Agrobacterium rhizogenes-mediated genetic transformation and regeneration of a conifer:Larix decidua

Summary Gene transfer and plant regeneration systems have been developed for European larch (Larix decidua Mill.) in our laboratory. Aseptically germinated young seedlings were hypocotyl wound-inoculated withAgrobacterium rhizogenes strains 11325 containing a wild-type Ri (root-inducing) plasmid. Swollen stems appeared at infected wounds followed by either abundant hairy roots or adventitious shoot buds that developed within 3 to 4 wk after inoculation. No symptoms were seen on wounded but uninoculated seedlings. We demonstrated agrobacteria attached to larch cells by examination of scanning electron micrographs. Subsequently, calli derived from symptomatic tissues exhibited phytohormone autotrophic growth. Adventitious buds were elongated and rooted in vitro before being transferred to the greenhouse where the transformed whole plants grew normally. Transformants tested positive for opine production and transformation was further confirmed by Southern blot analysis with larch genomic DNAs isolated from both proliferated calli and needle tissue of transgenic plants.