Agrobacterium tumefaciens-mediated transformation of Swingle citrumelo (Citrus paradisi Macf.×Poncirus trifoliata L. Raf.) using thin epicotyl sections

Transgenic plants of the important citrus rootstock Swingle citrumelo (Citrus paradisi Macf. × Poncirus trifoliata L. Raf.) were obtained using Agrobacterium tumefaciens-mediated transformation of seedling epicotyl tissue. Thin sections were co-cultured with Agrobacterium strain EHA105 carrying pBI121, a plasmid that contains the nptII (pnos) gene and the uidA (p35S) gene for scorable marker β-glucuronidase (GUS). The use of thin sections and the application of increasing selection pressure (25 and 50 mg l?1 kanamycin) reduced the occurrence of escapes.With the procedure described here, a transformation efficiency of 8.6% was achieved, with less than 10% of escapes. Stable integration of the transgene sequence was confirmed by histochemical assay of
-glucuronidase, PCR and Southern hybridization.