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 Add this item to the list  828497 Original description
   
Remarks (public):Notes ― Lactarius populicola has been confused with L. stephensii (Nuytinck et al. 2003, Gori 2005) because of their multiple similarities. Microscopically, L. populicola has the same pileal and hymenial structure, and identical spore shape with L. stephensii, but spores are intensely amyloid and ornamented with robust conical or tooth-like warts, while L. stephensii has weakly amyloid spiny spores. Macroscopically, L. populicola is distinguished by the violaceous coloration of pileus in mature specimens and smaller locules in the hymenophore. While L. stephensii is probably associated with Fagaceae and Betulaceae hosts, L. populicola is linked to Salicaceae plants. Genetically, L. populicola is a monophyletic taxon significantly related with L. stephensii, both forming a significantly monophyletic clade with a third species, L. soehneri. These angiocarpic species were also related (PP 1.00, BP 88) with a clade formed by samples identified as L. evosmus and L. zonarius. The only sequenced specimens of Lactarius populicola are by now the type proposed here, and a sample from Belgium (RW2930 GENT) treated as L. stephensii by Nuytinck et al. (2003). 
Description type:Original description 
Description:Basidiomata 1.5–4 cm wide, gasteroid, angiocarpic, subglobose or irregular, lobate, reniform, tuberiform, sessile or with a minute sterile base, attached to soil by thin mycelial threads. Pileus smooth, viscid, persistent, open basally and exposing the locules in old specimens; at first pale orange (6A3), brownish orange (7C6) or orange-red (8A6) and finally reddish brown (8D6–9E5) to violet-brown (10E6). Hymenophore loculate, labyrinthoid, deeply coloured, reddish yellow (4A7), orange (5A6–6B7) to reddish orange (7A6), or orange-red (8A6–B6); locules very small, 0.2–0.5 × 0.02–0.1 mm (3–4 per mm), irregularly arranged, elongated, sinuous; septa 250–500 μm thick; fresh spore mass in locules pale yellow (4A4–A5); pale orange (5A3) to brownish orange (6C5) in exsiccata. Columella absent or inconspicuous. Latex watery-white in immature basidiomata and white in mature basidiomata, of mild taste. Odour strong, aromatic and fruity, reminiscent of pears. Spores 13–15 × 11–13 μm, Q = 1.07–1.2, subglobose to broadly ellipsoid, orthotropic, echinated, unigutulate, deep orange; warts deeply amyloid, robust, 1–2 μm long, conical or tooth-like, usually curved, with some verrucae among them; suprahilar plage absent; hilar appendix minute, usually united to a fragment of sterigma up to 4 × 2.5 μm. Basidia 1-spored, 35–50 × 8–10 μm, cylindrical, straight or sinuous, soon collapsed; initially hyaline and filled with oleiferous guttules, then of dark orange colour; sterigmata central or eccentric, 2–4 μm long. Basidioles similar to basidia. Macrocystidia and cystidioles absent. Paraphysoid cells 20–30 × 6–8 μm, usually with 1–2 septa, cylindrical or with a clavate apex. Pseudocystidia not observed. Subhymenium ramose, formed by septate, cylindrical hyphae, 10–30 × 3–9 μm, perpendicular to the tramal hyphae. Hymenophoral trama 60–90 μm thick, homoiomerous, formed by hyaline, thin walled, subgelatinized hyphae, 3–6 μm in diam, finally dark yellow, completely gelatinized, with a prosenchymatous aspect; laticifera abundant, 8–10 μm in diam, with thinner branches 3–5 μm in diam; sometimes penetrating into the hymenium and terminating as pseudocystidia; thromboplera yellow, 3–5 μm in diam. Pileipellis and context 300–500 µm thick; pileipellis 50–90 μm thick composed of (1) a trichodermal suprapellis of septate hairs and dermatocystidia, 20–40 × 2.5–4 μm, straight to sinuous, rounded to acute at the apex, with yellow granular content, that soon collapses in a brown granular mass, and (2) a prosenchymatous subpellis 20–50 µm thick, of densely entangled hyphae 1.5–3 μm in diam. Pileal context an ixocutis 250–400 µm thick, made by subgelatinized, entangled hyphae 2–4 μm in diam, crossed by some thromboplera and abundant laticifera. Habitat, Distribution & Season ― Gregarious, hypogeous to semi-hypogeous in riparian forests under Populus, on alluvial soils. Spring to autumn. Distributed in Temperate and Mediterranean regions, from Western to Southeastern Europe, from sea level up to 1000 m of altitude. 
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