In order to discover the causes of Clavibacter outbreaks, modern molecular DNA techniques are being brought in increasingly often. An outbreak of Clavibacter in a tomato crop lead to large-scale damage to the grower. It is really important to discover the source of such an outbreak. Does it come from the seed or has it come into the glasshouse in another way?
Years of DNA experience
Testing for Clavibacter consists of two steps: detection and confirmation, and research into the source of the bacteria. The last step takes place on a DNA level. Naktuibouw has been working for more than 10 years on molecular DNA techniques (fingerprint) to discover the source of transmitters such as Clavibacter. The application of the DNA technique 'AFLP' made it possible to trace the source of a large inumber of Clavibacter outbreaks in tomatoes. It came from two seed batches from a seed supplier.
A lot of info confirmed
Naktuinbouw have collected more than 800 Clavibacter isolates, from which they identified the AFLP profile. Due to their years of experience with AFLP and their database of AFLP profiles, Naktuinbouw has a really reliable system. In addition to the collection for Clavibacter, Naktuinbouw has isolate collections and AFLP profiles for various other seed transmittable pathogens.
Improvements in testing
During the 2007 Clavibacter outbreak in Holland, it became clear that the current Clavibacter test was unreliable. Clavibacter was sometimes not detected in an infected seed batch. That led to an improvement in the Clavibacter test by Naktuinbouw together with seed companies and NVMW. New growing medium and new PCR primers were developed to more accurately check whether seed was infected with Clavibacter.
This test has become the European standard for detection of Clavibacter in tomato seeds. This European standard, used by all the plant disease expert services in Europe, gives a high level of certainty of detection. This means that infected seed can be prevented from reaching the grower and causing damage. The standard was set up by the Belgian Institute for Agriculture and Fisheries research (ILVO) in collaboration with Naktuinbouw, the Dutch Food and Foodstuffs Authority, the French GEVES and various seed companies.
Parallel forensic research
Despite improvements, it is not always possible to detect the culprit. Parallels can therefore be drawn with forensic reseach where the culprit is not always detected. But in reality, microbiology and molecular DNA techniques are constantly developing whereby the chances of detection of Clavibacter in tomato seeds is increasing. Naktuinbouw is playing an important role by working together internationally to develop the best possible techniques. Research continues to be necessary, both in relation to testing as well as the prevention of spread (epidemiology) of Clavibacter.