Lactarius dirkii – Facesoffungi number: FoF 02521

Lactarius dirkii Uniyal, K. Das, A. Baghela & R.P. Bhatt

MycoBank: MB 817126 Facesoffungi number: FoF02521

Etymology: commemorating Dr. Dirk Stubbe for his contribution to Lactarius subg. Plinthogali.

Holotype: CAL 1332.

Pileus 20–86 mm. in diam.; convex when young, becoming planoconvex with shallowly depressed center with maturity; margin decurved, entire to irregularly undulating, often interrupted; surface dry, slightly wrinkled towards margin when mature; white to orange-white (6A2) with a pinkish-white (7A2) or paler tinge, spotted with reddish grey (7B2) scrobicules, changing to light yellow (2A5) with 10 % KOH. Lamellae subdecurrent, close to rather crowded (13–14/10 mm), some forked near the stipe apex, white to orange-white (5A2) to pale orange (5A3), becoming pinkish to pale red (7A2) to pastel red (7A3/4) when bruised or cut, lamellulae numerous. Stipe 30–58 x 5–8 mm., cylindrical, tapering toward base, central, dry, concolourous with pileus, white at base with minute hairs; Context whitish to yellowish-white (4A2), turning light orange on cutting, hollow in stipe; Latex abundant, white, unchanging when isolated, but drying pinkish on cut lamellae. Taste bitter to acrid. Odour insignificant. Spore print light yellow (4A5). Basidiospores 6.5–7.7–8.5 x 6–6.9–7.5 um, (n = 70, Q = 1.06–1.11– 1.21), subglobose to broadly ellipsoid, rarely broadly ellipsoid, winged; ornamentations amyloid, composed mostly of broad wings and few small ridges but never forming a reticulum, up to 2 um high, edges smooth, isolated warts also present between ridges, plage amyloid. Basidia 44–62 x 11–14 um, subclavate, 4-spored, sterigmata 4–7 um long. Hymenophoral trama composed of lactifers and rosettes of sphaerocytes. Pleurocystidia absent. Pseudocystidia abundant, emergent, cylindrical, sometimes tortuous, branched, up to 5.5 um wide. Lamellar edge sterile. Cheiloleptocystidia 24–35 x 4–5.5 um, mostly cylindrical, rarely subfusiform, thin walled. Subhymenium up to 20 um thick, pseudoparenchymatous. Lactifers in hymenophoral trama up to 7 um wide. Pileipellis trichopalisade, 55–121 um thick, suprapellis formed of cylindrical to subfusiform cells and septate hyphal elements 10–57 x 3.5–6.5 um; subpellis composed of cells with irregular shapes, cells up to 11 um wide; Lactifers in pilear trama up to 8 um wide, sometimes becoming gradually thin toward suprapellis and projecting in form of pileopseudocystidia, wide up to 4.5 um. Stipitipellis trichoderm, up to 100 um thick, hyphae up to 5 um wide.

Habitat & distribution: Under Quercus sp., Rhododendron arboreum in temperate mixed forest dominated by Abies, Cupressus, Quercus and Rhododendron.

Material examined: INDIA, Uttarakhand, Rudraprayag district, Baniyakund, 2630 m, N3028.9140 E7910.8540, 29 August 2015, P. Uniyal, PU 15-1004 (CAL 1332, holotype); ibid., Baniyakund, 2630 m, N3028.9140 E7910.8540, 9th Aug 2014, P. Uniyal, PU 15-360 (GUH); ibid., 25 August 2014, P. Uniyal, PU 15-451 (GUH); ibid., 1 August 2015, P. Uniyal, PU 15-803 (GUH).

