Lactarius lavandulus
Lactarius lavandulus H.T. Le & Stubbe
MycoBank number: 510724
Pileus 24-46 mm diam., plano-convex to infundibiliform with central papilla; surface dry, rugose, weakly striate on the margin, dark brown (6/8F8) to yellowish brown (5E8), paler towards the margin. Lamellae adnate to subdecurrent, close, 2-6 mm broad, 3-4 series of lamellulae, yellowish white (3A1/2) to pale yellow (4A3), staining purplish grey (12E4) or deep violet (16D8) when bruised; edge entire, concolourous, sometimes brown. Stipe 35-70 × 4-6 mm, central, equal to somewhat tapering upwards, cylindrical, often curved at the base, surface dry, smooth, yellowish brown (5E5) to pale brown (5D4/5), paler towards the base, to brownish white at the base. Context 1.5–3 mm thick in pileus, stuffed to hollow in stipe, white, staining deep violet (16D8), becoming pale yellow (4A4) with 10% KOH, brownish grey (5D3) with FeSO4; smell distinct, strong; taste mild. Latex abundant, watery white, unchanging when isolated. Spore print yellowish white (4A2). Basidiospores (7.3)7.4–8.0–8.1– 8.8(9.0) × (6.7)6.8–7.4–7.5–8.3 μm (Q = 1.02–1.07–1.08–1.14; n = 40), globose to subglobose; ornamentation amyloid, a complete and dense reticulum of fine, somewhat irregular ridges and interconnected spines ≤ 1-1.5 μm high, only few isolated warts present; plage distally amyloid. Basidia 40-50 × 9-13 μm, subclavate to subcylindrical, often with guttate contents, 4-spored; sterigmata 5-7 × 1.5-2 μm. Pleuromacrocystidia absent. Pleuropseudocystidia 3-5 μm diam., moderately abundant, often emergent, cylindrical, tortuous, sometimes branching, thin-walled. Lamellar edge sterile; cheiloleptocystidia 17-50 × 4-8 μm, long and slender, subcylindrical to subfusiform, sometimes clavate, hyaline or with brown, intracellular pigmentation, thin-walled. Hymenophoral trama predominantly filamentous with somewhat inflated hyphae, and scattered sphaerocysts. Pileipellis a palisade tending towards trichopalisade, or when subpellis reduced, tending towards hymeniderm, 40-90 μm thick; terminal elements 10-33 × 3-13 μm, subfusiform, subcylindrical or clavate, upright, containing dark brown, intracellular pigmentation; subpellis composed of a few to several layers of inflated cells, with dark brown, intracellular pigmentation in the upper cell layers. Stipitipellis a trichoderm, 40- 60 μm thick, containing dark brown, intracellular pigmentation in upper layers; hyphae 2-6 μm diam.; terminal elements repent or recumbent.
Habitat and distribution: Growing solitary or gregarious in mixed, montane rainforests with Castanopsis and Pinus. So far only known from Northern Thailand.
Material Examined: THAILAND: Chiang Mai Province, Doi Inthanon National Park, on Highway 1009 at 22 km marker, N18°32.54' E98°33.51', alt. 1076 m; dominated by Castanopsis spp. and Pinus kesiya, 27/06/2005, leg. D.E. Desjardin, Huyen T. Le 314 (holotypus CMU, isotype SFSU, GENT) – ibid., 27/06/2005, leg. A. Honnan, Huyen T. Le 315 (CMU, SFSU,GENT) –Chiang Mai Province, Doi Inthanon National Park, on Highway 1009 at 22 km marker, N18°32.54' E98°33.51', alt. 1076 m; dominated by Castanopsis spp. and Pinus kesiya, 25/06/2004, Huyen T. Le 144 (CMU, SFSU) = Verbeken-Walleyn 04/102 (GENT) – ibid., scattered under Quercus sp. and Pinus kesiya, 26/06/2003, DED 7576 (CMU, SFSU, GENT) – Chiang Mai Province, Doi Suthep-Pui National Park, Sangasabhasri Lane to Huai Kok Ma village, N18°48.62' E098°54.60', alt. 1200 m, solitary on the soil under Quercus sp. in montane primary rain forest dominated by Castanopsis spp. and Lithocarpus polystachyus, 06/07/2002,
DED 7469 (CMU, SFSU, GENT).
Notes: The brown cap with the small papilla, the concolourous stipe that is somewhat long and slender compared to the cap diameter and the pale, dense lamellae give L. lavandulus a stature comparable with the blackish brown L. lignyotus Fr. In addition to the different colour, L. lavandulus is distinguished by staining purplish grey in the lamellae when bruised and by a strikingly violet discoloration of the context. The description is based on the collections Huyen T. Le 314 and Huyen T. Le 315 which both clearly displayed a violet colour reaction. However, the colour reaction appears to be subject to variability. The other collections did not exhibit any obvious violet discoloration in the context, but a similar purplish brown to blackish staining was observed in the lamellae. The results of the phylogenetic analysis of the ITS-sequence did not show segregation between the violet staining and non violet staining specimens. This violet colour reaction is reminiscent of the North American species L. lignyotus var. nigroviolascens (Atk. in Burl.) Hesler & A.H. Sm. and L. lignyotus var. marginatus (A.H. Sm. & Hesler) Hesler & A.H. Sm. Comparison with the type material of both varieties revealed distinct differences in spore ornamentation and pileipellis structure. Lactarius lignyotus var. nigroviolascens (Atkinson 24257, CUP) possesses spores bearing an incomplete and fairly widespaced reticulum of irregular and rather acute warts partially interconnected by fine lines. Spore ornamentation of L. lignyotus var. marginatus (Smith 63004, MICH) consists of higher and coarser warts interconnected by fine lines, the warts often being blunt and slightly broader towards the apex. Its pileipellis is an unambiguous trichopalisade with elongated, chain-like arranged, inflated elements and slender terminal cells. These observations rule out conspecificity between the Thai and North American species.
Fig. 1 MP phylogeny of Lactarius subgenus Plinthogali in Northern Thailand based on ITS sequences. The 50% majority rule consensus tree resulting from the Maximum Parsimony analysis with the bootstrap values higher than 50% added on the internal nodes.
Fig. 2 Lactarius lavandulus. a. basidiomes, b. basidiospores, c. basidia, d. cheiloleptocystidia, e. pleuropseudocystidia. Scale bars = 10 mm (basidiomes) and 10 μm.
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