Parvixerocomus pseudoaokii

Parvixerocomus pseudoaokii G. Wu, K. Zhao & Zhu L. Yang, in Wu et al., Fungal Diversity 81(1): 1–24 (2015)

Etymology: “pseudoaokii” refers to the close relationship to Parvixerocomus aokii (Hongo) G Wu & Zhu L. Yang

Pileus 0.8–3 cm in diam., convex to applanate; surface yellowish red, grayish red to rose red (8B6–8B7, 12A8– 12B8), subtomentose, dry, sometimes incurved at the margin; context 2–4 mm thick, pale yellow to light yellow (2A3– 2A4), staining light blue to blue when cut. Hymenophore subdecurrent; surface pale yellow to light yellow (3A3– 3A5), staining blue when cut; pores irregular, angular to nearly, ca. 1–2/mm, tubes 0.7–2.5 mm long, concolorous with hymenophoral surface, staining light blue to blue when cut. Stipe central, cylindrical to subcylindrical, 1–2×0.15–0.2 cm, bluish red to grayish ruby (12B7–12C7) or reddish gold to brownish red (6C7–6C8); surface pruinose, staining blue when touched; context similar to that of pileus; basal mycelia cream to light yellow. Macrochemical reaction not observed.

Basidia 20–35×9–12 μm, clavate, 4-spored, rarely 2- spored. Basidiospores 7–8.5 (9)×4–5 (5.5) μm [Q=(1.4) 1.47–1.89 (2), Qm=1.66±0.11], ovoid and inequilateral in side view with indistinctly suprahilar depression, ovoid in ventral view, brownish yellow, smooth, inamyloid. Hymenophoral trama intermediate between boletoid and phylloporoid; hyphae cylindrical, 5–10 μm wide. Cheilocystidia 23–52×6– 10 μm, fusoid-ventricose to clavate with subacute apex, rarely with a long beak, thin walled. Pleurocystidia 30–65×8– 15 μm, fusoid-ventricose to broadly fusoid-ventricose, with a long beak, thin walled. Pileipellis an epithelium, up to 100 μm thick, composed of submoniliform to moniliform hyphae 7– 16 μm wide, with cystidioid terminal cells 18–41×8–17 μm. Pileal trama composed of interwoven hyphae 7–15 μm wide. Stipitipellis thin, ca. 20–40 μm thick, hymeniform, with clavate terminal cells 33–44×6.5–20 μm. Stipe trama composed of parallel hyphae 9–15 μm wide. Clamp connections absent.

Habitat: scattered, in subtropical forests of Fagaceae (Lithocarpus, Castanopsis, Quercus etc.) or mixed forests of Fagaceae and Pinus massoniana.

Known distribution: Currently only from southwestern, southeastern and southern China.

Index Fungorum number: IF811421

Notes: Parvixerocomus pseudoaokii is characterized by its small basidioma staining blue when hurt and small basidiospores. Phylogenetically and morphologically, Parvixerocomus aokii is closely related to P. pseudoaokii, but P. aokii differs from the latter by its longer basidiospores (9– 12.5×4–5 μm) (Hongo 1984). Morphologically, Xerocomus parvulus Hongo and Boletus pseudoparvulus Bi are similar to P. pseudoaokii. However, X. parvulus differs from P. pseudoaokii by its broader basidiospores (7.5–11×5– 6.5 μm) and longer pleurocystidia (70–89×12–15 μm) (Hongo 1963); and B. pseudoparvulus differs from P. pseudoaokii by its narrower basidiospores 6.6–10×3–3.3 μm and different discoloration when hurt (staining purplish red) (Bi et al. 1982).