Calocybella swetha K. N. A. Raj & Manim., 2016

Deepna Latha, K. P., Anil Raj, K. N., Cherolil, Thushara, Sharafudheen, Shahina A. & Manimohan, Patinjareveettil, 2016, Three new species of Calocybella from India based on morphology and molecular phylogeny, Phytotaxa 255 (2), pp. 133-143 : 139-140

Calocybella swetha K. N. A. Raj & Manim. , sp. nov. Figs. 1F–G ; 4A–G

MycoBank MB 815578

Etymology:— swetha (Sanskrit) , whitish; refers to the overall whitish color of the basidiomata of this species.

Diagnosis:—Differing from Calocybella pudica in having whitish, slenderly tricholomatoid basidiomata not discoloring on bruising, a velutinous pileus, smooth basidiospores, a trichoderm-type pileipellis and a distinctive ITS sequence (KU366467).

Holotype:— INDIA. Kerala State: Malappuram District, Calicut University Campus , 21 May 2015, K. N. Anil Raj, AR1000 ( CAL 1290 ).

Description:— Basidiomata small, slenderly tricholomatoid. Pileus 17–26 mm diam., somewhat hemispheric, with or without a slightly raised center when very young, becoming broadly conico-convex or convex with a small low, broad central umbo at mature stages; surface chalk white or off-white all over, not hygrophanous, not striate, rather velutinous all over, somewhat tacky when wet; margin inrolled or incurved, initially entire, becoming somewhat crenate or somewhat fluted and rarely somewhat lobate at maturity. Lamellae sinuate or emarginate with a small decurrent tooth, moderately crowded, initially off-white, becoming yellowish white (4A2/OAC857), up to 3 mm wide, with lamellulae of 3 lengths; edge entire, concolorous with the sides. Stipe 21–30 × 2–4 mm, central, terete or slightly compressed, occasionally with a slight longitudinal groove, equal or slightly tapering towards the base, solid when young, becoming stuffed at maturity; surface chalk white all over, finely appressed-fibrillose and scarcely pruinose all over; base with thick, white basal mycelium. Context soft, up to 3 mm thick at the center of the pileus, off-white. Odor and taste not distinctive.

Basidiospores 4–6 × 3–4 (5.05±0.98 × 3.37±0.48) μm, Q = 1–2, Qm = 1.52, ellipsoid to broadly ellipsoid or somewhat ovoid, smooth, thin- to slightly thick-walled, inamyloid. Basidia 23–32 × 5–7 μm, clavate, hyaline, thin-walled, siderophilous, 4-spored; sterigmata up to 2 μm long. Crassobasidia occasional. Lamella-edge fertile. Pleuro- and cheilocystidia absent. Lamellar trama subregular; hyphae 2–8 μm wide, thin-walled, hyaline, not discoloring in KOH, inamyloid. Subhymenium poorly developed. Pileus trama subregular; hyphae 2–4 μm wide, thick-walled, hyaline, not discoloring in KOH, inamyloid. Pileipellis a trichoderm; hyphae 2–5 μm, thin- to slightly thick-walled, hyaline; terminal elements 57–94 × 1.5–2 μm, narrow, flexuous, faintly gelatinized, hyaline, thin-walled. Stipitipellis a cutis often disrupted by flaring-out hyphae; hyphae 1.5–4 μm wide, thin-walled, hyaline; terminal elements 47–80 × 2–2 μm, narrow, flexuous, hyaline, thin-walled, inamyloid. Caulocystidia absent. Clamp connections present on all hyphae.

Habitat:— scattered or in small groups, on the ground, among grass or leaf litter.

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

Additional specimens examined:— INDIA. Kerala State: Malappuram District, Calicut University Campus, 18 June 2015, K. N. Anil Raj, AR1001 (CAL 1291).

Comments:— Calocybella swetha resembles C. pudica in having an umbonate pileus, siderophilous basidia, somewhat similar-sized, inamyloid basidiospores, a hymenium devoid of both cheilo- and pleurocystidia and clamped hyphae. However, C. pudica differs in having a dry, smooth, orange to brownish-orange pileus, a solid, yellowish, fibrillose-striate stipe, a context reddening on bruising, differently shaped, verrucose basidiospores, both 2- and 4- spored basidia, and a cutis-type pileipellis ( Vizzini et al. 2015). Calocybella lohitha differs from C. swetha in having reddish, collybioid basidiomata, verrucose basidiospores, hyphae of pileus trama with pale reddish brown to maroon plasmatic pigment and a cutis-type pileipellis. A pair wise sequence alignment of the ITS sequences of both C. swetha (KU366467) and C. lohitha (KU366465) showed only 87% sequence similarity. Calocybella babruka differs from C. swetha in having a brown pileus, verrucose basidiospores, a yellowish brown pileus trama, a cutis-type pileipellis with yellowish brown wall pigment and a cutis-type stipitipellis coated with a resinous material. Additionally, a pair wise sequence comparison using ITS sequences of both C. swetha (KU366467) and C. babruka (KU366466) showed only 87% sequence similarity.

Comparison of sequence data generated from C. swetha with the nucleotide sequences of taxa available in GenBank indicates that C. swetha has distinct ITS (KU366467: 717 bp) and nrLSU (KU366468: 799 bp) sequences. BLASTn searches using the ITS and the nrLSU sequences of C. swetha showed Calocybella pudica (KP858003 (87% identity; e-value: 4e-101) and KP858007 (95% identity; e-value: 0)) as the closest hit in both cases.

Figures

FIGURE 1. A–F: Basidiomata of the three new species of Calocybella. A–C. C. lohitha. D–E. C. babruka. F–G. C. swetha. Scale bars: A–G = 10 mm. Photos: A–E. By K.P.D. Latha; F–G. By K.N.A. Raj.

FIGURE 4. A–G: Calocybella swetha (CAL 1290, holotype). A. Basidiospores; B. Basidiospore under SEM; C. Crassobasidium; D. Siderophilous basidium; E. Hyphal septum showing clamp connection; F. Pileipellis. G. Stipitipellis.Scale bars: A, C–G = 10 μm; B = 1 μm.