Mutation breeding

Mutation breeding, sometimes referred to as "variation breeding", is the process of exposing seeds to chemicals or radiation in order to generate mutants with desirable traits to be bred with other cultivars. Plants created using mutagenesis are sometimes called mutagenic plants or mutagenic seeds. From 1930 to 2014 more than 3200 mutagenic plant varietals have been released[1][2] that have been derived either as direct mutants (70%) or from their progeny (30%).[3] Crop plants account for 75% of released mutagenic species with the remaining 25% ornamentals or decorative plants.[4] However, although the FAO/IAEA reported in 2014 that over 1,000 mutant varietals of major staple crops were being grown worldwide,[1] it is unclear how many of these varieties are currently used in agriculture or horticulture around the world, as these seeds are not always identified or labeled as being mutagenic or having a mutagenic provenance.[5]

Process

There are different kinds of mutagenic breeding such as using chemical mutagens like ethyl methanesulfonate and dimethyl sulfate, radiation and transposons are used to generate mutants. Mutation breeding is commonly used to produce traits in crops such as larger seeds, new colors, or sweeter fruits, that either cannot be found in nature or have been lost during evolution.[6]

Radiation breeding

Exposing plants to radiation is sometimes called radiation breeding and is a sub class of mutagenic breeding. Radiation breeding was discovered in the 1920s when Lewis Stadler of the University of Missouri used X-rays on maize and barley. In the case of barley, the resulting plants were white, yellow, pale yellow and some had white stripes.[7] In 1928, Stadler first published his findings on radiation-induced mutagenesis in plants.[8] During the period 1930-2004, radiation-induced mutant varieties were developed primarily using gamma rays (64%) and X-rays (22%).[4]:187

Radiation breeding may take place in atomic gardens;[8] and seeds have been sent into orbit in order to expose them to more cosmic radiation.[9]

Use of chemical mutagens

High rates of chromosome aberrations resulting from ionizing radiation and the accompanied detrimental effects made researchers look for alternate sources for inducing mutations. As a result, an array of chemical mutagens has been discovered. The most widely used chemical mutagens are alkylating agents. Ethyl methanesulfonate (EMS) is the most popular because of its effectiveness and ease of handling, especially its detoxification through hydrolysis for disposal. Nitroso compounds are the other alkylating agents widely used, but they are light-sensitive and more precautions need to be taken because of their higher volatility. EMS has become a commonly used mutagen for developing large numbers of mutants for screening such as in developing TILLING populations.[10] Although many chemicals are mutagenic, only few have been used in practical breeding as the doses need to optimised and also because the effectiveness is not high in plants for many.

History

According to garden historian Paige Johnson

After WWII, there was a concerted effort to find 'peaceful' uses for atomic energy. One of the ideas was to bombard plants with radiation and produce lots of mutations, some of which, it was hoped, would lead to plants that bore more heavily or were disease or cold-resistant or just had unusual colors. The experiments were mostly conducted in giant gamma gardens on the grounds of national laboratories in the US but also in Europe and countries of the former USSR.[11]

Comparison to other agronomic techniques

In the debate over Genetically Modified foods, the use of transgenic processes is often compared and contrasted with mutagenic processes.[12] While the abundance and variation of transgenic organisms in human food systems, and their effect on agricultural biodiversity, ecosystem health and human health is somewhat well documented, mutagenic plants and their role on human food systems is less well known, with one journalist writing "Though poorly known, radiation breeding has produced thousands of useful mutants and a sizable fraction of the world's crops...including varieties of rice, wheat, barley, pears, peas, cotton, peppermint, sunflowers, peanuts, grapefruit, sesame, bananas, cassava and sorghum."[7] In Canada crops generated by mutation breeding face the same regulations and testing as crops obtained by genetic engineering.[13][14][15][16] Mutagenic varieties tend to be made freely available for plant breeding, in contrast to many commercial plant varieties or germplasm that increasingly have restrictions on their use[4]:187 such as terms of use, patents and proposed genetic user restriction technologies and other intellectual property regimes and modes of enforcement.

