The new techniques and their potential

Carole P. Meredith Assistant Professor, Viticulture and Enology, Davis

Inone sense, genetic engineering of plants not? In quantitative terms, great savings in plant function are still not well understood. is really nothing new. Since the beginnings of time and space are foreseen. It will become The ultimate practical value of genetic en- agriculture, when crop species were first do- possible to engineer, in one step, a specific gineering will vary from crop to crop. Some mesticated, people have modified plants to genetic change that would require several major agronomic crops, such as corn, can suit their needs. In saving seed from only generations in a breeding program. Whereas already be engineered quite effectively as a re- their best plants, ancient farmers practiced existing breeding programs commonly re- sult of highly sophisticated breeding technol- genetic selection. Systematic and scientific quire considerable amounts of land for plant- ogy that has developed around them. Genetic plant breeding began about 200 years ago and ing and evaluating the progeny of each cross, engineering, in the cellular and molecular has evolved into a powerful technology. Crop plant scientists employing the new technology sense, will be an alternative only for specific plants are now deliberately improved through can grow and evaluate 100 million cells, each breeding objectives that cannot otherwise be controlled pollinations to achieve defined ob- a potential plant, in a single small flask. achieved. At the other end of the spectrum jectives. But although genetic engineering is are the crops that are difficult to breed by ex- in a way as old as agriculture itself, in current Obstacles remain isting techniques, typically the large woody usage the term refers collectively to a number The most awesome aspect of the new tech- perennial plants. Their size, genetic complex- of very new techniques for changing plants nology is certainly the vastly extended range ity, and long generation time severely restrict genetically- techniques that do not rely on of genetic variability that will become avail- breeding progress. With these crops, genetic pollination, but instead involve genetic ma- able to the plant breeder. No longer will a engineering may become the method of choice nipulations at the cellular and molecular breeding program be limited to those charac- for many breeding objectives. levels. This technology promises to be a teristics that already exist within a species or Prospects for crop improvement are powerful adjunct to modern plant breeding. its very near relatives. Protoplast fusion, for expanding, not only because of cellular and The history of the new technology is very example, permits a breeder to use desirable molecular techniques, but also as a result of brief, beginning around 1970. At about that traits from other species that are related to advances in breeding technology. New cyto- time plant protoplasts were shown to be the crop, but not closely enough to permit genetic strategiesenable breeders to move spe- capable of regenerating entire plants. Other standard crossing. Other techniques, such as cific chromosomes into crop species. Crosses aspects of plant cell and tissue culture, such mutant selection, can generate new genetic between distant relatives are facilitated by as mutant selection and protoplast fusion, variants within a crop species. The rapidly de- novel embryo rescue techniques. Isozyrne were also developing rapidly, and plant scien- veloping recombinant DNA technology may technology is emerging as a powerful analyti- tists were beginning to recognize the potential ultimately enable us to use genes from any cal tool for several aspects of plant breeding. of cultured plant cells for genetic research. other organism to improve a crop. These are dazzling notions, certainly, but An exciting time Recombinant DNA the new technology is still in its infancy, and a Impressive as all these new techniques are, Simultaneously, breakthroughs in molecu- number of major obstacles must be overcome they are not likely to replace conventional lar biology led to the development of recom- before genetic engineering can become gener- plant breeding. They will instead be com- binant DNA techniques by which a gene ally useful for crop improvement. At present, bined with the existing methods in an inte- could be isolated from one kind of organism most of the new techniques are limited to very grated approach to crop improvement, each and introduced into another organism, per- few crop species-those in which plants can technique being used when it is the most ef- manently changing the genetic makeup of the be regenerated from single cells. Progress in fective and economical means to an end. recipient. Within the last few years, plant mo- this area is steady, however, and the list of The prospects for manipulating plants ge- lecular biologists have been able to isolate tractable crops is growing. Genetic changes netically have spurred plant scientists to un- specific important plant genes and study their other than those being sought often arise in precedented levels of activity. As the follow- structure and regulation. Research with sev- regenerated plants. We don’t yet know how ing articles illustrate, University of California eral plant pathogens has contributed signifi- to control this phenomenon. Some important scientists are playing a significant role in de- cantly to the development of techniques for traits-yield and flavor, for example-are velopment of this new technology. They are transferring genes into plant cells. The simul- extremely complex and are the net result of involved at all levels, from discovering new taneous advances in all these areas are rapidly many interacting components. It will no knowledge about plant genes to assessing ag- bringing together the components necessary doubt be quite some time before we under- ricultural needs. New techniques are being in- to genetically engineer crop plants. stand these traits well enough to orchestrate tegrated with old in a wide range of specific But what does the new technology offer them successfully at the cellular and molecu- crop improvement programs. For agricul- that existing plant breeding technology does lar levels. Even many less complex aspects of tural research, it is indeed an exciting time.

CALIFORNIA AGRICULTURE, AUGUST 1982 5