In the DuRPh project, various potato varieties have been successfully given one or more resistance genes against Phytophthora. Beginning next year, field tests of management strategies can be conducted.
Photo: Researchers Anton Haverkort (in front) and Ronald Hutten on a test field with genetech potatoes.
‘In DuRPh, we are determining if we can use genetic modification to make potatoes resistant to Phytophthora', explains researcher Ronald Hutten of the Laboratory of Plant Breeding. ‘It would be ideal if we could control Phytophthora by giving an existing variety a series of different resistance genes. If you have series of genetically transformed plants of one variety, then you could plant them on capture fields and determine which genes are working at that time, at that location. You can then use this information to attune your cultivation methods and Phytophthora control.’
For example, if your potato crop has three resistance genes, and one of the resistances has been broken, then there is still no problem. However, if two of the resistance genes have been broken, then you must spray preventively; if the final active resistance is broken, then the crop will become infected.
The advantage of building in resistance genes against Phytophthora using genetic modification is that you can determine whether a resistance is durable at a much earlier stage than with classical breeding, and you can use the best resistance genes or combinations of genes. ‘At Wageningen UR Plant Breeding, we have cloned a number of resistance genes against Phytophthora, one of which is now being used in the DuRPh project. Before they are cloned, classical breeding is generally used to determine that these resistance genes are valuable. DuRPh therefore benefits more from classical breeding than the other way around.’
With classical plant breeding, the genes always end up at the same location in the genome, but if you make GMOs, then they end up at random locations in the genome. ‘This could be one of reasons why you find many transformed plants that deviate from the original variety’, explains Hutten.
The DuRPh study has shown that approximately half of the transformed plants with one new gene deviate to some extent from the original variety. ‘We expect that building in more resistance genes will make it increasingly difficult to obtain good GMOs. It takes longer before you have a new plant following the laboratory phase; as a result the percentage of deviating transformants increases.’ However, you can see the deviating plants at an early stage on the test field. For example, they may be smaller, have a different type of leaf, ripen later or flower differently. The cooking quality is sometimes different as well.
The researchers will need a few more years before genetically modified potatoes can be marketed that look exactly like the original variety. ‘This year we have 1000 plants for seed potato production. Beginning next year, we can begin testing management strategies with these strains’, Hutten concludes.