Kneiffiella pseudoabdita Xue W. Wang & L.W. Zhou, sp. nov.

Index Fungorum number: IF 900289; Mycobank number: MB 900289; Facesoffungi number: FoF 14052; Figs. 1, 2

Etymology – pseudoabdita (Lat.) referring to the similarity to Kneiffiella abdita.

Holotype – LWZ 20210624-6b (HMAS).

Diagnosis – Characterized by annual, resupinate, adnate basidiomes, poroid hymenophore, the presence of two types of generative hyphae, subcylindrical to subclavate cystidia, clavate basidia, and ellipsoid, thick-walled basidiospores. Basidiomes annual, resupinate, adnate, cracked and brittle when dry, without odour. Hymenophore poroid with angular and variable pores, buff to buff-yellow. Margin thinning out, paler than hymenial surface, indeterminate, sometimes pruinose.

Hyphal system monomitic; two types of generative hyphae: 1) with clamp connections, hyaline, dichotomous branching, interwoven, slightly thick-walled, 2.5–3.5 μm in diam; 2) simple septate, brown, slightly thick-walled with a wide lumen, usually dichotomous branching, interwoven, 3–4 μm in diam. Cystidia subcylindrical to subclavate, 25–45×4.5–5.5 μm. Basidia clavate, 16.5–20×4.5–5.5 μm, with four sterigmata and a basal clamp; basidioles similar in shape to basidia, but smaller. Basidiospores narrowly to broadly ellipsoid, with a small oily drop, hyaline, smooth, thick-walled, IKI–, CB–, (5.2–)5.3–6.4(–6.5)×(3.1–)3.2–4 .3(–4.4) μm, L=5.76 μm, W=3.81 μm, Q=1.51 (30/1).

Material examined – China, Jiangxi Province, Jiujiang, Lushan Mountain, on fallen trunk of Pinus, 24 June 2021, L.W. Zhou, LWZ 20210624-6b (HMAS, holotype).

GenBank numbers – ITS=OQ540894; LSU=OQ540852.

Notes – Kneiffiella pseudoabdita is distinct in this genus by the presence of two types of generative hyphae. Phylogenetically, Kneiffiella pseudoabdita groups with K. abdita (Fig. 3). These two species share similar poroid hymenophore, tubular cystidia and clavate basidia; however, K. abdita differs in its narrowly allantoid basidiospores (3–4 × 0.5–1 μm, Wang et al. 2021a). Kneiffiella pilaecystidiata resembles K. pseudoabdita by sharing ellipsoid basidiospores, but differs in having odontioid hymenophore and capitate cystidia (Eriksson and Ryvarden 1976). Moreover, K. pilaecystidiata grows on decayed wood of Salix and Populus (Eriksson and Ryvarden 1976), while K. dimitica was found on Pinus.

Figure 1 – Basidiomes of Kneiffiella pseudoabdita (LWZ 20210624-6b, holotype)

Figure 2 – Microscopic structures of Kneiffiella pseudoabdita (LWZ 20210624-6b, holotype). a Basidiospores. b Basidia and basidioles. c Cystidia. d Tramal hyphae. e Section in hymenium. Scale bars: a–e=10 μm

Figure 3 – Phylogram generated by the maximum likelihood algorithm based on combined nLSU and ITS sequence data is presented along with the bootstrap values and the Bayesian posterior probabilities above 50% and 0.8, respectively, at the nodes. Type specimens are in bold and the isolates of new species characterized are in blue