Leucocoprinus cretaceus (Bull.) Locq., Bull. mens. Soc. linn. Soc. Bot. Lyon 14: 93 (1945).

Index Fungorum number: IF 287726; Mycobank number: MB 284426; Facesoffungi number: FoF 3137; Fig. 1

Pileus 30–90 mm in diameter, at first ovoid then convex to broadly conical, umbonate in maturity, white (1A1), covered by easily removed, granular floccose, white (1A1) to yellowish white (1A2) squamules, conical to pyramidal on the umbo; margin entire, sulcate. Lamellae distantly free, rather broad, thin; white, edge slightly fimbriate, white (1A1). Stipe 50–80×4 mm, broad at apex, gradually enlarged downward to a broadly clavate to somewhat fusiform 6–14 mm broad base; sometimes coarsely farinose to slightly flocculosefarinose below annulus, subfarinose above; white (1A1) to yellowish white (1A2). Annulus white, very soft, rather flaring, median to superior. Spore print white.

Basidiospores 7–11×5–8 μm, Q =1.31–1.47 (n=50), dextrinoid, ellipsoid to amygdaliform, thick-walled, with
an apical germ pore covered with a hyaline lens. Basidia 16–24×8–12 μm, pyriform to clavate with a bulbous base, hyaline, thin-walled, bearing four sterigmata, 1.0–3.0 μm long, surrounded by 4 pseudoparaphyses. Pseudoparaphyses 10–13×7–10 μm, sphaeropedunculate to broadly clavate to pyriform, very broad point of attachment. Pleurocystidia absent. Cheilocystidia 25–65 × 6.5–18 μm, thin-walled, hyaline, subcylindrical to narrowly fusiform to slightly narrowly lageniform, mucronate, rarely obtuse, moderately pedicellate. Pileipellis made up of hyaline hyphae with smooth walls and cylindric terminal elements with excrescences, branched in different shapes (H, T and Y), 24–45×7.5–15 μm. Stipitipellis a cutis of narrowly cylindrical, 2–7 μm broad hyphae. Clamp connections absent.

Habit and distribution – Solitary to gregarious, on decomposed wood. Known from Argentina, Brazil, Europe, North America, Sri Lanka and Thailand (Candusso and Lanzoni 1990; Birkebak 2010; Ferreira and Cortez 2012; Niveiro et al. 2012; Tipbromma 2017; this study).

Material examined – Thailand, Chiang Mai Province, Muang District, Chiang Mai University, 18°48′14″N 98°57′14″E, elevation 331 m, solitary to gregarious on decomposed wood, 27 July 2019, J. Kumla and N. Suwannarach, SDBR-CMUNK0559 (new record for Thailand); Sukhothai Province, Si Satchanalai National Park, Natural trail; 17°55′12″N 99°48′44″E, elevation 277 m, solitary to gregarious on decomposed wood, 23 August 2020, N. Wannathes, J. Kumla, N. Suwannarch and S. Khuna, SDBR-CMUNW1461 (new record for Thailand).

GenBank numbers – SDBR- CMUNK0559 : ITS=OP503474; SDBR-CMUNW1461: ITS=OP503476.

Notes – Leucocoprinus cretaceus is easily recognized by its fleshy white basidiomes covered by floccose squamules that are easily removed when touched and by a fusoid stipe inflated toward the base. Phylogenetic analysis indicated that L. cretaceus forms monophyletic clade and clearly separated from other species of Leucocoprinus (Fig. 2). Morphologically, this species is related to L. squamulosus and L. cepistipes. Leucocoprinus cretaceus differs from L. squamulosus by its which lacks an annulus and an inflated stipe base (Dennis 1952; Wartchow et al. 2008). Leucocoprinus cepistipes separate from L. cretaceus based on the ochraceus to pale brown squamules covering the pileus surface (Candusso and Lanzoni 1990; Wartchow et al. 2008; Rother and Silveira 2009).

Figure 1 – Leucocoprinus cretaceus (SDBR-CMUNK0559). a Basidiomes. b Basidiospores. c Basidia. d Cheilocystidia. Scale bars: a=50 mm, b‒d=10 μm

Figure 2 – Phylogenetic tree derived from maximum likelihood analysis of ITS gene of 19 sequences and the aligned dataset was comprised of 787 characters including gap. The average standard deviation of the split frequencies of the BI analysis was 0.00563. A best scoring RAxML tree was established with a final ML optimization likelihood value of -3057.9735. The matrix had 296 distinct alignment patterns with 13.97% undetermined characters or gaps. Estimated base frequencies were found to be: A=0.2280, C=0.2242, G=0.2429, T=0.3047; substitution rates AC=0.4870, AG=4.0084, AT=1.4356, CG=0.2018, CT=3.7781, GT=1.0000. Leucoagaricus laoensis HNL501802 and Leucoagaricus umbonatus LAHSHL1 were used as outgroup. Numbers above branches are the bootstrap statistics percentages (left) and Bayesian posterior probabilities (right). Branches with bootstrap values≥70% and PP≥0.90 are shown at each branch. The bar represents 0.1 substitutions per nucleotide position. Type strains are in bold. The newly generated sequences are indicated in blue