Agrobacterium rhizogenes inserts T-DNA into the genomes of the host plant root cells.

Chilton was the first (1977) to demonstrate the presence of a fragment of Agrobacterium Ti plasmid DNA in the nuclear DNA of crown gall tissue. Her research on Agrobacterium also showed that the genes responsible for causing disease could be removed from the bacterium without adversely affecting its ability to insert its own DNA into plant cells and modify the plant's genome. Chilton described what she had done as disarming the bacterial plasmid responsible for the DNA transfer. Using Agrobacterium carrying the disarmed Ti plasmid, in 1983 Chilton and her collaborators produced the first genetically modified plants.