Abstract:
The pulp and paper industry is expanding world-wide to supply the needs and
demands of the consumer. Due to this rapid expansion of commercial forests and our
ever changing climate including the sporadic increase and decrease in rain and the
increasing temperature caused by global warming, previously described and new
pathogens are emerging which infect and cause diseases on commercial forest trees
and agricultural crops. Research efforts are required to investigate mechanisms of
disease control and eradication to prevent the propagation and rapid spread of these
pathogens and ensure that there is limited economical loss of forestry and other
agriculturally important plants and trees.
Since both Xanthomonas and Pantoea species are becoming increasing important as
emerging bacterial pathogens, their rapid and accurate identification is crucially
important. Little is known about bacterial pathogens on forestry trees since the most
prominent diseases of these hosts are caused by fungi. The focus of this study was
to investigate and identify the bacterial pathogens associated with Eucalyptus.
However, as has been seen in various studies including this one, the identification of
these pathogens is not always straightforward and often time consuming. In this
study the use of polyphasic identification approach was used which employs a
combination of phenotypic and genotypic identification techniques.
Both of the genera investigated in this study, namely Pantoea and Xanthomonas,
have been found to infect a variety of agriculturally important plant hosts. Pantoea
species have previously been isolated from Eucalyptus trees suffering from blight
and dieback symptoms. The species isolated have included P. eucalypti from
Uruguay, P. vagans isolated from Argentina, Colombia, Uganda and Uruguay and P.
deleyi from Uganda. Since the first report of Pantoea on Eucalyptus trees from South
Africa in 2002 it has spread locally causing sporadic outbreaks. This pathogen has
also been isolated from Eucalyptus trees in other parts of the world including,
Argentina, Colombia, Thailand, Uganda and Uruguay. Xanthomonas campestris pv.
eucalypti was previously found to cause disease on Eucalyptus trees in Australia.
Since then, three other Xanthomonas species have been isolated from Eucalyptus,
namely, Xanthomonas spp. from Brazil (Goncalves et al., 2008), X. vasicola from
South Africa and X. fuscans from Uruguay as seen in this study.