Unlike genetically modified crops, which typically involve the insertion of one or two target genes, plants developed via mutagenic processes with random, multiple and unspecific genetic changes[17] have been discussed as a concern[18] but are not prohibited by any nation's organic standards. Reports from the US National Academy of Sciences state that there is no scientific justification for regulating genetic engineered crops while not doing so for mutation breeding crops.[5]

Several organic food and seed companies promote and sell certified organic products that were developed using both chemical and nuclear mutagenesis.[19] Several certified organic brands, whose companies support strict labeling or outright bans on GMO-crops, market their use of branded wheat and other varietal strains which were derived from mutagenic processes without any reference to this genetic manipulation.[19] These organic products range from mutagenic barley and wheat ingredient used in organic beers[20] to mutagenic varieties of grapefruits sold directly to consumers as organic.[21]

New Mutagenic Techniques

Restriction Endonucleases

Interest in the use of bacterial restriction endonucleases (RE) to study double-stranded breaks in plant DNA began in the mid-nineties. These breaks in DNA, otherwise known as DSBs, were found to be the source of much chromosomal damage in eukaryotes, causing mutations in plant varietals. REs induce a result on plant DNA similar to that of ionizing radiation or radiomimetic chemicals. Blunt ended breaks in the DNA, unlike sticky ended breaks, were found to produce more variations in chromosomal damage, making them the more useful type of break for mutation breeding. While the connection of REs to chromosomal aberrations is mostly limited to research on mammalian DNA, success in mammalian studies caused scientists to conduct more studies of RE-induced chromosomal and DNA damaged on barley genomes. Due to restriction endonucleases’ ability to facilitate damage in chromosomes and DNA, REs have the capability of being used as a new method of mutagenesis to promote the proliferation of mutated plant varietals.[22]

Space-Breeding

The ability of plants to develop and thrive is dependent on conditions such as microgravity and cosmic radiation in space. China has been experimenting with this theory by sending seeds into space, testing to see if space flights will cause genetic mutations. Since 1987, China has cultivated 66 mutant varieties from space through their space-breeding program. Chromosomal aberrations greatly increased when seeds were sent into aerospace compared to their earth-bound counterparts. The effect of space flight on seeds depends on their species and variety. For example, space-bred wheat saw a large growth in seed germination in compared to its Earth-bound control, but space-bred rice had no visible advantage compared to its control. For the varietals that were positively mutated by space flight, their growth potential exceeded that of not only their Earth-grown counterparts, but also their irradiated counterparts on Earth. Compared to traditional mutagenic techniques, space-bred mutations have greater efficacy in that they experience positive effects on their first generation of mutation, whereas irradiated crops often see no advantageous mutations in their first generations. Though multiple experiments have shown the positive effects of space flight on seed mutation, there is no clear connection as to what aspect of aerospace has produced such advantageous mutations. There is much speculation around cosmic radiation being the source of chromosomal aberrations, but so far, there has been no concrete evidence of such connection. Though China’s space-breeding program has been shown to be very successful, the program requires a large budget and technological support that many other countries are either unwilling or unable to provide, meaning this program is unfeasible outside of China. Due to such restraints, scientists have been trying to replicate space condition on Earth in order to promote the same expedient space-born mutations on Earth. One such replication is a magnetic field-free space (MF), which produces an area with a weaker magnetic field than that of Earth. MF treatment produced mutagenic results, and has been used to cultivate new mutant varieties of rice and alfalfa. Other replications of space conditions include irradiation of seeds by a heavy 7Li ion beam or mixed high-energy particles.[23] These space-bred varietals are already being introduced to the public. In 2011, during the National Lotus Flowers Exhibition in China, a mutant lotus, called the “Outer Space Sun”, was shown at the flower show.[24]

