Genetic Engineering in Crop Plants Using Tissue Culture and Tissue Culture-Free Environment

Genetic engineering is a new plant breeding technique for the efficient and precise transfer of desired gene into a host plant for increasing its quality and productivity. By virtue of totipotency, an isolated cell can regenerate into a new plant, which is a prerequisite for carrying out genome editing of plant cells. The majority of transformation methods include Agrobacterium tumefaciens and biolistic approaches for introducing gene of interest into host plants. Tissue culture plays pivotal role in regeneration of selected calli on a chemically defined growth medium followed by the selection of transformants. Transformants are sub-cultured onto new culture media before being cultivated in the field in accordance with government-regulated biosafety rules. It is an expensive process and requires expert tissue culture personnel; in addition, there are chances of occurrence of somaclonal variations that hinders the affluence of tissue culture approach. Therefore, the genetically engineered plants are also developed under the tissue culture-free environments, namely pollen transformation, co-cultivation approach, floral dip method, agro-infiltration, and in planta transformation in which Agrobacterium infects the seeds or plantlets, thus overcoming the steps of regeneration in tissue culture medium in the incubation room for successful transformation. The transgenic plant production in environment free from tissue culture conditions holds promise for crop improvement in the functional genomics era as it leads to insertion of novel genes of interest into the plants genome with no prerequisite of tissue culture expertise. This chapter explains the different approaches utilized for genetic transformation of different crop plants, as well as current and emerging trends and their applications in diverse fields.