title: Genetic transformation and plant regeneration of watermelon using Agrobacterium tumefaciens.
abstract: Adventitious shoots formed on the proximal cut edges of different cotyledonary explants of watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai; cvs. Sweet Gem and Gold Medal] cultured on Murashige and Skoog's (MS) medium with 1 mgl(-1) 6-benzyladenine (BA). Light (16-h photoperiod, about 7 Wm(-2) cool-white fluorescent lamps) was essential for shoot formation. To obtain transformed plants, cotyledonary explants of 'Sweet Gem' were cocultured with Agrobacterium tumefaciens LBA4404, a disarmed strain harboring a binary vector pBI121 carrying the CaMV 35S promoter-β-glucuronidase (GUS) gene fusion used as a reporter gene and NOS promoter-neomycin phosphotransferase gene as a positive selection marker, for 48 h on MS medium with 1 mgl(-1) BA and 200 μM β-hydroxyacetosyringone. After 48 h of culture, explants were transferred to medium with 1 mgl(-1) BA 250 mgl(-1) carbenicillin, and 100 mgl(-1) kanamycin and cultured in the light. Adventitious shoots formed on the explants after 4 weeks of culture. When subjected to GUS histochemical assay, young leaves obtained from the shoots showed a positive response at a frequency of up to 16%. Preculturing cotyledonary explants on MS medium with 1 mgl(-1) BA for 5 d enhanced the competence of the cells to be transformed by Agrobacterium. Southern blot analysis confirmed that the GUS gene was incorporated into the genomic DNA of the GUS-positive regenerants. The transformed plants were grown to maturity.
authors.affiliation: Plant Cell Biology Laboratory, Genetic Engineering Research Institute, KIST, Taejon, Korea.
authors.forename: P S
authors.initials: PS
authors.lastname: Choi
authors.forename: W Y
authors.initials: WY
authors.lastname: Soh
authors.forename: Y S
authors.initials: YS
authors.lastname: Kim
authors.forename: O J
authors.initials: OJ
authors.lastname: Yoo
authors.forename: J R
authors.initials: JR
authors.lastname: Liu