Lactarius austrotorminosus H.T. Le & A. Verbeken.
Pileus 30–80 mm diam., convex with slightly depressed center to broadly infundibuliform, slightly depressed and involute at margin, with very small papilla; surface scaly, especially scaly when young, hairy and strigose, with zones of hairs, especially zonate in the centre, pale greyish orange (6AB3–4) to pale orange or pink (5A3) when young, light orange (5A4) in center and pale yellow (4A2–3) on margin when old; greyish orange (5B3–4) where bruised; margin incurved when young, very hairy, wavy, with small triangles of (33L+l/cm), with abundant lamellulae of different lengths, with 3 lamellulae between 2 lamellae, 1–2 mm broad, pale yellow (4A3–4), brownish orange (5CD5) when broken or bruised. Stipe 30–70 × 5–16 mm, cylindrical, curved, tapering downwards, smooth, greasy, with small scrobicules, yellowish white (4A2) near gills, light greyish orange (5AB3) or orange white (5A1–2), locally more dirty or brownish pink, with paler to whitish zone on top (4A1–2, 5A2) and base; some specimens scrobiculate with light yellow (4B4–5) scrobicules, brownish orange (6C4) when broken or bruised. Context rather firm in pileus, 2.5–5 mm thick in pileus, hollow in stipe, brownish cream near pileus, pinkish cream near gills, with zonation present inside the pileus, pale yellow (3A3) with 10% KOH, unchanging with FeSO4; taste slightly acrid to very acrid; smell sweetish, agreeable. Latex white, unchanging, unchanging with 10% KOH. Spore deposit white. Basidiospores 6–7–7.5–8.3 × 4.5–6–6.5–7.3, (n = 80, Q = 1.05–1.17–1.3), subglobose to broadly ellipsoid; ornamentation up to 1 (–1.5) μm high, composed of ridges forming an incomplete reticulum, with slight zebroid aspect; plage inamyloid. Basidia 35–60 × 8–10 μm, with sterigmata 2–7 × 1–2 μm, (1–) 4-spored, sometimes with pigmentation, with guttate and granular contents, thin-walled, subclavate to cylindrical. Pleuromacrocystidia 40–75 × 5–11 μm, very abundant, emergent, subfusiform to cylindrical, with acute or moniliform apex, hyaline, sometimes with granular and needle-like contents, thin-walled. Pleuropseudocystidia abundant, not emergent, 3–6 μm diam., thin-walled, tortuous to cylindrical, tapering upwards at apex. Hymenophoral trama composed of interwoven, filamentose hyphae and lactiferous hyphae. Lamellar edge heteromorphous; marginal cells 10–25 × 4–7 μm, cylindrical, hyaline, sometimes with pigmentation, thin-walled, 1-septate. Pileipellis a cutis to a trichoderm, 30–80 μm thick, composed of hyphae 3–4 μm diam., thin- to slightly thick-walled; underlying layer composed of filamentous hyphae and sphaerocytes; lactifers present. Stipitipellis a trichoderm, 20–50 μm thick; underlying layer composed of filamentous hyphae and sphaerocytes. Clamp connections absent.
Habitat and distribution: solitary on the soil under Castanopsis diversifolia in primary montane forest.
Material examined: THAILAND, Chiang Mai Prov., Doi Suthep-Pui National Park, Sangasahasri Lane to Huai Kok Ma village, N18°48.62' E098°54.60', 1145 m alt., solitary on the soil under Castanopsis diversifolia in primary montane forest, dominated by Castanopsis spp., Lithocarpus polistachyus and other trees, 30 June 2003, leg. D. E. Desjardin, DED 7596 (GENT, CMU, SFSU) – ibid., primary montane rainforest with Dipterocarpus, Castanopsis etc., in naked soil along trail, 24 June 2004, leg. A. Verbeken & R. Walleyn 04/84 (GENT), leg. Huyen T. Le 130 (holotypus CMU; isotypes SFSU, GENT) – ibid., on soil and leaves, in rain forest dominated by Castanopsis and Lithocarpus trees, 24 July 2004, leg. Huyen T. Le 191 (CMU, GENT SFSU, MRC) – ibid., solitary on the soil amongst leaves of Castanopsis armata, rainforest dominated by Castanopsis armata and Lithocarpus polistachyus and other trees, 22 June 2005, leg. Huyen T. Le 290 (CMU, GENT, SFSU) – ibid., solitary on the soil amongst leaves of Castanopsis armata, rainforest dominated by Castanopsis armata, Lithocarpus polistachyus and other trees, 24 June 2005, leg. Huyen T. Le 301 (CMU, GENT, SFSU) – Chiang Mai Prov., Mae Taeng Distr., Tung Joaw village, forest trail, 1300 m alt., N19°08.07' E98°38.90', secondary forest with Pinus kesiya, Castanopsis, 13 June 2004, leg. Huyen T. Le 111 (CMU, GENT, SFSU).
Notes: Lactarius austrotorminosus is easily recognized in the field by the pinkish orange colours and the strongly hairy strigose, zonate pileus. It resembles the European species L. torminosus (Schaeff.: Fr.) Pers. and L. torminosulus Knudsen & T. Borgen. Both European taxa differ by the more reticulate and lower spore ornamentation and the distinct ixocutis as a pileipellis structure. In addition, the ITS data (Fig. 13) clearly indicate that the Thai L. austrotorminosus is distinct from European L. torminosus. The most similar Asian species appears to be L. strigosus Verbeken & E. Horak, described from Papua New Guinea. L. strigosus has smaller basidiocarps (up to 35 mm diam.) and the spores are less zebroid and have a more spiny and acute aspect. Lactarius atrosquamulosus X. He, described from China, is possibly related and shares the zebroid aspect of the spore ornamentation, but has very small basidiocarps (up to 10 mm diam.) and more purplish tinges. Macroscopically specimen Huyen T. Le 111 is distinctive because of the orange, strongly zonate cap with ciliate margin and the pale and slender stipe, but the ITS data show that the specimen belongs to L. austrotorminosus.
Fig. 1 Lactarius austrotorminosus. a. Basidiocarp. b. Spores. c. Basidia. d. Marginal cells. e. Pleuromacrocystidia. f. Pleuropseudocystidia. Scale bars = 10 mm (basidiocarp) and 10 μm.