Abstract:
The Eucalyptus stem canker pathogen Teratosphaeria zuluensis was discovered in South
Africa in 1988 and it has subsequently been found in several other African countries as well
as globally. In this study, the population structure, genetic diversity and evolutionary history
of T. zuluensis were analysed using microsatellite markers to gain an enhanced understanding
of its movement in Africa. Isolates were collected from several sites in Malawi, Mozambique,
Uganda and Zambia. Data obtained were compared with those previously published for a
South African population. The data obtained from 334 isolates, amplified across eight
microsatellite loci, were used for assignment, differentiation and genetic diversity tests.
STRUCTURE analyses, θst and genetic distances revealed the existence of two clusters, one
dominated by isolates from South Africa and the other by isolates from the Zambezi basin
including Malawi, Mozambique and Zambia. High levels of admixture were found within and
among populations, dominated by the Mulanje population in Malawi. Moderate to low
genetic diversity of the populations supports the previously held view that the pathogen was
introduced into Africa. The clonal nature of the Ugandan population suggests a very recent
introduction, most likely from southern Africa.
