title: Agrobacterium-mediated transformation of apple (Malus x domestica Borkh.): an assessment of factors affecting gene transfer efficiency during early transformation steps.
abstract: The factors influencing transfer of an intron - containing β-glucuronidase gene to apple leaf explants were studied during early steps of an Agrobacterium tumefaciens-mediated transformation procedure. The gene transfer process was evaluated by counting the number of β-glucuronidase expressing leaf zones immediately after cocultivation, as well as by counting the number of β-glucuronidase expressing calli developing on the explants after 6 weeks of postcultivation in the presence of 50 mg/l kanamycin. Of three different tested disarmed A. tumefaciens strains, EHA101(pEHA101) was the most effective for apple transformation. Cocultivation of leaf explants with A. tumefaciens on a medium with a high cytokinin level was more conducive to gene transfer than cocultivation on media with high auxin concentrations. Precultivation of leaf explants, prior to cocultivation, slightly increased the number of β-glucuronidase expressing zones measured immediately after cocultivation, but it drastically decreased the number of transformed calli appearing on the explants 6 weeks after infection. Other factors examined were: Agrobacterium cell density during infection, bacterial growth phase, nature of the carbon source, explant age, and explant genotype.
authors.affiliation: F. A. Janssenslaboratorium voor Genetica, Katholieke Universiteit Leuven, Willem de Croylaan 42, B-3001, Heverlee, Belgium.
authors.forename: A
authors.initials: A
authors.lastname: De Bondt
authors.forename: K
authors.initials: K
authors.lastname: Eggermont
authors.forename: P
authors.initials: P
authors.lastname: Druart
authors.forename: M
authors.initials: M
authors.lastname: De Vil
authors.forename: I
authors.initials: I
authors.lastname: Goderis
authors.forename: J
authors.initials: J
authors.lastname: Vanderleyden
authors.forename: W F
authors.initials: WF
authors.lastname: Broekaert