The introduction of DNA episomes into plant cells to reduce or prevent the expression of endogenous plant genes is described. Geminivirus vectors to provide silencing, preferably systemic silencing, of endogenous plant genes in a plant are described. Further provided are methods of silencing one or more plant genes, for example, to reduce unwanted gene products or for rapid screening of gene function in plants.
 This invention was made with government support under United States Department of Agriculture grant number NRICGP 97-35303-4538 and Tri-Agency Training Grant number NSF BIR9420689 from the National Science Foundation, United States Department of Energy, and the United States Department of Agriculture. The United States government has certain rights to this invention.