Modern Techniques in Rice Breeding: Mutation Breeding
Plant breeding is estimated to have begun 9,000 – 11,000 years ago and mutation breeding is simply a new device in the breeder’s toolkit. Mutation breeding has been used since the 1930s. It’s a means of accelerating the process of developing different traits for selection, such as disease resistance, tolerance to harsh growing conditions, and other valuable agronomic traits. It does not involve gene modification, also known as gene splicing.
Mutations are the primary source of all genetic variations existing in any organism, including plants. The resulting variation provides the raw material for natural selection and is also a driving force in evolution. Mutation breeding involves the development of new varieties by generating and utilizing genetic variability through chemical and physical mutagenesis. It is now a pillar of modern plant breeding, along with recombinant breeding and transgenic breeding.
Mutagenesis is the process whereby sudden heritable changes occur in the genetic information of an organism not caused by genetic segregation or genetic recombination, but induced by chemical, physical or biological agents.
Genetic variability as a result of induced mutation by various mutagens has contributed to modern plant breeding. Over the past five decades, it has played a major role all over the world in the development of superior plant varieties with characteristics of high-yield, early maturity, lodging resistance among others.
- To review achievements and new developments in the field of plant mutation breeding.
- Increasing awareness in methods of mutation breeding.
- Assessing the challenges of mutation breeding.
- Surveying the application of mutation in rice breeding.
- Radiation breeding
Exposing plants to radiation is sometimes called radiation breeding. High energy radiation from a radioactive material or from X-rays is absorbed by the atoms in water molecules surrounding the DNA. This energy is transferred to the electrons which then fly away from the atom.
- Use of chemical mutagens
Chemical mutagens are standard tools for mutagenesis in a variety of organisms, and they are a primary means of creating mutations.
- New mutagen techniques
- Restriction endonucleases
Restriction enzyme, also called restriction endonuclease, a protein produced by bacteria that cleaves DNA at specific sites along the molecule.
Compared to the plant growing conditions on Earth, a totally unusual space environment, such as high-energy ion radiation, microgravity, space magnetic field, ultra-vacuum, may have either direct or indirect effects on plant growth and metabolic activities.
- Ion beam technology
Ion beams mutate DNA by deleting multiple bases from the genome. Compared to traditional sources of radiation, like gamma rays and X-rays, ion beams have been shown to cause more severe breaks in DNA that are more difficult to weave back together, causing the change in DNA to be more drastic than changes caused by traditional irradiation.
- Mature pollen treated with gamma radiation
Gamma radiation is widely used to induce mutations in breeding studies than chemical mutagens. Ionizing radiation could cause several DNA damages randomly; therefore, several mutations (from point mutation to chromosome aberrations) could be induced.