Different ways of plant breeding
Last month the European Commission came with a new proposal regarding the genetic modification of crop plants. They propose crops breed using new genetic techniques not to classify as genetically modified. But which ways of plant breeding are there? Here I will highlight four of them.
During breeding of crops a breeder is selecting for favoured traits, like a high yield, resistance against diseases, or being better able to deal with a drought. The reason why one plant has a particular trait and another not, is due to a difference in genetic information. A change in this genetic information can therefore result in a new trait.
During traditional breeding, a change in the genetic information is a result of copying mistakes or DNA damage. Most of those changes do not result in new traits, but some do. Creating variation in a population. Something breeders use when breeding new crops. For example, when crossing a plant with disease resistance with a high yielding plant, to generate a crop that has both disease resistance and a high yield. Unfortunately, new traits don’t appear often, and getting new traits in this way is a slow and random process.
Gene editing is a new tool in the breeder’s toolbox
Around 1930 researchers discovered a way to increase the frequency of new trait occurrence. Radiating plants or treating them with chemicals, they noticed caused more new traits. The number of changes in the DNA of the plant increased. Creating new crops using this method is called mutation breeding. While new traits are obtained much faster, the breeder has no control about which new traits develop.
This changed at the start of the eighties last century. Researchers developed a way to introduce foreign DNA into a plant. This enabled breeders to introduce specific traits, like resistance to specific insects. Producing new crops using this technique we call genetic modification. This involves introducing pieces of DNA from one organism in another organism. The advantage for the breeder is that he can control which new trait emerges. But the breeder has no control where in the genome the foreign DNA ends up.
With the new genomic techniques or gene editing, like CRISPR-Cas, breeders have control where the DNA changes. Using gen editing breeders can change specific genes inside the organism, without introducing foreign DNA. In this gives breeders control over which trait they adjust and where this adjustment is made. A disadvantage, compared to traditional breeding is that the responsible gene must be known.
In this regard gene editing is closer to traditional breeding and mutational breeding than classic genetic modification. Each of the above discussed techniques has its own advantages and disadvantages. Gene editing is therefore not the holy grail, but only a new tool in the breeder’s toolbox.
Literature
Bevan, M., Flavell, R. & Chilton, MD. A chimaeric antibiotic resistance gene as a selectable marker for plant cell transformation. Nature 304, 184–187 (1983). https://doi.org/10.1038/304184a0
Kunling Chen, Yanpeng Wang, Rui Zhang, Huawei Zhang, Caixia Gao (2019) CRISPR/Cas Genome Editing and Precision Plant Breeding in Agriculture. Annual Review of Plant Biology 2019 70:1, 667-697 https://doi.org/10.1146/annurev-arplant-050718-100049
Stadler LJ. Mutations in Barley induced by x-rays and radium. Science. (1928) 68:186–7. DOI: 10.1126/science.68.1756.186
In addition, I talked with Dirk Inzé, Cathy Martin, and Jan Schaart
Plant en Zo 