Novel species of microfungi described in the present study include the following from Australia: Phytophthora amnicola from still water, Gnomoniopsis smithogilvyi from Castanea sp., Pseudoplagiostoma corymbiae from Corymbia sp., Diaporthe eucalyptorum from Eucalyptus sp., Sporisorium andrewmitchellii from Enneapogon aff. lindleyanus, Myrmecridium banksiae from Banksia, and Pilidiella wangiensis from Eucalyptus sp. Several species are also described from South Africa, namely: Gondwanamyces wingfieldii from Protea caffra, Montagnula aloes from Aloe sp., Diaporthe canthii from Canthium inerne, Phyllosticta ericarum from Erica gracilis, Coleophoma proteae from Protea caffra, Toxicocladosporium strelitziae from Strelitzia reginae, and Devriesia agapanthi from Agapanthus africanus. Other species include Phytophthora asparagi from Asparagus officinalis (USA), and Diaporthe passiflorae from Passiflora edulis (South America). Furthermore, novel genera of coelomycetes include Chrysocrypta corymbiae from Corymbia sp. (Australia), Trinosporium guianense, isolated as a contaminant (French Guiana), and Xenosonderhenia syzygii, from Syzygium cordatum (South Africa). Pseudopenidiella piceae from Picea abies (Czech Republic), and Phaeocercospora colophospermi from Colophospermum mopane (South Africa) represent novel genera of hyphomycetes. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

To identify monophyletic groups within the smut fungi and related taxa, characteristics of hyphal septation and zones of host–parasite interaction were analyzed by serial-section electron microscopy of 139 species belonging to 50 smut and 10 allied genera. Our results support the hypothesis of the existence of two phylogenetically separate lines of smut fungi. The first line, the Microbotryales, is composed of Aurantiosporium, Fulvisporium, Liroa, Microbotryum, Sphacelotheca, and Ustilentyloma, which are distributed into the Ustilentylomataceae and Microbotryaceae. The second monophyletic line, the Ustilaginomycetes, is formed by the remaining smut fungi studied here together with the Exobasidiales, Graphiolales, and Cryptobasidiales (in the traditional sense). The ultrastructural analysis identifies three lineages within the Ustilaginomycetes. The Entorrhizomycetidae are represented by Entorrhiza. The Ustilaginomycetidae consist of the Urocystales and Ustilaginales. The Exobasidiomycetidae are composed of the Doassansiales, Entylomatales, Exobasidiales, Georgefischeriales, Graphiolales, Microstromatales, and Tilletiales. The Entorrhizomycetidae, Exobasidianae, Entorrhizales, Entylomatales, Doassansiales, Georgefischeriales, Microbotryales, Microstromatales, Tilletiales, Urocystales, Entorrhizaceae, Entylomataceae, Georgefischeriaceae, Mycosyringaceae, Rhamphosporaceae, and Ustilentylomataceae are proposed as new taxa. The descriptions of the Exobasidiomycetidae, Ustilaginomycetidae, Exobasidiales, Ustilaginales, Doassansiaceae, Tilletiaceae, and Ustilaginaceae are emended. Some species of Ustilago are transferred to Microbotryum. Key words: basidiomycetes, classification, Exobasidiales, Graphiolales, phylogeny, smut fungi, ultrastructure.

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The genera Ustilago, Sporisorium and Macalpinomyces are a polyphyletic complex of plant pathogenic fungi. The four main morphological characters used to define these genera have been considered homoplasious and not useful for resolving the complex. This study re-evaluates character homology and discusses the use of these characters for defining monophyletic groups recovered from a reconstructed phylogeny using four nuclear loci. Generic delimitation of smut fungi based on their hosts is also discussed as a means for identifying genera within this group. Morphological characters and host specificity can be used to circumscribe genera within the Ustilago-Sporisorium-Macalpinomyces complex.