Micropsalliota dentatomarginata R.L. Zhao, J.X. Li & M.Q. He, 2021

Li, Jia-Xin, He, Mao-Qiang & Zhao, Rui-Lin, 2021, Three new species of Micropsalliota (Agaricaceae, Agaricales) from China, Phytotaxa 491 (2), pp. 167-176 : 174

Micropsalliota dentatomarginata R.L. Zhao, J.X. Li & M.Q. He , sp. nov. Figure 4

Fungal Name: FN570749

Etymology: in reference to the dentate margin of its pileus.

Diagenesis: this species is characterized by its pure white appendiculate, curved and elongated cheilocystidia and bigger basidiospores.

Holotype: CHINA, Guangxi Zhuang Autonomous Region, Longzhou county and Ningming county , Nonggang National Nature Reserve , 1 August 2017, Xin-Yu Zhu , ZRL20150202 ( HMAS290760 )

Macroscopic description: Pileus 12–15 mm in diam., convex to applanate, surface dry, white, sometimes with appressed fine fibrils, with pure white appendiculate, dentate margin. Context up to 1 mm, white. Lamellae free, subdistant, with 2–3 series of lamellulae, 2–3 mm broad, sometimes ventricose, gray to light brown. Stipe 25–35 × 2–3 mm, white, cylindrical, covered with fibrils, occasionally tomentose. Annulus membranous, single, white, fragile. Odor not distinctive. Stipe staining brown on bruising and cutting.

Microscopic description: Basidiospores 5.8–6.3 × 3.4–4 μm, [x = 6.1 ± 0.2 × 3.8 ± 0.1, Q = 1.5–1.7, Q m = 1.6 ± 0.066, n = 22], ellipsoid, sometimes amygdaliform, with an apical endosporal thickening, without germ pore, brown. Basidia 15.6–18.3 × 7.8–9.4 μm, clavate, 4-spored, sometimes 2-spored. Cheilocystidia 31.4–35.4 × 3.2–5.2 μm, capitate, up to 3–6 μm at the apex with a sinuous or straight neck and a thickened base. Pleurocystidia absent. Pileipellis a cutis of hyphae 4–9 μm diam., hyaline, smooth, branched, incrusted, constricted at septa. Annulus composed hyphae of 2–4 μm diam., smooth, hyaline and branched.

KOH reaction: unknown.

Habit and habitat: solitary on soil in forest.

Known distribution: China.

Notes: In the phylogenetic analyses, this new species is represented by GX20170202 clustered with M. subarginea Heinem , M. bifida R.L. Zhao, Desjardin, Soytong & K.D. Hyde , M. arginophaea Heinem. , M. pseudoarginea Heinem. , M. allantoidea R.L. Zhao, Desjardin, Soytong & K.D. Hyde , M. albosericea Heinem. & Leelav. , M. gracilis Heinem. , M. subalba Heinem. & Little Flower , and M. pusillissima R.L. Zhao, Desjardin, Soytong & K.D. Hyde , M. albella M.Q. He & R.L. Zhao and M. delicatula with high support values (87/1.0). Among them, M. subalba , M. subarginea , M. bifida and M. pseudoarginea have similar phenotypes with M. dentatomarginata , pure white color of pileus and medium sized basidiomata in diam. Compared with M. subarginea , M. bifida and M. pseudoarginea , M. dentatomarginata could be easily distinguished in having bigger basidiospores (5.8–6.3 × 3.4–4 μm) and M. subalba , phylogenetically close to this new species, differ in having broader cheilocystidia (6.8–8 μm) and white to light gray pileus ( Heinemann & Little Flower 1983).