Understanding the biology of the bacterial pathogen Dickeya solani and its potential to affect GB potato production
At the time the project was commissioned there was concern about the risks to potato production posed by the bacterial pathogen, Dickeya solani. Preliminary research had indicated that it might be significantly more aggressive than other bacteria such as Pectobacterium atrosepticum. The project built on previous Dickeya research funded by AHDB Potatoes and the Scottish Government.
FERA, SASA and James Hutton Institute (JHI)
Data from both England and Scotland indicated that the movement of infected seed, and not the environment, is the principle route of spread of D. solani.
No Dickeya infections had been found in Scotland since introducing legislation concerning the pathogen in 2010.
Only very few waterways show contamination by D. solani, although in one case there was evidence of re-isolation of the pathogen from the same waterway over several years. The numbers isolated from water appear to be below that needed for disease to spread via irrigation.
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 of the pathogen, although it was able to survive, and in some cases increase slightly, on stored tubers.
D. solani did not survive well on surfaces and standard disinfectants used at the correct concentration were able to control the pathogen.
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 in determining the amount of disease that develops.
As part of the project, two PCR-based diagnostics were developed to detect and identify D. solani. Three further DNA-based methods for tracking different isolates of D. solani were also developed and their use investigated. As all isolates are highly similar, the methods had limitations in their ability to track D. solani outbreaks.