TOOLS OF GENETIC ENGINEERING IN PLANTS
Transfer and expression of foreign genes in plant cells, now routine practice in several laboratories around the world, has become a major tool to carry out gene expression studies and to obtain plant varieties of potential agricultural interest. The capacity to introduce and express diverse foreign genes in plants, first described for tobacco in De Block (1984), has been extended to many species. Transgenic crops such as tomato, papaya, cotton, maize, soybean etc., are now available for human consumption and by complementing traditional methods of crop improvement (and thus becoming an integral part of agriculture), they will have a profound impact on food production, economic development and on the development of a sustainable agricultural system during the 21st century. Although the capacity to introduce and manipulate specific gene expression in plants provides a powerful tool for fundamental research, much of the support for plant transformation research has been provided because of the generation of plants with useful and rapidly discernible phenotypes which are unachievable by conventionalplant breeding i.e., resistance to viruses, insects, herbicides, or post-harvest deterioration (Nelson et al., 1988; Staskawicz et al., 1995). In this chapter the technical aspects of the state of the art in plant engineering are described. It also identifies technical problems remaining in the development of systems of plant transformation applicable to crop improvement.