Leucoagaricus croceus S.M. Tang & K.D. Hyde
Pileus 30–60 mm in diam., subumbonate or plano-concave with obtuse umbo, reddish-orange (7A6-8) at center, becoming white (7A1) to pastel red (7A4) towards margin; volval remnants on pileus floccose to pulverulent when basidiomata young, smooth with age; trama white, unchanging. Stipe 30–50 × 3–5 mm, cream (1A2) to white (1A1); context white (1A1), unchanging, clavate; basal 8–12 mm diam., subglobose, thickening toward base. Annulus simple, located at the middle to upper part of the stipe, white (1A1), membranous. Basidia 15–20 × 9–10 μm clavate, 4-spored. Basidiospores (3.5–)4.1–7.2(–7.9) × (2.4–)2.6–4.4(–4.6) μm, Q = (1.00–)1.14 × 2.00 (–2.39) μm, N = 114, Qm = 1.59±0.25, ovoid to ellipsoid, colourless, thin-walled, smooth. Lamellar edge appearing as a sterile strip, composed of subglobose to ellipsoid cells (15–18 × 7–9 μm) thin-walled, colourless. Pleurocystidia and Cheilocystidia are absent. Lamellar trama 15–25 μm wide composed of abundant elongate cells. Pileipellis 60–80 μm thick, composed of parallelly, thin-walled, cylindrical, light brown to reddish-brown filamentous hyphae 6–8 μm thick. Clamp connections absent.
Material examined: THAILAND, Chiang Rai, Mae Fah Luang University, 3 June 2019, S.M. Tang (MFLU19-1331, holotype).
Notes: In our multi-locus (ITS, LSU, rpb2) phylogenetic analysis, Leucoagaricus croceus developed a clade to L. asiaticus. However, L. asiaticus has a dark brown to reddish-brown pileus and has relatively larger basidiospores 8–10 × 6–7 μm (Ge et al. 2015). Leucoagaricus crystallifer has basidiomata cream to pale ochre and cheilocystidia cylindrical to fusiform (Vellinga 2000). Leucoagaricus sultanii has yellowish-pink to dark yellowish-pink pileus and relatively wide basidia 21–27 × 7–10 μm (Hussain et al. 2018). Leucoagaricus croceus is also similar to L. croceus in their red basidiomata. However, L. badius has a clavate to fusiform cheilocysitidia, and has narrower basidia (6–8 μm; Hussain et al. 2018). Based on both morphological and molecular phylogeny we introduce Leucoagaricus croceus as a novel species.