Xanthagaricus thailandensis J. Kumla, N. Suwannarach & S. Lumyong, 2018

Kumla, Jaturong, Suwannarach, Nakarin, Sri-Ngernyuang, Kriangsak & Lumyong, Saisamorn, 2018, Xanthagaricus thailandensis sp. nov. (Agaricales, Basidiomycota), from northern Thailand, Phytotaxa 348 (2), pp. 109-117 : 111-114

Xanthagaricus thailandensis J. Kumla, N. Suwannarach & S. Lumyong sp. nov. Figure 2

MycoBank: 823445

Diagnosis:—Distinguished from most other Xanthagaricus species by the presence of caulocystidia, and from X. neocopinatus and X. ochraceoluteus by its narrower caulocystidia and larger spores.

Etymology:— thailandensis refers to Thailand, where the holotype of the new species was found.

Holotype:— THAILAND, Lampang Province, Mae Moh District , (18°40'52"N 98°52'11"E), on ground in a tropical deciduous forest, May, 2015, J. Kumla & N. Suwannarach, SDBR-CMUJK 010, ITS sequence GenBank MG256663 and LSU sequence GenBank MG256665 .

Pileus 3−4.5 cm in diameter, conico-campanulate, hemispherical to convex, not umbonate, surface dry, pale orange (6A2), without any greenish tinge during development, at first covered by a smooth, pale orange (6A2) to grayish orange (6B3), plate-like squamule, with minute, scattered squamules towards the margin; margin at first incurved, appendiculate with white membranous remnants of annulus ( Fig. 2A ). Lamellae free, white to pinkish (7A2) when young, then becoming grayish pink (7B2) to brownish orange (5C4), up to 3.5 mm wide, densely crowded, with 2−3 tiers of lamellulae. Stipe 3.5−5.5 × 0.5−0.8 cm, central, cylindrical with or without bulbous base, hollow; surface white, becoming pale yellow (4A3) when bruised, smooth, sometimes covered with white fine squamules or fibrils. Annulus membranous, whitish, superior, attached to upper third of stipe.

Basidiospores 6−7.5 × 4−4.5 μm, Q = 1.33−1.75, Q = 1.56 ± 0.14, ellipsoidal to elongate, brownish yellow, smooth, thick-walled ( Fig. 2B ). Basidia 19.5−25 × 7−8 μm, clavate, hyaline, 4-spored; sterigmata up to 3 μm long ( Fig. 2C ). Pleurocystidia absent. Cheliocystidia 14−27 × 7−8.5 μm, varying in shape from subcylindrical to clavate, sometimes ovate, hyaline, thin-walled ( Fig. 2D ). Subhymenium layer composed of thin-walled, inflated subglobose cells 5−12.5 μm diameter. Lamellar trama regular to sub-regular, composed of subcylindrical hyphae, thin-walled, hyaline, 2.5−5 μm wide. Pileipellis (squamules from pileal surface) epithelial, pseudoparenchymatous, composed of agglutinated, subglobose to oblong ellipsoidal cells, thin-walled, terminal cells 5−26 × 4.5−8.5 μm ( Fig. 2E ). Caulocystidia 15−30 × 3−5 μm, abundant, varying in shape from cylindrical to clavate, sometimes ovate, hyaline, slightly thick-walled; basal cells variable in shape, cylindrical to clavate, sometimes ovate, 15−35 × 2−5 μm, smooth, thin-walled to slightly thick-walled ( Fig. 2F ). Clamp connections absent in all tissues.

Ecology and distribution: Fruiting solitary or gregarious on soil during the rainy season in a tropical deciduous forest. Known only from Thailand.

Additional collections examined: THAILAND, Lampang Province, Mae Moh District, (18°40’51”N, 98°52’13”E), on ground in a tropical deciduous forest, July 2015, N. Suwannarach, J. Kumla & S. Lumyong, SDBR-CMUNK 0115.

Note: Only three species of Xanthagaricus ( X. neocopinatus I. Hosen, T.H. Li & G.M. Gates , X. ochraceoluteus (D.A. Reid & Eicker) Hussain and X. thailandensis ) have caulocystidia. However, the caulocystidia of X. thailandensis (15−30 × 3−5 μm) are narrower than those of X. neocopinatus (18−25 × 5−7 μm) and X. ochraceoluteus (20−35 × 5−13 μm) ( Reid & Eicker 1998; Hosen et al. 2017b). Basidiospores of X. thailandensis (6−7.5 × 4−4.5 μm) are larger than those of X. neocopinatus (4−5 × 2.7−3.2 μm) and X. ochraceoluteus (4−5.2 × 3−3.2 μm) ( Reid & Eicker 1998; Hosen et al. 2017b).

Figures

FIGURE 2. Xanthagaricus thailandensis SDBR-CMUJK 010 (holotype).A. Basidiome, B. Basidiospores, C. Basidia, D. Cheliocystidia. E. Squamules on pileus. F. Caulocystidia. Scale bars: A = 1 cm; B, E and F = 5 μm; C, D = 10 μm.