Which is the more common method of mutagenesis chemical or radiation?

Expert response from Dr. L. Curtis Hannah

Professor, University of Florida

Friday, 21/08/2015 12:08

Thanks for the question. I had to do some digging on this one. In terms of which person-directed mutagenesis method is more common among commercial varieties, Ahloowalia et al (Euphytica 135: 187-204, 2004) state that radiation is the most frequently employed method used by plant scientists. This work is somewhat dated (2004), but since people have been using X-rays since 1927 to create gene variants in plants, I would be surprised if the story has changed in the last 12 years.

These investigators also note that some 2250 plant varieties now on the market were derived via these unnatural forms of mutagenesis. I found that large number surprising.

Note that the spectra of mutations caused by chemicals versus radiation are different. Radiation normally invokes more global changes: deletions of portions of chromosomes, chromosomal inversions and sometimes exchange of DNA from one chromosome to another. Chemical mutagenesis, on the other hand, usually causes much smaller changes, for example the substitution of one nucleotide for another, deletion/insertion of a single nucleotide, etc.

Note also that while the created variant can be selected by the plant breeder, it is impossible to remove all the unknown changes made by mutagenesis. Because mutations occur at random and cannot be directed by the investigator, experiments usually involve heavy doses of mutagens to efficiently create the change wanted. Usually, “kill” rates (loss of germination or the ability of the mutagenized seed to grow and produce seed) are high, in the neighborhood of 50 percent or so. Lots and lots of changes are made and some of these unknown changes will be found in the resulting cultivar or variety.

So, compared to genetic engineering (called GMO in the popular literature) chemical and radiation mutagenesis involve infinitely more unknown changes. Hence, to label GMOs and not varieties derived by person-directed mutagenesis is yet another case of scientific nonsense we are exposed to today. It is unfortunate that some anti-science groups use political campaign tactics simply to line their pockets with money. We need this technology to feed a growing human population in the face of climate change. To place unnecessary hurdles in the way of some tools that can be used for this purpose is categorically morally reprehensible.

Expert response from Dr. L. Curtis Hannah

Professor, University of Florida

Friday, 21/08/2015 12:08

Thanks for the question. I had to do some digging on this one. In terms of which person-directed mutagenesis method is more common among commercial varieties, Ahloowalia et al (Euphytica 135: 187-204, 2004) state that radiation is the most frequently employed method used by plant scientists. This work is somewhat dated (2004), but since people have been using X-rays since 1927 to create gene variants in plants, I would be surprised if the story has changed in the last 12 years.

These investigators also note that some 2250 plant varieties now on the market were derived via these unnatural forms of mutagenesis. I found that large number surprising.

Note that the spectra of mutations caused by chemicals versus radiation are different. Radiation normally invokes more global changes: deletions of portions of chromosomes, chromosomal inversions and sometimes exchange of DNA from one chromosome to another. Chemical mutagenesis, on the other hand, usually causes much smaller changes, for example the substitution of one nucleotide for another, deletion/insertion of a single nucleotide, etc.

Note also that while the created variant can be selected by the plant breeder, it is impossible to remove all the unknown changes made by mutagenesis. Because mutations occur at random and cannot be directed by the investigator, experiments usually involve heavy doses of mutagens to efficiently create the change wanted. Usually, “kill” rates (loss of germination or the ability of the mutagenized seed to grow and produce seed) are high, in the neighborhood of 50 percent or so. Lots and lots of changes are made and some of these unknown changes will be found in the resulting cultivar or variety.

So, compared to genetic engineering (called GMO in the popular literature) chemical and radiation mutagenesis involve infinitely more unknown changes. Hence, to label GMOs and not varieties derived by person-directed mutagenesis is yet another case of scientific nonsense we are exposed to today. It is unfortunate that some anti-science groups use political campaign tactics simply to line their pockets with money. We need this technology to feed a growing human population in the face of climate change. To place unnecessary hurdles in the way of some tools that can be used for this purpose is categorically morally reprehensible.