Lactarius austrorostratus

Lactarius austrorostratus Wisitrassameewong & Verbeken

MycoBank number: MB811742; Facesoffungi number: FoF00635

Pileus: 10−30 mm diameter, at first convex to broadly convex with incurved margin, later expanding and with a more depressed center, or slightly infundibuliform, papillate in center; surface smooth when young, then becoming rugulose, particularly in center, dark brown (9F7) initially, turning dark brown (9F6−7) to reddish brown (9E8); margin inflexed, short striation, crenulate. Lamellae 1−3 mm broad, crowded, with 1−2 series of lamellulae, subdecurrent, cream to dark cream; edge minutely crenulate. Stipe 30−43 × 4 mm, cylindrical, central to slightly eccentric, fragile, fistulose; surface wrinkled, reddish brown (8D7) to dark brown (7F6) at base in youth, turning darker brown (8F8) when mature. Context 0.5−2 mm broad, fragile, pale reddish brown, unchanging when cut; odor like L. quietus or Pentatomidae bugs, taste mild. Latex somewhat watery white to whey-like, sparse to moderately abundant, unchanging on exposure, unchanging with 10% KOH, unchanging on white tissue paper and on white cotton handkerchief, taste mild. Macrochemical reaction no reaction on the context with 10 % KOH and with FeSO4. Basidiospores subglobose to ellipsoid, (6.1−)6.4−7.1−7.8 ×(5.6−)5.7−6.2−6.8(−6.9) μm; Q = 1.07−1.14−1.15−1.30, (n = 40); ornamentation amyloid, up to 1 μm high, consisting of blunt irregular ridges, forming an incomplete reticulum, at times with a zebroid aspect; isolated warts abundant; plage distally amyloid. Basidia 34−52 × 10−17 μm, mostly 4-spored, sometimes 1-or 2-spored, irregularly subclavate, some irregularly cylindrical, with guttate contents and fine granules. Pleuromacrocystidia abundant, 54−107 × 9−18 μm, lanceolate to subfusiform, somewhat slender, protruding up to 40 μm, rostrate apex, often tortuous particularly near the apex, mostly with refractive contents containing fine granules. Pleuropseudocystidia abundant, 3−6 μm diam., cylindrical, but tortuous near the base, with fine granules, needle-like contents and sometimes with crystalline contents. Lamellar edge sterile, with marginal cells and cheilocystidia; marginal cells 13−26 × 8−18 μm, clavate to obovoid; cheilocystidia 32−58 × 10−16 μm, scattered to abundant, subfusiform with mucronate to rounded apex, with refractive contents containing fine granules, protruding up to 15 μm. Lamellar trama consisting of smaller and larger globose cells, septate hyphae and lactiferous hyphae. Pileipellis a hyphoepithelium, suprapellis a thin layer of repent hyphae; subpellis about 60−80 μm thick, consisting of large globose cells which are up to 35 μm diam.

Habitat: solitary or gregarious on ground in evergreen rainforest, under Castanopsis. Collections examined: THAILAND, Chiang Mai province, Jomthong district, Bahn Luang sub-district, Doi Inthanon, nature trail at highest spot, N18º35.20 E98º29.03, alt. 2565 m, 06/07/2011, KW108 (holotype, GENT!, isotype, MFLU!);−ibid., 06/07/2011, KW109 (GENT!, MFLU!);−ibid., 06/07/2011, KW110 (GENT!, MFLU!).

Notes: This species is in some aspects similar to L. rostratus, e.g., in basidiocarp size, color and latex features. Both species have rostrate pleuromacrocystidia but the Asian species has larger pleurocystidia. Both species also share basidiospore ornamentation characteristics (an incomplete reticulum with a slightly zebroid pattern) and a hyphoepithelium pileipellis. Lactarius austrorostratus grows under Castanopsis whereas L. rostratus is associated with Fagus in moss cushions. Another closely related species, L. rubrocorrugatus, is a small reddishbrown species with completely transparent latex. The other distinguishable character between L. austrorostratus and L. rubrocorrugatus is the pleuromacrocystidia. L. austrorostratus has conspicuous protruding cystidia (up to 40 μm) with acute apex whereas in L. rubrocorrugatus the cystidia are not protruding to slightly protruding up to 20 μm with a mucronate to moniliform apex.

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.