Lactarius keralensis V. A. Farook & Manim., 2016

Deepna Latha, K. P., Anil Raj, K. N., Farook, V. Adnaan, Sharafudheen, Shahina A., Parambil, Neeraja K. & Manimohan, Patinjareveettil, 2016, Three new species of Russulaceae from India based on morphology and molecular phylogeny, Phytotaxa 246 (1), pp. 61-77 : 71-73

Lactarius keralensis V. A. Farook & Manim. , sp. nov. Figs. 1E–F ; Figs. 4A–H ; Fig. 5C

MycoBank MB 815043

Etymology:—The specific epithet refers to Kerala State, India, from where this species was first discovered.

Diagnosis:— Lactarius keralensis has a dry pileus, a stipe without a strigose base, milky-white latex, an indistinct odor, globose basidiospores with a partial, reticulate ornamentation and cystidia with scanty, granular contents.

Holotype:— INDIA. Kerala State: Palakkad District, Silent Valley National Park, Core zone, Walakkad Section , on the way to Kozhippara , 01 December 2014, V. Adnaan Farook, AF773 ( CAL 1281 ).

Description:— Basidioma medium-sized. Pileus 53 mm diam., broadly infundibuliform; surface dark brown with some grayish white granularity at the disc, paler towards the margin, showing alternate brown (6E4/OAC640) and pale brown (6D4/OAC647, OAC653) zonations, dry, almost glabrous; margin white, uplifted, entire and slightly wavy. Lamellae adnexed to subdecurrent, moderately crowded, sometimes furcate, pale cream, up to 6 mm wide, with lamellulae of 8-9 lengths; edge entire, concolorous with the sides. Stipe 32 × 11 mm, central, terete, equal, solid; surface entirely pale brown (6C3/OAC661, OAC704), finely pruinose; base devoid of basal mycelium, associated with tree roots. Latex milky-white, unchanging, copious, slightly glutinous. Context solid, up to 5 mm at the center, pale cream. Odor and taste not distinctive.

Basidiospores 6–8 (9) × 6–8 (7.3 ± 0.76 × 7.0 ± 0.8) μm, Q = 1.0–1.16, Qm = 1.04, globose, distinctly amyloid with an ornamentation composed of warts with connectives forming a partial reticulum. Basidia 34–54 × 9–12 μm, clavate to broadly clavate, with refractive contents, hyaline, mostly 4-spored, rarely 2-spored; sterigmata up to 7 μm long. Lamella edge heterogeneous with copious marginal cells and scattered cheilocystidia. Cheilocystidia 71–74 × 6–7 μm, cylindric with a flexuous outline and an obtuse apex, with few refractive, granular contents. Marginal cells 9–25× 4–10 μm, cylindric to shortly clavate, often septate, hyaline, without any contents. Pleurocystidia occasional, 52–90 × 5–10 μm, flexuous-cylindric with subcapitate to moniliform apices, thin- to slightly thick-walled, with pale yellowish, refractive contents. Lamellar trama irregular, hyphae 2.5–14 μm wide, thin-walled, hyaline. Pileus trama somewhat compactly arranged towards the hymenium, loosely interwoven towards the pileipellis; hyphae 3.5–8 μm wide, mostly thin-walled, at times slightly thick-walled, hyaline. Both lamellar and pileus trama have abundant lactiferous hyphae up to 12 μm wide, with a pale yellow wall pigment and refractive contents. Pileipellis a transition between a cutis and a trichoderm; hyphae 3–6.5 μm, with a pale yellow wall pigment, thin- to slightly thick-walled, slightly gelatinized; terminal elements 24–45 × 3–6.5 μm, cylindric with an obtuse apex, hyaline, thick-walled (up to 2 μm thick). Stipitipellis a cutis often disrupted by ascending to erect fascicles of hyphae; hyphae 3–6 μm wide, mostly covered with a hyaline to pale yellowish resinous material, thick-walled. Stipe trama composed of both normal and lactiferous hyphae; hyphae up to 13 μm wide, hyaline, thin-walled. Clamp connections absent.

Habitat:—solitary, on soil, among litter, close to the roots of an unidentified dicotyledonous tree.

