Abstract:
Teratosphaeria suttonii (= Kirramyces epicoccoides) is a leaf pathogen that can cause premature
defoliation, reduced growth and vigosr and subsequent tree death of many Eucalyptus species.
Although the fungus primarily infects mature leaves in the lower canopy, infections can spread to
younger leaves during continued epidemics or when trees are stressed. Teratosphaeria suttonii has a
wide distribution in Australia and has been introduced to many other parts of the world, most
probably with germplasm used to establish plantations. The aim of this study was to establish the
phylogenetic relationships between T. suttonii isolates from different countries and to consider
whether cryptic species exist in a species complex. DNA from parts of the nuclear ribosomal
internal transcribed spacer (ITS), β-tubulin and elongation factor-1α genes was sequenced and
analyzed for isolates from throughout the range of T. suttonii in Australia, and from six countries
(China, Indonesia, South Africa, Uruguay, USA and Vietnam) where the pathogen is introduced.
Morphometrics of conidia produced both in vivo and in vitro were also considered. Analysis of the
sequence data resulted in incongruent genealogies. Furthermore, groups of isolates in the
genealogies could not be linked to area of origin. Likewise differences in conidial morphology could
not be linked to any of the phylogenetic groups. There was no evidence of distinct species boundaries and isolates from Australia were closely related to those from other parts of the world.
The results of this study support the treatment of T. suttonii as a morphologically and genetically
diverse species in its natural range in Australia. The diversity is reflected in introduced populations.
