The basic principle of classical plant breeding is to combine advantageous traits in crops like disease resistance and high yield and at the same time eliminate unfavorable traits like bitter taste. For this purpose, the breeder is crossing an elite cultivar of a crop with close relatives. The genetic information coding for all traits is coded in genes, which are linearly packed like beads on a string on a smaller number of individual chromosomes. By crossing, an exchange of traits between parental chromosomes can be achieved. However, in many cases individual traits cannot be combined due to their specific position on a chromosome, especially if they are close to each other. Thus, it is often not possible for the breeders to obtain crops resistant to certain pests and the farmer has to use pesticides to protect the harvest. Also due to global warming, the heat and salt resistance of various crop plants needs to be improved, to avoid deleterious effects in future. These very important challenges for our global agriculture could be achievable by the development of specific technologies that allow controlled changes of plant chromosomes. Thus, it should be possible to change the structure of individual chromosomes as well as to the exchange segments between different chromosomes. Till now, the use of molecular scissors like CRISPR/Cas was restricted to the change of an individual and or a few genes. With this project we were worldwide the first to establish novel CRISPR/Cas based technologies for plant chromosome engineering. We were not only able to demonstrate that Mbp-sized intrachromosomal inversions can be obtained but that also arms between different chromosomes can be exchanged. Moreover, we also developed a new technology for the controlled elimination of specific tissues, “CRISPR-Kill”, which could be used e.g. to eliminate specifically cells that produce toxins. Thus, we established a novel kind of breeding that will help us to cope with the challenges of the 21th century. Closely linked traits can now be separated and genetic exchange can be induced in regions of the plant genome that were inaccessible for breeding before.
