Resolving thePhomaenigma

Abstract

TheDidymellaceaewas established in 2009 to accommodateAscochyta,DidymellaandPhoma, as well as several related phoma-like genera. The family contains numerous plant pathogenic, saprobic and endophytic species associated with a wide range of hosts.AscochytaandPhomaare morphologically difficult to distinguish, and species from both genera have in the past been linked toDidymellasexual morphs. The aim of the present study was to clarify the generic delimitation inDidymellaceaeby combing multi-locus phylogenetic analyses based on ITS, LSU,rpb2andtub2, and morphological observations. The resulting phylogenetic tree revealed 17 well-supported monophyletic clades inDidymellaceae, leading to the introduction of nine genera, three species, twonomina novaand 84 combinations. Furthermore, 11 epitypes and seven neotypes were designated to help stabilise the taxonomy and use of names. As a result of these data,Ascochyta,DidymellaandPhomawere delineated as three distinct genera, and the generic circumscriptions ofAscochyta,Didymella,EpicoccumandPhomaemended. Furthermore, the genusMicrosphaeropsis, which is morphologically distinct from the members ofDidymellaceae, grouped basal to theDidymellaceae, for which a new familyMicrosphaeropsidaceaewas introduced.