Xanthagaricus retisporus Kun L. Yang, Jia Y. Lin & Zhu L. Yang

Yang, Kun L., Lin, Jia Y., Li, Guang-Mei, Liu, Zhen-Chao, Hosen, Md. Iqbal & Yang, Zhu L., 2024, Heinemannomyces, Hymenagaricus and Xanthagaricus revisited (Basidiomycota, Agaricaceae), Phytotaxa 659 (2), pp. 112-164 : 144-146

Xanthagaricus retisporus Kun L. Yang, Jia Y. Lin & Zhu L. Yang , sp. nov. ( Fig. 14 )

Registration identifier:— FN571944

Etymology:— Referring to the basidiospores with slightly reticulate ornamentation of this species.

Diagnosis:— Differing from other Asian Xanthagaricus species by a combination of strongly caespitose basidiomata, pileus more than 20 mm in diameter, with yellowish, orangish to brownish but not reddish or greenish squamules, and cheilocystidia 11–13 μm long.

Type:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, April 1, 2024, Kun L. Yang & Jia Y. Lin, K 24013 ( HKAS133450 , holotype! (ITS: PP736660; nrLSU: PP732891; tef-1α: PP746824 ); HTBM1868 , isotype!) .

Description:— Basidiomata small. Pileus 20–36 mm in diameter when mature, hemispherical to plano-convex, sometimes slightly umbonate when mature; background ceramic white (#FEFEFA), pale dirty orange (#FAF4E3) to dull orange (#E3C4A3), becoming lighter towards margin; squamules more or less flaky at center, becoming woolly to fibrous towards margin, pudding orange (#FFE8A3), cherrywood brown (#DAB697) to coffee-bean brown (#483625), becoming lighter towards margin; margin with appendices concolorous with the pileus background; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) after damaged. Lamellae free, nearly crowded, ceramic white (#FEFEFA) to dull silk red (#BBA8A2), with an entire to slightly serrate edge; lamellulae abundant. Stipe 30–77 mm long, 1.5–3 mm thick, cylindrical, slightly curved; background pale dirty orange (#FAF4E3) to dull orange (#E3C4A3); squamules fibrous, usually more abundant below the annulus, merino white (#F9F5EC); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) after damaged; base with moderately abundant to abundant tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor strongly fungal when immature, becoming indistinct. Taste fungal.

Basidiospores [40/4/3] 5–6 [5.41 ± 0.29, 5.50] × 3–4 [3.43 ± 0.26, 3.50] µm, Q = (1.38) 1.43–1.83 (2.00) [1.59 ± 0.15, 1.57], ellipsoid to oblong, slightly thick-walled, smooth under LM, slightly reticulate under SEM, tinged lion orange (#EFD871) to pumpkin orange (#CEB640) in both water and 5% KOH, with a small apiculus, with an indistinct germ pore. Basidia 13–15 × 5–6 μm, subcylindrical to clavate, 4-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 8–12.5 × 3.5–5 μm. Lamella trama subregular, composed of 5–12 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia abundant, 11–13 × 8–9 µm, broadly clavate to clavate, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid to subhymeniform, composed of globose, subglobose, broadly ellipsoid to subcylindrical, slightly thick-walled and encrusted cells measured 4–13 × 4–9 µm, tinged milky yellow (#FFF07A) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 3–9 µm wide, cylindrical to subcylindrical, thin- to slightly thick-walled and encrusted hyphae, tinged milky yellow (#FFF07A) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Gregarious, strongly caespitose, scattered on soil as clusters, in urban green belts. Currently known from China (South China).

