Lactarius austrozonarius

Lactarius austrozonarius H.T. Le & A.Verbeken.

Mycobank: 510281

Pileus 50–135 mm diam., convex with distinct depression and inrolled margin to plano-convex with deep funnel-shaped depression, infundibuliform; surface pale yellow (3A2–3 in young specimens) or slightly darker and more brownish (sometimes 4B5 in older specimens) with darker to reddish brown scales, with darker zonations, more orange brown on disc, viscid, not hygrophanous, in some specimens woolly; zonations sometimes formed out of the woolly covering, sometimes formed out of watery spots; distinct scales present in some specimens, composed of ascending hairs especially in the center, sometimes dirty brown mottled; margin involute and strongly tomentose in young specimens, bearded, then decurved and with hairs forming pendulous agglutinations, brownish to dirty reddish brown; margin not striate but some slightly grooved aspect visible in between the zonations. Lamellae subdistant (6 L+l/cm), decurrent with very long tooth (more than 10 mm in some specimens), with abundant lamellulae (especially short ones), brittle, rather thick, up to 11 mm broad, cream-coloured, staining dirty greyish brown by the latex with some pinkish brown shade; some intervenation present close to the stipe in young specimens; edge concolourous, entire. Stipe 25–115 × 15–35 mm, cylindrical in younger basidiomes to subcylindrical and ventricose or very irregular in older basidiomes, tapering downwards; surface pale yellow (3A2–3) or darker, locally dirty brownish, smooth, often with very large, ellipsoid scrobicules that are sometimes concolourous, sometimes slightly darker. Context very firm and thick in the pileus, hollow in the stipe, creamcoloured to whitish, with watery zonation present inside the pileus, changing slowly greyish when cut; taste very acrid after a while in young specimens, less distinct in older specimens; smell sweetish, like Lactarius zonarius. Latex very abundant, white to watery cream-coloured, unchanging, but staining paper slowly yellowish, staining lamellae dirty greyish brown, but unchanging when drying; taste burning acrid. Basidiospores 7.2–8.9–10.5–12.2 × 7–8.4–9.2–10.2 μm (n = 160, Q = 1–1.05–1.14–1.28(–1.33) subglobose to broadly ellipsoid; ornamentation up to 2.5 (–3.5) μm high, forming an incomplete reticulum, often in a partly spiral

pattern, composed of acute and locally high ridges that are connected by lower and fines lines; plage inamyloid. Basidia 50–65 × 13–18 μm, sterigmata 5–11 × 2–3.5 μm, hyaline, 4-spored, thin-walled, subclavate. Pleuropseudocystidia abundant, rarely emergent, 6–9 μm diam., thin-walled, tortuous to cylindrical, with lactiferous contents. Pleuromacrocystidia abundant, sometimes with refringent contents, emergent and arising from deep in the subhymenium, 55–100 × 9–20 μm, subclavate to subfusiform with tapering, sometimes moniliform, sometimes rather rounded apex, thin-walled; contents granular and guttate. Hymenophoral trama composed of interwoven, filamentous hyphae. Lamellar edge heteromorphous; marginal cells hyaline, thin-walled, 13–26 × 3–8 μm, 1-septate, shortly clavate, irregularly cylindrical to fusiform. Pileipellis an ixocutis to an ixotrichoderm, 90–240 μm thick, underlying layer composed of filamentous hyphae and sphaerocytes. Stipitipellis an ixocutis, 70–160 μm thick, underlying layer composed of filamentous hyphae and sphaerocytes. Clamp connections absent.

Habitat and distribution: solitary on the soil, in rainforest dominated by Castanopsis sp., Dipterocarpus sp., and Lithocarpus sp.; so far only known from Thailand.

