The so-called Ti-Plasmid (Ti stands for tumour-inducing) is a small, circular DNA molecule common among bacterial pests in plants (e.g. Agrobacterium tumefaciens). The bacteria transfer the plasmid into plant cells resulting in genetic modifications that trigger the development of plant tumours.
In the 1970s, Prof. Dr Marc van Montagu and Prof. Dr Jozef Schell of the Max Planck Institute for Plant Breeding Research in Cologne developed the concept of using the Ti-Plasmid to introduce novel genes into plants by replacing the gene responsible for tumour development with the desired gene. The method opened up a new area of plant breeding as it allows for the introduction of genes from other species into a plant. The method is still unsurpassed by other technologies.