One of the most promising approaches currently available to improve the quality, diversity, and yield of our crop plants is genetic engineering. In a broad sense, the genetic engineering of plants connotes a manipulation of plant cells and organs at the molecular level leading to the introduction, integration, and expression of specific and useful segments of foreign genetic material in a host plant. The application of genetic manipulative techniques has resulted in the production of plants with altered metabolic pathways and useful agronomic traits such as insect, viral, or herbicide resistance; it has also generated custom-made male-sterile plants useful in hybrid seed production. Other genetic engineering approaches, such as improving the post-harvest qualities of fruits and vegetables and creating crops that synthesize useful vaccines, Pharmaceuticals, or chemicals, are already at an advanced stage on the drawing board or are well into the developmental phase.

Historically, engineering of the first transgenic plants relied on the ability of the natural vector Agrobacterium tumefaciens to introduce recombinant DNA molecules into plant cells; in later years, this has become the most widely used procedure for the genetic transformation of various dicotyledonous plants. Cocultivation of isolated protoplasts with bacteria was the method of choice in some of the early attempts at Agrobacterium-mediated transformation.