Crepidotus chiangraiensis

Crepidotus chiangraiensis Phonemany, thongkl. & Sysouph

Faces of fungi number: FoF 15096, MycoBank: MB 850908.

Basidiomata pleurotoid, small. Pileus 35–45 × 20–40 mm; orbicular, rounded flabelliform, with an involute margin when young and becoming straight when mature; white, becoming yellowish white (4A2) to pale yellow (4A3); densely velutinous with white hairs longer near the attachment zone, not hygrophanous, covered with white woolly hyphae at the attachment zone; margin wavy, split when mature. Lamellae 1 mm wide, adnexed, white when young, then pale yellow (4A3) to yellowish white (4A2) near the point of attachment, with dark brown spots on the surface of the lamellae, becoming brown (6D6) when fully mature, with 4 tiers of lamellulae, with smooth edge, moderately crowded. Stipe 1 mm wide, present in primordial stages, equal, white, rudimentary when mature, knob-liked. Context very thin, white. Odour mild. Taste not observed. Spore print brown (6D6).

Basidiospores [150/3/2] (6.1–)6.6–8.1–9.6(–9.6) × (4.8–)5.3–6.2–7.5(–7.7) µm, Q = (1.08–)1.13–1.3–1.59(–1.85), subglobose to obovoid, buff yellow to light orange-yellow in KOH and water, smooth, thick-walled. Basidia (14.1–)14.2–16–18.4(–18.4) × (5.2–)5.2–6.5–7.4(–7.4) µm, clavate to subcylindrical, 4-spored, hyaline, smooth, thin-walled. Cheilocystidia (22.5–)22.5–36.4–61.3(–61.3) × (6.2–)6.2–11.8–25(–25) µm, various in shape, narrowly utriform to utriform, fusiform, lecythiform to sublecythiform, with subcapitate at apex, hyaline, smooth, thin-walled. Pleurocystidia absent. Hymenophoral trama regular, hyphae 2–5 µm wide. Pileipellis is a trichoderm composed of parallel hyphae 2–5 µm wide, branched, hyaline, with cylindrical terminal elements 45.6–90.54 × 5.15–7.08 µm. Oleiferous hyphae present in hymenophoral trama. Clamp connections present in all observed tissues.

Habitat and distribution: — Saprobic on dead branch, scattered, or gregarious with at least 10 basidiomata.

Additional specimens examined: — THAILAND. Chiang Rai Province, Mae Fah Luang District, Tambol Mae Sa long nork, Khlang moo 6 village, 14 June 2019, Monthien Phonemany (MFLU23-0439).

Notes: — Crepidotus chiangraiensis has the main characteristic of having small orbicular basidiomata, densely velutinous with white hairs longer near the point of attachment, not striate with wavy and split with age, smooth globose basidiospore. According to morphology related species include C. epibryus (Fr.) Quél., C. martini Singer, C. palodensis C.K. Pradeep & A.M. Kumar, C. variabilis (Pers.) P. Kumm. However, the species different from C. chiangraiensis are the following: Crepidotus epibryus was described as Agaricus epibryus Fr. differs by having smaller basidiomata (2–3 mm), wrinkled verruculose basidiospores and lack of clamp connections(Quélet 1888). Crepidotus martini described from Panama differs by having smaller (2–9 mm), punctate basidiospores, cylindric to ventricose cheilocystidia, and a pileipellis as an epicutis (Singer 1955). Crepidotus palodensis described from India differs by having broadly elongate to cylindrical, finely verrucose basidiospores, cheilocystidia that present clavate to cylindro-clavate with irregular excrescences(Kumar et al. 2018). Crepidotus variabilis described from Norway differs by having verrucose, cylindric to elliptic basidiospores, and a pileipellis as a cutis (Nordstein 1990).

According to the phylogenic tree, C. chiangraiensis was related to C. praecipuus (PDD:72624) with high support (Figure 1). However, the morphology comparison of both species was different, C. praecipuus has tomentose-scaly and yellowish basidiomata, yellowish-brown to brown fibrillose scales, and ellipsoid basidiospores (Kim et al. 2021). Another related was C. martini (MCA640), and the morphology comparison found that both species were different, C. martini has brownish-white and convex pileus, smaller cheilocystidia (19–30 × 7.8–13.5 µm) (Singer 1955).