Ion Beam Technology

Ion beams mutate DNA by deleting multiple bases from its code. 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. Ion beams change DNA in a manner that makes it look vastly different than its original makeup, more so than when traditional irradiation techniques are used. Most experimentation, using ion beam technology, has been conducted in Japan. Notable facilities using this technology are TIARA of the Japan Atomic Energy Agency, RIKEN Accelerator Research Facility, and various other Japanese institutions. During the process of ion beam radiation, seeds are wedged between two kapton films and irradiated for roughly two minutes. Mutation frequencies are notably higher for ion beam radiation compared to electron radiation, and the mutation spectrum is broader for ion beam radiation compared to Gamma ray radiation. The broader mutation spectrum was revealed through the largely varied amount of flower phenotypes produced by ion beams. Flowers mutated by the ion beams exhibited a variety of colors, patterns, and shapes. Through ion beam radiation, new varieties of plants have been cultivated. These plants had the characteristics of being ultraviolet light-B resistant, disease resistant, and chlorophyll-deficient. Ion beam technology has been used in the discovery of new genes responsible for the creation of more robust plants, but its most prevalent use is commercially for producing new flower phenotypes, like striped chrysanthemums.[25]

Mature Pollen Treated with Gamma Radiation

Gamma radiation is used on mature rice pollen to produce parent plants used for crossing. The mutated traits in the parent plants are able to be inherited by their offspring plants. Because rice pollen has a very short lifespan, researchers had to blast Gamma rays at cultured spikes from rice plants. Through experimentation, it was revealed that there was a greater variety of mutation in irradiated pollen rather than irradiated dry seeds. Pollen treated with 46Gy of gamma radiation showed an increase in grain size overall and other useful variations. Typically, the length of each grain was longer after the crossing of irradiated parent rice plants. The rice progeny also exhibited a less chalky visage, improving on the appearance of the parent rice plants. This technique was used to develop two new rice cultivars, Jiaohezaozhan and Jiafuzhan, in China. Along with facilitating the creation of these two rice cultivars, the irradiation of mature rice pollen has produced roughly two hundred mutant rice lines. Each of these lines produce rice grains of both a higher quality and larger size. The mutations produced by this technique vary with each generation, meaning further breeding of these mutated plants could produce new mutations. Traditionally, gamma radiation is used on solely adult plants, and not on pollen. The irradiation of mature pollen allows mutant plants to grow without being in direct contact with gamma radiation. This discovery is in contrast to what was previously believed about gamma radiation: that it could only elicit mutations in plants and not pollen.[26]

Notable mutagenized varietals

 Argentina

 Australia

 Bangladesh

 Cuba

 People's Republic of China

 Czech Republic

 Egypt

 Finland

 Germany

 Ghana

 India

 Italy

 Japan

 Myanmar

 Pakistan

 Peru

 Sudan

 Thailand

 United Kingdom

 United States

 Vietnam

In 2014, it was reported that 17 rice mutant varietals, 10 soybean, two maize and one chrysanthemum mutant varietals had been officially released to Vietnamese farmers. 15% of rice and 50% of soybean was produced from mutant varietals.[41]

Release by nation

As of 2011 the percentage of all mutagenic varietals released globally, by country, were:[4]:187[42]

