Lactarius sarthalanus Verma K., Uniyal, Sharma Y.P & Mehmood, 2021

Verma, Komal, Mehmood, Tahir, Uniyal, Priyanka, Kapoor, Rupam & Sharma, Yash Pal, 2021, Two new species of genus Lactarius (Russulaceae) from North-western Himalaya, India, Phytotaxa 500 (4), pp. 253-265 : 256-260

Lactarius sarthalanus Verma K., Uniyal, Sharma Y.P & Mehmood sp. nov. Figs. 2 , 3

MycoBank:—MB838921

GenBank: MW578947 , MW555577 .

Etymology:—“ sarthalanus ” (Lat.) refers to the type locality (Sarthal), Kathua, Jammu and Kashmir, India.

Typification:— INDIA. Jammu and Kashmir: Kathua district , Sarthal, Bani, 9 September 2020, K . Verma , T . Mehmood , & Y. P Sharma KV-LK013, ( CAL 1838 , holotype) .

Diagnosis:—Distinct from all the known species of L. subg. Plinthogalus by a combination of the following characters: light brown to dark brown pileus; yellowish white to brownish orange, crowded lamellae that bruise to deep orange when injured, with yellowish white margins; white latex turning pastel red on exposure; the absence of pleuromacrocystidia and cheilomacrocystidia, presence of abundant cheiloleptocystidia, a pileipellis and stipitipellis as trichopalisades, globose to subglobose basidiospores with ornamentation composed of ridges never forming a reticulum, and its occurrence in coniferous forests under Cedrus deodara .

Description:— Pileus 35–55 mm diam., convex when young, plano-convex with slightly depressed centre when mature, surface smooth, dry, slightly rugulose, reddish blond (5C4) when young, light brown to dark brown (5D4–5), yellowish grey (4C3) towards centre; margin entire to undulate. Lamellae subdecurrent to broadly adnate, crowded (18–20/cm including lamellulae), 4–5 mm wide, yellowish white to light yellow (4A2–4) when young, light orange (5A5) to brownish orange (5C5) when mature, orange to deep orange (6A7–8) on bruising after 10–15 minutes, margins yellowish white (4A2); lamellulae numerous, unevenly distributed, 3–4 tiers. Stipe 40–65 × 6–13 mm, cylindrical, equal, sometimes tapering toward base, dry, central, brittle, concolorous with the pileus, sometimes white at base. Context yellowish white (4A2), pale to light orange (6A4–5) on exposure; stuffed in stipe, brownish red (8D7–8) in guaiacol, light yellowish in KOH and unchanging in FeSO 4; taste light acrid, odour mild. Latex moderately abundant, white, turning pastel red (8A4) on exposure. Spore print not obtained.

Basidiospores 9–11.53–12.8 × 9–10.78–12 μm, (n = 40, Q = 1.0–1.04–1.10), globose to subglobose, amyloid, ornamentation composed of ridges (0.9–1.8 μm high) with entire to wavy edges, some shorter and irregular ridges are present in between main ridges, often with isolated warts, never forming a reticulum; plage distally amyloid. Basidia 55–81 × 16–19 μm, clavate to subclavate, hyaline, thin-walled, 2–4 spored; sterigmata 5–10 μm long. Pleuromacrocystidia absent. Pleuropseudocystidia abundant, 7–9 μm wide, emergent up to 17–37 μm, unbranched. Cheilomacrocystidia absent. Gill edge sterile. Cheiloleptocystidia abundant, 38–70 × 6–9 μm and emergent up to 22–40 μm, cylindrical to clavate, round apex; sometimes with swollen base, with one to two cells at the base. Hymenophoral trama composed of abundant lactifers, up to 10 µm wide. Pileipellis a trichopalisade, 48–110 µm thick; suprapellis 25–35 µm deep made up of cylindrical to subclavate cells with brown intracellular pigmentation; subpellis composed of cylindrical to subround cells. Stipitipellis a palisade to a trichopalisade, 38–55 µm thick; stipitipellis hyphae 6–8 µm wide, terminal cells with intracellular brown pigment. Clamp connections absent in all tissues.

Habitat and distribution:—Solitary to scattered, on soil in coniferous forest dominated by Cedrus deodara .

Specimens examined:— INDIA. Jammu and Kashmir: Kathua, Sarthal, Bani , 2563 m elev., N 32 o 49.950ʹ E 079 o 47.237ʹ, 9 September 2020. K. Verma and Y. P. Sharma KV-LK013, KV-LK014 .

