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R437 Dickeya spp. Affecting GB Potato

Publication Date: 
16 April 2014
Author/Contact :
Author/Contact: 
Ian Toth

Contractor :
Contractor: 
James Hutton Institute (JHI)

Full Research Project Title: Investigating the biology and appropriate control of Dickeya spp. affecting GB potato
Duration: July 2010 - June 2013

Aim: To improve the understanding of the epidemiology of ‘Dickeya solani’ and to identify the risk of pathogen establishment and spread.

Industry Challenge

Preliminary research indicates that 'D. solani' may be significantly more aggressive than D. dianthicola and P. atrosepticum.  It appears to be able to rapidly induce blackleg symptoms and rot developing progeny tubers at low inoculum levels. In the Netherlands, where ‘D. solani’ has become more widespread and certification tolerances are higher, over 20% of seed stocks were downgraded or rejected in 2007, resulting in direct losses to seed growers of €25m.

Collaboration

FERA, SASA and James Hutton Institute (JHI)

Aims and Approach

This project built on previous Dickeya research funded by AHDB Potatoes (R290) and ongoing studies funded by the Scottish Government.  The objectives were as follows:

a) The extent of infection in England and Wales;

b) The spread of the pathogen from infected potato plants under controlled conditions and in commercial production;

c) The role of alternative hosts;

d) The survival of the pathogen in soil and in store.

The research was conducted in close association with collaborators in Europe and Israel already engaged in studying D.solani.

Key Findings

Independent data from both England/Wales and Scotland suggest that the movement of infected seed and not the environment is the principle route of spread of D. solani. No Dickeya infections have been found in Scotland since introducing legislation in 2010 and the numbers of non-Scottish origin seed is dwindling. Only very few waterways show contamination by the pathogen and, although in one case there is evidence of re-isolation over several years, the numbers isolated from water appear to be below that needed for disease to spread via irrigation. However, advice remains not to irrigate from such sources.

D. solani was able to spread from infected plants to neighbouring tubers at very low levels but there was no evidence that weeds were being contaminated, in contrast to findings in continental Europe where spread between potato plants and between potato and weeds is more efficient, perhaps due to differences in climatic conditions. Although no spread to or from weeds in the field / raised beds was observed under UK conditions, colonisation of some weeds and subsequent disease development in annual nettle was seen under glasshouse conditions.

There was little evidence for overwintering, although the pathogen was able to survive and in some cases increase slightly on stored tubers. The pathogen did not survive well on surfaces even in the presence of common materials, and standard disinfectants used at the correct concentration were able to control the pathogen on such surfaces. However, direct contact between healthy and rotting tubers was very likely to pass on contamination potentially leading to extensive disease development in the field.

Like P. atrosepticum, disease incidence caused by D. solani is related to the level of tuber contamination but seasonal conditions also have a major role. As part of the project, two new PCR-based diagnostics have been developed to detect and identify D. solani and these are in regular use. Three further DNA-based methods for tracking different isolates of D. solani have been developed and their use investigated. However, as all isolates are highly similar these methods have some limitations in their ability to track outbreaks.

A Grower advice leaflet has been updated with information generated by the project.

Reports

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