2.1 Organism
R. rhizogenes strain LBA9402 is a rifampicin-resistant derivative of wild-type strain NCPPB1855, which was isolated in our laboratory (Hooykaas 1979), and which causes prolific hairy roots on infected plants. The bacterium was grown on TY medium (Difco tryptone 5 g/l, Difco yeast extract 3 g/l, CaCl2.6H2O 1.3 g/l). The bacterium was tested for virulence by puncturing the plant stems with a sterile wooden toothpick that had been dipped into a colony of the bacterium.