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Protecting seed crops from Dickeya-blackleg threat

2 August 2011

Data from the recently approved project on ‘Dickeya solani’ will be collated over three years to result in a comprehensive picture with a view to recommending appropriate control measures.

Although not a quarantine disease, Dickeya is an increasing threat to the potato industry and has become a major cause of seed downgrading and rejections in Northern Europe.

The newly emerging species, proposed to be named ‘Dickeya solani’ causes an aggressive form of blackleg, especially under warm spring conditions, and has appeared  across a number of European countries. Its distribution in Britain is not yet fully understood,  but evidence collected by the Scottish Government demonstrates that Dickeya species have never been found in potatoes grown from seed of Scottish origin.

New research will lead to a better understanding of the epidemiology of the Dickeya pathogen, including its potential for survival and spread in the wider environment, including watercourses, soil and on contaminated machinery and graders. Furthermore, it will examine the risks of spreading the disease during handling of infected stock. It will also look to improve diagnostic techniques for more accurate and cost-effective detection of the pathogen in addition to examining sources of infection, alternative hosts, how and where it survives and the influence of climatic conditions.  Furthermore, it will monitor the distribution of the new Dickeya species compared with the older established cause of blackleg (Pectobacterium atrosepticum) in affected crops in England and Wales.

A number of  Dickeya spp. have been detected in  water courses in Northern Europe, therefore the risk of infection from irrigation will also be investigated.

 “This is quite a new pathogen and there are still many questions to be answered. The full extent of the risks this disease poses are still to be understood,” explains Dr John Elphinstone from Fera.

“However, the threat from Dickeya is also an opportunity for our seed industry, as the Safe Haven Scheme helps protect seed and ware from this potentially devastating disease. The high health status of seed certified by this scheme offers tangible advantages to our industry so we must do our utmost to protect it,” continues John.
“Fewer than 3% of plantings in Scotland are from non-Scottish origin seed.  This, along with current freedom from the disease in Scottish origin seed, presents an opportunity to keep this form of blackleg out of Scotland,” says John. “The project will also examine options that would increase the effectiveness of the current Safe Haven Scheme in preventing the entry of Dickeya.”

There are differences in regulation between Scotland and England and Wales. Scotland has introduced a nil tolerance policy, whereas in England and Wales there is a tolerance of up to 2% blackleg in certified seed.
All seed introduced to Scotland now has to have a pre-planting tuber test for Dickeya. Acknowledging that testing a sample of tubers before planting may not always spot the presence of the pathogen, the subsequent growing crops will also be closely monitored by inspectors. Samples from plants showing blackleg symptoms will be taken from all plantings of non-Scottish origin seed and 10% of Scottish origin crops.

“If the industry allows this disease to become established, growers will have a potentially more difficult form of blackleg to manage in both seed and ware crops, adding cost to potato production in Britain,” concludes John.

 The £470,000, three year project on ‘Dickeya solani’ is funded on a 50:50 spit between AHDB Potatoes and the Scottish Government and will involve collaboration between scientists at Fera, SASA and SCRI.   The project will also ensure co-ordination with research efforts elsewhere in Europe on control of this important pathogen.

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