sdu faculty of forestry journal special edition 2009 - Orman Fakültesi

SDU Faculty of Forestry Journal
Serial: A, Number: Special Issue, Year: 2009, ISSN: 1302-7085, Page: 131-135
HORSE CHESTNUT BLEEDING CANKER – BAGGING THE BUG !
Sarah GREEN 1* , Bridget LAUE 1 , Grace MACASKILL 1 , Heather STEELE 1
1 Forest Research, Northern Research Station, Roslin, Midlothian, Scotland EH25 9SY
ABSTRACT
*sarah.green@forestry.gsi.gov.uk
Bleeding canker of horse chestnut, caused by the bacterial pathogen, Pseudomonas
syringae pv. aesculi, has rapidly established and become widespread throughout parts of
northern Europe, including Great Britain, over the last five years. Despite the fact that this
disease is having a devastating effect on an important amenity tree species, very little is
known about the infection processes of this pathogen, or the genetic and physiological
factors which cause it to be so highly damaging. One difficulty associated with studying
this pathogen is the lengthy procedure required to confirm its presence on the host. Realtime
PCR primers were developed based on gyrase B gene sequence data for the specific
detection of P. syringae pv. aesculi in infected horse chestnut. This quantitative real-time
PCR assay provides the facility to study several important aspects of the biology of P.
syringae pv. aesculi on horse chestnut including its potential for epiphytic survival on
healthy trees, as well as its dissemination in different environmental substrates, such as soil,
water and infected tree debris. As part of ongoing work, the complete genome of P.
syringae pv. aesculi is currently being sequenced to determine its complement of virulence
and fitness genes. Molecular tools are also being used to determine the origin of P. syringae
pv. aesculi, the location/s and time of its introduction and geographical routes of spread
within Great Britain and Europe.
Keywords: Pseudomonas syringae pv. aesculi, bleeding canker, Aesculus
hippocastanum, real-time PCR.
1. INTRODUCTION
In the last 10-15 years, there has been an unprecedented increase in the numbers
of hitherto unrecognised diseases attacking trees throughout the world. Many of the
causal organisms have been inadvertently introduced into new ecosystems through
the increase in global commerce, via pathways such as trade in live plants
(including soils), poorly treated timber products and international trade in bonsai
(Brasier, 2008). European horse chestnut (Aesculus hippocastanum), an important
amenity tree species throughout much of Great Britain and northern Europe, is
suffering from two major problems of recent introduction into the continent:
bacterial bleeding canker and the horse chestnut leaf miner. Native to northern
Greece and Albania (Phillips, 1978), horse chestnut was introduced into the UK in
the late 16 th Century and was planted widely in parks and gardens in both urban
and rural areas, often in avenues bordering roads. Horse chestnut is highly regarded
for its qualities as a shade tree, for its showy white flowers in spring and the
production of its fruits or ‘conkers’.
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