−36 × 5−12 μm, mostly cylindrical to subcylindrical to subclavate. Lamellar trama a combination of globose cells, septate hyphae and lactiferous hyphae. Pileipellis a transition between epithelium and hyphoepithelium, with or without a thin layer of about 5−10 μm thick, repent hyphae, subpellis layer consisting of small to large, globose cells, up to 35 μm diam., layer about 70−100 μm thick.   
 Habitat: gregarious in montane tropical forests with Fagaceae.   
 Collections examined: THAILAND, Chiang Mai province, Jomthong district, Bahn Luang sub-district, Doi Inthanon National Park, junction of highway 1009 and road to Mae Cham, N19º31.58 E98º29.64, alt. 1703 m, 25/06/2004, LTH149 (GENT!, CMU!, SFSU!); Mae Hong Son province, Huai Nam Dang National Park, nature trail, alt. 1538 m, N19º18.29 E98º35.88, 29/06/2005, LTH334 (GENT!, CMU!, SFSU!); Chiang Mai province, Mae-On district, Huaikaew sub-district, Bahn Mae Kampong, N18º51.43 E99º22.09, alt. 1450 m, 15/07/2012, KW356 (AV12- 044) (holotype, GENT!, isotype, MFLU!).   
 Comments: Lactarius rubrobrunneus is recognized by its reddish brown to orange-brown cap with a darker brown shade in the center. Lactarius rubrobrunneus differs from L. fuscomaculatus by the lack of dark brown spots on cap. Compared to L. fuscomaculatus, all collections of L. rubrobrunneus have a thinner layer of terminal hyphae in the pileipellis, which is a transition between an epithelium and a hyphoepithelium. In addition, we have observed cheilocystidia in L. fuscomaculatus collections, while they are completely absent in L. rubrobrunneus.
description: Published as part of 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, pp. 215-241 in Phytotaxa 207 (3) on pages 231-233, DOI: 10.11646/phytotaxa.207.3.1, http://zenodo.org/record/13637261