On-site real-time PCR detection of Phytophthora ramorum causing dieback of Parrotia persica in the UK
1 Central Science Laboratory (CSL), Sand Hutton, York, YO41 1LZ, UK
2 Department for Environment, Food and Rural Affairs (Defra), Plant Health and Seeds Inspectorate (PHSI), Suite B, Tile Works Office Block, Whitestone Business Park, Withington, Hereford HR1 3SE, UK
Accepted: 20 Mar 2006
In Europe Phytophthora ramorum mainly causes dieback of Rhododendron and Viburnum, but in the UK it has also been reported on other ornamentals including Hamamelis (Giltrap et al., 2004) as well as on a limited number of tree species (Brasier et al., 2004).
In November 2004, Defra's PHSI collected samples from a public garden in south Wales where P. ramorum was under eradication. Each sample was tested on-site by CSL using real-time (TaqManÂ®) PCR for P. ramorum on a Cepheid SmartCycler (Tomlinson et al 2005). This identified P. ramorum on Parrotia persica (Persian ironwood; Hamamelidaceae), which was causing necrotic leaf lesions and twig dieback (Fig. 1). Duplicate material was also sent to CSL where P. ramorum was consistently isolated from both stem and leaf tissue following surface decontamination and isolation onto semi-selective medium (Lane et al., 2002). An ITS sequence was obtained from a culture of P. ramorum isolated from P. persica (GenBank DQ066919) and this was identical to other P. ramorum isolates on GenBank. Pathogenicity of the isolate was confirmed by wound-inoculating healthy leaves of P. persica with mycelial plugs and incubating these in a damp chamber at room temperature (ca. 20°C) in the laboratory for six days. Extensive lesions developed on the leaves and the pathogen was re-isolated from the leading edge; thus completing Koch's postulates. Healthy wounded leaves, inoculated with agar alone, did not develop symptoms.
This is the first report of P. ramorum affecting P. persica. The infected plant was destroyed and measures were taken to eradicate the pathogen according to EC phytosanitary legislation and the EC was notified.
We would like to thank Mr T. Davies for his help in confirming the identity of the host and for technical assistance with sampling. Funding for this work was provided by Defra's Plant Health Division and quarantine material was processed and held under Defra licence PHL 251A5016 (02/2005).
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This report was formally published in Plant Pathology
©2006 The Authors