Lactarius exilis X.H. Wang, 2019

Wang, Xiang-Hua, Das, Kanad, Bera, Ishika, Chen, Yu-Hui, Bhatt, Rajendra Prasad, Ghosh, Aniket, Hembrom, Manoj Emanuel, Hofstetter, Valérie, Parihar, Arvind, Vizzini, Alfredo, Xu, Tai-Min & Zhao, Chang-Lin, 2019, Fungal Biodiversity Profiles 81 - 90, Cryptogamie, Mycologie 20 (5), pp. 57-95 : 74-76

85. Lactarius exilis X.H. Wang , sp. nov.

( Figs 9 ; 10B ; 13 )

A small slender species with pileus with a conical center, white latex, globose reticulate spores, absence of pleuromacrocystidia, numerous cheilomacrocystidia and pileipellis a (hymeno)epithelium. A long INDEL in the ITS1 region is also characteristic.

TYPUS. — China. Shanxi Prov., Xia Co., Sijiao, Tanghui , under Quercus trees, 15.VIII.2015, coll. X.H. Wang, no. 3683 (holo-, KUN [ HKAS 89954 ]!).

MYCOBANK. — MB 829288.

GENBANK. — MK351982 - MK351984 (ITS).

ETYMOLOGY. — Referring to the slender fruiting bodies.

ADDITIONAL SPECIMENS EXAMINED. — China. Henan Prov., Xinyang, Jigong Mt., between Laoyingwo and Xiannütan, 295 m a.s.l., 25.VIII.2015, coll. X.H. Wang, no. 3783 (KUN[HKAS 90043]).

South Korea. Seoul, Donggureung Nine Royal Tombs, under Quercus trees, 15.VIII.2011, coll. X.H. Wang, no. 2966 ( KUN [ HKAS 73523]).

HABIT, HABITAT AND DISTRIBUTION. — Caespitose or 1-4 individuals growing together, in fagaceous forests. Northern (Shanxi Prov.) and central (Henan Prov.) China and South Korea.

DESCRIPTION

Basidiomata

Small, slender.

Pileus

6-15 mm in diam., at first convex with a pointed papilla, becoming plano-convex with a depressed center when mature, ± sulcate, margin sometimes crenate; surface dry, somewhat areolate-rimose, dark brown or dark reddish brown when young, later remaining so or becoming yellowish brown, orange brown, hygrophanous, radially rugose.

Context

Very thin (<0.5 mm), concolorous with the lamellae.

Lamellae

1-3mm broad, decurrent, subdistant, pale yellow,grayish orange.

Stipe

20-40 × 1-2 mm, cylindrical, equal or gradually enlarged downward; surface dry, smooth, with silky luster, nearly concolorous with the lamellae or light brown.

Latex

White, watery, neither discoloring nor staining.

Odor

None.

Spore print

Not obtained.

Basidiospores

(80/4/3) 7.0-7.7-8.5 (9.0) × 6.5-7.2-8.0 (8.5) Μm [Q = 1.00- 1.12 (1.14), Q = 1.06 ± 0.03] [holotype (40/2/1) 7.0-7.7-8.5 (9.0) × 6.5-7.3-8.0 (8.5) Μm, Q = 1.00-1.10 (1.14), Q = 1.06 ± 0.03], globose, subglobose; ornamentation 0.8-1.5 (2.0) Μm high, of ridges connected, forming an incomplete to complete reticulum, often with subtransparent (less amyloid) dots in the ridges or at the crossing points of ridges; plage not amyloid or slightly distally amyloid.

Basidia

4-spored, 35-52 × 8-13 Μm, clavate.

Pleuromacrocystidia

Absent.

Pseudocystidia

Uncommon to common, 2-4 Μm broad, often slightly enlarged at the apex, some forking.

Lamella edge

Sterile, rarely with scattered basidia; cheilomacrocystidia numerous, 25-60 × 4-7 Μm, subfusiform, cylindrical, apex mostly mucronate or moniliform, with sparse to agglomerated contents.

Pileipellis

An epithelium, 50-100 Μm thick; cells 15-30 Μm in diam., globose, ellipsoid, terminal cells often ellipsoid, colorless, hyphae beneath globose cells 5-10 Μm broad, colorless.

Stipitipellis

A cutis, 40-50 Μm thick, closely packed; hyphae 3-5 Μm broad, pale yellowish brown.

Pileus and stipe trama

With numerous rosettes.

NOTES

The combination of pileipellis an epithelium, absence of pleuromacrocystidia and abundant cheilomacrocystidia of L. exilis X.H. Wang , sp. nov., is shared by L. castanopsidis and L. resinosus X.H. Wang , sp. nov. (described below). Those two species have spores with deeply winged zebroid ornamentations and brownish hyphae underlying the pileipellis. Lactarius exilis X.H. Wang , sp. nov., is similar to European L. obscuratus , L. cyathuliformis and L. omphaliformis and Thai L. crenulatulus Wisitrassameewong & Verbeken in the slender habit and the pileipellis an epithelium. The three European species have pleuromacrocystidia and ellipsoid spores (Heilmann-Clausen et al. 1998; Basso 1999). The Thai species lacks cheilomacrocystidia and has a more crenulate pileus and white pruinose stipe base ( Wisitrassameewong et al. 2014). Japanese L. cyathula f. japonicus Hongo looks similar. It has bigger ellipsoid spores and lacks macrocystidia ( Hongo 1971) .

The long INDEL in the ITS1 region in L. castanopsidis , L. exilis X.H. Wang , sp. nov., and L. resinosus X.H. Wang , sp. nov., is unique among the members of L. subg. Russularia . This long INDEL is also present in several species of L. subg. Lactarius with violeting latex [e.g. L. cascadensis Hesler & A.H. Sm. and L. luridus (Pers.) Gray ]. Using the whole ITS or ITS1 region to BLAST gave hits to these not closely related species.

Figures

FIG. 9. — Original tree generated by Neighbor-Joining (NJ) phylogenetic analysis, rooted with midpoint. NJ analysis was conducted in MEGA X, using bootstrap method (1000 replicates),p-distance as substitution model,transitions and transversions both included,uniform rates among sites,homogeneous pattern among lineages and pairwise deletion for gaps treatment. The bootstrap proportions higher than 70% are indicated above the nodes. New species are in bold. Sample labels are provided in the order of species name, GenBank accession, and geographical origin. For new species, sample numbers with initials of collectors are provided after GenBank accessions.

FIG. 10. — Basidiocarps:A, Lactarius aurantiobrunneus X.H.Wang,sp.nov.(HKAS 101912,holotype);B, L.exilis X.H.Wang,sp.nov.(HKAS 90043);C, L. collybioides X.H. Wang,sp. nov.(HKAS 76002, holotype);D, L. flaviaquosus X.H. Wang,sp. nov.(HKAS 104207,holotype); E, L. resinosus X.H. Wang,sp. nov.(HKAS 104241).

FIG. 13. — Lactarius exilis X.H. Wang, sp. nov. (HKAS 89954, holotype): A, basidiospores; B, cheilomacrocystidia; C, lamella edge; D, pileipellis. Scale bars: A, 5 μm; B, 20 μm; C, D, 25 μm.