Russulales » Russulaceae » Lactarius

Lactarius kesiyae

Lactarius kesiyae Verbeken & K.D. Hyde

MycoBank number: MB811745; Facesoffungi number: FoF00638

Basidiocarps medium-sized. Pileus 18−49 mm diam., at first convex to broadly convex, then becoming planoconvex with a more depressed disc, finally infundibuliform; surface smooth and slightly glossy, slightly sticky when moist; color darkest in immature specimens, dark blond (5D4) when young, grayish yellow (3−4C4), brownish gray (5C2), reddish blond (5C3−4) to brownish orange (5C5) when mature, in some collections with grayish green (25B4−B6) tints, color paler in dry condition, pale orange (5A3) to pale grayish orange (5B3−4); margin, paler, yellowish white (2A2), estriate when immature, later becoming striate and slightly crenulate with age. Lamellae subdecurrent to decurrent, 1−3 mm broad, crowded, with 2 series of lamellulae, pale cream to cream, to grayish orange (6B5) when bruised. Stipe 30−56 × 3−8 mm, cylindrical, centrally attached; apex becoming concolorous with lamellae, darker when moist, brownish orange (5C5), pale orange when dry. Context 3−5 mm broad in pileus, whitish, hollow in stipe; smell fruity; taste mild, a bit sweet after a while, then faintly acrid. Latex watery white, moderately abundant, unchanging on exposure, unchanging with 10% KOH, unchanging on white tissue paper, soon turning yellow on a white cotton handkerchief; taste mild to slightly astringent. Macrochemical reaction no reaction on the context with 10% KOH, but becoming brownish (5E7) to light brown (6D6) with FeSO4 after a while. Basidiospores globose to broadly ellipsoid, 6.3−6.9−7.1−7.8(−7.9) × 5.7−6.1−6.3−6.8(−7.0) μm; Q = 1.02−1.10−1.13−1.19 (n=60); ornamentation amyloid, up to 1.2 μm high, composed of irregular to crenulate ridges, obtuse, forming an incomplete reticulum; isolated warts common; plage distally amyloid. Basidia 48−54 × 12−18 μm, 4-spored,clavate, with fine granules and guttate contents. Pleuromacrocystidia abundant, 54−100 × 11−16 μm, protruding up to 30 μm, irregular narrowly fusiform, slender, thin-walled, partially with granular and needle-like or guttate contents; apex mucronate, occasionally ramified. Pleuropseudocystidia abundant, 4−6 μm diam., not protruding, cylindrical to broadened at apex, tortuous. Lamellar edge heterogeneous, with basidia, cylindrical to subclavate, thin-walled marginal cells 14−28 × 6−10 μm,; cheilocystidia scarce to fairly abundant, 37−58 × 10−14 μm, slightly protruding up to 10 μm, narrowly fusiform, with mucronate apex, with granules. Lamellar trama consisting of abundant lactifers and sphaerocysts. Pileipellis an ixocutis to ixotrichoderm, covered by a thin glutinous layer; upper layer 150−200 μm thick, composed of repent to erect hyphae; subpellis composed of cylindrical and inflated hyphae with a few globose cells.


Habitat: gregarious or scattered on ground, in coniferous forest with P. kesiya.

Collections examimed: VIETNAM, Lam Dong province, Lac Duong district, Xa Lat, Lang Biang National park, alt. 1545 m, N12º01.57 E108º25.58 , 12/06/2011, KW032 (holotype, GENT!, isotype, MFLU!);−ibid., 12/06/2011, KW033 (GENT!, MFLU!); −ibid., 12/06/2011, KW034 (GENT!, MFLU!);−ibid., 12/06/2011, KW035 (GENT!, MFLU!);−ibid., 12/06/2011, KW036 (GENT!, MFLU!); THAILAND, Chiang Rai province, Mae Fah Luang district, Doi Mae Salong Nok sub-district, Doi Mae Salong, N20º08.67 E99º40.17, alt. 1015 m, 15/05/2012, KW207 (GENT!, MFLU!);−ibid., 19/05/2012, KW210 (GENT!, MFLU!),−ibid., 24/05/2012, KW219 (GENT!, MFLU!);−ibid., 30/05/2012, KW224 (GENT!, MFLU!);−ibid., 13/07/2012, KW353 (GENT!, MFLU!);−ibid., 13/07/2012, AV12-022, (GENT!, MFLU!); Mae Hong Son province, coniferous forest along highway 1095, near Huai Nam Dang national

park, alt. 1322 m, N19º16.07 E98º37.86, 08/07/2012, KW346 (GENT!, MFLU!); Lampang province, Muangparn district, Chaesorn sub-district, forest along highway 1252, N18º55.43 E99º23.40, alt. 1420 m, 15/06/2013, KW427 (GENT!, MFLU!).

Notes: Lactarius kesiyae grows in coniferous forests dominated by P. kesiya. It can be recognized by its sticky and glossy appearance in moist conditions, and its pale brownish gray to pale brownish orange color with greenish or orange to even pinkish tints on the pileus. The latex is watery white and turns yellow on a white cotton handkerchief. Microscopically, the pileipellis is an ixotrichoderm and the pleuromacrocystidia, which are up to 100 μm long in length, protrude conspicuously from the hymenium. Microscopically, the sticky pileus is reflected as an ixocutis and it is not a common character for this subgenus. A sticky pileus occurs in a few temperate species such as L. decipiens, L. duplicatus, and L. badiosanguineus Kühner & Romagn. and it seems to be less common in tropical Asia. There are two tropical Asian species recorded as having a thin slime layer in the pileipellis stucture, L. austrotabidus Verbeken & E. Horak, with an ixocutis or ixotrichoderm and L. inconspicuus with an ixotrichoderm. In the field L. kesiyae could be confused with representatives of L. subg. Lactarius (syn. L. subg. Piperites (Fr.) Kauffman) on account of this surface feature which is one of the dominant characters of that subgenus. However, the overall brownish orange colors of L. kesiyae suggest it is a member of subg. Russularia.


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.