The new classification of the smut fungi, exemplified by Australasian taxa

Abstract

The 150 years old classificatory system for smut fungi was recently replaced by a new one, based on ultrastructural and molecular studies and also on classical morphological characters. The c. 1450 known ‘classical’ smut fungi (those possessing ustilospores) are classified into two classes, eight orders, 18 families and 73 genera. The surprising result in this new system is that the Microbotryales, with 93 species in eight genera, are more closely related to the rust fungi than to the remaining group of smut fungi. This is supported by biochemical, ultrastructural and molecular data. In the new system, some groups of fungi are lacking ustilospores (Microstromatales, Exobasidiales). Through convergent evolution, similar, complex spore ball structures, composed of spores and empty sterile cells, evolved from different ancestors as adaptation to parasitism on water plants (Doassansiopsiaceae and Doassansiaceae). The presence (or absence) of spore balls does not always reflect a close relationship as was previously thought: in the Doassansiaceae, characterised so far mainly by spore balls, Doassinga has single spores. Examples of Australasian taxa and their place in the new classification, presented are Doassansiopsis, Doassingaand Pseudotracya of the ‘Doassansia’ group, Mundkurella, Heterotolyposporium, Websdanea, Restiosporium and within the Microbotryales Microbotryum (Microbotryaceae), Fulvisporium and Bauerago (Ustilentylomataceae).