sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

4. DISCUSSION
SDÜ Faculty of Forestry Journal
A novel, quantitative real-time PCR assay has now been developed to detect the
pathogenic bacterium, P. syringae pv. aesculi, which is currently causing a severe
bleeding canker disease of horse chestnut trees in several European countries
(Green et al., 2009). The real-time PCR primers were shown to be both highly
specific, giving exponential amplification only with the target pathogen, and highly
sensitive, allowing detection of P. syringae pv. aesculi down to 1 pg DNA in
diseased horse chestnut tissues with the optimised reaction conditions used (Green
et al., 2009). This advance in methodology now provides a tool for the accurate and
sensitive quantitative detection of P. syringae pv. aesculi in host tissues, as well as
in different environmental substrates. This assay will be used to examine the ability
of P. syringae pv. aesculi to survive epiphytically in host material, and its potential
to contaminate rainwater and soil. The aim of this is to determine the routes for
transmission of the pathogen, and to explain the reason for its high mobility.
Research into P. syringae plant pathogens is currently of high profile
internationally due to their detrimental impact in the horticultural, agricultural and
forestry sectors (Kennelly et al., 2007; Perez-Martinez et al., 2008). Ongoing
research into the dentification of the key virulence and fitness genes of P. syringae
pv. aesculi through genome sequencing, combined with in vivo studies on
pathogenicity, will provide novel insights into the factors determining the
pathogenicity and fitness of an important and newly damaging P. syringae
pathovar on a woody host; this being an area for which information is currently
scarce.
The effectiveness of import and quarantine regulations and disease management
strategies designed to protect the agricultural, horticultural and forest industries
against exotic pathogens relies on a thorough understanding, based on sound
scientific data, of the routes of introduction and spread of exotic pathogens in new
locations. This is reflected in the current high priority given to these types of
studies within the European Union (EU), particularly given the recent, rapid
expansion of the international plant trade and an appreciation of the threat that this
presents. Current research on P. syringae pv. aesculi will identify the most suitable
genetic markers, based on genome sequence data, for studying the recent
evolutionary history of P. syringae pv. aesculi. These markers will then be used for
phylogenetic analyses to elucidate whether this pathogen is a new introduction to
Europe, and if so, when and from where it was introduced and routes of subsequent
spread within regions. The research briefly described here will be essential for the
development of more effective phytosanitary measures and disease management
strategies to guard against future threats posed by exotic bacterial pathogens. The
project will ultimately inform and guide management and mitigation strategies for
an important bacterial disease of an amenity tree species through increased
understanding of the causal agent.
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