Biotechnology- Gene Transfer: Terminology, Techniques, and Problems Involved

crosses with one of the parents are often required, adding time to the process. Likewise, conventional breeding is limited to a relatively narrow genetic base since the trait must be present in a sexually compatible species. Even within a species, there is often considerable incompatibility, impeding the incorporation of selected traits into new cultivars. The use of recombinant DNA opens the door to a vast array of beneficial genes-genes that are not restricted to a given plant species, but may be obtained from any organism. The ability to isolate, clone, and insert specific genes into plants allows specific improvements in superior lines. At present, however, only traits controlled by one or very few genes can be transferred. Likewise, our knowledge of the mechanisms controlling gene expression is limited. Insertion of a gene that is transcribed in the wrong tissue, at the wrong time, or to an undesired degree is of little value. Two approaches that have been proposed for the incorporation of superior genes using recombinant DNA are: 1) insertion in a superior line from a conventional breeding program; or 2) insertion in a sexually compatible line that then can be used as a parent in a conventional breeding program. With either, it is evident that gene transfer using recombinant DNA technology will not replace conventional breeding programs. Rather, it represents a powerful new tool for plant breeders that will allow them to achieve previously unthinkable accomplishments with their individual crops. Since the number of horticulturists using recombinant DNA represents only a minute percentage of our total Society, our intent was to present a colloquium directed toward horticulturists not involved in recombinant DNA research. In the following reports, we hope to provide: 1) an overview of how recombinant DNA is used to produce transgenic plants; 2) an understandable critique of the new vocabulary that has emerged; 3) the state of genetic engineering for horticultural crops; 4) a description of some of the problems that are slowing progress; and 5) the potential for the use of recombinant DNA in horticulture.