Inocybe distincta K. P. D. Latha & Manim., 2016

Deepna Latha, K. P., Manimohan, Patinjareveettil & Matheny, P. Brandon, 2016, A new species of Inocybe representing the Nothocybe lineage, Phytotaxa 267 (1), pp. 40-50 : 43-48

Inocybe distincta K. P. D. Latha & Manim. , sp. nov. Figs. 1A–G ; Figs. 2A–E ; Figs. 3A–C

MycoBank MB 816970

Etymology:—The specific epithet refers to the distinctive evolutionary lineage of this species.

Diagnosis:— Inocybe distincta has small basidiomata with a finely squamulose-rimulose pileus with mostly reflexed margin, a fibrillose-pruinose stipe with an abrupt base, smooth, phaseoliform to ovo-ellipsoid basidiospores occasionally showing a slight angular outline; copious, versiform, often septate cheilocystidia covered with a resinous substance towards the apex; a hymenium devoid of pleurocystidia and a cutis-type stipitipellis with plentiful caulocystidia formed of modified terminal cells of stipitipellis hyphae towards the apex.

Holotype:— INDIA. Kerala State: Malappuram District, Calicut University Campus , 13 May 2015, K. P. Deepna Latha, DKP336 ( CAL 1310 ).

Description:— Basidiomata small. Pileus 6–17 mm diam., conico-convex when young, becoming broadly convex to somewhat applanate with a subumbonate center; surface initially grayish orange (5B4/OAC791) all over, becoming light brown (5D6/OAC776) at maturity, dull, finely squamulose around the center and rather rimulose towards the margin; margin decurved to straight, mostly becoming reflexed, crenate or somewhat wavy. Lamellae emarginate, subventricose, close, initially whitish, becoming orange gray (5B2/OAC815) or grayish orange (5B3/OAC814), up to 2.5 mm deep, with lamellulae of 2–3 lengths; edges fimbriate, whitish. Stipe 9–31 × 2–4 mm, central, terete, equal or slightly tapered towards the apex, solid; surface initially whitish, becoming grayish orange (5B3/OAC814) with age, appressed-fibrillose and finely pruinose all over, densely so towards the apex; base whitish, ending abruptly. Context soft, up to 1 mm wide, orange gray (5B2/OAC815). Odor and taste not distinctive.

Basidiospores 6–12 × 5–7 (9.3±1.7 × 5.8±0.6) μm, Q = 1.2–2.2, Qm = 1.6, phaseoliform in side view, ovo-ellipsoid in top view, smooth, occasionally with a slight angular outline, thick-walled. Basidia 23–34 × 8–12 μm, clavate or narrowly clavate, occasionally septate or short-pedicellate, thin-walled, hyaline, mostly guttulate, 4-spored or rarely 2-spored; sterigmata up to 5 μm long. Pleurocystidia absent. Lamella-edge sterile or occasionally heterogeneous with copious cheilocystidia. Cheilocystidia 17–70 × 7–10 μm, versiform: clavate, cylindrical, cylindrical with a truncate or capitate apex, flexuouso-cylindric, utriform, utriform with a median constriction, vesiculose or spathulate, mostly septate, rarely branched, slightly thick-walled, hyaline, often coated with a resinous substance especially towards the apex. Lamellar trama subregular; hyphae 3–20 μm wide, thin-walled, hyaline or pale yellow. Subhymenium pseudoparenchymatous. Pileus trama subregular composed of compactly arranged, inflated hyphae; hyphae 13–26 μm wide, thin-walled, hyaline. Pileipellis a cutis often disrupted by small patches of ascending hyphae towards the center; hyphae 6–20 μm wide, thin- to slightly thick-walled, with a pale yellow wall pigment and yellowish brown, spiral encrustations. Stipitipellis a cutis often disrupted with small bunches of caulocystidia especially towards the apex; hyphae 3–9 μm wide, thin-walled, hyaline. Caulocystidia formed of modified terminal cells of hyphae of the stipitipellis, 17–70 × 7–10 μm, clavate, cylindrical, flexuous, utriform with a capitate apex, occasionally coated with a resinous substance especially towards the apex, thin- to slightly thick-walled, hyaline. Clamp connections seen on all hyphae.

Habitat:—scattered or in small groups, on soil, in Acacia groves.

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

Other material examined:— SRI LANKA. Central Province: Kandy District, Peradeniya, 15 October 1914, T. Petch, 4176 (K(M)203103, holotype of I. cutifracta ); Western Province: Colombo District, Waga forest, amongst Hevea logs, 05 November 1974, D. N. Pegler, 2173 (K(M)203101, a collection labeled as I. cutifracta ).

