The 168-year taxonomy of Claviceps in the light of variations: From three morphological species to four sections based on multigene phylogenies

Abstract

Ergot fungi produce toxic sclerotia that have significant impacts on the agricultural, food and pharmaceutical industries. These fungi were classified in various genera (such as Sclerotium clavus, or Spermoedia clavus) before Tulasne, in 1853, erected Claviceps and described three species based on variations in morphology and host ranges, viz. C. purpurea, C. microcephala, and C. nigricans. Since then, knowledge regarding the biological, clinical, and pharmaceutical perspectives of ergot has accumulated rapidly. However, a serious taxonomic examination was lacking until Langdon’s revision accepted 25 species in 1952. That was followed by intensive regional studies by Loveless in the 1960s for Rhodesia (now Zimbabwe, Africa), and Tanda in Japan (1970s–1990s). More species names were reported and currently over 90 named taxa (species, varieties) are recorded in fungal name repositories (Mycobank and Index Fungorum). Most species were described based on morphological characteristics (sclerotia, ascomata and conidia) and host ranges. Some were characterized by their alkaloid profiles. Recently, DNA multi-locus sequence analyses (MLSA) were applied to resolve species complexes. For instance, the C. purpurea complex was separated into four species, and additional new species were recognized from South Africa and Canada. Infra- and supra-specific level genetic variations were identified via multi-locus and genomic studies. Based on five-locus phylogenies, Píchová and colleagues separated Claviceps into four sections: C. sect. Claviceps, C. sect. Citrinae, C. sect. Paspalorum and C. sect. Pusillae, for 60 species. Among these sections, several doubtful species names require clarification. Careful research on type specimens combined with molecular analyses is essential for clarifying these names.