See also

References

  1. 1 2 (2014) Plant Breeding and Genetics Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Retrieved 31 July 2014
  2. ↑ Schouten, H. J.; Jacobsen, E. (2007). "Are Mutations in Genetically Modified Plants Dangerous?". Journal of Biomedicine and Biotechnology. 2007: 1. doi:10.1155/2007/82612.
  3. ↑ M.K. Maluszynsk, K. Nichterlein, L. van Zanten & B.S. Ahloowalia (2000). "Officially released mutant varieties – the FAO/IAEA Database". Mutation Breeding Review (12): 1–84.
  4. 1 2 3 4 5 6 7 8 9 10 11 Ahloowali, B.S. (2004). "Global impact of mutation-derived varieties" (PDF). Euphytica. 135: 187–204. doi:10.1023/b:euph.0000014914.85465.4f. Retrieved 20 April 2011.
  5. 1 2 Kaskey, Jack (21 November 2013) The Scariest Veggies of Them All Bloomberg Business Week, Retrieved 31 July 2014
  6. ↑ "New Citrus Variety Released by UC Riverside is Very Sweet, Juicy and Low-seeded".
  7. 1 2 Broad, William J. (28 August 2007). "Useful Mutants, Bred With Radiation". New York Times. Retrieved 20 April 2011.
  8. 1 2 Atomic Gardens: Public Perceptions & Public Policy, Life Sciences Foundation Magazine, Spring 2012.
  9. ↑ Smith, Peter (2011-04-12). "How Radiation is Changing the Foods that You Eat". GOOD. GOOD Worldwide, Inc. Retrieved 2011-07-16.
  10. ↑ Pathirana, R. Plant Mutation Breeding in Agriculture. CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources. 2011 6 No 032
  11. ↑ Johnson, Paige. "Atomic Gardens". Retrieved 20 April 2011.
  12. ↑ UK Government Science Review First Report, Prepared by the GM Science Review panel (July 2003). Chairman Professor Sir David King, Chief Scientific Advisor to the UK Government, P 9: "...it is necessary to produce about 100 GM plants to obtain one that has the desirable characters for its use as a basis of a new GM crop variety. ... Most of these so-called conventional plant breeding methods (such as gene transfer by pollination, mutation breeding, cell selection and induced polyploidy) have a substantially greater discard rate. Mutation breeding, for instance, involves the production of unpredictable and undirected genetic changes and many thousands, even millions, of undesirable plants are discarded in order to identify plants with suitable qualities for further breeding."
  13. ↑ The Canadian regulatory system is based on whether a product has novel features regardless of method of origin. In other words, a product is regulated as genetically modified if it carries some trait not previously found in the species whether it was generated using mutation breeding or genetic engineering (or any other method including selective breeding).
  14. ↑ Evans, Brent and Lupescu, Mihai (15 July 2012) Canada - Agricultural Biotechnology Annual – 2012 GAIN (Global Agricultural Information Network) report CA12029, United States Department of Agriculture, Foreifn Agricultural Service, Retrieved 7 August 2014
  15. ↑ McHugen, Alan (September 14, 2000). "Chapter 1: Hors-d'oeuvres and entrees/What is genetic modification? What are GMOs?". Pandora's Picnic Basket. Oxford University Press. ISBN 978-0198506744.
  16. ↑ Rowland, G.G. (2009). "Chapter 110: The Effect of Plants With Novel Traits (PNT) Regulation on Mutation Breeding in Canada". In Shu, Q. Y. Induced Plant Mutations in the Genomics Era. Plant Breeding Section, Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency, Vienna, Austria. pp. 423–424. ISBN 978-92-5-106324-8.
  17. ↑ Useful Mutants, Bred With Radiation, by William J. Broad, New York Times, August 28, 2007.
  18. ↑ Discussion Document Excluded Methods Terminology, National Organic Standards Board GMO ad hoc Subcommittee paper, U.S. Agricultural Marketing Service, published February 6, 2013.
  19. 1 2 Mendel in the Kitchen: A Scientist's View of Genetically Modified Foods, By Nina V. Fedoroff and Nancy Marie Brow, pg. 17, Joseph Henry Press, 2004.
  20. ↑ Golden Promise Organic Ale
  21. ↑ Wasatch Organic Rio Red Grapefruit
