Taxonomy and phylogeny of <i>Stereaceae</i> (<i>Russulales</i>, <i>Basidiomycota</i>): two new genera, nine new species and twenty new combinations

An in-depth study of the taxonomy and phylogeny of the <i>Stereaceae</i> was conducted. Specimens collected from East Asia were studied by using morphological and molecular systematic methods. The phylogenetic analyses were based on a concatenated ITS1-5.8S-ITS2 (ITS) and the D1-D2 domains of nuc 28S rDNA (LSU) sequence data of <i>Stereaceae</i> by using the maximum parsimony, maximum likelihood and Bayesian inference methods. Fourteen lineages including two new genera, <i>Confertotrama</i> and <i>Gelatinostereum</i>, are recognized in the phylogenetic tree. <i>Confertotrama</i>, typified by <i>Merulius rugulosus</i>, is segregated from <i>Gloeocystidiellum</i> s. lat. <i>Gelatinostereum</i> is sister to <i>Stereum</i> in the tree but differs in having gelatinous basidiomes and lacking thick-walled pseudocystidia. <i>Conferticium</i> is shown to be restricted to include species with smooth basidiospores, while species with ornamented basidiospores are nested within the <i>Gloeocystidiopsis</i> lineage. The delimitation of <i>Megalocystidium</i> is expanded based on the phylogenetic analyses. It includes species with or without clamp connections and acanthohyphidia and with a large variety of basidium size. <i>Neoaleurodiscus</i> is treated as a later synonym of <i>Aleurodiscus</i> sensu stricto, since their type species <i>N. fujii</i> and <i>A. amorphus</i> were nested within the same lineage. With this disposal, <i>Aleurodiscus</i> s. str. now includes species with smooth or ornamented basidiospores. The generic name, <i>Gloeomyces</i> is applied for the lineage of species of <i>Aleurodiscus</i> s. lat. with resupinate basidiomes, well-developed acanthohyphidia and smooth basidiospores, while <i>Acanthophysellum</i> is regarded as a synonym of <i>Xylobolus</i>. Nine new species, <i>Aleurodiscus globisporus</i>, <i>Conferticium subtropicum</i>, <i>Gelatinostereum phlebioides</i>, <i>Gloeocystidiopsis shenghuae</i>, <i>Gloeomyces subcerussatus</i>, <i>Megalocystidium brunneum</i>, <i>M. effusum</i>, <i>Stereum rhododendri</i> and <i>S. tropicum</i> are described and illustrated from China. Twenty new combinations, <i>Aleurodiscus fujii</i>, <i>Confertotrama aspella</i>, <i>Ca. macrospora</i>, <i>Ca. rugulosa</i>, <i>Ca. rajchenbergii</i>, <i>Gloeocystidiopsis ravum</i>, <i>Gs. tenuissimus</i>, <i>Gloeomyces bambusinus</i>, <i>G. bicornis</i>, <i>G. cerussatus</i>, <i>G. dextrinoideocerussatus</i>, <i>G. dextrinoideophyses</i>, <i>G. formosanus</i>, <i>G. parvisporus</i>, <i>G. persicus</i>, <i>G. thailandicus</i>, <i>G. thoenii</i>, <i>G. tropicus</i>, <i>Megalocystidium chinense</i> and <i>Xylobolus lividocoeruleus</i> are proposed. <i>Aleurodiscus isabellinus</i> is treated as a synonym of <i>Gloeomyces graminicola</i>. Morphological differences between closely related genera are discussed, and an identification key to all 14 genera of <i>Stereaceae</i> is presented. <b>Citation:</b> Xu YL, Cao YF, Liu SL, Nakasone KK, He SH (2025). Taxonomy and phylogeny of <i>Stereaceae</i> (<i>Russulales</i>, <i>Basidiomycota</i>): two new genera, nine new species and twenty new combinations. <i>Persoonia</i> <b>54</b>: 119-145. doi: 10.3114/persoonia.2025.54.04.