Disclosed herein are viral vectors based on modifications of the Citrus Tristeza virus useful for transfecting citrus trees for beneficial purposes. Included in the disclosure are viral vectors including one or more gene cassettes that encode heterologous polypeptide s. The gene cassettes are positioned at desirable locations on the viral genome so as to enable expression while preserving functionality of the virus. Also disclosed are methods of transfecting plants and plants transfected with viral vector embodiments.