THERE'S a new "biotech" revolution under way that promises a big payoff for farmers.
It uses modern methods of molecular biology borrowed from the worldwide effort to chart the human genetic blueprint to map out the simpler genetic blueprints of plants and animals. With these methods, breeders can dramatically speed up improvement of crops and livestock without having to use controversial and highly regulated "genetic engineering" techniques. That's the message a panel of agricultural scientists brought to the recent annual meeting of the American Association for the Advancement of Scien ce (AAAS).
Plant breeder Mark Sorrells of Cornell University at Ithaca, N.Y., told a press conference that "recent advances in biotechnology are having a fairly dramatic impact on plant breeding." He added: "Many of these changes ... are paralleling ... human genome research projects. They use the same techniques and often are applied in precisely the same way."
This is an important early spinoff from the effort to map the human genome - the set of genetic instructions that govern human biological development from conception to birth - in which the United States alone expects to invest several billion dollars over the next 10 to 20 years.
Genome instructions for people, plants, and animals are encoded in the chemical structure of long molecules of a compound called deoxyribonucleic acid or DNA. Coherent segments of DNA that control different aspects of biological development are called genes. The DNA molecules carrying the genes are grouped together in bodies called chromosomes. These chromosomes carry the genetic heritage that parent organisms pass to their offspring generation after generation. Precise mapping
What the genome explorers are trying to do is map the precise location of various genes on the chromosomes. They want to tag the genes with distinctive markers the way a "dig safe" crew tags underground cables with distinctive little flags.
The tags are DNA sections that do not themselves take part in gene action. They may be small repetitive sequences called microsatellites or other structures that biochemical probes can recognize.
Gene-tagging technology is developing fast to meet the needs of human genome mapping. That is a long-term project. The practical payoff today lies in the fact that the technology already is at a stage where rapid progress is being made in mapping crop plant and livestock genomes. This is what is beginning to revolutionize plant and animal breeding.
Gene mapping is not new to breeders. They have worked for many decades to find on which chromosome and where on that chromosome genes for valuable plant or animal traits were located. But the only way they could tell what genes they were working with was to wait for the plants or animals to reach a stage where the effects of the genes were evident.
According to Gary Kochert of the University of Georgia at Athens, "That was a very difficult process." He explained that "if you were interested in plant genes you might look at how tall a plant was or what color it was."
He added that "very few plants or animals had good maps of genes because it took so much time and effort to make them." Quicker pace of crossbreeding
Now, with the new genetic markers, breeders can see what genes an organism has by studying the chromosomes of embryos and seedlings. This enables breeders quickly to find genes that confer such desirable traits as disease or pest resistance or enhanced milk production. Then breeders can readily know which strains to cross with each other to produce new strains with desired traits.
According to animal geneticist James Womack of Texas A&M University at College Station, "at any stage of development, even in the embryo, you could potentially test whether this individual is going to have certain carcass traits."
He adds that "we can produce [new] breeding stock in one generation instead of the three or four it takes now."
Dr. Sorrells notes that, with plants, tagged genes in a seedling can tell a breeder if the plant has resistance to certain pests. The breeder would not have to test the plants by exposing them to the actual pests in a greenhouse or experimental field.
Furthermore, Sorrells pointed out to an AAAS symposium that breeding with the aid of gene-tagging technology does not produce unnatural "genetically engineered" organisms. "Thus," he said, "there are no government restrictions on their release and public concern is not an issue."
At this point, genome maps of both crop plants and of cattle, swine, and chickens are rapidly approaching a degree of completeness where they should be able to aid the new high tech breeding within a few years.
Dr. Womack notes, for example: "We anticipate that we need a 250 to 300 marker map to utilize it for mapping economically important traits and we have a little over a hundred of those markers. So we're on our way."