Transgene inactivation in Agrobacterium-mediated chrysanthemum (Dendranthema grandiflorum (Ramat.) Kitamura) transformants.

To compare transformation frequency and to investigate the developmental alterations in transgene expression, two cut-flower chrysanthemums ‘Yamabiko’ (spray-type) and ‘New Summer Yellow’ (standard-type) were transformed with three disarmed Agrobacterium tumefaciens strains C58C1, MP90 and LBA4404, all strains having the pBI121 plasmid. No marked difference was observed in transformation efficiency among cultivar/bacterial strain combinations. β-glucuronidase (GUS) activity levels in transformants were fairly low and varied among the different transgenic lines, ranging from 30 to 250pmol min-1 (mg protein)-1. GUS expression was not observed in the transgenic lines transformed with strain LBA4404. The alterations of GUS activity levels were examined for a long term, and it was observed that GUS activities reduced to zero level in most of transgenic lines 12 months after the inoculation of bacteria.