Cells/Tissues Conditioning for Facilitating T-DNA Delivery

Many review papers covered transformation protocols, and discussed factors influencing T-DNA delivery for an individual plant or for some related plant species. This chapter reviews and discusses extensively the factors enhancing T-DNA delivery and transformation efficiency in monocot, dicot and gymnosperm species. These factors are from four principal components involved in the Agrobacterium-mediated transformation process, namely Agrobacterium biology, plant biology, physical conditions and medium composition. Some factors enhance the competency of plant cells/explants, such as antioxidant, osmoticum and plant growth regulators pretreatment; or enhance the competency of Agrobacterium, such as chemical induction of vir genes. Other factors facilitate the interaction of Agrobacterium and plant cells, such as desiccation, temperature, light density, and silver nitrate in the co-culture medium. Optimization of these transformation factors has greatly increased transformation efficiency in many plant species. The challenges ahead include a better understanding of these factors and how they can be manipulated to generate protocols with increased efficiencies across genotypes and species. The development of technically “friendly” and robust protocols for gene transfer to an ever wider list of plant species should help the development of the next generation of transgenic plants.