Material examined: THAILAND, Chiang Mai Prov., Doi Suthep-Pui Nat. Park, Sangasabhasri Lane to Huai Kok Ma village, N19°48.62' E98°54.60', 1145 m alt., primary montane rainforest with Dipterocarpus, Castanopsis etc., 24.06.2004, leg. A. Verbeken & R. Walleyn 04/81 (GENT), leg. Huyen T. Le 129 (Holotypus CMU, Isotypes SFSU, GENT) – 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 299 (CMU, GENT, SFSU) – ibid., solitary on the soil amongst leaves of Castanopsis armata,

rainforest dominated by Castanopsis armata, Lithocarpus polistachyus and other trees, 02 July 2005, leg. Huyen T. Le and Dennis E. Desjardin, Huyen T. Le 338 (CMU, GENT, SFSU) – ibid., solitary on the soil amongst leaves of Castanopsis armata, rainforest dominated by Castanopsis armata, Lithocarpus polistachyus and other trees, 07 June 2006, leg. Huyen T. Le and Dennis E. Desjardin, Huyen T. Le 413 (CMU, GENT, SFSU) – ibid., solitary on the soil amongst leaves of Castanopsis armata, rainforest dominated by Castanopsis armata, Lithocarpus sp. and other trees, 13 June 2006, leg. Huyen T. Le and Dennis E. Desjardin, Huyen T. Le 438 (CMU, GENT, SFSU) – Chiang Mai Prov., Doi Suthep-Pui National Park, Huai Kok Ma village, N18°48.402' E98°54.617', 1146 m alt., primary montane rainforest with Castanopsis, Lithocarpus etc., 14 August 2003, leg. Huyen T. Le 43 (CMU, GENT, SFSU) – ibid., on soil, primary montane forest with Castanopsis spp., Lithocarpus polistachyus and other trees, 14 August 2003, leg. Huyen T. Le 44 (CMU, GENT, SFSU) – ibid., on soil, primary montane forest with Castanopsis spp., Lithocarpus polistachyus and other trees,14 August 2003, leg. Huyen T. Le 47 (CMU, GENT, SFSU) – ibid., on soil, primary montaneforest with Castanopsis spp., Lithocarpus polistachyus and other trees, 29 August 2003, leg. Huyen T. Le 54 (CMU, GENT, SFSU) – ibid., solitary on soil, relatively wet forest, primary montane forest with Castanopsis spp., Lithocarpus polistachyus and other trees, 07 October 2003, leg. Huyen T. Le 82 (CMU, GENT, SFSU) – ibid., solitary on soil, relatively wet forest, primary montane forest with Castanopsis spp., Lithocarpus polistachyus and other trees, 07 October 2003, leg. Huyen T. Le 83 (CMU, GENT, SFSU).

Notes: Lactarius austrozonarius is very similar to L. austroscrobiculatus Verbeken & E. Horak, described from Java (Verbeken et al., 2001). It differs by the dominantly yellow colours while L. austroscrobiculatus is characterized by pale flesh-coloured, pale hazel and pale lilac tinges. Furthermore, the spores of L. austrozonarius are more ellipsoid and with higher ornamentation than those of L. austroscrobiculatus. L. austrozonarius is recognizable in the field by its large basidiomes with zonate, viscid cap and hairy margin, distinct scrobicules on the stipe and white, unchanging latex. Based on overall morphological features, the species belongs to Lactarius subgenus Piperites sect. Zonarii. Both, L. austroscrobiculatus and L. austrozonarius differ from all other known representatives of L. section Zonarii by the very dense reticulum and very high spore ornamentation. Most other species have rather low ornamented spores and a less dense reticulum. The two specimens of L. austrozonarius included in the molecular analyses cluster with a bootstrap support of 100% and are well-separated from all other species in L. subgenus Piperites. It should be noted that in our ITS phylogenies, sect. Zonarii is polyphyletic (see also Eberhardt, 2000), and hence the exact relationships of L. austrozonarius remain unclear. Macroscopically, L. austrozonarius is also reminiscent of L. wenquanensis Y. Wang & Z.X. Xie, described from China (Wang and Xie,1984), which shares the large basidiomes with yellowish colours, very scrobiculate stipe and zonate pileus with hairy margin. The latex in L. wenquanensis is also white and unchanging. Microscopically however, the spores of L. wenquanensis are ornamented with isolated ridges and warts of up to 1 μm high and connected by fine lines.

Fig. 1 Lactarius austrozonarius. a. Basidiocarp. b. Spores. Scale bars = 10 mm (basidiocarp)

and 10 μm.