contains the amchs 5 u2032 bpf3 u2032 5 u2032 h 40 petd8 3 u2032 expression cassette and the petunia genomic dfr a pet gen dfr genes along with a camv35s 5 u2032 ds carn dfr 35s 3 u2032 expression cassette and the 35s 5 u2032 surb selectable marker gene the disarmed agrobacterium tumefaciens strain used was agl0 lazo et al 1991 supra plasmid dna was introduced into the agrobacterium tumefaciens strain agl0 by adding 5 u03bcg of plasmid dna to 100 u03bcl of competent agl0 cells prepared by inoculating a 50 ml lb culture sambrook et al molecular cloning a laboratory manual cold spring harbor laboratories cold spring harbor ny usa 1989 and incubation for 16 hours with shaking at 28 u00b0 c the cells were then pelleted and resuspended in 0 5 ml of 85 v v 100 mm cacl 2 15 v v glycerol the dna agrobacterium mixture was frozen by incubation in liquid n 2 for 2 minutes and then allowed to thaw by incubation at 37 u00b0 c for 5 minutes the dna bacterial mix was then placed on ice for a further 10 minutes the cells were then mixed with 1 ml of lb sambrook et al 1989 supra media and incubated with shaking for 16 hours at 28 u00b0 c cells of a tumefaciens carrying the plasmid.