Agrobacterium-mediated transformation of somatic embryos as a method for the production of transgenic plants

Summary Somatic embryos have been successfully used as a target tissue for transformation and regeneration of transgenic walnut plants. Walnut somatic embryos, initiated originally from developing zygotic embryos, proliferate numerous secondary embryos from single cells in the epidermal layer. These single cells in intact somatic embryos are susceptible to transformation by genetically engineeredAgrobacterium tumefaciens and provide a means to regenerate nonchimeric transgenic plants. This gene transfer system has been made more efficient using, a) vector plasmids containing two marker genes encoding -glucuronidase (GUS) and aminoglycoside phosphotransferase (APH(3)II) and B) a more virulent strain ofAgrobacterium. This system should be applicable to any crop that undergoes repetitive embryogenesis from singleAgrobacterium-susceptible cells.