Genetic Transformation: A Means to Add Disease Resistance to Existing Grape

Methods for initiating embryogenic cultures, the starting material for genetic transformation, have been improved and large numbers of embryogenic cultures suitable for transformation have been produced from Chardonnay and Thompson Seedless. A better strain of Agrobacterium (the gene delivery organism) was obtained. Methods for selecting and isolating putatively transformed somatic embryos have been improved. Transformation experiments with liquid cultures have not been successful. Several experiments with solid cultures of Chardonnay, Thompson Seedless and St. George, however, have yielded cultures that appear to be uniformly transgenic in that they express the blue color of the introduced GUS marker gene throughout the tissue. Some of these putatively transgenic embryos are being induced to germinate into plants so that they can be further tested for the presence and expression of the introduced gene.