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

The aim of this project is to develop a means by which genes can be introduced into existing grape varieties. The genes being used at this early stage are model genes that are easy to detect in the laboratory but ultimately genes will be introduced that are intended to confer new characteristics without otherwise altering the distinctive characteristics of the variety. Genes conferring resistance to specific diseases and pests are of particular interest. During 1998-99, six transformation experiments were initiated and monitored for 6 to 9 months each. The experiments involved Chardonnay, Thompson Seedless, St. George and 11 OR and the experimental factors tested in the experiments included the culture medium, the gene vector and the selection conditions. Two of the experiments have yielded both somatic embryos and a few plantlets that developed after co-cultivation with the gene vector and exposure to selective pressure designed to allow only cells carrying the introduced genes to survive. Some of the embryos exhibit the blue color that indicates expression of the introduced GUS marker gene. However, none of the three plantlets that were tested expressed GUS. Several additional transformation experiments are in progress and it is still too early to evaluate them. During April and May 1999, approximately 8,000 immature grape flowers were dissected in order to culture their anthers to produce new embryogenic cultures. We initiate new cultures each spring so as to always have a supply of relatively young cultures for transformation experiments. Older cultures may accumulate genetic errors and can lose their ability to regenerate plants. Several research groups in other countries and in private companies are already well along in this kind of research, but public research in California has lagged behind because funding was not available for such long-term research. Now that financial support for viticulture research has increased, public research in this field can be undertaken at the University of California. It may lead to better pest and disease management and ultimately to better control of fruit composition.