Lactifluus mexicanus Montoya, Caro, Bandala & Ramos

Montoya, Leticia, Caro, Abraham, Ramos, Antero & Bandala 1, Victor M., 2019, Two new species of Lactifluus (Fungi, Russulales) from tropical Quercus forest in eastern Mexico, MycoKeys 59, pp. 27-45 : 27

Lactifluus mexicanus Montoya, Caro, Bandala & Ramos sp. nov. Figs 2c, d , 4 , 5c, d

Holotype.

MEXICO, Veracruz State, Veracruz, Alto Lucero Co., 12 km SW Palma Sola (road Veracruz-Nautla) 11 July 2016, Montoya 5276 (XAL). Ectomycorrhizal, under Quercus oleoides .

Diagnosis.

Recognised by the combination of pileus disc faintly rugose, margin rugose to strongly venous-rugose, lamellae close to very close, the stipe including pinkish tinges and by the size of lamprocystidia and pileipellis terminal elements.

Gene sequences ex-holotype.

MK211181 (ITS), MK211190 (LSU), MK258871 (rpb 2).

Etymology.

referring to Mexico.

Pileus 33-125 mm diam., convex, plano convex to depressed at centre, subvelvety, smooth or at times faintly rugose at centre, at remaining disc surface smooth, vinaceous-brown or vinaceous (7D6-8; 7E8; 8C7; 8D4-8) when young, then ferruginous-brown, cinnamon-brown, frequently pale vinaceous (7C4-6), dull vinaceous (7D6) or pinkish-wine over a yellowish base, other reddish-brown to vinaceous (7C8-E8, 7D7-8; 2.5YR 4-5/6), at times with orange-brown (6C7; 6D7-8; 5YR 5/6-6/6; 7.5YR 5/4, 5/6-8) areas; margin decurved, straight in age, at times undulated, rugose to strongly venous-rugose. Lamellae 2-9 mm broad, close to very close, adnate to subdecurrent, arcuate, with entire edge, some furcate at different levels, at times sinuous especially towards the stipe attachment, pale yellowish to yellowish (2.5Y 8/1-3, 8/6; 7.5YR 8/4; 10YR 8/3-6), straw-yellow, yellow-orange (4A2-6 surfaces, 5A3-5 edges in group) with brown to cinnamon-brown tinges, with faint vinaceous stains or brown colour (2.5YR 5/3; 7.5YR 5/4) when handled; lamelullae of different sizes, 1-4 per lamellae. Stipe 35-115 × 9-27 mm, cylindrical, faintly broadened towards the base, subtomentose, dry, solid, in general concolorous but paler than pileus surface, at apex pale pinkish-orange (5YR 8/3-4), pinkish-brown, pale orange-brown or pinkish-red (6B3-4, 6B6-C6; 5YR 7/4-6, 8/2), continuing in pale orange (6A2-3), brown-orange with pinkish-grey tinges (6B2-5, 6C2) and pinkish-brown (6-7B3, 6-7B4) colours, becoming darker towards the base (7C4-6) (2.5YR 4/6; 5YR 6/4; 5YR 6/6; 7.5YR 6/3, 5/4, 8/4, 8/6), with some dark brown areas; base whitish and with whitish mycelium. Context compact, whitish to yellowish, staining brown-vinaceous. Odour faintly disagreeable, fishy; taste mild to somewhat bitter. Latex whitish to cream colour (2.5Y 8/3-6), milky, abundant, secreting from the whole basidiome, staining the lamellae and white paper pale brown; taste mild. KOH darkens the pileus surface.

Basidiospores 8 –10(– 11) × 7 –9(– 10) µm, X̄ = 8.7-9.2 × 7.5-9.0 µm, Q̄ = 1.1-1.2, subglobose to broadly ellipsoid, thin-walled; ornamentation up to 0.2-1.2 µm high (measured under SEM), a rather complete reticulum with irregular ridges, at times with thin connecting lines, rarely with some isolated ridges; plage in most spores inamyloid, rarely faintly amyloid; under SEM, the basidiospores wall appears rugose and with some isolated verrucae, with a complete reticulum composed of continuous regular or irregular ridges, some parts of the reticulum having rounded or irregular nodulose elevations, these later seen in the light microscope as verrucae, plage area smooth or with ornamentation reminiscences. Basidia 38-47 × 8-13 µm, clavate to faintly cylindrical, with 3-4 sterigma (at times with 2), thin-walled, with refractive contents. Pleurolamprocystidia 47-63 × 5-8 µm, lanceolate, at times mucronate, with wall 1.0-2.0 (-3.0) µm thick (in some elements, the wall is so thick that the lumen is very narrow). Cheilolamprocystidia 40-55 × 5-8 µm, lanceolate, some subcylindrical, at times mucronate, with wall up to 1.0 µm thick, without dense contents, hyaline. Pseudocystidia absent. Pileipellis a lampropalisade, elements of the suprapellis 45-63 × 3-6 µm, most cylindrical, others clavate, ventricose or even ovoid 10-12 × 5-6 µm, without dense contents, some septate, hyaline, compact, at times, the elements arranged in mounds, wall up to 0.5 µm thick; subpellis 42-70 µm thick, composed of cells 9-30 × 7-20 µm, inflated, some subisodiametric, others irregular in form, wall 0.5-1.0 µm thick, not gelatinzied, pale yellowish in KOH. Context hyphae in an irregular arrangement, 5.0-8.0 µm diam., cylindrical, septate, wall up to 0.5 µm thick, laticiferous hyphae 4-7 µm diam., with refractive contents, yellowish in KOH; sphaerocytes 14-20 × 16-22 µm, yellowish, wall 1-1.5 µm thick scarce. Hymenophoral trama with hyphae 4-8 µm diam., cylindrical, septate, wall up to 0.5 µm thick, with scarce refractive contents, intermixed with laticiferous hyphae 4-8 µm diam., with refractive contents, yellowish in KOH; sphaerocytes 19-27 µm diam., hyaline, with a faint yellowish tinge. Clamp connections absent.

Habitat.

Solitary or gregarious, under Quercus oleoides .

Additional studied material.

MEXICO, Veracruz, Alto Lucero Co., 12 km SW Palma Sola (road Veracruz-Nautla) 25 June 2015, Montoya 5189, 5192; 3 July 2015, Montoya 5193; 5 July 2016, Montoya 5266; 4 October 2016, Montoya 5294, 5295; 29 June 2017, Caro 109, Montoya 5329, 5330, 5331; 4 July 2017, Corona 1370, 1371; 10 July 2017 Montoya 5340; 12 September 2017, Montoya 5398; 16 September 2017, Montoya 5411, 5412; 19 September 2017, Caro125, 126; 25 September 2017 Corona 1423, 1424 (all at XAL).

Figures

Figure 2. Lactifluus species basidiomes and pileipellis a, b L. lorenae; c, d L. mexicanus. Scale bars: 40 mm (a), 20 mm (c), 2 μm (b, d).

Figure 4. Lactifluus mexicanus microscopical characteristics a basidiospores b basidia c pleurocystidia d cheilocystidia. Scale bar: 5 µm (a), 10 µm (b-d).

Figure 5. SEM microphotographs of Lactifluus species a, b Lactifluus lorenae c, d L. mexicanus. Scale bar: 2 μm.