Agrobacterium tumefaciens is a pathogen of several dicot plants. Ti plasmid in Agrobacterium has the ability to induce tumor in plants. This plasmid is 'disarmed' by suitable modification and then it can be used as a cloning vector for delivering gene of interest to plants and animals. Therefore, Agrobacterium tumefaciens is able to deliver a piece of DNA known as ‘T-DNA’ to transform normal plant cells into a tumor and direct these tumor cells to produce the chemicals required by the pathogen.