Taxonomy and biology of Quambalaria spp. infecting eucalypts in South Africa

Abstract

The genus Quambalaria (Microstromatales, Exobasidiomycetes) includes six species, five of which are pathogens of Eucalyptus and Corymbia species. The only exception is Q. cyanescens, which has been shown to be non-pathogenic to plants, but can be an opportunistic human pathogen. The symptoms on trees include shoot and leaf blight, which is characteristic of Q. eucalypti and Q. pitereka and stem cankers caused by Q. coyrecup. The studies in this dissertation arose from the discovery of a Quambalaria-like species infecting Eucalyptus seed capsules. The complete body of research on Quambalaria is reviewed here, focusing on the taxonomy, pathogenicity, host range and geographical distribution. The review revealed a lack of knowledge on basic aspects of its biology, especially in terms of its mating behaviour and sexual reproduction. For this reason, these two aspects in related in species of the Ustilaginomycetes were also considered. This revealed that whole genome sequences and some knowledge regarding mating genes in14 species of Ustilaginomycetes have been published. This knowledge provided a framework in which a whole genome sequence of a Quambalaria species could be explored for the presence of genes related to sexual reproduction. It is suggested that such knowledge could shed light on many unknown aspects of the reproduction and life cycle of Quambalaria species.