Hygrocybe indica K. P. D. Latha & Manim., 2018

Deepna Latha, K. P. & Manimohan, Patinjareveettil, 2018, A new species of Hygrocybe from Kerala State, India, Phytotaxa 385 (1), pp. 13-22 : 14-20

Hygrocybe indica K. P. D. Latha & Manim. , sp. nov. Figs. 1 , 2

MycoBank MB 827890

Etymology:—The epithet “indica ” refers to India, the country where this species was first observed.

Diagnosis:—Characterized by small, orange-colored basidiocarps; a convex pileus with an appressed-squamulose surface; decurrent, furcate lamellae; a stipe with an appressed-squamulose surface and a swollen base; smooth, globose to subglobose, inamyloid basidiospores; the presence of pseudocystidia; a lamella-edge with cheilocystidia; a subregular lamellar trama; a trichoderm-type pilei- and stipitipellis; and clamped hyphae. Differing from Hygrocybe parvispora in having appressed-squamulose pileus and stipe surfaces, a swollen stipe base lacking yellowish coloration, a hymenium showing pseudocystidia, a subregular lamellar trama, a trichoderm-type pilei- and stipitipellis showing slight gelatinization and a stipitipellis devoid of caulocystidia.

Holotype:— INDIA. Kerala State: Malappuram District, Calicut University Campus , 27 June 2018, K. P. Deepna Latha DKP508 ( CAL 1726 ). GenBank accessions: MH938534 (nrITS); MH938535 (nrLSU).

Description:— Basidiocarps small. Pileus 3–25 mm diam., convex with a slight central depression when young, becoming broadly convex or somewhat plano-convex still with a slight central depression; surface initially brownish orange (7C7/OAC664), becoming reddish orange (7B7, 7B8/OAC649) at maturity, strongly hygrophanous and becoming orange white (5A4, 6A2/OAC815), dry, glabrous to the naked eye, with appressed- to slightly recurved squamules all over under a lens, at times finely striate towards the margin; margin incurved when young, becoming decurved or occasionally reflexed with age, crenate, slightly wavy or somewhat lobate at times. Lamellae adnate with a small decurrent tooth or decurrent, waxy, furcate, close, orange (6A7, 6B7/OAC691) or reddish orange (7B7/ OAC649), up to 3 mm wide, with lamellulae in 2–3 tiers; edge entire to the naked eye, finely torn under a lens, rather wavy, concolorous with the sides. Stipe 6–33 × 1.5–5 mm, central, somewhat flexuose, terete or sometimes compressed towards the base, equal or slightly tapered towards the apex or at times tapered towards the base, fistulose; surface brownish orange (7C7/OAC664) all over when young, becoming reddish orange (7B7/OAC649) towards the apex and grayish orange (6B4, 6B5/OAC633, OAC653) towards the base with age, hygrophanous and becoming orange white (6A2/OAC794), dry, glabrous to the naked eye, rather squamulose all over under a lens, finely pruinose towards the apex; base swollen with a dense, white mycelium. Odor strong, unpleasant. Taste not distinctive. Spore print pale orange (5A3).

Basidiospores 5–6 × 4.5–5(6) (5.32 ± 0.40 × 4.87 ± 0.35) μm, Q = 1.00–1.37, Qm = 1.09, smooth, globose or subglobose, with a single, prominent oil guttule, thin-walled, inamyloid. Basidia 28–39 × 6–8 μm, clavate or at times with a narrow pedicel, with prominent oil guttules, hyaline or with pale yellowish contents, thin-walled, 4-spored; sterigmata up to 5 μm long. Lamella-edge heteromorphous. Cheilocystidia scattered on the edge of the lamellae, 29–62 × 4–11 μm, cylindrical or flexuose-cylindrical, hyaline or pale yellow, thin-walled. True pleurocystidia absent. Pseudocystidia present on the sides of lamellae, 23–49 × 4–7 μm, similar to cheilocystidia in morphology. Lamellar trama subregular, composed of both narrow hyphae and inflated hyphal elements of 36–110 × 9–14 μm size; hyphae 3–15 μm wide, hyaline or pale yellow, thin-walled, inamyloid. Pileus trama subregular, composed of inflated hyphal elements intermixed with narrow hyphae; narrow hyphae 2–5 μm wide, inflated hyphal elements 32–60 × 10–14 μm, hyaline or pale yellow, thin-walled, inamyloid. Pileipellis a trichoderm; hyphae 5–10 μm wide, with a pale yellow wall pigment, thin-walled, slightly gelatinized; terminal elements 50–135 × 5–11 μm, cylindrical or sometimes cylindrical with an acute apex or flexuose-cylindrical. Stipitipellis a cutis often disrupted by trichodermal patches or sometimes a true trichoderm towards the apex and the middle of the stipe and a cutis towards the base; hyphae 2–9 μm wide, often closely septate, hyaline or with a pale yellow wall pigment, thin-walled, slightly gelatinized; terminal elements 42–90 × 3–12 μm, cylindrical or sometimes cylindrical with a constriction at the middle or flexuose-cylindrical. Caulocystidia absent. Clamp connections (medallion-type) observed on all hyphae.

