Tissue culture and regeneration: A prerequisite for alien gene transfer

Abstract

Introgression of genes from alien species into crop plants could be achieved through distant hybridisation aided by tissue culture-based embryo rescue techniques. Beside this, in vitro mutagenesis, gametoclonal/somaclonal variation and transgenesis are the other tools which can generate additional variability. However, all these tissue culture-based tools require totipotent tissues. The direct regeneration of plants from an explant without a callus stage via organogenesis or somatic embryogenesis is the quickest path for micropropagation. Because of their speed and low costs of culture phase and the fidelity of the genotype in the cloned progeny, systems with direct somatic embryogenesis or organogenesis are often recommended and subjected to transformation. On the other hand, most micropropagation procedures with a callus stage can be applied as a basis for transformation, and the fresh friable calli can be directly used as the transformation target. Cell and microspore suspension cultures have also been seen as the ideal targets for genetic transformation due to the largeamount of homogenous material, easy selection of the targeted cells and less chances of chimeric regeneration, while protoplasts due to exposed plasma membrane can introduce foreign DNA very easily and therefore form the ideal targets for generating unique and novel plants. This chapter discusses various plant regeneration methods andthe factors affecting them towards achieving alien gene transfer in crop plants.