The present invention provides systems and methods for generating clonal root lines, clonal root cell lines, clonal plant cell lines, and clonal plants and for expressing gene products in such cell lines and plants. In some embodiments, a viral vector containing a polynucleotide of interest operably linked to a promoter is introduced into a plant or portion thereof to generate clonal root lines, clonal root cell lines, clonal plant cell lines, and clonal plants. According to certain inventive methods, a viral vector containing a polynucleotide of interest operably linked to a promoter is introduced into cells of a plant cell line that is maintained in culture to generate clonal plant cell lines and clonal plants. The invention provides clonal root lines, clonal root cell lines, clonal plant cell lines, and clonal plants generated using inventive methods.