Pluteus hongoi Singer (1989: 95)

Reschke, Kai, Lotz-Winter, Hermine, Fischer, Christian W., Hofmann, Tina A. & Piepenbring, Meike, 2021, New and interesting species of Agaricomycetes from Panama, Phytotaxa 529 (1), pp. 1-26 : 19

Pluteus hongoi Singer (1989: 95) , Fig. 14g

Description: —Basidiocarps pluteoid. Pileus 5.5–6.0 cm diam., convex to almost plane, with a low, broad umbo, and a straight and even margin, surface smooth, innately fibrillose, slightly viscid when moist, yellowish brown to light brown (5 E45, 6 D5), centre darker, whitish to somewhat translucent at the margin. Lamellae free, ventricose, crowded, initially white, later pink. Stipe 7.0–7.5 × 0.6–0.8 cm, subcylindrical, somewhat broadening towards the base, greyish white, sometimes with yellow tints, somewhat to distinctly fibrillose-flocculose. Smell raphanoid, taste not tested.

Basidiospores 5.5–6.9–8.0 × 4.5–5.2–6.5 µm, Q = 1.10–1.33–1.65 (n = 30 spores of 1 specimen), ellipsoid to broadly ellipsoid, smooth, hyaline, thin-walled. Basidia 17.5–36 × 5.0–11.0 µm, clavate, hyaline, 4-spored. Lamellar edge sterile. Cheilocystidia 55–76 × 16–21 µm, narrowly clavate, sometimes slightly constricted, hyaline, thinwalled. Pleurocystidia abundant, 69–85 × 19–27 µm, metuloid, narrowly utriform, with 2–4 apical, predominantly bifid, sometimes entire hooks. Pileipellis partly a cutis or an ixocutis with cylindrical or tapering terminal elements, with brown, intracellular pigment. Stipe surface composed of cylindrical hyphae, sometimes with brown, intracellular pigment. Clamp connections absent.

Habitat: —Basidiocarps solitary or in a group of two basidiocarps on dead angiosperm wood in montane Quercus - dominated forests in Chiriquí Province, Panama.

Notes: — Pluteus hongoi was described by Singer (1989) from Japan, a more recent revision, supported by DNA sequences, is provided by Justo et al. (2014). Pluteus hongoi has a wide, Holarctic distribution in warm temperate to transitional boreal/temperate forests. The southernmost known occurrences are from Louisiana and Florida, USA ( Justo et al. 2014). The specimens from Panama distinctly extend the known distribution area southwards. The ITS sequence of the specimen PAN413 from Panama has a p-distance of 1.8% compared to the sequence of the holotype of P. hongoi (Acc. KJ009564 ). However, only three differences between these sequences are at sites without ambiguities or other quality problems. Morphologically, the specimens from Panama fit well into the concept of P. hongoi , especially by their bifid pleurocystidia, the most remarkable characteristic of this species.

Specimens examined: — PANAMA. Chiriquí Province: near Cerro Punta, Entre Rios, Montaña Azul, montane forest, 2330 m a.s.l., N 08°53’49’’ W 82°35’03.2’’, 28 July 2015, H. Lotz-Winter, S. Cáceres, J. de León, J. Rodríguez PAN413 (M-0312085)!; near Volcán, Paso Ancho, montane forest with abundant Quercus spp. and Comarostaphylis arbutoides, 2020 m a.s.l., N 08°48’55.4’’ W 82°34’41.7’’, 03 June 2017, K. Reschke, J. Rodríguez KaiR372 (M-0312084)!.