Plant breeding for resource-efficient farming
Climate change, pests, population growth and ever-scarcer resources pose major challenges for farmers around the world. And being able to produce sufficient food in a manner that is as environmentally-friendly as possible requires increasingly robust plant varieties. Plant breeding is therefore a crucial area of research for resource-efficient and sustainable agriculture. A fact sheet produced by the Swiss Academy of National Sciences (SCNAT) presents four key breeding methods.
Thursday, June 11, 2020
- Global agricultural production must be able to keep pace with population growth in the long term.
- Climate change and increasing pest pressure make this task more difficult.
- The breeding of new plant varieties with adapted characteristics must be advanced.
The fact sheet makes an important contribution to understanding the different types of breeding. Gene editing has enormous potential to protect crops. Plants’ own defense systems against pests and fungi can be strengthened in a targeted manner. This also reduces the need for pesticides. In the view of researchers, it makes no sense to continue prohibiting the cultivation of plants that have been optimized using gene editing. Given the enormous potential for sustainable agriculture, a legal distinction must be made between gene editing and traditional genetic engineering as quickly as possible.
A new variety in three steps
Irrespective of the crop species and the type of breeding used, plant breeding always works the same way in principle. The first step involves expanding genetic diversity. There are several ways of doing so. The desired genetic characteristics can be found in existing wild and cultivated plants and added to another variety through crossbreeding. Random mutations contribute to the expansion of genetic diversity as well and can also be used in breeding. However, new processes make it possible to create gene variants artificially too, inserting them in plants or modifying them in a targeted manner. In the second step, plants with the desired characteristics are selected and then planted, tested and optimized under controlled conditions. New candidates that may be suitable for cultivation emerge at the end of this process. Following years of testing, the candidates are then submitted, in the third step, to the Federal Office for Agriculture for approval and inclusion in the catalogue of varieties. As the conditions for doing so, the varieties must be different from one another, homogeneous and genetically stable. Over the course of decades, breeding methods have constantly changed and evolved. The following four methods are now considered to be especially important:
1. Crossbreeding (traditional breeding)
With traditional crossbreeding, existing gene variants are recombined. A desired characteristic – for example, resistance against a certain disease – is added to an existing plant variety from a wild or cultivated plant. Because crossbreeding passes on more than just the desired characteristics to the offspring, it is necessary to backcross with the existing variety in order to optimize the result. This is generally very time-intensive. After the authorities complete the testing process, the variety can be included in the catalogue of varieties and then cultivated.
2. Mutation breeding
New gene variants can be created artificially using mutation breeding. Random mutations are produced using chemicals or radiation. In addition to the desired mutations, however, a number of undesired gene mutations are also created. For this reason, the undesired changes must be removed from selected offspring from these plants through backcrossing. And this takes a very long time. If the variety meets the requisite criteria, it is included in the catalogue of varieties and can be cultivated.
3. Traditional genetic engineering
With traditional genetic engineering, the genes of another (transgenic) or the same type (cisgenic) are added to a plant. As part of this process, a new gene is placed in a random location in the genome. This can lead to undesired mutations. Selected offspring are then freed of the undesired characteristics and optimized through backcrossing. Compared with traditional backcrossing and mutation breeding, this process is much more time-intensive. Following a 2005 moratorium, genetically modified plants cannot be grown in Switzerland. For this reason, plants that have been modified using traditional genetic engineering cannot receive approval for cultivation.
4. Gene editing
Gene editing enables the targeted modification of certain genes in a plant. Genetic scissors (e.g. CRISPR/Cas9) can be used to cut a genome in a certain location. This makes it possible to deactivate plant genes precisely. However, this method can also be used to transfer genes or insert entirely new ones (transgenic or cisgenic). There are very few undesired mutations in the rest of the genome as part of this process because it is so precise. Backcrossing is only necessary in rare cases. The method therefore accelerates the breeding of new varieties and is very efficient. As with traditional genetic engineering, however, plants modified using gene editing cannot currently be cultivated in Switzerland.
Resource efficiency means the efficient use of technological, economic and natural resources. It is defined as “the ratio of a certain benefit or result to the resources that must be used to achieve it.” Resource-efficient agricultural product aims to optimize the crop yield using as few production resources (such as labor, energy, land, water, fertilizer or pesticides) and placing as little pressure on natural resources (water, soil, biodiversity, air, incl. climate) with the largest and highest-quality harvest possible.
scienceindustries POINT Newsletter June 2020: “Plant breeding: Researchers and breeders explain the process in a new fact sheet published by the Swiss Academy of National Sciences (SCNAT)” (in German).
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