Geographical distribution range:—known only from the type locality in Kerala State, India.

Comments:—A brown, dry pileus with alternate dark and pale concentric zonations, an unchanging, white-colored latex, a non-scrobiculate stipe, a pileipellis that is a transition between cutis and a trichoderm and basidiospores that form an incomplete reticulum place this species in the subg. Piperites ( Le et al. 2007; Das & Sharma 2005) of genus Lactarius . Lactarius changbainensis Y. Wang & Z.X. Xie (1984: 81) , a species from China ( Wang 2007), seems to be very close to the present species in most of the macro- and microscopic features, but differs by virtue of its subviscid pileus surface, strigose stipe base, watery latex, distinctive odor recalling rosin and ellipsoid basidiospores with short ridges and isolated warts that never form a reticulum. Lactarius dafianus K. Das, J.R. Sharma & Verbeken (2003: 338) , an Indian species belonging to the subgenus Piperites , has a similar zonation, similarly attached lamellae, similar basidiospore ornamentation and similar pleurocystidia. That species, however, differs in having differently-colored basidiomata with a larger (65–75 mm) pileus, a basidiospore ornamentation composed mostly of isolated warts and ridges that never form a complete reticulum, cystidia with needle-like contents and growth in close association with Rhododendron arboreum in temperate deciduous Himalayan forests ( Das et al. 2003).

Comparison of the ITS sequence generated from Lactarius keralensis with the sequences available in the GenBank indicates that L. keralensis has a distinct sequence. In a megablast search of the GenBank database using ITS sequence of the species, the closest hit was L. hatsudake (GenBank KF432967; Identities = 610/701 (87 %), Gaps = 36/701 (5 %)) followed by L. horakii (GenBank EF685070; Identities = 608/701 (87 %), Gaps = 36/701 (5 %)). Lactarius hatsudake Tanaka (1890: 393) , a species originally described from Japan ( Tanaka 1890) and subsequently from Thailand ( Le et al. 2007), shows some similarity to L. keralensis in having zonations in the pileus and similar marginal cells. However, L. hatsudake differs in having a larger (up to 100 mm diam.), papillate, greasy to viscid pileus with red zones and translucent-striate margin, pale reddish to vinaceous red lamellae, a dull red, hollow stipe, a vinaceous red latex, broadly ellipsoid basidiospores with a complete reticulate ornamentation and smaller (42–48 × 7–9 μm) pleurocystidia. Lactarius horakii Nuytinck & Verbeken (in Nuytinck et al. 2006: 185), an Indonesian species ( Nuytinck et al. 2006), shares a few characters with L. keralensis such as a glabrous pileus, short decurrent lamellae and short, clavate to irregularly shaped marginal cells. Lactarius horakii , however, differs from L. keralensis in having a reddish brown, plano-convex to deeply infundibuliform pileus with an occasional papilla and a translucent-striate margin, pale pink lamellae that turns green on bruising, a stipe with a whitish mycelial tomentum at the base that becomes green on bruising, a vinaceous red latex, smaller pleurocystidia, abundant pseudocystidia and a lamella edge lacking cheilocystidia.

Figures

FIGURE 1. A–F: Basidiomata of the three new species. A–B. Lactifluus umbonatus. C–D. Lf. indicus. E–F. Lactarius keralensis. Scale bars: A, C–F = 10 mm; B = 5 mm. Photos: A–B. By K.P.D. Latha; C–D. By K.N.A. Raj; E–F. By V.A. Farook.

FIGURE 4. A–H: Lactarius keralensis (CAL 1281, holotype). A. Basidioma; B. Basidiospores; C. Basidia; D. Pleurocystidia; E. Cheilocystidia; F. Marginal cells; G. Pileipellis. H. Stipitipellis Scale bars: A = 10 mm; B = 2 μm; C–H = 10 μm.

FIGURE 5. A–C: SEM images of basidiospores of the three new species: A. Lactifluus umbonatus (CAL 1241, holotype). B. Lactifluus indicus (CAL 1282, holotype). C. Lactarius keralensis (CAL 1281, holotype). Scale bars: A–B = 5 μm; C = 2 μm.