Entoloma tropicum K. N. A. Raj & Manim., 2017

Anil Raj, K. N. & Manimohan, Patinjareveettil, 2017, Four new species of Entoloma subgenus Pouzarella from India, Phytotaxa 307 (2), pp. 101-112 : 109-110

Entoloma tropicum K. N. A. Raj & Manim. , sp. nov. Figs. 4A–F

MycoBank MB 820066

Etymology:—The specific epithet refers to the tropical location of this species.

Diagnosis:—Characterized by dark brown, omphalinoid basidiomata; a plano-convex pileus with a shallow central depression; decurrent lamellae; versiform cheilocystidia with hyaline encrustations, basidiospores measuring 10–12.5 × 7–9 μm, and distinctive ITS (KY643749) and nLSU (KY643722) sequences. Differing from Entoloma violaceovillosum in having smaller basidiospores and a completely sterile lamella edge with versiform cheilocystidia showing hyaline encrustations.

Holotype:— INDIA. Kerala State: Wayanad District, Tirunelli Forest , 16 November 2010, K. N. Anil Raj, AR523 (K(M) 191744).

Description:— Basidiocarps small, omphalinoid. Pileus 8–14 mm diam., somewhat plano-convex with a shallow central depression; surface dark brown (6F5, 6F6/OAC637) at the center and on the squamules, brown (6E6/OAC636) on striations and light brown (6D4/OAC639) elsewhere, not hygrophanous, finely striate, appressed- to recurved-squamulose all over; margin deflexed to straight, crenulate, finely fissile. Lamellae subdecurrent to decurrent or arcuate, close, orange-gray (6B2/OAC669) or brownish orange (6C3/OAC613), up to 3 mm wide, with lamellulae in 2–3 tiers; edge finely torn or somewhat wavy, concolorous with the sides. Stipe 18–28 × 2–2.5 mm, central, equal or slightly tapering towards the apex, hollow; surface grayish brown (6E3/OAC640) or brown (6E4/OAC638), whitish towards the base, with fine appressed fibrils as well as slightly recurved squamules all over; base with whitish mycelium. Odor and taste not distinctive.

Basidiospores 10–12.5 × 7–9 (11.4 ±0.69 × 7.9±0.73) μm, Q = 1.2–1.71, Qm =1.45, nodulose-multiangled, heterodiametric-ovate, with 5–7 plane or concave facets, pale brownish yellow, thick-walled. Basidia 27–44 × 9–14 μm, clavate, pale yellow, thin- to slightly thick-walled, 4-spored; sterigmata up to 5 μm long. Lamella-edge sterile. Cheilocystidia abundant, 22–84 × 10–29 μm, versiform: oblong, ellipsoid, fusiform, clavate, conical, narrowly utriform or cylindrical with an acute apex, pale yellow, thin- to slightly thick-walled, with fine hyaline encrustations. Pleurocystidia none. Lamellar trama subregular, made up of both narrow and inflated hyphae; hyphae 4–20 μm wide, with a yellowish brown wall pigment and fine brown external encrustations, thin- to slightly thick-walled. Subhymenium distinct, made up of pseudoparenchymatous cells. Pileus trama subregular; hyphae 3–20μm wide, with a pale yellow or pale grayish yellow wall pigment and fine hyaline external encrustations, thin- to slightly thick-walled. Pileipellis a cutis with a transition to a trichoderm; hyphae 10–31 μm, with brown plasmatic contents and fine hyaline external encrustations, thin- to slightly thick-walled; terminal cells 32–75 × 7–15 μm, cylindrical or gradually tapering with an obtuse or acuminate apex. Stipitipellis a cutis often disrupted by isolated or clustered ascending hyphae; hyphae 3–16 μm wide, with pale grayish or brownish plasmatic contents and hyaline external spiral encrustations, thin- to slightly thick-walled; Caulocystidia absent. Clamp connections not observed on any hyphae.

Habitat:—scattered, on the forest floor, among decaying leaf litter, under broadleaf trees.

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

Comments:—Characters such as the dark brown pileus with a squamulose surface, the nodulose-angular basidiospores and the presence of encrustations on all hyphae including cheilocystidia suggest the section Dysthales of subg. Pouzarella . Entoloma violaceovillosum Manim. & Noordel. in Manimohan et al. (2006: 52) a species described from Kerala shows some similarity to E. tropicum in having a plano-convex pileus, a similar type of pileipellis with a brown plasmatic pigment and a somewhat similar stipitipellis. However, E. violaceovillosum differs from E. tropicum owing to its larger, violet-brown basidiocarps, a heteromorphous lamella-edge, larger basidiospores (12–16 × 8.5–11 μm) and thin-walled, smaller-sized and differently-shaped cheilocystidia devoid of any encrustations. Moreover, a pairwise comparison of nLSU sequences of E. tropicum and E. violaceovillosum (GQ289205) showed only 91% sequence similarity. ITS sequence of E. violaceovillosum is not available for comparison.

The distinct status of the ITS and the nLSU sequences of Entoloma tropicum was confirmed in the megablast searches. In the megablast search using the ITS (584 bp) sequence, no close hit was obtained with an e-value of zero. While using the nLSU (899 bp) sequence, the closest hit was an unnamed Entoloma species from China, Entoloma sp. XLH-2013b (GenBank KC555558), with 94% sequence identity. The pairwise comparison of the ITS sequence of E. tropicum with the other three species described in this paper showed no similarity with an e-value of zero. However, the nLSU sequence of E. tropicum showed 89% similarity with that of E. wayanadense , 91% with that of E. silvanum and 88% with that of E. peechiense .

Figures

FIGURE 4. A–F: Entoloma tropicum (K(M) 191744, holotype). A. Basidiomata. B. Basidiospores; C. Basidium; D. Cheilocystidia; E. Pileipellis; F. Stipitipellis. Scale bars: A= 10 mm; B–D= 10 μm; E=100 μm; F=20 μm. Photos by K. N. Anil Raj.