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What is Mutation Breeding?

Unlike genetically modified crops, mutation breeding goes largely under the radar, but has been ongoing since at least 1942 when scientists Freisleben and Lenn induced mildew resistance in barley through the use of X-rays. The same scientists coined the term in 1944, defining it as “the utilisation of induced mutations in crop improvement”. Mutations are the “sudden heritable change in an organism” and crop improvement is induced “desirable changes in the genetic constitution of plants” and improved “performance of a cultivated variety” whether that be increased drought resistance or early flowering (and hence fruiting).

Standing at over 30 billion dollars, the seed market is a huge industry with such firms as the maligned Monsanto, which has run into public disdain and increasingly legislative hurdles as it tries to introduce new GM varieties into the world’s markets. A large chunk of this is mutation breeding that has no such regulation and offers an opportunity for companies to circumvent anti-GM laws and public scrutiny, while introducing new patented strains of seeds.

Before delving into the science and the question of whether foodstuffs derived mutagenesis are dangerous, it will be first worthwhile telling the fascinating history of mutation breeding.  

Mutation breeding was first proposed at the turn of century when Hugo de Vries suggested using radiation to induce mutations in plants and animals. By 1927 his ideas were confirmed when scientists Gager and Blakeslee carried out radium ray treatment of a Datura stramonium, inducing mutations. It was however Hermann J. Muller’s work in the 1910s and 1920s that provided the chief principles of spontaneous gene mutation, which eventually won him the Nobel Prize in Physiology and Medicine in 1946.

Mutation breeding achieved popularity in the 1950s, when it became part of the atoms for peace movement – a movement dedicated to the use of atomic energy for peaceful ends. The movement was kickstarted by the United States government that funded both research into peaceful applications of the technology and the construction of nuclear power plants around the world. The program was seen as a way to resolve the atomic dilemma as summarised in Dwight D.Eisenhower’s 1953 speech to the U.N. General Assembly that the “miraculous inventiveness of man shall not be dedicated to his death, but consecrated to his life”. This speech was followed by multiple conferences in the 50s that sought to bring together scientists from both East and West and reduce animosity between the two blocs.

The atoms for peace symbol, used during the 1955 Atoms for peace conference.

As part of the research into the application of atomic technology, mutation breeding was funded with the establishment of gamma gardens, in which crops were arranged in concentric circles around around a radiation source – usually a cobalt-60. The experiments were crude with crops near the source simply dying, and the ones further away riddled with growth abnormalities. It was the ones further away apparently healthy, but with alterations that were of interest.

Some experiments proved fruitful and gave us varieties that overcame limitations and now dominate as a percentage of production. Peppermint for example was extremely susceptible to Verticillium wilt, a fungal disease and cause of plant death, and it was experiments at the Brookhaven National Laboratory that led to the release of the ‘Todd’s Mitcham’ cultivar. A variety which underpins the $930 million global mint oil industry, which is used in everything from chewing gum to toothpaste. Another resultant variety from such experiments is the ‘Rio Star’ grapefruit, which is more red in colour and produces more flesh and juice. The variety accounts for 75% of grapefruit production in Texas.

Atoms for peace inspired certain sections of the public to conduct their own experiments such as Muriel Howorth in the United Kingdom and C.J. Speas in the United States, part of the atomic gardening movement.

Muriel, a laywoman, was extraordinarily passionate about the technology and promoted all things nuclear: publishing books (including Atomic Gardening for the Layman) and journals, forming multiple societies (including the Atomic Gardening society) and even staging a “Radioactivity Jubilee”. She was a maverick, who at the time was the only person speaking to women about the new science, founding the Ladies Atomic Energy Club. In 1959, she was the host of a dinner party of the Royal Commonwealth Society and decided to surprise her guests with irradiated peanuts as big as almonds. To her disappointment, they did not take off. Unruffled, she planted the peanuts in her greenhouse, which upon growing rapidly to two feet, she phoned the press to make the best out of a bad situation.

Holworth presenting her two-foot peanut plant to Beverley Nichols, a popular garden writer at the time.

C.J. Speas, another enthusiast, managed to obtain a license from the Atomic Energy Commission for a cobalt-60 source, which he encased in a cinderblocks in his back garden. From this he irradiated trays of seeds of which he reportedly sent millions (of seeds) to the Atomic Gardening Society, who distributed them to nearly a thousand members. He used to give tours of his cinderblock bunker to tourists and school groups. Separately, as pictures from Life magazine document, ‘super atomic energized seeds’ and ‘atom blasted seeds’ were sold at store and fairs in the late 50s and early 60s.

Atom-blasted seeds on sale in 1958. Photo by Grey Villet for Life.
Speas giving a tour of his bunker. Photo by Grey Villet for Life.