Notes: The combination of morphological features such as whitish dry pileus, concolourous (to pileus) stipe, light yellow spore print, winged basidiospores, trichopalisade pattern of pileipellis and absence of hymenial macrocystidia undoubtedly place Lactarius dirkii under L. subg. Plinthogali (Burl.) Hesler & A.H. Sm. (Basso 1999; Das and Sharma 2004; Stubbe et al. 2008). Among this subgenus, the new species is fairly easy to recognize in the field by its white to orange-white basidiomata with pinkish tinge and darker scrobicules on cap surface, yellow reaction with KOH, close to rather crowded lamellae turning pinkish to orange on bruising, hollow stipe and abundant white latex that remains unchanged when isolated but becoming pinkish on cut lamellae. Micromorphologically, occurrence of subglobose to broadly ellipsoid basidiospores with up to 2 um high wing like ornamentations and warts that never form a reticulum, abundant emergent pseudocystidia and sterile lamellar edges containing cylindrical cheiloleptocystidia are also worth mentioning. In the field, L. dirkii can be mistaken for L. oomsisiensis Verbeken & Halling (probably morphologically closest species, which was reported from Papua New Guinea and Thailand and labeled with GenBank accession numbers EF560680 and EF560679). Both have whitish basidiomata but the latter can be distinguished macromorphologically by distant orange-brown lamellae, white latex drying cream on gills and mild taste (Le et al. 2007) and micromorphologically, by comparatively narrow pileipellis (40–80 um thick) with brown intracellular pigmentation in upper layer and absence of pileopseudocystidia in suprapellis. Lactarius dirkii is also closely related to another Asian taxon, L. friabilis H.T. Le & Stubbe (reported from Thailand as well and labelled with GenBank accession numbers EF560663 and EF560664 but, the latter differs from L. dirkii in having distant (to subdistant) lamellae, larger spores (7.8–7.9–8.4–9.1 x 7.1– 7.5–7.8–8.7 um) with incompletely reticulated ornamentation of warts and ridges with mostly crenulate edges (Le et al. 2007). Phylogenetically, both L. oomsisiensis (95 %identity with L. dirkii for 95 % query coverage using BLAST) and L. friabilis (94 % identity with L. dirkii for 98 % query coverage using BLAST) are also distinct. In L. subg. Plinthogali, molecular phylogeny already confirmed the existence of eight European species (Stubbe and Verbeken 2012) of which, seven species: L. acris (Bolton: Fr.) Gray (GenBank acc. nos. JQ446084 and JQ446083), L. azonites (Bull.) Fr. (GenBank acc. nos. JQ446094 and JQ446095), L. fuliginosus (Fr.: Fr.) Fr. (GenBank acc. nos. JQ446111 and JQ446110), L. picinus Fr. (GenBank acc. nos. JQ446129 and JQ446130), L. pterosporous Romagn. (GenBank acc. nos. JQ446138 and JQ446136), L. romagnesii Bon (GenBank acc. nos. JQ446143 and EF560662) and L. ruginosus Romagn. (GenBank acc. nos. JQ446106 and EF560660) are found to be closely related (93–95 % identity with L. dirkii for 95–98 % query coverage using BLAST) to L. dirkii (showing significant support with the Asian taxa of L. subg. Plinthogali). However, mostly these species are dark coloured in contrast to the white basidiome of L. dirkii, making it easily distinguishable from them in the field. Moreover, L. acris shows a completely different pattern of pileipellis i.e., ixooedotrichoderm to ixotrichopalisade with capitate terminal elements (Heilmann- Clausen et al. 1998); L. fuliginosus and L. picinus (also reported from India) have dark coloured cap, scarce latex, trichoepithelium pattern of pileipellis and lower (1 um) spore ornamentations (Heilmann-Clausen et al. 1998) and strictly conifer association in later species (Stubbe and Verbeken 2012). Among other close European taxa, L. romagnesii and L. ruginosus have fuscous colour of pileus, irregularly crenate to grooved margin, distant gills and rather sparse latex and spores with high ornamentations that are reticulate in L. romagnesii but zebroid in L. ruginosus (Stubbe and Verbeken 2012), while L. azonites can be separated from the present taxon by distant gills, larger spores (7.3–9.3 x 6.8–8.3 um), lower ornamentations (up to 1 um) and hyphoepithelium to trichoepithelium type of pileipellis (Heilmann-Clausen et al. 1998). Lactarius pterosporus shares similar pileipellis structure (a trichopalisade of 80–120 um thick), but differs in having dark greyish-buff coloured cap, sparse latex and higher (up to 2.5 um) spore ornamentations (Heilmann-Clausen et al. 1998). Molecular data also indicates genetic closeness (95 % identity with L. dirkii for 95 % query coverage using BLAST) of L. dirkii with L. fumosibrunneus A.H. Sm. & Hesler (reported from North American continent and labelled with GenBank acc. nos. JQ797634 and JQ797633, which is different from the former in brownish, rugose cap, negative reaction of KOH on surface and reddening ofmtissue by latex. Micromorphologically, hymenoepithelium nature of pileipellis and presence of abundant cheilocystidia in L. fumosibrunneus are also quite distinct (Bandala and Montoya 2010). Few Indian species of L. subg. Plinthogali namely, L. crenulatus K. Das & Verbeken, L. montoyae K. Das & J.R. Sharma, L. croceigalus K. Das & Verbeken and L. vesterholtii K. Das & D. Chakr. partly resemble micromorphologically (nature of pileipellis, absence of macrocystidia, pinkish discoloration of flesh and high spore ornamentations). But, L. crenulatus has distinctly smaller papillate dark-coloured pileus and slender stipe (Das and Verbeken 2012). Lactarius montoyae (also reported from Thailand) shows subdistant to distant lamellae, brown coloured basidiomata, white unchanging latex which does not stain tissues (Le et al. 2007; Das and Sharma 2005). Lactarius croceigalus differs from L. dirkii on the basis of larger, papillate and dark colored pileus, distant lamellae and larger spores (9–9.2–10.1 x 7.8–8.7–9.5 um) as mentioned by Das and Verbeken (2012). Finally, Lactarius vesterholtii, which was recently discovered from Himalayan India under L. subg. Plinthogali, can be separated morphologically from the present species by crowded lamellae, typically orange discolouration of latex on exposed gills, brown to greyish- brown pileus, lack of pileopseudocystidia and showing palisade to lampropalisade nature of stipitipellis (Das and Chakraborty 2014).