Tissue culture-based Agrobacterium-mediated and in planta transformation methods

Gene transformation can be done in direct and indirect (Agrobacterium-mediated) ways. The most efficient method of gene transformation to date is Agrobacterium-mediated method. The main problem of Agrobacterium-method is that some plant species and mutant lines are recalcitrant to regeneration. Requirements for sterile conditions for plant regeneration are another problem of Agrobacterium-mediated transformation. Development of genotype-independent gene transformation method is of great interest in many plants. Some tissue culture-independent Agrobacterium-mediated gene transformation methods are reported in individual plants and crops. Generally, these methods are called in planta gene transformation. In planta transformation methods are free from somaclonal variation and easier, quicker, and simpler than tissue culture-based transformation methods. Vacuum infiltration, injection of Agrobacterium culture to plant tissues, pollen-tube pathway, floral dip and floral spray are the main methods of in planta transformation. Each of these methods has its own advantages and disadvantages. Simplicity and reliability are the primary reasons for the popularity of the in planta methods. These methods are much quicker than regular tissue culture-based Agrobacterium-mediated gene transformation and success can be achieved by non-experts. In the present review, we highlight all methods of in planta transformation comparing them with regular tissue culture-based Agrobacterium-mediated transformation methods and then recently successful transformations using these methods are presented.