The Eucalyptus stem canker pathogen Teratosphaeria gauchensis represents distinct genetic groups in Africa and South America

Summary Teratosphaeria gauchensis (Capnodiales) causes a serious stem canker disease on commercially propagated Eucalyptus species in South America. Recently, this pathogen was detected for the first time in Africa. Very little is known regarding the biology or origin of T. gauchensis, but it has been suggested that it is native to South America. The aim of this study was to compare isolates from Africa and South America using microsatellite markers. Bayesian analysis conducted in STRUCTURE, principal coordinates analysis and a UPGMA dendrogram revealed two distinct genetic groups for these isolates. The South American isolates were more genetically diverse than those from Africa. Patterns of genetic diversity in Africa suggest that T. gauchensis could have been introduced into Zimbabwe before spreading north‐eastwards. The existence of the two genetic groups and high haplotype richness associated with the South American and Zimbabwean populations suggest that it will be more difficult to reduce the impact of disease caused by T. gauchensis in these regions than in those areas where there is limited genetic diversity.