ABSTRACT
Genetic engineering of crop plants represents a major milestone in modern agricultural science. The advent of recombinant DNA technology in the early 1970s and the subsequent development of DNA transfer techniques provided exciting opportunities for plant scientists to insert foreign genes from both prokaryotic and eukaryotic organisms into the genome of crop plants and achieve transgene expression. Technological advancements in plant tissue culture techniques facilitated introduction of foreign genes into the plant genome to produce transgenic plants. Transgenic plants expressing novel traits now are being widely cultivated for their improved yield, quality, and other value-added characteristics. It should be noted, however, that in most instances genetic engineering techniques provide only an alternative approach to conventional breeding programs. In crop improvement, conventional breeding and hybrid seed production are the mainstay in ongoing efforts directed toward varietal development (Morandini and Salamini, 2003). Nonetheless, modern genetic engineering technologies offer several unique advantages over conventional hybridization approaches. For example,
in vitro
DNA transfer techniques permit introduction of genes and other genetic elements among sexually unrelated organisms, thereby bypassing biological barriers. Such genetic manipulation can be accomplished using a large quantity of plant materials in a relatively small space with a year-round artificially controlled growth environment. Hence, use of genetic engineering techniques complements and expedites conventional breeding programs by increasing
diversity of genetic resources, enhancing efficiency and reducing length of time needed to introgress desirable traits into existing elite crop varieties. Genetic engineering also allows utilization of exotic genes for development of transgenic plants to produce proteins with novel nutritive, pharmaceutical, agrichemical, and industrial characteristics (Fischer and Emans, 2000).
