ABSTRACT
Yield enhancement of crops has been the most important goal in agriculture, and genetic manipulations in plants are pivotal in this effort. Until the early 1980s, traditional breeding had been virtually the only effort in altering plant genetic makeup so that desirable agricultural traits could be obtained. Although these breeding efforts have generated numerous new plant varieties that contribute enormously to the success of agriculture, recent advances in genetic engineering based on recombinant DNA and plant transformation technologies have allowed a much faster and more precise approach in manipulating plant genetics. Furthermore, the genetic engineering approach is not limited to introducing genes among plant species that can be cross-pollinated. Virtually any genes from diverse sources can be introduced to desirable plants. Both the Agrobacterium-based and biolistic plant transformation techniques have been well developed, and most crops, including wheat, rice, maize, soybean, and potatoes, are now routinely transformed by using these methods. These technical advancements, in conjunction with the vast amount of knowledge gained in plant biochemistry and physiology, have allowed researchers to alter plant functions by over-or underexpressing specific genes involved in key metabolic pathways, so that desirable metabolites are accumulated for the enhancement of plant productivity.
