Phenotypically normal petunia plants carrying chromosomal inserts of either the tomato golden mosaic virus (TGMV) A or the B component DNA, as single or tandem inserts, were obtained using an Agrobacterium tumefaciens Ti plasmid-based transformation system. Southern hybridization analysis revealed that the tandem, direct-repeat A plants contained free single and double stranded A component DNAs. No free B component DNA was detected in plants carrying tandem repeats of the B component. Progeny of self-fertilized plants appeared normal. In contrast, one-quarter of the progeny from tandem A by tandem B plant crosses showed chlorotic lesions on their leaves similar to virus symptoms. The significance of these results and the use of this method for the study of virus functions involved in TGMV replication and symptom production are discussed.