Gerronema keralense K. P. D. Latha & Manim., 2018

Latha, K. P. Deepna, Nanu, Salna, Sharafudheen, Shahina A. & Manimohan, Patinjareveettil, 2018, Two new species of Gerronema (Agaricales, Basidiomycota) from Kerala State, India, Phytotaxa 364 (1), pp. 81-91 : 85-88

Gerronema keralense K. P. D. Latha & Manim. , sp. nov. Figs. 2A–H

MycoBank MB 824928

Etymology:—The specific epithet refers to Kerala State, India where this species was first observed.

Diagnosis:—Characterized by omphalinoid basidiomes, decurrent lamellae, a central stipe, smooth, oblong ellipsoid to subamygdaliform or amygdaliform, inamyloid basidiospores, a pileipellis disrupted by clusters of pileocystidia, sarcodimitic pileus trama, a stipitipellis disrupted by caulocystidia and clamped hyphae. Differing from G. subclavatum in having smaller basidiomes with an applanate pileus, a solid stipe with an appressed-fibrillose surface, smaller, oblong-ellipsoid to subamygdaliform or amygdaliform basidiospores, and a distinctive nrITS sequence.

Holotype:— INDIA. Kerala State: Ernakulam District, Kothamangalam Taluk, Kuttampuzha Panchayat , Pooyamkutty , islets on River Pooyamkutty , 22 November 2014, K. P. Deepna Latha DKP325 ( CAL 1666 ). GenBank accessions: MH156555 (nrITS); MH153979 (nrLSU).

Description:— Basidiomes small, somewhat omphalinoid. Pileus 4–17 mm diam., convex or hemispherical with a central depression when young, becoming applanate still with a slight central depression at maturity; surface brownish gray (5F 2, 5E 3/OAC639) at the center and on the fibrils when young, becoming grayish brown (5F3/OAC640) at the center and on the fibrils, yellowish brown (5E4/OAC743) elsewhere, not hygrophanous, not pellucid-striate, appressed-fibrillose all over; margin initially incurved, becoming decurved to somewhat straight with age, entire or slightly wavy. Lamellae decurrent, distant, initially pale grayish yellow (4B3/OAC807), becoming grayish yellow (4C5, 4C6/OAC817), up to 2 mm wide, with lamellulae in 4 tiers, strongly interveined; edge crenate, concolorous with the sides. Stipe 7–23 × 1–2 mm, central, terete, equal, solid; surface grayish yellow (4C5/OAC818) at the apex and middle, grayish brown (5F3/OAC736) towards the base, appressed-fibrillose all over; base slightly enlarged, with white, scanty basal mycelium. Odor and taste not distinctive. Spore print not obtained.

Basidiospores 6–8 × 4–5 (6.85± 0.67× 4.5± 0.46)μm, Q =1.2–1.88, Qm =1.53,oblong-ellipsoid, subamygdaliform or amygdaliform, smooth, thin-walled, inamyloid. Basidia 29–33 × 5–6 μm, clavate, hyaline, thin-walled, 4-spored; sterigmata up to 4 μm long. Lamella-edge heteromorphous. Cheilocystidia scattered, 30–39 × 4–6 μm, flexuose or irregular in shape, thin- to slightly thick-walled, hyaline. Pleurocystidia absent. Lamellar trama subregular to slightly regular; hyphae 2–14 μm wide, thin-walled, hyaline, inamyloid. Pileus trama subregular, sarcodimitic; generative hyphae 3–23 μm wide, thin-walled, hyaline, inamyloid, interspersed with elongate-fusoid hyphae, 143–272 × 5–13 μm, slightly thick-walled, hyaline, inamyloid. Pileipellis a cutis disrupted by clusters of erect or semi-erect pileocystidia; hyphae 3–9 μm wide, hyaline or often with a dark brown plasmatic pigment, thin-walled. Pileocystidia 22–81 × 6–9 μm, flexuose, clavate or vesiculose, with a dark brown cytoplasmatic pigment. Stipitipellis a cutis disrupted by caulocystidia and occasional ascending or erect hyphae; hyphae 2–8 μm wide, hyaline or with a brown plasmatic pigment, thin- to slightly thick-walled. Caulocystidia 18–61 × 3–5 μm, cylindrical, fusoid, clavate or sometimes irregular in shape, with or without a dark brown plasmatic pigment, thin- to slightly thick-walled. Clamp connections observed on all hyphae.

Habitat: — Growing in small groups on decaying dicot twigs on forest floor.

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

Comments:—Characters such as the omphalinoid basidiomes with a pigmented pileus, decurrent lamellae, thin-walled, smooth basidiospores, sarcodimitic tramal tissues, the presence of abundant cystidia on pileus and stipe, and a lignicolous habitat lead the present species to the genus Gerronema ( Singer 1970, 1986). BLASTn search results and subsequent nrITS-based phylogenetic analysis also placed the present species among the other species of Gerronema . In a megablast search of the GenBank nucleotide database using the nrITS (686 bp) sequences of G. keralense , the closest hit was an unnamed Gerronema species from Gabon (JQ657793) with only 91% identity.

Gerronema subclavatum ( Peck 1900: 612) Singer ex Redhead (1986: 301) , as described by Bigelow (1970) (as Omphalina subclavata ( Peck 1900: 612) Murrill (1916: 347)) based on collections from North America, shows some similarities to G. keralense in having a plano-convex pileus with a depressed center and an incurved margin at first, an appressed fibrillose pileus surface with yellowish gray or yellowish brown color, decurrent lamellae with yellow shades, smooth, inamyloid basidiospores of somewhat similar size, 6–8.5(‒10) × 4–5.5 μm, lamella-edges with scattered cheilocystidia, a hymenium devoid of pleurocystidia, the hyphae of pileipellis with a brown cytoplasmatic pigment, versiform pileocystidia with a cytoplasmatic pigment, clamped hyphae and a lignicolous habitat. However, G. subclavatum differs from G. keralense in having relatively larger basidiomes (pileus 25 mm diam. and stipe 35 mm long), a subhygrophanous, infundibuliform pileus at maturity, a hollow stipe with a tomentose base, ellipsoid or ovate basidiospores, and interwoven to subregular lamellar trama. Additionally, a pair-wise alignment of nrITS sequence of present species with that of G. subclavatum (U66434) showed only 85% identity.

Gerronema nemorale also shows some similarities to G. keralense in having a convex to applanate pileus with a depressed center and a radially fibrillose surface, decurrent lamellae, a stipe with basal mycelium, the presence of cheilocystidia, the absence of pleurocystidia, a pileus trama with sarcodimitic hyphae, a stipitipellis with caulocystidia and the presence of clamp connections on all hyphae. However, G. nemorale differs from G. keralense in having a basidiome when that is tomentose when young, abundant cheilocystidia on lamella-edge, and absence of true pileocystidia ( Antonin et al. 2008). Gerronema kuruvense , a species described above, differs from G. keralense in having an infundibuliform, hygrophanous pileus, a fistulose stipe with a pruinose surface, larger basidiospores (8–11 × 4–6 μm), only 2-spored basidia, lamella-edges devoid of cheilocystidia, pigmentless hyphae of pilei- and stipitipellis, and pileo- and caulocystidia devoid of pigments.

Figures

FIGURE 2. A–H: Gerronema keralense (CAL 1666, holotype). A & B. Basidiomes; C. Basidiospores; D. Basidium; E. Cheilocystidia; F. Pileipellis. G. Terminal elements of pileipellis; H. Stipitipellis. Scale bars: A-B = 10 mm; C–E, G = 10 μm; F, H = 20 μm.