Abstract
Abstract From 2006 through 2015, a research project on Durable Resistance in potato against Phytophthora (DuRPh) was carried out at Wageningen University and Research Centre. Its objective was to develop a proof of principle for durable resistance against late blight by cisgenesis. This public-funded project aimed at stimulating research on genetic modification and public debate on innovative genetic techniques. It was decided to clone and transfer late blight resistance (R) genes of crossable wild potato species (cisgenes) by Agrobacterium tumefaciens-mediated transformation without non-potato genes. A stack of multiple R genes were planned to be inserted into established varieties, thereby creating a dynamic variety in which the composition of the stacks may vary over space and time. Cisgenic plants were selected based on the expression of all inserted R genes and trueness-to-type. Within the project, 13 R genes from wild potato species were genetically mapped and three of them were cloned. Four varieties were transformed with one to three R genes. This was initially done using kanamycin resistance provided by a selectable marker gene of synthetic origin in order to quickly test the performance and stability of the introduced R genes and stacked R gene combinations. Once the functioning thereof was confirmed, marker-free transformations were conducted; thus, true cisgenic events were selected. The results about the different R genes, their chromosomal location, their specificity, the background dependence, the maximum size of a stack, its regeneration time and associated somaclonal variation frequency and its stability were studied. After selection and characterisation in the laboratory, the best cisgenic events were assessed in field trials for late blight resistance. This showed that inserted R genes were capable of turning a susceptible variety into a resistant one. Maximising longevity of the resistance was assured through resistance management research. It was shown that stacking of multiple R genes and monitoring how to deploy these stacks spatially and temporally could reduce fungicide use by over 80%. Communications through media and field demonstrations were manifold to allow public and policymakers to decide if cisgenesis is an acceptable tool to make potato farming more sustainable. Future deployment of the DuRPh strategy will depend largely on its status as a genetically modified crop or its exemption thereof. Worldwide near eradication of late blight would increase global annual potato production by close to 80 million tons, thereby contributing considerably to the needed additional global future food supply.
Highlights
In 2005, an interdepartmental group of policymakers of the Netherlands government came to Wageningen University and Research Centre to commission a research project on genetic modification in crops
A vision on biotech and innovation, expressed by a joint project group of several Netherlands ministerial departments, identified important stumbling blocks for the acceptance of genetically modified crops. These were that citizens are informed too little or unilaterally; that the government, science and industry were insufficiently transparent; and that these parties offered citizens too few possibilities to learn and comment when it comes to research and development with respect to genetic modification (GM) crops
It was, repeatedly shown that R gene-mediated host resistance was overcome by P. infestans (e.g. Black et al 1953), especially if the resistance is based on a single R gene
Summary
In 2005, an interdepartmental group of policymakers of the Netherlands government came to Wageningen University and Research Centre to commission a research project on genetic modification in crops. A vision on biotech and innovation, expressed by a joint project group of several Netherlands ministerial departments, identified important stumbling blocks for the acceptance of genetically modified crops These were that citizens are informed too little or unilaterally; that the government, science and industry were insufficiently transparent; and that these parties offered citizens too few possibilities to learn and comment when it comes to research and development with respect to GM crops. An R gene that is overcome results in an initially tiny fraction of the P. infestans population that is compatible with this R gene This fraction is dynamic and will increase or decrease depending on circumstances (Skelsey et al 2005, 2010). P. infestans is continuously involved in an internal competition from which the most rapidly reproducing genotype(s) will prevail and become dominant resulting in increasingly aggressive P. infestans genotypes and clonal lines such as EU13_A2 (Cooke et al 2012)
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