Lactarius madhuriensis, Bera & Das, 2023

Bera, Ishika & Das, Kanad, 2023, Two new species of genus Lactarius Pers. (Russulaceae) from Arunachal Pradesh, India, Cryptogamie, Mycologie 20 (11), pp. 147-158 : 154-157

Lactarius madhuriensis sp. nov.

( Figs 5 ; 6 )

A medium-sized Lactarius with the umbonate, brownish orange pileus, light brown stipe, watery white latex turning yellowish and occurring in association with Abies .

HOLOTYPE. — India. Arunachal Pradesh, Sangestar Tso (Madhuri Lake), Tawang district, 27°43.215’N, 91°49.473’E, alt. 3715 m a.s.l., scattered on moss bed in association with Abies in sub-alpine forest, 26.VII.2021, I. Bera, IB 21-032 (holo-, CAL [ CAL 1899 ]!).

ADDITIONAL SPECIMENS EXAMINED. — India. Arunachal Pradesh, Sangestar Tso ( Madhuri Lake ), Tawang district, 27°43.276’N, 91°49.581’E, alt. 3705 m a.s.l., scattered on moss bed in association with Abies in sub-alpine forest, 26.VII.2021, I. Bera, IB 21-035 ( CAL [ CAL 1900 ]) .

ETYMOLOGY. — Referring to the type locality Sangestar Tso which is famously known as “Madhuri” Lake.

GENBANK. — OP808232 (nrITS, holotype) andOP808233 (nrITS, IB 21-035), OP811194 (nrLSU, holotype) and OP811195 (nrLSU, IB 21-035).

MYCOBANK. — MB 848907.

HABITAT AND DISTRIBUTION. — Growing scattered on moss bed in association with Abies in sub-alpine forest of Tawang district of Arunachal Pradesh.

DESCRIPTION

Pileus 15-45 mm in diam., convex with a central umbo when young, gradually becoming planoconvex to infundibuliform, center with a broad shallow depression and an umbo; surface moist, viscid, smooth; brownish orange (7C6) with darker at the central region gradually becoming greyish orange to orange (6B4-6) and paler towards the margin; brittle in consistency; margin incurved, wavy, regular. Lamellae decurrent, rather crowded (17-18 L+l/cm at pilear margin), sometimes forked; lamellulae in five series; orange white to pale orange (5A2-3) turning brownish on maturity; edge entire. Stipe 30-55× 2-5 mm, central, cylindrical, longitudinally striate, striation translucent; combination of light brown and brown (6D 5, 7E 7). Context thin at pileus, hollow in stipe, concolorous to stipe, turning faint yellow with 3% KOH after one minute, no change with FeSO4 and immediately becoming greyish turquoise (24E5) with guaiac. Latex moderate, watery white changing to yellowish after few minutes, chalky when dry, turning exposed lamellae brownish after few minutes, bitter. Taste astringent. Odor mild pleasant. Spore print chalky white (1A1-2).

Basidiospores 7.2-8.1-8.9(9.6)×5.2-6.3-6.9(7.6) µm, (n=40, Q = 1.11-1.30-1.50[1.54]), usually subglobose to ellipsoid; ornamentation amyloid; up to 0.9 µm high, irregular to linear warts sometimes connected with low ridges but never forming complete reticulum, presence of isolated warts; suprahilar spot inamyloid. Basidia 35-46 × 9-11 µm, subclavate, 4-spored; sterigmata up to 8.7× 1.6 µm. Pleuromacrocystidia abundant, 73.4-112.9 × 6.3-9.7 µm, emergent up to 44.7 µm, cylindric to subcylindric with fusoid, subfusoid, mucronate to appendiculated apices, rarely branched, originating from subhymenium region. Pleuropseudocystidia up to 2.3-2.8 µm wide, mostly non-emergent, cylindrical to sometimes tortuous at apex, rarely branched. Lamellae edge heteromorphous with basidia, basidioles and cystidia. Cheilomacrocystidia 39-51.1× 3.8-6 µm, emergent up to 21.8 µm, cylindric to subcylindric with rounded, fusoid, subfusoid to appendiculate apices. Subhymenium up to 20.13 µm thick, pseudoparenchymatous. Lamellar trama composed of lactifers, sphaerocytes, and connecting hyphae. Pileipellis up to 126 µm thick, hyphoepithelium; suprapellis composed of multiseptated, mostly repent hyphae (12.2-55 ×2-3.1 µm); subpellis pseudoparenchymatous composed of rounded to elongated or somewhat irregularly shaped cells (12.9-31.4× 8-13 µm). Stipitipellis up to 65 µm thick, hyphoepithelium; suprapellis composed of hyphal elements; subpellis is of rounded to elongated to somewhat irregularly shaped cells.