Additional collections examined:— China, Guangdong Province, Guangzhou City, Haizhu District, a green belt along Xinjiao West Rd. , on soil, 23°04’39”N, 113°18’23”E, elevation 3 m, May 15, 2022, Kun L. Yang, S 2380 ( HTBM0323 (ITS: PP736758; nrLSU: PP732988; tef-1α: PP746811 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , Insecticidal Plant Garden , on soil, 23°09’29”N, 113°20’47”E, elevation 30 m, April 11, 2023, Kun L. Yang, K 2396 ( HKAS133448 , partly isolated as HTBM0611 (ITS: PP736702; nrLSU: PP732932; tef-1α: PP746810 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, April 25, 2023, Kun L. Yang, K 23172 ( HTBM0687 (ITS: PP736699; nrLSU: PP732929; tef-1α: PP746809 )) ; same location, June 27, 2023, Jia Y. Lin, L 23104 ( HTBM0937 ) & L23106 ( HTBM0939 (ITS: PP736642; nrLSU: PP732873 )) ; same location, August 27, 2023, Jia Y. Lin, L 23326 ( HTBM1307 (ITS: PP736643; nrLSU: PP732874 )) & L23327 ( HKAS133449 , partly isolated as HTBM1308 (ITS: PP736655; nrLSU: PP732886; tef-1α: PP746816 )) ; same location, August 29, 2023, Jia Y. Lin, L 23333 ( HTBM1314 (ITS: PP736644; nrLSU: PP732875 )), L23334 ( HTBM1315 (ITS: PP736654; nrLSU: PP732885; rpb2: PP746791; tef-1α: PP746815 )) & L23334B (completely used up (ITS: PP736645; nrLSU: PP732876 )) ; same location, August 30, 2023, Jia Y. Lin, L 23348 ( HTBM1329 (ITS: PP736646; nrLSU: PP732877 )) ; same location, April 1, 2024, Kun L. Yang & Jia Y. Lin, K24014 ( HTBM1869 (ITS: PP736661; rpb2: PP746796; tef-1α: PP746825 )) & K24015 ( HTBM1870 (ITS: PP736662; nrLSU: PP732892; rpb2: PP746797; tef-1α: PP746826 )) ; China, Guangdong Province, Guangzhou City, Haizhu District, a green belt along Xinjiao West Rd. , on soil, 23°04’39”N, 113°18’13”E, elevation 3 m, April 1, 2024, Kun L. Yang & Jia Y. Lin, K 24016 ( HTBM1871 (ITS: PP736671; nrLSU: PP732901 )), K24017 ( HTBM1872 (ITS: PP736672; nrLSU: PP732902 )) & K24018 ( HTBM1873 (ITS: PP736673; nrLSU: PP732903 )) ; China, Guangdong Province, Guangzhou City, Haizhu District, Shangchong Fruit Trees Park , on soil, 23°04’36”N, 113°18’21”E, elevation 2 m, April 3, 2024, Jia Y. Lin, L 24047 ( HTBM1921 (ITS: PP736675; nrLSU: PP732905 )), L24048 ( HTBM1922 (ITS: PP736676; nrLSU: PP732906 )) & L24049 ( HTBM1923 (ITS: PP736677; nrLSU: PP732907 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , Qilin South Sports Field , on soil, 23°09’29”N, 113°22’07”E, elevation 20 m, April 9, 2024, Jia Y. Lin, L 24078 ( HTBM1952 (ITS: PP736688; nrLSU: PP732918 )) .

Additional notes: This species is variable in morphology. The color of pileus squamules is particularly variable and ranges from whitish to yellowish to brownish. The basidiomata growing in poorly lit habitats are palely colored, and those growing in habitats with deep leaf litter have very long and slender stipes.

Figures

FIGURE 14. Xanthagaricus retisporus (Photos by Kun L. Yang & Jia Y. Lin; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133450 (holotype) & HKAS133448). a. Habitat of HTBM1871. b–n. Basidiomata (b–c. HTBM1872; d. HTBM1952; e. HTBM0687; f. HKAS133448; g–h.HTBM0323;i–j.HKAS133450 (holotype);k.HTBM1869;l. HKAS133449;m–n.HTBM1923).o–p (o. Line drawing; p. SEM photo of HTBM1871). q. Hymenium and subhymenium. r. Squamules at pileus center. s. Cheilocystidia. t. Stipe squamules. Bars: b–c = 50 mm, d–h, k–l = 20 mm, i–j = 5 mm, m–n = 30 µm, o–s = 5 µm, t = 10 µm.