  22. ↑ Stoilov, L.; Gecheff, K. (2009). Shu, Q.Y., ed. "Restriction Endonucleases as a Tool for In Vivo Induction of Chromosomal and DNA Damage in Barley Genome" (PDF). Induced Plant Mutations in the Genomics Era – via Food and Agriculture Organization of the United Nations.
  23. ↑ Liu, L.X.; Guo, H.J.; Zhao, L.S.; Wang, J.; Zhao, S.R. (2009). Shu, Q.Y., ed. "Achievements and Perspectives of Crop Space Breeding in China" (PDF). Induced Plant Mutations in the Genomics Era – via Food and Agriculture Organization of the United Nations.
  24. ↑ "Mutant Lotus Bred in Space on Display in Chongqing, China".
  25. ↑ Tanaka, A. (2009). Shu, Q.Y., ed. "Establishment of Ion Beam Technology for Breeding" (PDF). Induced Plant Mutations in the Genomics Era – via Food and Agriculture Organization of the United Nations.
  26. ↑ Wang, H.; Qiu, S.; Zheng, J.; Jiang, L.; Huang, H.; Huang, Y. (2009). Shu, Q.Y., ed. "Generation of New Rice Cultivars from Mature Pollen Treated with Gamma-Radiation" (PDF). Induced Plant Mutations in the Genomics Era – via Food and Agriculture Organization of the United Nations.
  27. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Kharkwal, M. C.; Shu, Q. Y. (2008). "The role of induced mutations in world food security" (PDF). Induced plant mutations in the genomics era. Proceedings of an International Joint FAO/IAEA Symposium, 2008 2009. Vienna, Austria: Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, International Atomic Energy Agency: 33–38. ISBN 9789251063248.
  28. 1 2 3 4 5 6 Shu, Qing-Yao (2012). Forster, B. P.; Nakagawa, H., eds. Plant Mutation Breeding and Biotechnology. CABI Publishing. p. 17. ISBN 978-1780640853.
  29. ↑ "Lift-off for Chinese space potato". BBC News. 12 February 2007.
  30. 1 2 3 4 Ahloowalia, B. S.; Maluszynski, M. (2001). "Production Process in Old and Modern Spring Barley Varieties". Euphytica. 118 (2): 167. doi:10.1023/A:1004162323428.
  31. ↑ Lipavsky, J. Petr, J. and Hradecká, D, (2002) "Production Process in Old and Modern Spring Barley Varieties" Die Bodenkultur, 53 (1) 2, Page 19
  32. ↑ Rossi, Luigi (2010). "Il miglioramento genetico del grano duro in Casaccia. Il caso CRESO" [Genetic Improvement of Durum Wheat in Casaccia. The Creso Case] (PDF). Energia, Ambiente e Innovazione. ENEA. Retrieved 2016-11-29.
  33. ↑ van Harten, A. M. (1998). Mutation Breeding: Theory and Practical Applications. U. K.: Cambridge University Press. p. 239. ISBN 978-0521470742.
  34. ↑ Kotobuki, Kazuo. "Japanese pear tree named `Osa Gold`". Retrieved 20 April 2011.
  35. 1 2 3 (2008) NIAB - Plant Breeding & Genetics Division, Achievements Nuclear Institute for Agriculture and Biology, Faisalabad, Pakistan, Retrieved 16 May 2013
  36. 1 2 3 (2012) Improved barley varieties - Feeding people from the equator to the arctic Joint FAO/IAEAProgramme, Nuclear Techniques in Food and Agriculture, Retrieved 25 October 2013
  37. ↑ Forster, B. P. (2001). "Mutation genetics of salt tolerance in barley: An assessment of Golden Promise and other semi-dwarf mutants". Euphytica. 120 (3): 317–328. doi:10.1023/A:1017592618298.
  38. ↑ Broad, William (2007-08-28). "Useful Mutants, Bred With Radiation". New York Times. Retrieved 2013-06-19.
  39. ↑ (2012) Successful Mutation Breeding Programmes in Vietnam Joint FAO/IAEAProgramme, Nuclear Techniques in Food and Agriculture, Retrieved 25 October 2013
  40. 1 2 Vinh, M.Q. et al (2009) Current Status and Research Directions of Induced Mutation Application to Seeds Program in Vietnam in Induced Plant Mutations in the Genomics Era, FAO of the UN, Rome, Pp 341-345, Web page version retrieved 25 October 2013
  41. ↑ (2014) Successful Mutation Breeding Programmes in Vietnam Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Retrieved 31 July 2014
  42. ↑ Pathirana, Ranjith (September 6, 2011) Plant mutation breeding in agriculture CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources (CAB International); 20116 (032): 1 – 20; doi:10.1079/PAVSNNR20116032; ISSN 1749-8848; Retrieved August 6, 2014
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