Notes:— Lactarius sarthalanus is characterized by its light to dark brown pileus bruising deep orange when damaged; yellowish white to brownish orange, crowded lamellae with yellowish white margins, turning deep orange when injured; latex white turning pastel red on exposure, the absence of pleuromacrocystidia and cheilomacrocystidia, presence of abundant cheiloleptocystidia, a pileipellis and stipitipellis as trichopalisades and globose to subglobose basidiospores with ornamentation composed of ridges never forming a reticulum. The light brown to dark brown pileus turning deep orange when cut or bruised with a smooth, dry, velvety and slightly rugulose pilear surface, absence of macrocystidia, presence of cheiloleptocystidia, a trichopalisadal pileipellis with dark brown pigmented hyphal elements undoubtedly place this species in L. subg. Plinthogalus.

Phylogenetically, some European taxa, namely Lactarius acris , L. pterosporus , L. ruginosus , L. azonites are close to L. sarthalanus . They can be mistaken in the field due to their similar macromorphology (shape, colours of pileus and lamellae). However, L. acris , which is probably the closest known species (97–98% identity for 98% query coverage in BLAST search) to L. sarthalanus , can be differentiated by its creamy white to dark pinkish pileus, ixooedotrichodermal to ixotrichopalisadal pileipellis, an incomplete reticulum on the basidiospores and its fagaceous association. Lactarius pterosporus can be differentiated from L. sarthalanus by its olivaceous buff to dark greyish colour pileus, less abundant latex, subglobose to ellipsoid larger basidiospores (Q = 1.05–1.40, av. 1.09–1.21) with a spiral pattern of ridges forming an incomplete reticulum and occurrence under fagaceous trees. Lactarius ruginosus differs from our species by its crenate pileus margin, distant lamellae, basidiospores with a spiral pattern of ridges, never forming a reticulum, trichoepithelial pileipellis and its association with Fagus sp. and Carpinus sp. L. azonites can be segregated from L. sarthalanus by its pale ochraceous to clay-buff pileus with whitish stem, distant gills, basidiospores with incomplete reticulum, hyphoepithelium to trichoepithelium pileipellis and its ectomycorrhizal association with Quercus sp. ( Heilmann-Clausen et al. 1998, Stubbe & Verbeken 2012).

Morphologically, Lactarius albidocinereus whichwasoriginallyreportedfromChina,alsoresembles L. sarthalanus in having a cream to greyish brown pileus, white latex turning reddish, and crowded lamellae that are orange to deep orange when bruised but the species differs in its broadly ellipsoid (Q 1.11–1.25, (1.16) basidiospores, trichoepithelial pileipellis, cutis-type stipitipellis and its occurrence under oaks ( Shi et al. 2017).

Lactarius pleuromacrocystidiatus Uniyal, K. Das & R.P. Bhatt (2019: 8) (with GenBank acc. nos. MF405081 , MG791871 ), an Indian species, is closely related to L. sarthalanus ( Fig.1 ). Both species share some characteristics in the field in having light brown to brown basidiomata and white latex ( Uniyal et al. 2019). However, L. pleuromacrocystidiatus can be easily differentiated by having a radially rugose pileus, white latex changing to pale greyish orange on the lamellae and yellow on the context, and the presence of hyaline pleuromacrocystidia.

Figures

FIGURE 1. Phylogram resulting from ITS-rDNA sequences: The evolutionary history was inferred by applying maximum likelihood in RAxML GUI 2.0. Bootstrap support values (>50%) obtained from the ML analysis are shown above or below the branches at nodes. Lactarius sarthalanus is highlighted in bold.

FIGURE 2. Lactarius sarthalanus. a–b. Basidiomata in the field; c. Gills showing latex; d. Cheiloleptocystidia; e. Pseudocystidia; f. Basidia; g. Transverse section through pileipellis; h. Marginal cells; i. Basidiospores under light microscope; j,k. Basidiospores under SEM. Scale bars: d–j = 10 μm. k=2 μm. Photos by: Komal Verma.

FIGURE 3. Lactarius sarthalanus. a. Basidia; b. Basidiospores; c. Pseudocystidia; d. Marginal cells; e. Pileipellis; f. Paracystidia. Scale bars: a, c–f = 10 μm b =2 μm. Drawings by: Komal Verma.