Omphalotus yunnanensis: A New Poisonous Mushroom Discovered from China Based on Morphological, Molecular and Toxin-Detection Evidence

In the past few years, several mushroom poisoning incidents caused by <i>Omphalotus</i> species have occurred in China. In addition to <i>O. guepiniformis</i> and <i>O. olearius</i>, a new white <i>Omphalotus</i> species, <i>O. yunnanensis</i>, was discovered in Southwestern and Southern China based on morphological, molecular and toxin-detection evidence. <i>Omphalotus yunnanensis</i> is characterized by its small, cream to white basidiomata with a hygrophanous pileal surface, non-bioluminescent lamellae, broadly ellipsoid to subglobose basidiospores (8-12.5 × 7-10 μm), fusoid to ventricose cheilocystidia with occasional apical outgrowths, cream to white pileipellis composed of thick-walled, subsoil to solid hyphae, clavate, and fusoid to ventricose caulocystidia with occasional apical outgrowths. The species has been discovered in tropical to subtropical areas in Southwestern and Southern China. Phylogenetic analyses based on ITS and nrLSU showed that the new species clustered with the Australasian species <i>O. nidiformis</i>, but can be easily distinguished by its smaller, white to cream pileus, non-bioluminescent lamellae, larger basidiospores and growing on Fagaceae species. Illudin S was detected in this new species using UPLC-MS/MS, at 6.98 to 86.1 mg/kg of the content (dry weight), while no illudin M was detected.