Virus Vectors - Many viruses or their isolated genomes are capable of infecting intact plant tissue. This made them suitable for use as plant transformation vectors. But since viral genomes can not integrate with plant genome, they can be used only for a study of transient expression of transferred genes.

All the three kind of viruses including caulimoviruses (double stranded DNA), gemini viruses (single stranded DNA) and tobacco mosaic virus (RNA) are capable of delivering genes into intact plant tissues, where they are expressed.

However, virus vectors can not be used for the production of stably transformed plants, popularly described as transgenic plants.