Armin Braun already speculated in 1947 that DNA may be involved in this transformation process. But research really took off in 1967, when Rob Schilperoort showed that Agrobacterium RNA could hybridize with crown gall DNA,indicating that bacterial DNA had indeed been transferred.

This paper was also what got Mary-Dell Chilton interested. She had previously pioneered a new, more sensitive DNA-hybridization technique, which she intended to use identify the transferred DNA. However, she failed to detect any agrobacterial chromosomal DNA in the plant tumors.