Lactarius rubrobrunneus H.T. Le & Nuytinck, 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 : 231-233

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 .

Figures

FIGURE 8. L. rubrobrunneus: a. basidiospore, b. marginal cell, c. pleuromacrocystidia, d. pseudocystidia, e. basidia, f. pileipellis (a−f: AV12-044, holotype) (scale bar = 10 μm).

FIGURE 11. basidiocarps a. L. aquosus (KW231), b. L.fuscomaculatus (KW373), c. L.rubrobrunneus (AV12-044, photo byA.Verbeken), d. L. inconspicuus (KW339, photo by F. Hampe), e–f. L. tangerinus (EDC14-475, photo by E. De Crop), g–h. L. kesiyae (g: KW032, h: KW353), i. L. rubrocorrugatus (KW384), j. L. chichuensis (KW271).