Improving crops through transgenic breeding—Technological advances and prospects

Genetic transformation involving the manipulation of the plant's cellular DNA through recombinant DNA techniques is an effective method for crop improvement. Plant cellular genome could be modified genetically through different biological, physical, and chemical approaches and the transformation process is complemented by in vitro plant tissue culture methods or through a few in vivo methods. The success of the genetic transformation is dependent on the young and juvenile explant sources, treatment conditions, strains of the Agrobacterium deployed, genotype specificities, physiology of explants, etc. The soil borne gram-negative bacterium Agrobacterium spp., being a natural genetic engineer, has been utilized for genetic transformation of a wide variety of plant species. Physical techniques involve particle bombardment/biolistic method, sonication, microinjection, macroinjection, electroporation, nanoparticles, and silicon carbide fiber-mediated transformation, whereas the chemical methods maneuver transgenesis through application of chemical mediators. Success in the generation of transgenic plants has paved the way for advances such as multigene transfer, site-specific integration, regulated gene expression besides the utilization of synthetic promoters, transcriptional activators and repressors, and tools for the assembly, synthesis, and transformation of large DNA inserts to achieve high frequency and precise genetic manipulation. Genetic transformation techniques have also been applied in genome editing technology, and there has been significant success in developing genome-edited crops. Deployment of state-of-the-art technologies should foster the actualization of genetically improved plants for superior economic and commercial traits for their utilization in agriculture and industry.