Detecting the presence of the bacterium Erwinia in a shipment of seed potatoes that has already been approved is, unfortunately, still quite a common problem. Wageningen UR scientists have therefore developed a new test methodology which significantly reduces the chance of a false negative result for bacterial diseases. The approach can also be used to improve tests for bacterial diseases in other areas, such as seeds for sowing.
Below par bacterial disease diagnosis
Potato planting is in need of a new method to ascertain the presence of Erwinia (Pectobacterium and Dickeya) with greater certainty. “The current method only detects Erwinia in large concentrations,” explains Sjefke Allefs, director of cultivation and research at Agrico Research. “If only a fraction is present in the seed potatoes the chance of detection is very small.”
This is a highly undesirable situation for traders, growers and certification services: stocks should not be declared pathogen-free unless they actually are. If bacteria are present in the seedlings this can lead to reduced yield and quality during the growing season. It also harms the image of the grower and trader, and can lead to damage claims.
Reliable detection test for Erwinia
Scientists at Wageningen UR, together with colleagues from the private sector, have successfully developed a new test within the Delta Plan Erwinia. The major difference from the old method is the way in which the random sample is taken. Where the old method involved taking a sample from the entire batch of potatoes, the new one only looks at rejected tubers with defects that caused them to be removed by farmers on the sorting belt. This is because Erwinia is more likely to be found in these potatoes than in a batch taken as a whole. Moreover, the test looks at the entire tuber instead of just a section.
Considerably higher chance of finding bacterial diseases
The entire rejected tubers are kept under vacuum in plastic bags for seven days, so that any Erwinia present has the best possible chance to develop. This detects ten times more contaminations than when testing a piece of a regular sample. The likelihood of finding Erwinia is thus considerably greater.
The new test is especially useful for traders as they can give better guarantees to growers that there is no Erwinia in their seed potatoes. The General Netherlands Inspection Service for Field Seeds and Seed Potatoes (Nederlandse Algemene Keuringsdienst voor zaaizaad en pootgoed van landbouwgewassen, NAK) may be less able to handle this as it uses the same tubers for the detection of other pathogens.
Detection of Xanthomonas or Clavibacter
The above method can also be used to find pathogenic bacteria in other crops. The Wageningen UR scientists are currently focusing on the detection of Xanthomonas in cabbage seeds and Clavibacter in tomato seeds. The focus is on increasing the number of bacteria in the seeds in order to increase the chance of detection.
To find out more about detection possibilities for Erwinia and other pathogenic bacteria in various raw materials, contact Jan van der Wolf.