Transgenic sweet potato plants obtained by Agrobacterium tumefaciens-mediated transformation

Stable expression of foreign genes was achieved in sweet potato (Ipomoea batatas (I,.) Lam) plants using an Agrobacterium tumefaciens mediated system. Embryogenic calluses produced from apical meristems of the cultivar White Star were multiplied and cocultivated with A. tumefaciens strain EHA101 harboring a binary vector containing the beta-glucuronidase (GUS) and neomycin phosphotransferase (NPT II) genes. The calluses were transferred to selective regeneration medium and kanamycin resistant embryos were recovered which developed into morphologically normal plants. Histochemical and fluorimetric GUS assays of plants developed from the kanamycin resistant embryos were positive. Amplified DNA fragments were produced in polymerase chain reactions using GUS-specific primers and DNA from these plants. Transformation was confirmed by Southern analysis of the GUS gene. With the developed method, transgenic sweet potato plants were obtained within 7 weeks. This method will allow genetic improvement of this crop by the introduction of agronomically important genes.