**2.3 Transformation of desired gene into the plant cells**

Transformation of transgenes into the plant cells can be carried out through indirect or direct gene transfer methods. An indirect gene transfer (vector-mediated) method involves the introduction of exogenous DNA into the plant genome via biological vectors, whereas direct gene transfer methods involve the introduction of exogenous DNA directly into plant genome through physical or chemical reactions. The important physical and chemical gene transfer methods are electroporation, microinjection, particle bombardment, Polyethylene glycol and Liposome mediated gene transfer. *Agrobacterium*-mediated transformation is the most common technique used in plant transformation as it is efficient and effective in a wide range of plants [10]. This method had successfully transformed a broad variety of plants such as rice, maize, barley, and tobacco. Among the physical methods particle bombardment biolistic is the most common one used in plant transformation [11]. Currently, transient and stable transformation can be achieved through the *Agrobacterium*-mediated and biolistic methods. In the *Agrobacterium*-mediated method, the T-DNA region is inserted into the plant genome forming a stable transformant, whereas the non-integrated T-DNA plasmid expresses the transgene transiently. In the biolistic method or other direct gene transfer methods such as electroporation, transient and stable expression of the transgenes are usually dependent on the plasmid or transgene constructs.
