Lactarius exilis X. H. Wang 2019, sp. nov.
Creators: name: Wang, Xiang-Hua
name: Das, Kanad
name: Bera, Ishika
name: Chen, Yu-Hui
name: Bhatt, Rajendra Prasad
name: Ghosh, Aniket
name: Hembrom, Manoj Emanuel
name: Hofstetter, Valérie
name: Parihar, Arvind
name: Vizzini, Alfredo
name: Xu, Tai-Min
name: Zhao, Chang-Lin
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Russulales
Russulaceae
Lactarius
Lactarius exilis

description: 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.
description: Published as part of 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, pp. 57-95 in Cryptogamie, Mycologie 20 (5) on pages 74-76, DOI: 10.5252/cryptogamie-mycologie2019v40a5, http://zenodo.org/record/7814899