Agrobacterium rhizogenes causes a disease in susceptible dicotyledonous plants characterized by a proliferation of differentiated root tissue (hairy root) at the site of bacterial injection and following the transfer and integration of the T-DNA from the Ri-plasmid into the host plant genome (1,2). Recently, there has been increased interest in transformation of plants by A. rhizogenes (3,4). The ease with which Ri-TDNA-transformed plant cells of some plant species can be regenerated to whole plants suggests that an Ri-vector system might be a useful alternative to a Ti-vector system.