Plant Viral Vectors- Viruses provide natural examples of genetic engineering, since viral infection of a cell results in the addition of new genetic material which is expressed in the host.

In both microbial and mammalian systems, viruses have played important roles in vector development, so it is not unexpected that plant viruses are considered as candidates for plant gene vectors.

Additional genetic material incorporated in the genome of a plant virus might be replicated and expressed in the plant cell along with the other viral genes. In fact, a simple but economically significant example of plant genetic engineering using a viral vector already exists.