Leucoagaricus croceus S.M. Tang & K.D. Hyde, sp. nov.

MycoBank number: MB 557764; Index Fungorum number: IF 557764; Faceoffungi number: FoF 08469;

Etymology – the epithet ‘croceus’ refers to the reddish-orange on the pileus.

Holotype – MFLU19-1331

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 30–51 mm long × 3–5 mm diam., cream (1A2) to white (1A1); context white (1A1), unchanging, clavate; basal 8-12 mm diam., shaped to subglobose, thickening toward base. Annulus simple, located at the middle to upper part of the stipe, white (1A1), membranous.

Basidia 15–22 × 9–11 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, colorless, thin-walled, smooth. Lamellar edge appearing as a sterile strip, composed of subglobose to ellipsoid cells (15–18 × 7–9 μm) thin-walled, colorless. 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 Fha Luang University, 3 June 2019, Song-Ming Tang, TSM20190701 (MFLU19-1331, holotype).

Genbank numbers – ITS:OL413492; LSU: MT515802; rpb2: MT518174

Notes – In our multi-locus (ITS, LSU, rpb2) phylogenetic analysis (Fig. 55), La. croceus is related to La. asiaticus. However, Leucoagaricus 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 a cream to pale ochre basidiomata and has a cylindrical to fusiform cheilocystidia (Vellinga 2000). Leucoagaricus sultanii has yellowish pink to dark yellowish pink pileus, has a relatively bigger basida 21–27 × 7–10 μm (Hussain et al. 2018). Leucoagaricus is also similar to La. croceus in their red basidiomata. However, La. badius has a clavate to fusiform cheilocysitidia, and has narrower basidia (6–8 μm; Hussain et al. 2018). Based on both morphological and molecular phylogey we introduce Leucoagaricus croceus as a novel species.

Leucoagaricus croceus (MFLU19-1331, holotype) a-c. basidiomata; d. basidiospores.