Lactarius rubrocorrugatus Wisitrassameewong & 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 : 233-235

Lactarius rubrocorrugatus Wisitrassameewong & Nuytinck , sp. nov. ( Figure 9 and 11i )

MycoBank number: MB811747; Facesoffungi number: FoF00640

Diagnosis: A small to medium sized species, cap red to reddish brown with a rugulose surface, latex transparent, basidiospore ornamentation consisting of low ridges forming an incomplete reticulum, pleuromacrocystidia present and pileipellis a hyphoepithelium.

Etymology: —‘rubrocorrugatus’ refers to the red and wrinkled pileus.

Typus: — THAILAND, Chiang Rai province, Muang district, Thasai sub-district, forest at Doi Pui Reverse Signal Station, Doi Pui, alt. 740 m, N19º49.00 E99º52.03, 31/07/2012, KW384 (holotype, GENT!, isotype, MFLU!).

Basidiocarps small to medium sized. Pileus 7−44 mm diam., plane to infundibuliform, papillate initially, becoming depressed with or without a papilla; surface dry, smooth in immature specimens, later becoming wrinkled in mature specimens, hygrophanous, red (9B7−8) to reddish brown (9D7−8−E8), typically with dark brown (7F5) shade in center; margin not striate in young specimens, becoming slightly striate in age, incurved, crenulate. Lamellae decurrent, 1−2 mm broad, very crowded, sometimes forked, with 1−3 series of lamellulae, yellowish white to light yellow (4A4) to cream, turning brown (6E5−E6) when bruised; edge slightly crenulate to even. Stipe 11−42 × 2−8 mm, cylindrical, fistulose; surface dry, smooth to slightly wrinkled, brownish orange (7C7) to brown (7E7−E8), turning dark brown (7F8) when older, whitish pruinose at base. Context 1−3 mm broad in pileus, pale yellow (4A3) to cream, unchanging when cut; odor reminiscent of L. quietus or Pentatomidae bugs; taste mild, sometimes sweetish and bitter. Latex transparent, unchanging on exposure, unchanging on tissue paper and on a white cotton handkerchief. Macrochemical reaction on the context: unchanging or slowly turning pale yellow with 10 % KOH, grayish green (26E6) with FeSO 4.

Basidiospores globose to broadly ellipsoid, 5.8− 6.4−7.0 −7.9 × 5.2− 5.8−6.3 −6.9 μm; Q = 1.01− 1.09−1.13 −1.25 (n=120); ornamentation amyloid, composed of ridges up to 0.7 μm high, forming an incomplete reticulum; isolated warts common, sometimes clustered; plage inamyloid to distally amyloid. Basidia 45−73 × 9−18 μm, mostly 4-spored, sometimes 1-spored, subclavate to subcylindrical, with guttate contents. Pleuromacrocystidia 44−87 × 11−20 μm, abundant, not protruding to protruding up to 20 μm, subfusiform, with a mucronate to moniliform apex, with granules and guttate contents. Pleuropseudocystidia abundant, 3−6 μm diam., cylindrical, tortuous, with fine granules. Lamellar edge heterogeneous, with basidia, marginal cells and cheilocystidia; marginal cells 24−40 × 8−15 μm, subcylindrical, subclavate to clavate; cheilocystidia 25−51 × 7−13 μm, rare to abundant, subfusiform, bent or irregular, with a mucronate to moniliform apex, with granular contents. Lamellar trama consisting of globose cells, septate hyphae and lactiferous hyphae. Pileipellis a hyphoepithelium, with an upper layer of repent to oblique hyphae; suprapellis a thin layer of repent hyphae about 10−25 μm thick; subpellis 40−60 μm thick, consisting of globose cells up to 30 μm diam.

Habitat: gregarious on soil, in coniferous forest, dominated by P. kesiya and in tropical rain forests, dominated by Shorea sp. , Quercus sp. and Castanopsis sp.

Collections examined: VIETNAM, Dalat province, Xa Xuan Truong , at km 7, left side of the main road, alt. 1499 m, N11º54.94 E108º32.01, 13/06/2012, KW042 ( GENT!, MFLU!) ;— ibid. 13/06/2012, KW043 ( GENT!, MFLU!) ;− ibid. 13/06/2012, KW045 ( GENT!, MFLU!) ; THAILAND, Chiang Mai province, Mae Taeng District, Pa Pae sub-district, Bahn Pha Deng village , Pathummikaram Temple , forest trail, alt. 1050 m, N19º06.28’ E98º44.47, 9/06/2012, KW294 ( GENT!, MFLU!) ; Chiang Rai province, Muang district, Thasai sub-district, forest at Doi Pui Reverse Signal Station , Doi Pui , alt. 740 m, N19º49.00 E99º52.03, 31/07/2012, KW381 ( GENT!, MFLU!) ;− ibid. 31/07/2012, KW384 (holotype, GENT!, isotype, MFLU!) ;− ibid., 08/07/2013, KW453 ( GENT!, MFLU!) ; Chiang Rai province, Chiang Khong district, forest near Bahn Nurnsomboon, alt. 450 m, N20º07.77 E100º26.40, 26/08/2011, KW123 ( GENT!, MFLU!), Chiang Mai province, Mae Taeng District , Bahn Thapa, 22 marker on highway 1095, alt. 750 m, N19º07.41 E98º45.57, 31/07/2014, EDC14-505 ( GENT!, MFLU!) ; Loei province, Phu Ruea district , junction from highway 203, alt. 1045 m, N17º28.09 E101º26.18, 27/06/2013, KW443 ( GENT!, MFLU!) .

Comments: Lactarius rubrocorrugatus can be easily distinguished from the other Southeast Asian species with transparent latex because of its small size, and a hygrophanous and rugulose cap. The other species with transparent latex described in the present work are L. aquosus and L. tangerinus . Lactarius aquosus differs from L. rubrocorrugatus by the zonate, smooth cap and a cutis for a pileipellis. Lactarius tangerinus has a reddish orange cap and a trichoderm pileipellis. Lactarius rubrocorrugatus is also similar to the European L. rostratus Heilmann-Clausen because of the characters mentioned above. The major difference can be found in the macrocystidia. Lactarius rubrocorrugatus has larger cystidia and the apex is not as acute as in L. rostratus . Lactarius rubrocorrugatus has been found in Vietnam and Thailand. The putative host range of the species is broad. The Vietnamese specimens were found in coniferous forest dominated by P. kesiya at higher altitude, around 1500 m above sea level, while the Thai specimens were found in evergreen forests dominated by members of the Fagaceae at lower altitude (alt. between 700–1000 m).

Figures

FIGURE 9. L. rubrocorrugatus: a. basidiospore, b. basidia, marginal cell, d. pseudocystidia, e. pleuromacrocystidia, f. cheilocystidia, g. pileipellis (a: KW384, holotype, b−g: KW294) (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).