Abstract:
This study considers the population diversity and structure of D. pinea in South Africa at different spatial
scales from single trees to plantations, as well as comparing infections on healthy and diseased trees. A
total of 236 isolates were characterized using thirteen microsatellite markers. Analysis of these markers
confirmed previous results that D. pinea has a high level of gene and genotypic diversity in South Africa,
with the latter values ranging from 6 % to 68 % for the different plantations. The data also reflect a
fungus with randomly associated alleles in populations at local plantation scales and for the population as
a whole. These results suggest that recombination is occurring in D. pinea and that it most likely has
cryptic sexual state. The study also reveals the sources of endophytic infection and stress related disease
out-breaks as diverse infections that have occurred over a long time period. In contrast, wound-associated
die-back appears to be caused by clones of the pathogen occurring in narrow time frames.