NOTES

The somewhat sticky, brownish orange colored pileus with watery white latex turning yellowish on drying and pileipellis of hyphoepithelium nature are typical features of subg. Russularia ( Heilmann-Clausen et al. 1998) which also correspond to the studied species. The unique characters of the novel species are planoconvex to infundibuliform shaped, umbonate, brownish orange, moist pileus with longitudinally striate light brownish stipe; latex changing to yellowish and turning exposed area brownish; positive reaction with guaiac and hyphoepithelial pileipellis.

The described species is quite identical to European L. subdulcis (Pers.) Gray , due to its small to medium-sized fruitbodies with similar colored convex to funnel shaped pileus, white bitter tasting latex, alike sized and ornamented basidiospores, similar pleuro- and cheilomacrocystidia. However, occassionally forked lamellae, wider stipe (25-65× 4-18 mm), white unchanging latex, shorter cystidia of both lamellar face (40-90[-105] × 6-12 µm) and edge ([15-]20-35× 4-8 µm), pileipellis oedotrichoderm and occurrence with Fagus L. are the striking differences possessed by L. subdulcis that make it distinct from the current species ( Heilmann-Clausen et al. 1998). Another European Lactarius , L. tabidus Fr. can be confused with the studied species for similar characters such as orange brownish pileus with persistent umbo, latex turning pale yellow, astringent taste and hyphoepithelial pileipellis. But the radially wrinkled cap in matured basidiomata, basidiospores with mostly isolated acute warty ornamentation, and its association with Betula , clearly distinguish the former from the latter species ( Heilmann-Clausen et al. 1998).

The Indian species, L. lachungensis Verbeken & Van de Putte also can be confused with the studied species for its unicolored warm orange-brownish basidiomata and similar habitat. Yet the distant (12 L+l/cm), never forking lamellae, unchanging latex, and the ixohyphoepithelium to ixotrichoepithelium pileipellis clearly separate L. lachungensis from the discussed species ( Wisitrassameewong et al. 2016). The yellowing of the latex is shared by another Indian species, L. flavigalactus Verbeken & K.Das , but other specific characters like reddish brown basidiomata, ornamentation of the basidiospores with irregular ridges forming incomplete reticulum and the ixocutis nature of pileipellis clearly differentiate L. flavigalactus from the described species ( Wisitrassameewong et al. 2016).

Although L. atrii Van de Putte & K.Das (described from India) ( Fig. 2 ) is phylogenetically close to the studied species, morphological dissimilarities such as light brown basidiocarps with unchanging mild-tasting latex and ixocutis nature of pileipellis visibly distinguish the two species ( Wisitrassameewong et al. 2016).

Figures

FIG. 5. — Photoplate of Lactarius madhuriensis sp. nov. (holo-, CAL[CAL 1899]): A, B, D, fresh basidiomata in the field and basecamp; C, latex on lamellae; E, macrochemical reaction with guaiac; F, G, transverse section through pileipellis; H-M, pleuromacrocystidia; N, O, cheilomacrocystidia; P, transverse section through stipitipellis; Q, R, basidiospore. Scale bars: F-O, 10 μm; P, 20 μm; Q, R, 1 μm.

FIG. 6. — Line drawing of Lactarius madhuriensis sp. nov.(holo-, CAL[CAL 1899]):A, fresh basidiomata in the field and basecamp;B, basidiospore;C, pleuromac- rocystidia; D, cheilomacrocystidia; E, basidia; F, pleuropesudocystidia; G, transverse section through pileipellis. Scale bars: B, 2 μm; C-G, 10 μm.

FIG. 2. — Phylogram inferred from Maximum Likelihood (ML) analysis by raxmlGUI 2.0 and Bayesian Inference by Mr.Bayes v. 3.2.6 based on nrITS and nrLSU sequence data. Sequences derived from the novel Indian species are presented in red and bold and the respective clade is highlighted in yellow. Maximum Likelihood bootstrap support values (MLbs) ≥70% are shown on the left of “/” and Bayesian Posterior Probabilities (BPP) ≥ 0.95 are shown on the right or below of “/” at nodes.