Gerronema atrovirens Wannathes, N. Suwannarach, J. Kumla, Phonrob & S. Lumyong, sp.nov.
Index Fungorum number: IF 840183; MycoBank number: MB 840183; Facesoffungi number: FoF 10685, Figs. 1a, 2
Etymology – ‘atro’=dark; ‘virens’=green, refers to the dark green colour of basidiomata.
Holotype – BKF10264
Pileus 21–51 mm diam., convex with depress center when young and deeply infundibuliform in age, elastic, glabrous, translucent-striate to striate at margin, dull green (27E3) at center, dark green (27F3) at margin, grey (5E1) to brownish grey (5E2) in old specimen; Lamellar decurrent, subdistant to close (24–28) with 1–2 series of lamellulae, narrow (up to 1.5 mm), withe (27A1), non-marginate; Stipe 14–36×2.5–4.0 mm, cylindrical, slightly broadened at base, usually flatten, flexuose, hollow, elastic, central, pubescent, greenish grey (27F2) at apex fading paler to brownish grey (5C2) at base, basal mycelium. Context thin, elastic. Odor and taste not distinctive.
Basidiospore 7–8×4–5 µm [x=7.56±0.51×4.36±0.49, Q=1.4–2.0, q=1.75±0.21, n=25, s=3] ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia 21–27×6–7 μm, clavate, with 4 sterigmata, sometime with 2 sterigmata, thin-walled, inamyloid. Cheilocystidia abundant, 21–51×5–11 µm, cylindrical with 1–2 slight constrictions, flexuose, irregular in shape, sometimes 2-celled, hyaline, inamyloid, thin-walled. Pleurocystidia absent. Lamellar trama subregular to interwoven, arranged in two directions, hyphae 4–8 µm diam., cylindrical, smooth, hyaline, inamyloid, thin-walled, gelatinous. Pileipellis composed with cutis of repent hyphae, radially arrangement, 3–10 µm, cylindrical, incrusted, greyish green in KOH, inamyloid, thin-walled, true pileocystidia absent. Pileus trama sarcodimitic, subregular, composed of 2 type of hyphae: a) sarco-hyphae, elongate fusoid cell 162–195×5–15 µm, hyaline, smooth, inamyloid, thick-walled (up to 1 µm); b) generative hyphae 2–6 µm wide, cylindrical, branched, hyaline, smooth, inamyloid, thin-walled. Stipitipellis cutis, hyphae 3–8 µm diam., parallel, cylindrical, greenish brown in KOH, smooth, inamyloid, thin-walled. Stipe trama sarcodimitic, subparallel, composed 2 type of hyphae: a) sarco-hyphae, elongate fusoid cell 125–200×3–25 µm, hyaline, smooth, inamyloid, thickwalled (up to 1 µm); b) generative hyphae 2–13 µm wide, cylindrical, branched, hyaline, smooth, inamyloid, thinwalled. Caulocystidia abundant, 19–34×5–9 µm, cylindrical with 1–2 constrictions, flexuose, irregular in shape, hyaline to pale green in KOH, inamyloid, thin-walled. Clamp connections present in all tissues.
Habit, habitat and known distribution – Gregarious on decayed bamboo wood, known only from Thailand. Material examined: Thailand, Sukhothai Provinve, Si Satchanalai National Park, Natural trail, 22 Aug 2020, collector N Wannathes N Suwannarach and J Kumla, BKF10264 (holotype).
Additional material examined – Thailand, Sukhothai Province, Si Satchanalai National Park, Natural trail, 23 Aug 2020, collector N Wannathes N Suwannarach and J Kumla, BKF10265, NW1372 (isotype).
GenBank numbers – BKF10264- MZ452088(ITS), MZ452671(LSU). BKF10265- MZ452668(ITS), MZ452672 (LSU)
Notes – Gerronema atrovirens is characterized by a medium size of omphaliod, elastic basidiomata, convex with depress center to deeply infundibuliform, translucent striate at margin, dull green pileus, decurrent, subdistant lamellae, cylindrical, central, greenish grey stipe, ellipsoid basidiospores with mean 7.6×4.4 µm, pileipellis composed of incrusted hyphae with greyish green colour, present of irregular cylindrical cheilocystidia and cualocystidia, sarcodimitic trama tissue, and grow on decayed bamboo wood. A new species is morphologically similar to G. cyathiforme (Berk. & M.A. Curtis) Singer, species originally described from a Neotropic, differs in forming a distinct radial stripes pileus, absent of cystidia, and mahogany red (in KOH) lamellar trama (Singer 1970). Gerronema atrovirens is also closely related G. indigoticum T. Bau & L.N. Liu, a green–blue species from subtropical China. The latter species differs in forming smaller pilei (9–16 mm wide) with green–blue, shorter (20–27 × 8–12 µm), simple clavate cheilocystidia, and simple clavate cualocystidia (Lui et al. 2019), and the phylogenetic analyses inferred from combined sequences (Fig. 3) confirmed that G. atrovirens is closely allied with G. indigoticum and it distinct species
from related morphological species and other taxa in this genus.
Figure 1 – Basidiomata and habit. a Gerronema atrovirens (holotype: BKF10264), b G. kuruvense (BKF10266), c G. flavum (holotype: BKF10253), Scale bars=10 mm. Photographs by N. Wannathes
Figure 2 – Gerronema atrovirens (BKF10264, holotype). a Basidiomata, b Basidiospores, c basidium, d Cheilocystidia, e Caulocystidia f Pileipellis cell. Scale bars: a=20 mm, b–e=10 μm, f=20 μm. Drawing by W. Phonrob
Figure 3 – Phylogenetic tree derived from maximum likelihood analysis of a combined ITS and LSU genes of 21 sequences and the aligned dataset was comprised of 1700 characters including gap. The average standard deviation of the split frequencies of the BI analysis was 0.00612. Togia infundibuliformis KUN HKAS56709 and T. venenata KUN HKAS56679 were used as outgroup. Numbers above branches are the bootstrap statistics percentages (left) and Bayesian posterior probabilities (right). Branches with support values≥70%/0.90 are shown at each branch and the bar represents 0.1 substitutions per nucleotide position. Hyphen (-) represents support values≤70%/0.95. Ex-type strains are in black bold. The newly generated sequences are indicated in blue and bold type species