PW-ACTUA The Dutch General Inspection Service for Agricultural Seed and Seed Potatoes (NAK) is aware of importance of PCR technology It will be possible for the first time this year to have seed tested at the NAK – with the exception of virus infections – for all three types of Erwinia. This will be carried out with the aid of PCR technology, which makes it possible to determine accurately whether or not certain pathogens are present. So far, 280 samples have been sent in for Erwinia testing, which is disappointing. Managing director Pieter Oosterveld had expected this to be more. ‘We know that Erwinia is one of the biggest problems in the cultivation of seed potatoes’, he tells us somewhat amazed. He thinks that the reason must lie in the intangibility of the pathogen. ‘It is by no means certain that an infected lot will give problems in the following cropping year. It is also possible that we won’t find anything in the sample but Erwinia problems do occur anyway.’ It costs 195 euros to have a sample of two hundred tubers tested for Erwinia. This may be one of the reasons for the disappointing entry figures. ‘The PCR test is a quick one that is demonstrably effective in detecting the presence of a pathogen’, says NAK laboratory manager Miriam Kooman. The differences are due to the method of sampling, ‘For it is not possible to test all the tubers from a lot’, she concluded matter-of-factly. ‘Statistical analysis shows that, in the case of a sample consisting of two hundred tubers, the probability of catching the pathogen is reasonably high whether the sample contains DNA. This all happens fully automatically. In the end, the computer provides a graph which enables you to see whether a lot is infected or not, explains Kooman. In the end, the computer provides a graph, which enables you to see whether a lot is infected. and the costs are not too bad.’ PCR multiplies DNA Bacteria, and also viruses, in a sample often contain small quantities of DNA that can be immediately used for testing. Thanks to PCR technology, it is now possible to multiply the DNA in the samples. The PCR apparatus is, in fact, nothing more than a very accurate heating and cooling device, which contains the tubes with the DNA sample and other ingredients that are necessary for the reaction. The procedure starts with heating up the sample to a temperature between 900 and 950 C. As a result, each double DNA strand splits into two single strands. Subsequently, the temperature is again lowered. The primers can attach themselves to the individual strands so that a full DNA is formed. The DNA present is now doubled. The PCR machine starts warming up again, as a result of which all the DNA split again. This continues 36 times until there are finally 86 billion pieces of DNA. The specific Erwinia DNA has a ‘little lamp’ through which you check Practical tests To discover the exact the value of the Erwinia test, field staff manager, Ton Stolte, tells us that the NAK is going to compare the laboratory test results with the offspring tubers of the tested lots next year. In this way, the NAK hopes to get a picture of whether the test method is in line with practical reality. ● Production growth results in expansion at Tolsma Tolsma has started expanding and renovating its company premises in Emmeloord. In the past few years, the turnover, workforce and the activities of Tolsma have increased to such an extent that the company has had to expand and renovate its premises. The company, which is active in the development and production of storage technology for onions and potatoes, is constructing this new building next to the existing buildings in the village of Emmeloord. The new office will have a section especially geared to giving presentations and training. The transfer of knowledge about storage technology and the provision of total solutions are the most important pillars of the company. It is expected that an increasing portion of export activities will provide a further growth in the turnover in the future.● Potato World 2010 • number 1 7 Pagina 6
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