Morphological and phylogenetic analyses in Auriculariales (Basidiomycota, Agaricomycetes) reveal nine new species in Basidiodendron.

Auriculariales is an important order of wood-inhabiting fungi, accommodating a high diversity of taxa with complex evolutionary relationships. Within this order, the generic boundaries and species diversity of Basidiodendron have remained incompletely resolved. Morphologically, the genus is characterized by annual, resupinate basidiomata, a monomitic hyphal system with clamped generative hyphae, longitudinally septate four-celled basidia with well-developed or indistinct involucres, and globose to subglobose basidiospores exhibiting smooth, warted, or spiny walls. Based on an integrative approach combining morphological characterization and multigene phylogeny inferred from ITS, nrLSU, RPB1, RPB2, and TEF1 sequence data, nine new species of Basidiodendron are formally introduced, namely B. album sp. nov., B. arachnoideum sp. nov., B. dehongense sp. nov., B. fragilissimum sp. nov., B. odontoideum sp. nov., B. rigidum sp. nov., B. ruiliense sp. nov., B. tenissimum sp. nov., and B. zhaotongense sp. nov. Detailed morphological descriptions, illustrations, and phylogenetic evaluations are provided for all newly described taxa. The generated multilocus dataset represents a substantial advance in understanding species diversity and phylogenetic relationships within the genus. This study significantly enriches knowledge of wood-inhabiting fungi and provides a more robust taxonomic framework for future research on Basidiodendron and related taxa in Auriculariales.