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What is Mutation Breeding?

Nuclear Explained

Irradiation can be used for producing plant varieties with improved qualities, such as higher yields, shorter cultivation time or resistance to climate change, diseases and other stressors (Infographic: Adriana Vargas/IAEA)

Plant mutation breeding, also called variation breeding, is a method that uses physical radiation or chemical means to induce spontaneous genetic variation in plants to develop new crop varieties. “Mutation” is the source of most genetic variation and the motor of evolution. It is a natural process, which occurs spontaneously and slowly — over generations — in people, plants, animals and all living beings. It involves alteration of their DNA, leading to the development of changes within the organism. Mutation may be sped up by chemical or physical methods, such as the use of radiation (or “irradiation”), to achieve characteristics that are useful in, for example, agriculture.

Irradiation can be used for producing plant varieties with improved qualities, such as higher yields, shorter cultivation times, resistance to diseases, pests and the effects of climate change, such as extreme weather events. Cultivation and popularisation of those plant varieties helps to make global food production more stable and addresses the needs of farmers, particularly in developing countries and regions most vulnerable to the impacts of climate change.

Plant varieties bred using radiation are equally safe as the varieties developed through conventional or marker assisted breeding, since radiation does not pass on to further generations of the bred variety. Thus, plants can be bred for many generations to achieve the best result without suffering damage or becoming radioactive. Many crop varieties developed though mutation breeding have been grown all over the world in the last 100 years. Check out a few examples from Bulgaria, China, Cuba, Uganda and other countries.

How can radiation be used to make plants evolve faster?

Mutation breeding uses genetic variations induced at the beginning of the plant breeding process to quickly develop large populations of improved crops, which can be further bred until a desired result has been achieved. This grants the mutation breeding method many comparative advantages: it is cost effective, quick, proven and robust, as well as transferrable, ubiquitously applicable, non-hazardous and environmentally friendly. Moreover, it has withstood the test of time — for several decades such spontaneous genetic variations have been induced in laboratories by irradiation.

Exposure to radiation induces changes in DNA, boosting mutation rates by 1 000 to 1 million-fold, which enables breeding plants more effectively and producing more crop variations in shorter time. For example, in 2021 a new cotton variety with improved agronomic performance and fibre quality was developed in Bangladesh in only five years.

There are two dimensions to the science of mutation breeding: mutation induction and mutant selection.

Mutation induction

The Gamma Greenhouse in Malaysia, which continues to be used for plant irradiation (Photo:  U.S. Mission to International Organizations in Vienna)

Mutation induction is a process through which natural spontaneous mutation is sped up through biological, chemical or physical factors to improve desirable or targeted characteristics of a plant. Those include, but are not limited to, viruses and bacteria (biological), antibiotics and alkylating agents (chemical) or exposure to ionizing radiation (physical). Plant seeds are most commonly irradiated to induce mutations. However, for certain experiments whole plants, seedlings or only parts of the plant— pollen, spores or the stem of a plant — are irradiated. If the resulting mutations are not eliminated by the cell’s own repair mechanism, a heritable mutation is generated. The plants with the most promising mutations are bred further, until the researchers arrive at a substantially improved variant that can address the farmers’ needs.

Typically, scientists use specific technologies such as cobalt-60 radioactive sources or an X-ray machine for plant irradiation. Gamma rays from cobalt-60 have been the most commonly used mutagenic agent in the past decades. Other types of radiation such as α- and β-particles, fast neutrons or UV light have also been useful for plant mutation induction. Ion beam radiation and cosmic radiation are increasingly being used for this purpose as well, in order to explore the advantages of these methods in comparison with other types of radiation.

Mutant selection

Researchers at Indonesia’s National Nuclear Energy Agency (BATAN) use irradiation to induce genetic alteration in crops and then select plants with new and useful traits (Photo: Yustantiana / BATAN)

Mutant selection is the process of identifying plants that have been improved by induced mutation through irradiation. Mutations occur in such low frequencies that large numbers of seeds must be irradiated, grown and bred over different generations, until a desirable trait is developed. The time this process takes varies, since the development and analysis of mutant populations with, often, many thousands of individual plants, is a large undertaking and depends on the crop.

The process of identifying and selecting new plant varieties with improved traits involves two major steps: screening and validation. Screening and validation of visible and readily scorable characteristics of a new crop variety, such as early flowering or short stature, is straightforward. Other characteristics that are not so easily identifiable require the development and application of screening procedures specifically for the target characteristic, for example, salt tolerance in hydroponics or disease screening.

Inducing mutation in space: How does space affect plant biology?

The IAEA and FAO explore front-end technologies in crop improvement under climate change using radiation-induced genetic diversity, including space mutagenesis (Infographic: Adriana Vargas/IAEA)

Space can be considered the harshest growing environment, since seeds, plants and plant materials in space are affected by cosmic radiation and microgravity. On the other hand, cosmic rays can help to produce mutations that could make plant varieties more enduring to the conditions on Earth, which are worsening because of climate change and other stressors.

Space mutagenesis, is a method that involves the use of cosmic rays in outer space to induce spontaneous mutations. Scientists typically send plant seeds into space, and then grow, screen and breed them once they return to Earth. As in conventional mutation breeding, scientists try to identify the plants with the most useful traits, and those which may provide an advantage over more traditional crop varieties. Wheat, rice and cotton have already visited space.

Moreover, cosmic rays and microgravity affect plant biology itself. This is being explored in astrobotany studies for a different purpose — to determine the best ways of growing plants in space.

You can read more about this technology here.

What is the role of IAEA?

  • Jointly with the FAO, the IAEA assists countries in the development and application of mutation breeding technologies to speed up their breeding processes in variety development.
  • The IAEA plant breeding laboratories in Seibersdorf, Austria, serve as the global hub for nuclear mutagenesis. Countries can send their seeds, plant cuttings or seedlings to the laboratories for irradiation and to recieve expert guidance on improving crop breeding methodology.
  • The IAEA’s Mutant Variety Database documents new varieties voluntarily contributed by countries. Currently, it covers around 3400 varieties from 70 countries, covering more than 200 different types of crops.
  • The Joint FAO/IAEA Centre of Nuclear Techniques in Food and Agriculture explores front-end technologies in crop improvement under climate change using radiation-induced genetic diversity, including space mutagenesis. 

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