Abstract:
The rust pathogen, Puccinia psidii, was first detected
in South Africa in 2013 on a single non-native ornamental
Myrtus communis tree. This prompted surveys of the country
to determine its geographic distribution and host range.
Previously developed microsatellite markers where used to
characterize the genetic diversity of P. psidii isolates collected
from these surveys. In addition, artificial inoculation studies
and field observations were used to evaluate the susceptibility
of native Myrtaceae to infection by P. psidii. The pathogen
was found on native Myrtaceae in isolated natural situations
and it was also common on exotic Myrtaceae in nurseries and
gardens. Marker analysis showed that a single genotype of
the rust is present in South Africa and that this is different
to the so-called Bpandemic^ strain recorded in countries
outside Brazil. It was found to have a broad distribution in
South Africa with collections as far as 1500 km apart. The
data provide firm evidence for a single introduction of the
pathogen from an as yet unkown source. Its wide distribution,
particularly in relatively isolated natural areas,
suggests that P. psidii has been present in South Africa
for much longer than implied by its first detection in the
country.