Today, mutagenesis is practiced by chemical companies and conglomerates such as BASF and DuPont. (It is important to mention that mutagenesis can be instigated by three classes of agents – biological, chemical and physical mutagens, so radiation is not necessarily involved.) Although, the legacy of Atoms for peace lives on in the work of the International Atomic Energy Agency, which is commemorating its sixtieth birthday, and the Food and Agriculture Organization of the United Nations, who through their technical cooperation programme contribute to the UN sustainable development goals through providing scientific support to member states.

One fascinating example of mutagenesis was carried out by the RIKEN Nishina Center for Accelerator-Based Science, Japan, who used heavy ion beams to induce mutations in a cherry tree, creating a new cherry blossom that blooms in all four seasons. The tree is unique in that it does not need a period of cold weather to trigger growth in spring and ostensibly produces three times more flowers than standard trees and stays in bloom for twice as long when blooming in April.

Interestingly, mutagenesis has proved highly profitable for Japan with the country investing $69 million on mutant breeds from 1959-2001, which have yielded $62 billion worth of goods in the same period. Hence, bringing new cultivars to market through mutation breeding is significantly cheaper than through GM, with Monsanto spending up to $200 million to launch a single GM product. And as things stand, this offers a huge incentive for firms to abandon GM methods and switch to mutation breeding.

How does mutation breeding work?

Mutation breeding is a two stage process involving mutation induction and detection. It is extremely effective, increasing the natural mutation rate by a thousand to a million fold. Mutation induction works by damaging an organism’s cellular structure, causing a change in the DNA, which when not repaired by the cell’s repair mechanism, lives on as a heritable mutation. These mutations are induced through two classes of mutagens – chemical and physical with the latter generating 70% of released mutant variables.

Physical mutagens are primarily induced through ionising radiation from gamma and x rays. These rays form part of the electromagnetic spectrum, just like visible and infrared light, except are extremely high energy. Chemical mutagens work differently involving chemical reactions within the genome, which alter a section of the DNA. Unlike physical mutagens, chemical mutagens are varied, with a number of agents, altering DNA through different causal chains.

With physical mutagens, mutations can be induced through a number of methods such as the aforementioned gamma gardens or fields. Alternatively, seeds or plant propagules can be placed within a gamma cell with a Cobalt-60 source (similar to Speas) or simply irradiated with an x ray machine. More recently, ion beam technology has been used to introduce mutations.

Plants arranged in concentric rings around a Cobalt 60 source. C.1959 at the Brookhaven National Laboratory.

Usually, scientists set upon finding the optimal dose that will be high enough to cause mutations, without putting a halt to germination or growth. And with most methods, scientists will go through thousands of plants before a mutation imparts a desirable characteristic. In addition, as many mutations are recessive, these characteristics are not revealed till subsequent generations.

The true art of mutation breeding lies in the mutation detection stage that has long been a bottleneck in plant breeding due to the reliance on phenotypic screening. Put simply, genotypes and phenotypes are used to distinguish between a plant’s hereditary information and an organism’s observed properties. As these observed properties are influenced by both the environment and a plant’s genetic code, scientists can’t be sure an observed trait originates from genetics. Rather a plant’s ostensible disease resistance may originate from an absence of a pathogen, as opposed to an inbuilt resistance to disease.

More recently, the introduction of genotypic screening has allowed scientists to distinguish between putative mutants and true mutants, by identifying variations that are inherited and linked to a trait of interest. By identifying a variation in the DNA, populations can be then assayed, leading to the identification of molecular markers that allows breeders to introduce mutant traits into different cultivars for improvement. Next, putative mutants are evaluated under a set stringent conditions, leading to mutant confirmation.  

Are foodstuffs derived from mutants dangerous?

As previously mentioned, unlike GMO, mutagenesis is unregulated and to some hasn’t received the attention it deserves. Accordingly, the National Academy of Sciences has stated the risks of creating unintended genetic consequences from mutation breeding is higher than any other techniques due to the imprecise nature of the method and the random alteration of DNA. However, they also state that the risks are small relative to the incidence of other foodborne illnesses. Unsurprisingly, BASF, states that the crops are safe with the technique being used for many decades without concern.

In line with this, mutant breeds are relatively widespread, especially in Asia where countries such as China, India and Japan produce over 10% of their produce from such varieties. According to the UN, there are over 3200 mutant varieties released for commercial use in more than 210 plant species for use in more than 70 countries. Furthermore, there may be many more varieties with mutant genetic code that we have simply forgotten about due to the long history of mutant breeding. So, it is probable such foodstuffs have already entered our food supply.

Ultimately, mutation breeding has proven a vital tool to increase crop yields in our increasingly hungry world. Due to the work of the UN, mutant strains are widely used throughout the developing world and have done much to alleviate hunger. Certainly, neither GM, nor mutagenesis derived varieties should receive a blanket ban, but be assessed on a case-by-case bases. As with many ethical dilemmas, the truth lies hidden in the details.

Jorge at PrimroseJorge works in the Primrose marketing team. He is an avid reader, although struggles to stick to one topic!

His ideal afternoon would involve a long walk, before settling down for scones.

Jorge is a journeyman gardener with experience in growing crops.

See all of Jorge’s posts.

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