Habitat: — On soil, near rubber trees [ Hevea brasiliensis (Willd. ex A.Juss.) Müll.Arg. ], scattered or in small groups.

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

Additional specimens examined:— INDIA. Kerala State: Malappuram District, Calicut University Campus, 17 July 2018, K. P. Deepna Latha DKP521 (AMH 10034).

Comments:—In the traditional, morphology-based infrageneric classification of Hygrocybe , this new species would be placed in the subg. Pseudohygrocybe owing to its morphological features such as the adnate to decurrent lamellae, the subregular lamellar trama with hyphal elements that are up to 110 μm long and the monomorphic basidia and basidiospores. Within the subg. Pseudohygrocybe , the orange-colored basidiocarps with a dry, squamulose pileus, a dry stipe and a trichoderm-type pileipellis lead this species to the subsect. Squamulosae of sect. Coccineae ( Boertmann 1996; Lodge et al. 2014). However, BLASTn search results and subsequent phylogenetic analysis based on nrLSU sequences ( Fig. 3 ) revealed that H. indica was nested among other species of Hygrocybe within the subgenus Hygrocybe . Within this subgenus, the new species formed a distinct lineage together with an undescribed species of Hygrocybe collected from Malaysia, with full bootstrap support (100% BS). In the phylogram generated from the nrITS sequence data matrix ( Fig. 4 ), which exclusively encompassed members of the subg. Hygrocybe , H. indica was found to be clustered with H. subpapillata , a species reported from the United Kingdom, with significant bootstrap support (75% BS). Hygrocybe subpapillata was treated in the nrITS sequence-based phylogenetic analysis of the subgenus Hygrocybe by Lodge et al. (2014), where that species was not found belonging to any of the five sections of the subg. Hygrocybe . Similarly, the section-level placement of H. indica within the subgenus Hygrocybe also remains uncertain.

Hygrocybe parvispora T.K. Abraham, K.B. Vrinda & C.K. Pradeep (in Abraham et al. 1996: 361), an Indian species from Kerala State belonging to the sect. Coccineae of subg. Pseudoygrocybe (Abraham et al. 1996), is morphologically close to H. indica in having a basidiocarp of almost similar size (pileus 30 mm diam., stipe up to 30 mm long and lamellae 3 mm wide) and color (deep orange), a convex to plano-convex pileus with a slight central depression, rather similarly attached lamellae (broadly adnate with a decurrent tooth), basidiospores of almost similar size ((3)4.5–6 × 3–5.2 μm) and shape (subglobose), rather similar morphology of cheilocystidia (cylindrico-clavate) and the presence of clamp connections. Hygrocybe parvispora is distinguished, however by its glabrous pileus lacking a squamulose surface and a striate margin, non-furcate lamellae, an equal, glabrous stipe which is yellowish towards the base, occasional presence of single-spored basidia, a sterile lamella-edge, a hymenium devoid of pseudocystidia, a regular lamellar trama, a cutis-type pileipellis with semi-erect to erect, non-gelatinized hyphae, a stipitipellis with caulocystidia and the absence of a distinctive odor.

