GE PROBLEMS KNOWN FOR A QUARTER
OF A CENTURY
Recombinant DNA molecular research probably will have little direct
impact on the development of useful new crop varieties. Complex,
delicately balanced interactions among many genes determine the
phenotypes of successful crop varieties. Changes of only one or a few
genes have had important useful effects in relatively few instances; the
total benefit of single gene changes in crop varieties is negligible
compared to the importance of complexly inherited traits.
-Dr. Don Duvick, then R+D director for Pioneer Hybrid, 1977
1. Benbrook on Dr Duvick's paper
2. A Note from Ag BioTech InfoNet on Dr Duvick's paper
3. Duvick's original paper
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1. Benbrook on Dr Duvick's paper - originated: email@example.com
We have posted perhaps the most interesting short paper on agricultural biotechnology I have ever read. It is a presentation made in 1977 to the NRC committee assessing guidelines for the use of recombinant DNA technologies. Read what Dr. Don Duvick, then R+D director for Pioneer Hybrid had to say 24 years ago re the applications and impacts of ag biotechnology, and compare his thoughts and predictions to the next few items posted on the page -- especially the recent Pollack NY Times article, Bob Goodman's reflections delivered before the AAAS meeting, and a little further down, the Soil Association policy paper.
Very rich food for thought. Friends in Europe -- do get this around, it may restore some faith in the U.S. scientific community. Go to item number one at --
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2. A Note from Ag BioTech InfoNet --
In 1977 Dr. Don Duvick was the director of plant breeding research in
Pioneer Hybrid. With Pioneer colleagues, he was actively exploring the
potential for applications of molecular genetics
to crop varietal improvement. He was invited to make this April 13, 1977 presentation before the National Research Council committee that was developing guidelines governing applications of recombinant DNA technologies.
Dr. Duvick's comments from 24 years ago are remarkably prescient, especially
in light of new insights from genomics and the recent reconsideration of
the most rewarding applications of
biotechnology in improving plant productivity. This brief paper also demonstrates how much was known then about the practical realities and limitations of varietal improvement and how relevant these insights are in assessing today's applications of biotechnology.
Thanks to Dr. Duvick for providing the text of his original written
presentation delivered before the NRC committee. Dr. Duvick, now retired
but still active, can be reached at DND307@aol.com.
We also recommend Don's more recent andexcellent papers on heterosis from an important conference proceedings, "The Genetics and Exploitation of Heterosis in Crops," published by the Society of Agronomy and Crop Science Society of America.
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3. "Recombinant DNA Molecule Research Potential For Agricultural Crop Plants"
D.N. Duvick - Apri1 11, 1977 - Transcribed by D. N. Duvick, March 7, 2001
Recombinant DNA molecular research probably will have little direct
impact on the development of useful new crop varieties. Complex, delicately
balanced interactions among many genes determine the phenotypes of successful
crop varieties. Changes of only one or a few genes have had important useful
effects in relatively few instances; the total benefit of single gene changes
in crop varieties is negligible compared to the importance of complexly
inherited traits. But the in
vitro recombinant DNA molecular techniques deal basically with one or at most a few genes.
They are concerned with isolating and moving individual short segments
of DNA; they are not
suited to assorting and recombining very large numbers of genes into optimum genomic combinations. (This latter process has been accomplished within species and varieties in evolutionary time; modern plant breeding techniques are concerned largely with developing optimum recombinations of internally balanced chromosome segments - large blocks of genes.
In general, breeding processes which reshuffle the genes result in useless genomes as far as productive crop varieties are concerned.) Thus, it is not likely that recombinant DNA molecular techniques can be used to rebuild genomes in wholesale fashion.
An important accomplishment of recombinant DNA molecular research is
movement of operational DNA fragments from one organism into another entirely
alien organism. Whether or not this can be done reliably in higher plants
awaits demonstration, but it may be possible. A hypothetical example would
be to transfer the gene(s) allowing for fixation of atmospheric nitrogen
from bacteria to wheat. Another example might be transfer from sorghum
to corn, of a gene(s) for
immunity to corn root worm attack.
But even if these gene transfers could be made, and stable inheritance
of the transferred genes could be expected, such hypothetical transfers
would have very low likelihood of being useful to
plant breeders. In most cases so-called "single-gene" effects actually depend on a very complex background of supporting genes to produce their phenotype, even though the null form of the gene may cause complete disappearance of the phenotype.
Moving given genes from variety to variety often changes the intensity or even the nature of their effect; sometimes the gene produces unexpected deleterious effects. When genes are moved from one species or genus to another these unexpected and often deleterious effects can be even greater. The only genes that seem to move easily with minimum unexpected effects are those acting on terminal reactions such as pigment formation, or deposition of other chemical end-products, and even they are affected by background genotype.
Therefore, using recombinant DNA molecular techniques to move genes
across wide taxonomic
distances probably will give few direct practical benefits to plant breeding.
To list the reasons why in vitro DNA recombinant research may not help
produce new varieties does not, however, mean that it should not be tried.
Movement of nitrogen fixation genes from
bacteria to wheat might give us valuable new insights into the nature of the fixation process, which might then be used to improve nitrogen-fixing bacteria or their symbiosis with higher plants, or other completely unexpected pieces of useful knowledge about crop plants and their symbiosis might emerge from the work. Movement of genes producing products toxic to insect pests occasionally might be successful, because such products often are the ends of biochemical pathways and might not upset the functioning of adapted, productive varieties.
However, it is likely that the real use of in vitro recombinant DNA research in plant breeding will be to allow determination of nucleotide sequences and thus the gene products of key genes. It also should allow for more complete gene mapping (especially in organelles) and eventually it also might give new clues to gene action in development. Thus for plant breeders the technique is most useful as a tool to study genes, rather than as a tool to create new organisms.
Of course improved understanding of individual genes probably will suggest
to plant breeders ways in which they might improve those genes' action,
structure or numbers, in specific instances. Modification, substitution
or multiplication of genes for high amylose production in corn for, boll
weevil resistance in cotton or for rust resistance in wheat could give
highly useful and valuable improvements. But as noted earlier, it is likely
that the total effect of all such changes would be
minor in comparison to changes in total productivity that can be achieved by selecting in vivo genetic recombinations of delicately balanced sets of genomes or chromosome segments.
Meiosis and the very large scale on which its products can be selected, is still the most powerful tool available to plant breeders. It may be no accident that it also was selected as the chief tool of natural evolution in higher plants.
Nevertheless, business firms engaged in the plant genetic supply industry
will be interested in developing techniques and products with molecular
DNA research, even if not, in general, for
immediate use (for the reasons noted above). Because our survival depends on maintaining physical possession or legal protection of the products we develop, we will need to have either the right to hold these products within our organization or the ability to protect them by means of something like variety protection laws. Likewise, if we develop novel techniques we need to be able to either hold them within our organization or protect them with patents. In both cases, if we cannot use one of the two alternatives, there likely will be little financial incentive for doing the work.
The suggested guidelines for recombinant DNA research in connection
with plants seem to be reasonable, but it is important that they remain
open to modification, as new knowledge is
I would guess that pathogens require a delicate balance of many interacting genes for their survival, just like higher plants, and that the danger of creating super-pathogens by means of long-distance gene transfer is not at all great, in fact it probably is impossible. At any rate, pathogens of all sorts do very well now, in creating novel and highly efficient races, whenever a new evolutionary niche appears. It may be that we are presumptuous to suppose we can move a few genes at random into strange genetic backgrounds and surpass pathogen's present capabilities.