Lactarius crenulatulus Wisitrassameewong & Verbeken, 2014

Wisitrassameewong, Komsit, Nuytinck, Jorinde, Hampe, Felix, Hyde, Kevin D. & Verbeken, Annemieke, 2014, Lactarius subgenus Russularia (Russulaceae) in South-East Asia: 2. Species with remarkably small basidiocarps, Phytotaxa 188 (4), pp. 181-197 : 186-190

Lactarius crenulatulus Wisitrassameewong & Verbeken sp. nov. ( Figs 2 & 6A–B )

MycoBank: MB 808627

Typus:— THAILAND, Chiang Rai province, Muang district, Thasai sub-district, forest at Doi Pui Reverse Signal Station , Doi Pui , 740 m elev., N19°49.00 E99°52.03, KW383 (holotypus GENT!, isotypus MFLU!) .

Pileus small, 2–15 mm diam., convex to broadly convex, with a papilla when young, later infundibuliform without or with inconspicuous papilla; margin striate up to halfway the pileus, inflexed to slightly reflexed, wavy, crenulate; surface dry, smooth, olive brown (4D6–D7) when young, generally grayish yellow (4 B 5) to blond (4 C 6), orange, with paler patches (pale yellow, 4 A 3) in some parts of pileus, often with light brown (5D7) spots, light brown (5D7) when old. Lamellae adnate to decurrent, 0.5–3 mm broad, subdistant, with 3 series of lamellulae, pale yellow (3 A 3 to 4 A 3), grayish brown (6D3) when old; edge crenulate, concolorous. Stipe 10–19 × 1–2 mm, cylindrical, central; surface dry, smooth, mostly concolorous with pileus color, except at the base which is white and slightly pruinose to strigose. Context in pileus very thin, 0.5 mm broad, hollow in stipe, pale orange (5 A 3 or 6 A 3), unchanging with 10%KOH, unchanging with FeSO 4; smell faint, reminding of European L. quietus (like bugs); taste mild. Latex watery to watery white, sparse, unchanging on exposure, unchanging on white paper, unchanging with 10%KOH; taste mild.

Basidiospores globose to subglobose to ellipsoid, 6.3– 7.1 –7.8(–7.9) × 5.8– 6.4–6.6 –7.1(–7.2) µm, Q = 1.02– 1.07– 1.11 –1.21 (n=60); ornamentation amyloid, forming a complete and dense reticulum with small meshes, consisting of thick and irregular ridges which are up to 1 µm high and obtuse; isolated warts rare; plage inamyloid to distinctly distally amyloid. Basidia 41–61 × 11–14 µm, rather slender, mostly subclavate, sometimes clavate, 4−spored, rarely 2−spored, mostly with guttate contents, with sterigmata 5–8 × 1–2 µm. Pleuromacrocystidia absent. Pleuropseudocystidia 5–10 µm diam., numerous, emergent, aseptate, cylindrical to irregular, with obtuse apex. Lamellae edge sterile; marginal cells abundant, irregularly cylindrical to subclavate; cheilocystidia absent. Hymenophoral trama with abundant lactifers intermixed with rosettes of sphaerocytes. Pileipellis an epithelium, with transition to a palisade, 30–80 µm thick; suprapellis consisting of globose elements; subpellis composed of recumbent cylindrical hyphae. Stipitipellis a cutis, 30–45 µm thick, composed of cylindrical hyphae which are septate, thin-walled, forming a distinct layer; subpellis composed of slightly thick-walled isodiametric cells.

Diagnosis: this species differs from the other small species by the warm orange color, the base of stipe being slightly strigose and white, microscopically by the dense and complete reticulum on the spores and the absence of true cystidia.

Habitat: gregarious on soil between leaf litters in montane broad-leaved forest dominated by Castanopsis armata and Quercus aliena .

Etymology: —crenulatulus, meaning small and with crenulate margin

Studied material: THAILAND, Chiang Mai province, Mae Taeng District, Pa Pae sub-district, Bahn Pha Deng Village, Pathummikaram Temple, 1050 m elev. N19°06.28 E98°44.47, forest trail, 25/6/2012, KW312 (GENT!, MFLU!), THAILAND, Chiang Rai province, Muang district, Thasai sub-district, forest at Doi Pui Reverse Signal Station, Doi Pui, 740 m elev., N19°49.00 E99°52.03, 25/7/2012, KW368 (GENT!, MFLU!);−ibid., 25/7/2012, KW369 (GENT!, MFLU!);–ibid., 31/7/2012, KW382 (GENT!, MFLU!);−ibid., 31/7/2012, KW383 (holotype GENT!, isotype MFLU!);–ibid., 31/7/2012, KW387 (GENT!MFLU!), THAILAND, Chiang Mai Prov., Mae Taeng Distr., Highway 1095 at 22 km marker, 750 m elev., N19°07.57’ E98°45.65’, forest dominated by Castanopsis sp. , Dipterocarpus spp. and partly mixed with Pinus kesiya , 05/7/2004, LTH183 (GENT!, CMU!, SFSU!).

Comment: —This species was mentioned in Le (2007) as Lactarius sp. 19. It is recognized in the field by the small fruiting body with deeply striate pileus, strikingly crenulate margin and mostly a whitish pruinose base. It is most similar to L. perparvus , growing in the same habitats, because of the small size, the strongly striate margin, and the general stature. The color however is different because L. perparvus has less pure orange tinges and is dominantly grayish brown. One has to pay attention to the stipe base: the pruinose white layer is sometimes scarcely developed but usually present in L. crenulatulus , and absent in L. perparvus , where some strigose hairs may be present but they are never purely white. Microscopically, the completely reticulate spores and the lack of pleurocystidia and cheilocystidia make the species very different from L. perparvus .

Figures

FIGURE 2. L. crenulatulus (KW383): a. basidiospore, b. lamellae edge, c. basidia, d. pseudocystidia, e. pileipellis (scale bar = 10 μm).

FIGURE 6: Basidiocarps; A–B: L. crenulatulus (Photo A: Todd Elliott), C: L. perparvus (Photo: Todd Elliott), D: L. glabrigracilis (Photo: Felix Hampe), E: L. gracilis (Photo: Felix Hampe)