Recent reclassification of the Ceratocystidaceae (Microascales) based on multi-gene phylogenetic inference
has shown that the oak wilt fungus Ceratocystis fagacearum does not reside in any of the four genera
in which it has previously been treated. In this study, we resolve typification problems for the fungus,
confirm the synonymy of Chalara quercina (the first name applied to the fungus) and Endoconidiophora
fagacearum (the name applied when the sexual state was discovered). Furthermore, the generic placement
of the species was determined based on DNA sequences from authenticated isolates. The original
specimens studied in both protologues and living isolates from the same host trees and geographical area
were examined and shown to represent the same species. A lectotype was designated for Chalara quercina
and Endoconidiophora fagacearum and an epitype linked to a living ex-epitype isolate was designated.
Phylogenetic analyses confirmed that the species resides in a well-supported monophyletic lineage in the
Ceratocystidaceae, distinct from all other genera in the family. The new genus Bretziella is described to
accommodate the oak wilt fungus.