Fast molecular detection of Pseudomonas syringae pv. aesculi in diseased horse chestnut trees

Abstract

A molecular technique was used to detect the bacterium Pseudomonas syringae pv. aesculi in horse chestnut trees (Aesculus hippocastanum), affected by the recently recognized European ÔPseudomonas horse chestnut bark diseaseÕ. The technique helped identify the pathogen within 6 h of sample preparation including DNA extraction, polymerase chain reaction (PCR) and electrophoresis until gel documentation. PCR primer pairs derived from the gyrase B gene sequence were used. Because of the great similarity in the gyrase B gene sequences of the numerous closely related P. syringae pathovars, the primers were not only totally specific to the pathovar aesculi, but also detected a few other pathovars.The assumption that other bacteria should not occur at least near to a necrotic lesion of a horse chestnut tree was corroborated by sequence identity of the PCR products obtained with the gyrase B gene sequence of P. syringae pv. aesculi. KochÕs postulates were fulfilled for an isolate of P. syringae pv. aesculi obtained from a diseased horse chestnut tree sampled in Hamburg in 2007.

Bleeding canker of horse chestnut (Aesculus hippocastanum) in Ireland: incidence, severity and characterization using DNA sequences and real‐time PCR

“…aesculi cultures were isolated from two individual trees (Table a) from Beaulieu (1) and Tara (2). These gyrB sequences showed no differences from several isolates from the UK (; Green et al ., ), India (; Durgapal & Singh, ) and Germany (; Schmidt et al ., ) (Table ).…”

“…() from A. hippocastanum in the UK. The sequence also showed a 100% match to isolates from India (; Durgapal & Singh, ) and Germany (; Schmidt et al ., ). This supports the hypothesis that it is the same pathogen that is destroying horse chestnut trees elsewhere in Europe as well as A. indica in India.…”

“…Phytophthora is a destructive parasitic fungus‐like organism causing brown rot in plants (Brasier & Strouts, ). Each tree in the present study tested negative for Phytophthora , a finding consistent with several other authors (Bultreys et al ., ; Schmidt et al ., ; de Keijzer et al ., ; Mertelik et al ., ). However, Phytophthora is identified in one or two samples of horse chestnut a year (Forest Research, ).…”

“…Bleeding canker is an epidemic disease of horse chestnut ( Aesculus hippocastanum ) in many countries of northwest Europe (Green et al ., , ) that induces bark to exude a dark sticky fluid (Webber et al ., ; Schmidt et al ., ). The horse chestnut tree is native to northern Greece and Albania and was introduced into northern Europe in the late 16th century as an amenity tree and to Britain and Ireland c .…”

“…Since the early 2000s, the reported incidence of horse chestnut bleeding canker has dramatically increased and the disease has become severe in most areas of England, Wales and parts of Scotland. A similar increase in bleeding canker recordings has been found in the Netherlands (de Keijzer et al ., ), Belgium (Bultreys et al ., ), the Czech Republic (Mertelik et al ., ) and Germany (Schmidt et al ., ). In 2007, surveys showed 70% of horse chestnut trees in parts of England exhibited some signs of the disease, with 36% and 42% of the surveyed trees showing signs in Wales and Scotland, respectively (Forestry Commission, ).…”