Gerronema flavum Wannathes, N. Suwannarach, J. Kumla, Phonrob & S. Lumyong, sp.nov.
Index Fungorum number: IF 840184; MycoBank number: MB 840184; Facesoffungi number: FoF 10686; Figs. 1c, 2
Etymology – ‘flavum’ = yellow, refers to the colour of basidiomata.
Holotype – BKF10253
Pileus 4–11 mm diam., convex, umbonate when young and plano-convex with depress in center to infundibuliform in age, glabrous, radially fibrillose when young, translucent striate to striate at marging in age, dull, light yellow (4A5) overall when young, sunflower yellow (4A7) overall in age, hygrophanous, become yellowish white. Lamellar decurrent, subdistant (14–16) with 2–3 series of lamellulae, narrow, yellowish withe (4A2), non-marginate; Stipe 4–19×1–2 mm, tapering upward when young, cylindrical in age, elastic, hollow, central, flexuose, pubescent, yellowish withe (4A2) overall. Context thin, Odor and taste not distinctive.
Basidiospore 7–8(–9) × 4 – 5 (–6) μm [x=7.68±0.63×4.68±0.56, Q=1.3–2.25, q=1.66±0.23, n=25, s=1] broadly ellipsoid, smooth, hyaline, inamyloid, thin-walled. Basidia 25–32×6–9 μm, clavate, with 4 sterigmata, thin-walled, inamyloid. Cheilocystidia abundant, 25–40 × 5–8 µm, knobby cylindrical to clavate, irregular in shape, hyaline, inamyloid, thin-walled. Pleurocystidia abundant, 24–33×9–11 µm, clavate to cylindrical, sometime knobbed, hyaline, inamyloid, thin-walled. Lamellar trama interwoven, hyphae 3–6 µm diam., cylindrical, smooth, hyaline, inamyloid, thin-walled. Pileipellis composed with cutis
of repent hyphae, radially arrangement, 4–15 µm, cylindrical, non-incrustation, hyaline in KOH, inamyloid, thin-walled, true pileocystidia absent. Pileus trama sarcodimitic, interwoven, composed of 2 type of hyphae: a) sarco-hyphae, elongate fusoid cell 50–60×10–14 µm, hyaline, smooth, inamyloid, thin-walled; b) generative hyphae 3–11 µm wide, cylindrical, branched, hyaline, smooth, inamyloid, thin-walled. Stipitipellis cutis, hyphae 3–10 µm diam., parallel, cylindrical, hyaline to pale yellow in KOH, smooth, inamyloid, thin-walled. Stipe trama sarcodimitic, parallel, composed 2 type of hyphae: a) sarco-hyphae, elongate fusoid cell 87–165×4–15 µm, hyaline, smooth, inamyloid, thick-walled (1–4 µm); b) generative hyphae 3–12 µm wide, cylindrical, branched, hyaline, smooth, inamyloid, thin-walled. Caulocystidia abundant, 28–47×7–9 µm, cylindrical to clavate, irregular in shape, flexuose, hyaline KOH, inamyloid, thin-walled. Clamp connections present in all tissues.
Habit, habitat and known distribution – Gregarious on decayed wood, known only from Thailand.
Material examined – Thailand, Nakhon Ratchasima Provinve, Khao Yai National Park, trial to Pha Kluai Mai waterfall, 21 Sep 2018, collector N Wannathes, N Suwannarach J Kumla, S Lumyong, BKF10253 (holotype).
GenBank numbers – BKF10253- MZ1452142 (ITS), MZ452170 (LSU).
Notes – Gerronema flavum is characterized by a small omphaliod basidiomata that appears convex with depressed center infundibuliform, radially fibrillose, glabrous, yellow pileus, decurrent, subdistant lamellae, cylindrical, central, yellowish white stipe, broadly ellipsoid basidiospores with mean dimensions of 7.7×4.7 µm. The pileipellis is composed of hyaline with non-incrusted hyphae, the presence of irregular cylindrical cheilo-, pleuro- and cualocystidia, and sarcodimitic trama tissue. Gerronema kuruvense K.P.D. Latha & Manim and G. subchrysophyllum (Murrill) Singer are morphologically similar to a new species, namely Gerronema kuruvense, which was originally described from tropical India. It is distinguished by forming orange yellow pileus, bigger basidiospores with mean dimensions of 9.5×5.9 µm., an absence of cheilo- and pleurocystidia and the presence of diverticulate caulocystidia (Latha et al. 2018). Gerronema subchrysophyllum, a North American species, differs by having a larger basidiomata of nearly double the size (pilei 4–21 mm wide and stipe 4–32 mm long), simple clavate cheilocystidia and a lack a pleurocystidia (Singer 1970). The phylogenetic analyses inferred from combined sequences (Fig. 3) confirmed that G. flavum is a distinct species. This was further confirmed via an examination of other related morphological species and other taxa within 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 flavum (BKF10253, holotype). a Basidiomata, b Basidiospores, c Basidium, d Pleurocystidia, e Cheilocystidia, f Caulocystidia, g Pileipellis cell. Scale bars: a=20 mm, b–f=10 μm, g=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