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 that have been derived either as direct mutants (70%) or from their progeny (30%). Crop plants account for 75% of released mutagenic species with the remaining 25% ornamentals or decorative plants. However, although the FAO/IAEA reported in 2014 that over 1,000 mutant varietals of major staple crops were being grown worldwide, 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.
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.
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. In 1928, Stadler first published his findings on radiation-induced mutagenesis in plants. During the period 1930-2004, radiation-induced mutant varieties were developed primarily using gamma rays (64%) and X-rays (22%).:187
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. 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.
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.
Comparison to other agronomic techniques
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 have been discussed as a concern 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.
Somewhat controversially, several organic food and seed companies promote and sell certified organic products that were developed using both chemical and nuclear mutagenesis. 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. These organic products range from mutagenic barley and wheat ingredient used in organic beers to mutagenic varieties of grapefruits sold directly to consumers as organic.
Notable mutagenized varietals
- Rio Star Grapefruit:189
- Todd's Mitcham Peppermint (Verticillium wilt tolerance):189
- Murray Mitcham Peppermint (Verticillium wilt tolerance):189
- Calrose 76 Rice (short height rice induced with gamma rays):189
- Purple Orchard 3 Sweet potato
- Zhefu 802 (rice mutant)
- 26Zhaizao (indica rice mutant created with gamma rays)
- PNR-381 Rice:189
- Sharbati Sonora wheat:189
- 'MUM 2', 'BM 4', 'LGG 407', 'LGG 450', 'Co4', 'Dhauli' (TT9E), 'Pant moong-1' blackgram (YMC, (Yellow mosaic virus) resistance):189
- Basmati 370 (short height rice mutant)
- NIAB-78 (high yielding, heat tolerant, early maturing cotton mutant)
- CM-72 (high yielding, blight resistant, desi type chickpea mutant created with 150 Gy of gamma rays)
- NM-28 (short height, uniform and ealry maturing, high seed yield mungbean mutant)
- NIAB Masoor 2006 (early maturing, high yield, resistant to disease lentil mutant created with 200 Gy of radiation)
- UNA La Molina 95 (barley mutant developed in 1995 for growing above 3,000 m)
- Centenario (Amarinth "kiwicha" mutant developed in 2006 with high quality grain and exported as a certified organic product)
- Centenario II (barley mutant developed in 2006 also for growing in the Andean highlands with high yield, high quality flour and tolerance to hail)
- RD16 and RD6 (aromatic indica rice mutant created with gamma rays)
- Golden Promise barley (semi-dwarf, salt tolerant mutant created with gamma rays) Is used to make beer and whisky
- VND 95-20, VND-99-1 and VN121 (rice mutants developed to give increased yield, improved quality, resistance to disease and pests)
- DT84, DT96, DT99 and DT 2008 (soybean mutants developed using gamma rays to grow three crops a year, tolerance to heat and cold and resistance to disease)
In 2014, it was reported that 17 rice mutant variatals, 10 soybean, two maize and one chrysanthemum mutant variatals had been officially released to Vietnamese farmers. 15% of rice and 50% of soybean was produced from mutant variatels.
Release by nation
- (25.2%) People's Republic of China
- (15.0%) Japan
- (11.5%) India
- (6.7%) Russia
- (5.5%) Netherlands
- (5.3%) Germany
- (4.3%) United States
- (2.4%) Bulgaria
- (1.7%) Vietnam
- (1.4%) Bangladesh
- (2014) Plant Breeding and Genetics Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, Retrieved 31 July 2014
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- 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."
- 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).
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- Wasatch Organic Rio Red Grapefruit
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