RE S EARCH The first DuRPh field trials are encouraging R-gene: difference between life and death The trial in Wageningen was planted during April 2008 and infected with Phytophthora spores on July 1. Earlier infection is forbidden by the Hoofd Productschap Akkerbouw (HPA) (Main Commodity Board for Arable farming) on account of the significant risk of contamination in nearby potato fields. All trial plots were infected with a mixture of widely known Phytophthora strains. Via overhead irrigation, the foliage was being kept wet as much as possible, and after a month, the untreated early varieties were virtually completely dead, only the late maturing Aveka variety was able to hold on just a bit longer. There were big differences in the degree of infection in the fields. The plants with a resistant gene (R-gene) from a wild species were still beautifully green, whilst the plants of the non-adjusted original variety, or the wild type, were affected. Significant reduction in pesticides It is clear that the approach, inserting an R-gene, works effectively and can lead to a significant reduction in the use of pesticides. What we also see is that such varieties can be of real value. However, it is necessary that resistance is lasting and What is DuRPh and what is the obje In 2005, the Dutch government decided to stimulate potato breeding and genetic modification in particular. From the Economic Structure Enhancing Fund – FES (natural gas revenues), 10 million euros were made available to Wageningen University to research a Phytophthora-resistant potato. The terms of reference for this research were to explore the possibilities that genetic modification offers, because the Dutch government feared that, in the long run, the seed potato sector would lose the competitive battle. Especially if companies in other countries (America, China), where consumers and environmental organisations have fewer objections to GMO crops, were to continue on the path of genetic modification. At this moment – in 2009 – there are already more than 130 million hectares of genetically modified crops worldwide (that is more than 30 x the surface area of the Netherlands). These crops are predominantly maize, soya and cotton, which have been made resistant to insects or pesticides such as glyphosate or glufosinate: transgenetic crops with genes from other varieties than the plant variety itself (from the Baccillus thuringiensis bacteria or Bt, for example). Consumers in Europe have objections to these transgenes in particular. At all events, our chickens, pigs and cows are eating plenty of genetically modified feed from modified soya and maize from which oil and starch have been extracted for human consumption. Stimulus for sustainable resistance The government subsidy enabled us to give our aim for sustainable resistance a generous stimulus, as sustainable resistance had not yet been successful. This is due to the fact that the single gene introduction from the wild variety Solanum demissum was broken down by Phytophthora after a few years. This fear of broken down resistance also exists for prospective new varieties treated with a single gene from the wild Solanum bulbocastanum species. It is, however, not easy to combine both Phytophthora resistance and other characteristics such as colour of flesh and baking quality, as a result of which many varieties are many decades to more than a hundred years old. The programme is called DuRPh: Durable Resistance against Phytophthora (in dutch this means ‘courage’), and is based on a number of principles. The principles of DuRPh DuRPh uses modern laboratory techniques, which accelerate the breeding process enormously, in this case genetic modification. In doing so, we only work with cisgeneses. This is a method whereby, when transferring genes, we only use genes that are derived from wild potato species, the same genes as those that can also be used for normal crossing. The final product is therefore pure potato without genes from other crops. In doing so, we keep the varieties we have with all their historically-proven culinary characteristics. We want to avoid the risk whereby inserting a sin24 Potato World 2009 • number 1 Pagina 23

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