Lactarius spinosporus X.Y. Sang & L. Fan, 2016

Sang, Xiaoyu, Li, Xuedong, Wang, Yanwei & Fan, Li, 2016, Four new sequestrate species of Russulaceae found in China, Phytotaxa 289 (1), pp. 101-117 : 108

Lactarius spinosporus X.Y. Sang & L. Fan , sp. nov. ( Fig. 3 , Fig. 7A )

Mycobank: MB819368

Type:— CHINA. Sichuan: Panzhihua City, in soil under mixed woodlands dominated by Pinus armandii Franch. , 23 Nov 2014, CJZ 1536, FAN 445 ( BJTC!), collected by J. Z. Cao (Holotype: BJTC FAN 445).

Basidiomata 16–22 × 13–19 mm, irregularly subglobose or with flattened apex and depressed at base. Peridial surface dark brown, dry, glabrous, rugulose and deeply grooved. Gleba brown, loculate to alveolate. Stipe absent. Columella absent. Latex absent. Smell unremarkable.

Basidiaspores globose, 9–12.5 μm (x = 10.3 ± 1.0, n = 30) excluding ornamentation, Q = 1.00–1.03, sandy beige, slightly thick-walled, completely dissociated after maturity; ornamentation amyloid, composed of isolated spines which are 1–2 μm long, usually curved, rounded on the top. Hilar appendix 2–5 μm long. Basidia 30–60 × 5–10 μm, clavate to subclavate, broadly cylindrical, 2-spored. sterigmata up to 2–10 μm long. Pseudocystidia absent. Cystidia rare, 28– 37.5 × 5–8 μm, ventricose or clavate with rounded apices, hyaline. Hymenophoral trama 25–60 μm broad, composed of interwoven, hyaline hyphae of 3–6 μm diam.; laticiferous hyphae 5–10 μm diam.; subhymenium 20–50 μm wide, composed of pseudoparenchyma with 2–3 tiers of isodiametric cells 7–30 × 6–15 μm, some sphaerocytes occasionally present near subhymenium. Peridiopellis two-layered: suprapellis composed of a thin and strongly incrusted slime-layer and upright hyphal tips; subpellis a palisade to trichopalisade, composed of terminal elements usually thick-walled, subglobose or short hyphal parts, occasionally present polygonal elements. Peridial context 125–225 μm wide, composed of loosely intricate hyphae of 2–5 μm diam.; laticiferous hyphae 4–10 μm diam.; sphaerocytes absent.

Diagnosis:— Basidiomata 16–22 × 13–19 mm, irregularly subglobose. Peridial surface dark brown, glabrous. Gleba brown, loculate. Columella absent. Latex absent. Basidiospores globose, with isolated and curved spines. Basidia 2-spored. Pseudocystidia absent. Cystidia rare.

Etymology: —Latin, spinosporus = spiny spore, in reference to the basidiospores with isolated spines.

Habit, habitat and distribution: —hypogeous, gregarious, in soil under mixed woodlands dominated by P. armandii in Sichuan Province, China.

Commentary: —Morphologically, the combination of dark brown basidiomata, absence of latex, thick-walled terminal elements in subpellis and echinate basidiospores is distinct for L. spinosporus . The phylogenetic analysis ( Fig. 1 , 2 ) shows that the sequences of L. spinosporus and L. falcatus from Tailand form a strongly supported clade (BS = 99), indicating that they are closely related to each other, but they just shared the identity of 95% in ITS sequence and respectively have distinct features in morphology. Lactarius spinosporus has a brown gleba while L. falcatus has a cream-coloured, discolouring pale greyish brown gleba with light orange pinkish tinge and produces moderately abundant latex. The peridiopellis of L. falcatus is composed of a loose layer of intricate hyphae, arranged periclinally as well as anticlinally, and lacks a slime-layer ( Verbeken et al. 2014). Lactarius echinus Stubbe & Verbeken ( Verbeken et al. 2014: 21) is similar to L. spinosporus in peridiopellis, but L. echinus has white latex and basidiospores with longer spines (5 μm long) ( Verbeken et al. 2014). Moreover, the species Z. sinensis described from China has whitish basidiomata, a distinct columella and irregularly reticulate ornamentation of the basidiospores ( Tao et al. 1993), by which it can be distinguished from the present species.

Figures

FIGURE 1. Phylogeny from the most parsimonious analysis based on 5.8S-ITS2 sequences from the hypogeous gasteroid russuloid species of Russulaceae, Russula and Lactarius. Gloeocystidiellum aculeatum served as outgroups.With a consistency index (CI) of 0.454, retention index (RI) of 0.792, and a homoplasy index (HI) of 0.546. Nodes are labeled with parsimony bootstrap support values greater than 50%. Novel sequences are in bold.

FIGURE 2. Phylogeny from the most parsimonious analysis based on 5.8s-ITS2-nrLSU combined dataset from the hypogeous gasteroid russuloid species of Russulaceae, Russula and Lactarius. Gloeocystidiellum aculeatum served as outgroups. With a consistency index (CI) of 0.491, retention index (RI) of 0.726, and a homoplasy index (HI) of 0.509. Nodes are labeled with parsimony bootstrap support values greater than 50%. Novel sequences are in bold.

FIGURE 3. Lactarius spinosporus (BJTC FAN445, holotype).A. Basidiomata. B. Basidia. C. Hymenophoral cystidia. D. Basidiospores. E. Peridiopellis and peridial context. F. Hymenophoral trama and hymenium. Scale bar = 10 mm (A), 10 μm (B–F).

FIGURE 7. Scanning electron micrograph (SEM) of basidiospores. A. Lactarius spinosporus (holotype). B. Russula absphaerocellaris (holotype). C. Russula brevipileocystidiata (holotype). D. Russula megapseudocystidiata (holotype). Scale bar = 5 μm.