Micropsalliota gracilis Heinem., Bull. Jard. Bot. natn. Belg. 50(1–2): 60 (1980)

Index Fungorum number: IF 113559; MycoBank number: MB 113559; Facesoffungi number: FoF 09761; Figs. 1, 2

Pileus 10–30 mm, first conical, expanding to umbonate, applanate when mature, completely covered with crowded fibrillose when young, brownish red to violet brown (10 D6-8 to (10E6-8), with paler colour when mature, fibrillose, sometimes striate, with white background, margin appendiculate, with white and short velar remnants, fragile when mature. Lamellae free, white when young, becoming orange grey to greyish orange (6B2-3) when mature, ventricose 4–6 mm wide, moderately crowded, with eroded lamella-edge. Stipe 25–60×2–4 mm, cylindrical, wider at base (5–7 mm wide); surface covered with white fibrillose, on white background, turning orange-white (5A2) when touched. Annulus superior, persistent, white. Context in pileus white and thin, in stipe white and hollow, turning orange white (5A2) in both stipe and pileus when touched. Taste and oduor not observed. Spore pint orange grey (6B2). Basidiospores 5–6.5 × 3–4.5 µm, avl × avw =6 × 3.5 µm, Q =1.5–2, Qav=1.6, in side-view amygdaliform to ellipsoid, in frontal view ellipsoid to oblong, slightly thick-walled, hyaline to pale brown. Basidia 13–17 × 6–8 µm, clavate, hyaline and thin-walled, 4-spored. Cheilocystidia 25–50 × 7–12 µm, various in shape, versiform, narrowly utriform, narrowly lageniform, lecythiform, with a long neck and capitulum at apex. Pleurocystidia absent. Pileus covering a cutis composed of cylindrical to oblong to fusiform elements, up to 25 µm, with brownish red parietal and intracellular pigment. Clamp connections absent.

Material examined – LAOS, Vientiane Capital, Xaythany District, Houay Yang Preserve Forest, 17 November 2015, P. Sysouphanthong, PS205 (HNL503432); Chiang Rai Province, Muang District, Campus of Mae Fah Luang University, 08 Jun 2019, P. Sysouphanthong, PS2019-45 (MFLU 19-2358); ibidem, 17 November 2015, P. Sysouphanthong, PS209 (HNL503436, new record).

GenBank numbers – ITS=MW192914, MW192915.

Notes – Two specimens of saprotrophic Micropsalliota gracilis were found on rich humus soil of deciduous forest growing in solitary or in large groups from central Laos. This species has tiny basidiomata with brownish red to violet brown fibrillose pileus (Figs. 1 and 2). The taxonomic details have been well discussed by Zhao et al. (2010). Lao specimens are similar to Thai specimens based on morphology and nrITS sequence analysis (Fig. 3) indicating that they are conspecific. This is the first record of Micropsalliota gracilis in Laos.

Figure 1 – Micropsalliota gracilis (HNL503436, new record). a–c Basidiomata

Figure 2 – Microcharacters of Micropsalliota grcilis (HNL503436). a Basidiospores. b Cheilocystidia. c Element cells at pileus covering. Scale bars: a=5 µm, b=10 µm, c=20 µm

Figure 3 – Maximum likelihood phylogenetic tree of Micropsalliota based on nrITS sequences. The maximum likelihood (ML) analysis was performed in RAxML 7.2.6 (Stamatakis et al. 2008) and maximum parsimony (MP) analysis was performed the program PAUP* 4.0 b10 (Swofford 2004). Bootstrap values of ML/MP equal to or greater than 70% are given above branches. GenBank accession number is indicated after species name. Leucoagaricus meleagris (MT252565) is an outgroup. Newly sequences generated from Laos are in blue