Hygrocybe cantharellus , a widespread species reported from North America and Europe ( Boertmann 1996; Cantrell & Lodge 2004) and also from Kerala ( Leelavathy et al. 2006) shares a few features with H. indica in having a pileus of somewhat similar color (orange-red to deep orange) and surface features (squamose to squarrulose), almost similarly attached lamellae (adnate to subdecurrent or arcuate decurrent), somewhat similar-colored stipe (orange or deep orange), subregular lamellar trama and clamped hyphae. However, H. cantharellus has pale yellow to orange-white, non-furcated, subdistant lamellae, a smooth and hollow stipe, longer and ellipsoid to ellipsoid-oblong basidiospores, longer basidia (up to 60 μm long), a fertile lamella-edge devoid of cheilocystidia, the presence of laticifers in the lamellar trama, a trichoderm-type pileipellis restricted at the center and a cutis towards the margin, and a cutis-type stipitipellis with yellowish to reddish contents. Hygrocybe indica resembles H. miniata (Fr.) P. Kummer (1871: 112) , another widespread species ( Boertmann 1996; Young & Wood 1997; Young 2005), also reported from North East India by Berkeley (1852, as Hygrophorus miniatus (Fr.) Fries (1838: 330)) in having a similar looking pileus with almost similar surface features (covered with fine squamules) and color (scarlet to orange-red), somewhat similarly attached lamellae (broadly adnate or with a decurrent tooth), a dry stipe, occasional presence of cheilocystidia and a similar pileipellis. However, H. miniata differs from H. indica in having a pileus with a yellow margin, yellowish-tinted lamellae sometimes with a concolorous or whitish edge, a smooth, silky sheen stipe, longer [(7.5)8.0–10.0(11.5) × 5.0–6.5(7.0)] μm) and ovoid, ellipsoidal or amygdaliform basidiospores with or without faint constrictions, occasional presence of 2-spored basidia, a regular lamellar trama with inflated elements (up to 400 μm wide) and a cutis-type stipitipellis. Hygrocybe subpapillata Kühner (1979: 248) , the phylogenetically closely related species so far reported only from a few European countries ( Boertmann 1996), differs from H. indica by its papillate, lubricous pileus with occasionally upturned margin, pale yellow to orange lamellae with paler edges, a golden yellow to orange stipe with a fibrillose surface, larger ((5.5)7.0–9.0(10) × (3.5)4.5–5.5(7.0) μm) and ellipsoid to oblong basidiospores, 4-spored basidia mixed with 1-, 2- or 3-spored basidia, a regular lamellar trama with long and slender elements and an ixocutis- or an ixotrichoderm-type pileipellis and a dry, cutis-type stipitipellis. Also, a pairwise sequence alignment of H. indica with H. subpapillata (EU784350) showed 96% identity, but with only 27% query cover.

No close hits with a zero e-value were observed during the BLASTn search using the nrITS (611 bp) sequence of H. indica . However, H. chloochlora resulted as the first hit (Identities = 164/170(96%); Gaps = 0/170(0%); EU435147) that showed 96% identity having only 36% query cover (170 bp). An undescribed species of Hygrocybe from Malaysia, Hygrocybe sp. isolate DOB 2487, was the closest hit (Identities = 886/891(99%); Gaps = 3/891(0%); KY090818) while using the nrLSU sequence (954 bp).

Figures

FIGURE 1. A–E: Hygrocybe indica (CAL 1726, holotype). A–E. Basidiocarps in their natural habitat. Scale bars: A–E = 10 mm.

FIGURE 2. A–H: Hygrocybe indica (CAL 1726, holotype). A. Basidiospores; B. Basidium; C. Pseudocystidia; D. Lamella-edge showing cheilocystidia; E. Cheilocystidium; F. Pileipellis. G. Vertical section of stipitipellis towards the apex of the stipe; H. Vertical section of stipitipellis towards the base of the stipe. Scale bars: A–E = 10 μm; F–H = 20 μm.

FIGURE 3. ML phylogram based on nrLSU sequence data matrix depicting the placement of H. indica within the genus Hygrocybe s.s. The newly described species is indicated in bold face. GenBank accession numbers and geographical origin are given after the name of each taxon. Values at nodes indicate bootstrap support. BS values ≥50% are shown.

FIGURE 4. nrITS sequence-based ML phylogram showing the position of H. indica within the subgenus Hygrocybe. The newly described species is indicated in bold face. GenBank accession numbers and geographical origin are given after the name of each taxon. Values at nodes indicate bootstrap support. BS values ≥50% are shown.