Genetically modified crops (GM crops or biotech crops) are plants used in agriculture, the DNA of which has been modified using genetic engineering methods. In most cases, the aim is to introduce a new trait to the plant which does not occur naturally in the species. Examples in food crops include resistance to certain pests, diseases, environmental conditions, reduction of spoilage, resistance to chemical treatments (e.g. resistance to a herbicide), or improving the nutrient profile of the crop. Examples in non-food crops include production of pharmaceutical agents, biofuels, and other industrially useful goods, as well as for bioremediation.
Farmers have widely adopted GM technology. Acreage increased from
1.7 million hectares in 1996 to 185.1 million hectares in 2016, some
12% of global cropland. As of 2016, major crop (soybean, maize, canola
and cotton) traits consist of herbicide tolerance (95.9 million
hectares) insect resistance (25.2 million hectares), or both (58.5
million hectares). In 2015, 53.6 million ha of GM maize were under
cultivation (almost 1/3 of the maize crop). GM maize outperformed its
predecessors: yield was 5.6 to 24.5% higher with less mycotoxins (−28.8%), fumonisin (−30.6%) and thricotecens (−36.5%). Non-target organisms were unaffected, except for Braconidae, represented by a parasitoid of European corn borer, the target of Lepidoptera active Bt maize. Biogeochemical parameters such as lignin content did not vary, while biomass decomposition was higher.
A 2014 meta-analysis concluded that GM technology adoption had reduced chemical pesticide use by 37%, increased crop yields by 22%, and increased farmer profits by 68%. This reduction in pesticide use has been ecologically beneficial, but benefits may be reduced by overuse. Yield gains and pesticide reductions are larger for insect-resistant crops than for herbicide-tolerant crops. Yield and profit gains are higher in developing countries than in developed countries.
There is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, but that each GM food needs to be tested on a case-by-case basis before introduction. Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe. The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation.
However, opponents have objected to GM crops on grounds including environmental impacts, food safety, whether GM crops are needed to address food needs, whether they are sufficiently accessible to farmers in developing countries and concerns over subjecting crops to intellectual property law. Safety concerns led 38 countries, including 19 in Europe, to officially prohibit their cultivation.
A 2014 meta-analysis concluded that GM technology adoption had reduced chemical pesticide use by 37%, increased crop yields by 22%, and increased farmer profits by 68%. This reduction in pesticide use has been ecologically beneficial, but benefits may be reduced by overuse. Yield gains and pesticide reductions are larger for insect-resistant crops than for herbicide-tolerant crops. Yield and profit gains are higher in developing countries than in developed countries.
There is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, but that each GM food needs to be tested on a case-by-case basis before introduction. Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe. The legal and regulatory status of GM foods varies by country, with some nations banning or restricting them, and others permitting them with widely differing degrees of regulation.
However, opponents have objected to GM crops on grounds including environmental impacts, food safety, whether GM crops are needed to address food needs, whether they are sufficiently accessible to farmers in developing countries and concerns over subjecting crops to intellectual property law. Safety concerns led 38 countries, including 19 in Europe, to officially prohibit their cultivation.
History
Nature and traditional agriculture
Multiple natural mechanisms allow gene flow from one species to another. These occur in nature on a large scale – for example, it is one mechanism for the development of antibiotic resistance in bacteria. This is facilitated by transposons, retrotransposons, retroviruses, proviruses and other mobile genetic elements that naturally translocate DNA to new loci in a genome. Movement occurs over an evolutionary time scale.
Traditional crop breeders have long introduced foreign germplasm into crops by creating novel crosses. A hybrid cereal grain was created in 1875, by crossing wheat and rye. Since then traits including dwarfing genes and rust resistance have been introduced in that manner. Plant tissue culture and deliberate mutations have enabled humans to alter the makeup of plant genomes.
Direct manipulation
The term genetic engineering is applied to genetic modifications made using biotechnology. The first plant produced in that way came in 1982, an antibiotic-resistant tobacco plant. The first field trials occurred in France and the USA in 1986, using tobacco plants engineered for herbicide resistance. In 1987, Plant Genetic Systems (Ghent, Belgium), founded by Marc Van Montagu and Jeff Schell, was the first company to genetically engineer insect-resistant (tobacco) plants by incorporating genes that produced insecticidal proteins from Bacillus thuringiensis (Bt).
The People's Republic of China was the first country to allow commercialized transgenic plants, introducing a virus-resistant tobacco in 1992, which was withdrawn in 1997. The first genetically modified crop approved for sale in the U.S., in 1994, was the FlavrSavr tomato. It had a longer shelf life, because it took longer to soften after ripening. In 1994, the European Union approved tobacco engineered to tolerate the herbicide bromoxynil, making it the first commercially genetically engineered crop marketed in Europe.
