Gerronema kuruvense 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 : 82-85

Gerronema kuruvense K. P. D. Latha & Manim. , sp. nov. Figs. 1A–G

MycoBank MB 824927

Etymology:—The specific epithet refers to the Kuruva Islets on River Kabani in Kerala where this species was first observed.

Diagnosis:—Characterized by small, omphalinoid basidiomes; an infundibuliform, orange yellow pileus with an appressed-fibrillose surface; subdecurrent, grayish yellow lamellae, flexuose, slightly translucent, grayish yellow stipe with a subbulbous base; smooth, thin-walled, inamyloid basidiospores with variable forms, a fertile lamella-edge, a hymenium devoid of pleurocystidia, pileus trama with sarcodimitic hyphae, a cutis-type pilei- and stipitipellis with pileo- and caulocystidia respectively and clamped hyphae. Differing from Gerronema strombodes in having smaller basidiomes, oblong, obovoid or ellipsoid basidiospores, the presence of both pileo- and caulocystidia, and a distinctive nrITS sequence.

Holotype:— INDIA. Kerala State: Wayanad District, Mananthavady Taluk, Bavali , Kuruva islets on River Kabani , 26 September 2016, K. P. Deepna Latha DKP437 ( CAL 1665 ). GenBank accessions: MH156554 (nrITS); MH153978 (nrLSU).

Description:— Basidiomes small, omphalinoid. Pileus 4–11 mm diam., convex when very young, becoming plano-convex or applanate with a small umbo and infundibuliform or deeply infundibuliform at maturity; surface orange yellow (4B7/OAC852) all over, hygrophanous, becoming paler, faintly translucent-striate, glabrous when very young, becoming appressed-fibrillose all over with age, rather plicate towards the margin; margin almost incurved when very young, becoming decurved or straight to rather reflexed with age, wavy. Lamellae subdecurrent, somewhat waxy, narrow, grayish yellow (4B4/OAC806), up to 1.5 mm thick, distant, with lamellulae of 1–2 tiers; edge entire, concolorous with the sides. Stipe 3–18 × 2–3.5 mm, central, terete, equal, flexuose, fistulose; surface slightly translucent, grayish yellow (4B4/OAC847) all over, pruinose all over; base subbulbous. Odor and taste not distinctive. Spore print not obtained.

Basidiospores 8–11 × 4–6 (9.5 ± 1 × 5.88 ± 0.79) μm, Q = 1.29–2, Qm = 1.64, oblong, obovoid or ellipsoid, smooth, hyaline, thin-walled, inamyloid. Basidia 30–47 × 6–9 μm, clavate or broadly clavate, hyaline, thin-walled, inamyloid, 2-spored; sterigmata up to 7 μm long. Lamella-edge fertile. Cheilocystidia and pleurocystidia absent. Lamellar trama subregular to interwoven; hyphae 3–12 μm wide, hyaline, thin-walled, inamyloid. Pileus trama subregular, sarcodimitic, generative hyphae 4–12 μm wide, thin-walled, hyaline, inamyloid, interspersed with elongate-fusoid hyphae, 36–201 × 4–16 μm, slightly thick-walled, hyaline, inamyloid. Pileipellis a cutis with scattered ascending pileocystidia; hyphae 3–14 μm wide, hyaline, thin-walled, inamyloid. Pileocystidia 17–52 × 4–7 μm, narrowly utriform or cylindrical, thinto slightly thick-walled, hyaline, inamyloid. Stipitipellis a cutis with scattered or clustered diverticulate caulocystidia; hyphae 3–20 μm wide, thin- to slightly thick-walled, hyaline, inamyloid. Caulocystidia 21–42 × 3–6 μm, flexuose, broadly cylindrical or cylindrical, thin-walled, hyaline, inamyloid. Oleiferous hyphae present. 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:—Bright orange yellow, omphalinoid basidiomes, subdecurrent lamellae, smooth, inamyloid, thin-walled basidiospores, a subregular lamellar trama with sarcodimitic tissues, a cutis-type pileipellis with scattered pileocystidia, and a lignicolous habitat are the morphological features that indicate that this species belongs to the genus Gerronema . BLASTn search results and the subsequent phylogenetic analysis confirmed that this species indeed belonged to that genus.

A BLASTn search using the nrITS (704 bp) sequence of G. kuruvense showed G. strombodes (KY242504) as the closest hit with only 91% identity. Gerronema strombodes (Berk. & Mont. in Montagne 1856: 112) Singer (1961: 50), a species originally described from USA ( Singer 1961), is similar to G. kuruvense in having a pileus with appressed-fibrillose surface and an infundibuliform center, almost similar lamellae, somewhat similarly-colored stipe, absence of both pleuro- and cheilocystidia, basidiospores of somewhat similar size, (6‒)6.5–8.5(‒11) × (3.8‒)4.5–5.3(‒6.8) μm, and clamped hyphae. However, G. strombodes has larger basidiomes with a grayish white pileus, longitudinally striped stipe which is slightly pruinose at the apex, a slightly astringent-bitterish taste, ellipsoid basidiospores, 1-, 2-, 3- or 4- spored basidia, a pileipellis devoid of pileocystidia, a stipitipellis lacking caulocystidia, and occurrence on stumps of coniferous trees.

Gerronema nemorale Takahashi (2000: 16) , a species originally described from Japan and later published by Antonín et al. (2008) from Republic of Korea, shares some features such as somewhat similar pileus with a depressed center, subdistant lamellae with a concolorous edge, a stipe with a subbulbous base, almost similar-sized basidiospores, 8.0–10(‒11) × (4.5‒)5.0–6.0 μm, absence of pleurocystidia, and a stipitipellis with caulocystidia. However, G. nemorale is distinguished by its slightly larger basidiomes (pileus up to 17 mm diam.), grayish yellow to olive brown pileus with a fibrillose to striate-rugulose surface, 4-spored basidia, a lamella-edge with abundant cheilocystidia, and a pileipellis devoid of true pileocystidia ( Antonín et al. 2008). Gerronema keralense , a species described below, differs from G. kuruvense in having a convex to applanate, only slightly centrally depressed, non-hygrophanous pileus, a solid stipe with an appressed fibrillose surface, smaller basidiospores (6–8 × 4–5 μm), presence of only 4-spored basidia, lamella-edge with cheilocystidia, pigmented hyphae of pilei- and stipitipellis, and the presence of pileo- and caulocystidia. Also, a pair-wise alignment of nrITS sequences of these two species showed only 85% identity.

Figures

FIGURE 1. A–G: Gerronema kuruvense (CAL 1665, holotype). A. Basidiomes; B. Basidiospores; C. Basidium; D. Pileipellis; E. Terminal elements of pileipellis. F.Stipitipellis; G. Diverticulate caulocystidia. Scale bars: A = 10 mm; B–C, E, G = 10 μm; D = 50 μm; F = 20 μm.