Comments:—The distinct status of the ITS (KX171343: 484 bp), nrLSU (KX171344: 691 bp) and RPB2 (KX171345: 645 bp) sequences of I. distincta was confirmed in BLASTn searches. No close hits with zero e-values were obtained using the ITS sequence. Inocybe species ZT9250 was the closest hit with high sequence similarity (100% for nrLSU and 99% for RPB2) in BLASTn searches with both nrLSU (EU604546; Identities = 691/691 (100 %) and RPB2 (EU600904; Identities = 645/646 (99 %)) sequences.

The phylogram inferred from a ML analysis of the combined nrLSU and RPB2 - sequence dataset ( Fig. 4 ) shows the relative placement of I. distincta . The phylogenetic tree revealed seven distinct clades with maximum (100% ML BS) support where I. distincta was nested in the Nothocybe lineage. Inocybe distincta was found to be paired with Inocybe sp. ZT9250 with full (100% ML BS) support. Additionally, a pairwise alignment of RPB2 and nLSU sequences of I. distincta and Inocybe sp. ZT9250 showed 99% and 100% sequence similarities respectively.

As the Nothocybe lineage is assumed to have affinities to I. cutifracta (Matheny 2009) , and as there are different interpretations of that species, we examined the holotype of I. cutifracta collected by Petch and another collection from Sri Lanka identified as I. cutifracta by D. N. Pegler. Our observations are as follows: microscopic observation of the holotype specimen of I. cutifracta (K(M)203103) ( Fig. 5 ) reveal that it has ellipsoid or subphaseoliform and smaller basidiospores (8–10 × 5–6 μm) lacking any angularity, a sterile lamella-edge, typically clavate cheilocystidia that are hyaline or occasionally with a pale yellowish brown plasmatic-pigmented and devoid of resinous substances, a disrupted cutis-type pileipellis and a stipitipellis devoid of caulocystidia. The collection of I. cutifracta (K(M)203101) made by Pegler ( Fig. 6 ) show features that considerably differ from the type specimen of I. cutifracta as well as from I. distincta . Inocybe distincta differs from I. cutifracta in having slightly shorter (7–9(10) × 5–6 μm), ovo-ellipsoid to subamygdaliform basidiospores devoid of any angularity and with somewhat smaller Qm (1.5) value, the presence of both clavate and utriform cheilocystidia (sometimes with a median constriction) apart from the capitate forms and a stipitipellis devoid of caulocystidia. Pegler’s collection (K(M)203101) has slightly shorter (7–9(10) × 5–6 μm), ovo-ellipsoid to subamygdaliform basidiospores with somewhat smaller Qm (1.5) value, typically capitate cheilocystidia with refractive contents and secretions, a disrupted cutis-type pileipellis with scattered tufts of semi-erect hyphae and a stipitipellis devoid of caulocystidia. Unfortunately, no DNA was extracted from the type and additional specimen of I. cutifracta following the strict restrictions placed on the loan from Kew (M) Herbarium.

Inocybe sp. ZT9250 was assumed to have association with Casuarina trees (Matheny 2009). Remarkably, I. distincta was collected from an Acacia ( Fabaceae ) grove. This indicates that either it has no association with Casuarina as was previously assumed or it has a broad host range.

Figures

FIGURE 1. A–G: Inocybe distincta (CAL 1310, holotype). A. Basidiomata; B. Basidiospores; C. Basidium; D. Cheilocystidia; E. Pileipellis; F. Stipitipellis; G. Caulocystidia. Scale bars: A=10 mm; B–D, G=10 μm; E–F=100 μm. Photos by K.P. Deepna Latha.

FIGURE 2. A–E: Inocybe distincta (CAL 1310, holotype). A. Basidiomata; B. Basidiospores; C. Basidia; D. Cheilocystidia; E. Caulocystidia. Scale bars: A=10 mm; B–E=10 μm. Drawings by K.P. Deepna Latha.

FIGURE 3. A–C: SEM images of basidiospores of I. distincta (CAL 1310, holotype). Scale bars: A = 5 μm; B–C = 1 μm. Photos by K.P. Deepna Latha.

FIGURE 4. A combined nrLSU and RPB2-sequence based phylogram generated from ML analysis showing the placement of Inocybe distincta within the Nothocybe clade. Except the Mallocybella clade, which was proposed as the genus Tubariomyces by Alvarado et al. (2010), all other clade nomenclature follows Matheny et al. (2009). Values at nodes indicate bootstrap support. BS values ≥50% are shown.

FIGURE 5. A–E: Inocybe cutifracta (K(M)203103, holotype). A. Basidiomata; B. Basidiospores; C. Cheilocystidia; D. Pileipellis. E. Stipitipellis. Scale bars: A = 10 mm; B–E = 10 μm. Photos by K.P. Deepna Latha

FIGURE 6. A–F: Inocybe cutifracta (K(M)203101). A. Basidiomata; B. Basidiospores; C. Basidium; D. Cheilocystidia; E. Pileipellis. F. Stipitipellis. Scale bars: A = 10 mm; B–F = 10 μm. Photos by K.P. Deepna Latha.