Abstract
Many population studies on invasive plant pathogens are undertaken without knowing the center of origin of the pathogen. Most leaf pathogens of Eucalyptus originate in Australia and consequently with indigenous populations available, and it is possible to study the pathways of invasion. Teratosphaeria suttonii is a commonly occurring leaf pathogen of Eucalyptus species, naturally distributed in tropical and subtropical regions of eastern Australia where it is regarded as a minor pathogen infecting older leaves; however, repeated infections, especially in exotic plantations, can result in severe defoliation and tree deaths. Nine polymorphic microsatellite markers were used to assess the genetic structure of 11 populations of T.suttonii of which four where from within its native range in eastern Australia and the remaining seven from exotic Eucalyptus plantations. Indigenous populations exhibited high allele and haplotype diversity, predominantly clonal reproduction, high population differentiation, and low gene flow. The diversity of the invasive populations varied widely, but in general, the younger the plantation industry in a country or region, the lower the diversity of T.suttonii. Historical gene flow was from Australia, and while self-recruitment was dominant in all populations, there was evidence for contemporary gene flow, with South Africa being the most common source and Uruguay the most common sink population. This points distinctly to human activities underlying long-distance spread of this pathogen, and it highlights lessons to be learned regarding quarantine.
Highlights
Eucalyptus species, commercially propagated in plantations cover approximately 20 million ha, become the dominant source of hardwood fiber globally
Ecology and Evolution published by John Wiley & Sons Ltd
Indigenous populations of the Eucalyptus leaf pathogen T. suttonii were characterized by high allele and haplotype diversity, low gene flow, and geographic structure
Summary
Eucalyptus species, commercially propagated in plantations cover approximately 20 million ha, become the dominant source of hardwood fiber globally. Of the Eucalyptus leaf pathogens, there are approximately 150 species of Mycosphaerellaceae and Teratospheriaceae associated with exotic eucalypts, with most of the devastating being members of the Teratospheriaceae having Kirramyces-like spores, namely T. destructans, T. viscidus, T. eucalypti, T. pseudoeucalypti, and T. suttonii, all of which cause leaf blights, as opposed to the less damaging leaf spot diseases (Hunter et al 2011).
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