In 1995, Bt Potato was approved by the US Environmental Protection Agency, making it the country's first-pesticide producing crop. In 1995 canola with modified oil composition (Calgene), Bt maize (Ciba-Geigy), bromoxynil-tolerant cotton (Calgene), Bt cotton (Monsanto), glyphosate-tolerant soybeans (Monsanto), virus-tolerant squash (Asgrow), and additional delayed ripening tomatoes (DNAP, Zeneca/Peto and Monsanto) were approved.
As of mid-1996, 35 approvals had been granted to commercially grow 8
transgenic crops and one flower crop (carnation), with 8 different
traits in 6 countries plus the EU. In 2000, Vitamin A-enriched golden rice was developed, though as of 2016 it was not yet in commercial production.
In 2013 the leaders of the three research teams that first applied genetic engineering to crops, Robert Fraley, Marc Van Montagu and Mary-Dell Chilton, were awarded the World Food Prize for improving the "quality, quantity or availability" of food in the world.
In the US, by 2014, 94% of the planted area of soybeans, 96% of cotton and 93% of corn were genetically modified varieties. In developing countries, about 18 million farmers planted 54% of GM crops worldwide by 2013.
Methods
Plants (Solanum chacoense) being transformed using agrobacterium
Genetically engineered crops have genes added or removed using genetic engineering techniques, originally including gene guns, electroporation, microinjection and agrobacterium. More recently, CRISPR and TALEN offered much more precise and convenient editing techniques.
Gene guns (also known as biolistics) "shoot" (direct high energy particles or radiations against) target genes into plant cells. It is the most common method. DNA
is bound to tiny particles of gold or tungsten which are subsequently
shot into plant tissue or single plant cells under high pressure. The
accelerated particles penetrate both the cell wall and membranes. The DNA separates from the metal and is integrated into plant DNA inside the nucleus. This method has been applied successfully for many cultivated crops, especially monocots like wheat or maize, for which transformation using Agrobacterium tumefaciens has been less successful. The major disadvantage of this procedure is that serious damage can be done to the cellular tissue.
Agrobacterium tumefaciens-mediated transformation is another common technique. Agrobacteria are natural plant parasites.
Their natural ability to transfer genes provides another engineering
method. To create a suitable environment for themselves, these
Agrobacteria insert their genes into plant hosts, resulting in a
proliferation of modified plant cells near the soil level (crown gall). The genetic information for tumor growth is encoded on a mobile, circular DNA fragment (plasmid). When Agrobacterium infects a plant, it transfers this T-DNA
to a random site in the plant genome. When used in genetic engineering
the bacterial T-DNA is removed from the bacterial plasmid and replaced
with the desired foreign gene. The bacterium is a vector, enabling transportation of foreign genes into plants. This method works especially well for dicotyledonous plants like potatoes, tomatoes, and tobacco. Agrobacteria infection is less successful in crops like wheat and maize.
Electroporation is used when the plant tissue does not contain
cell walls. In this technique, "DNA enters the plant cells through
miniature pores which are temporarily caused by electric pulses."
Microinjection is used to directly inject foreign DNA into cells.
Plant scientists, backed by results of modern comprehensive
profiling of crop composition, point out that crops modified using GM
techniques are less likely to have unintended changes than are
conventionally bred crops.
In research tobacco and Arabidopsis thaliana
are the most frequently modified plants, due to well-developed
transformation methods, easy propagation and well studied genomes. They serve as model organisms for other plant species.
Introducing new genes into plants requires a promoter
specific to the area where the gene is to be expressed. For instance,
to express a gene only in rice grains and not in leaves, an endosperm-specific promoter is used. The codons of the gene must be optimized for the organism due to codon usage bias.
Types of modifications
Transgenic maize containing a gene from the bacteria Bacillus thuringiensis
Transgenic
Transgenic
plants have genes inserted into them that are derived from another
species. The inserted genes can come from species within the same kingdom
(plant to plant) or between kingdoms (for example, bacteria to plant).
In many cases the inserted DNA has to be modified slightly in order to
correctly and efficiently express in the host organism. Transgenic plants are used to express proteins like the cry toxins from B. thuringiensis, herbicide resistant genes, antibodies and antigens for vaccinations A study led by the European Food Safety Authority (EFSA) found also viral genes in transgenic plants.
Transgenic carrots have been used to produce the drug Taliglucerase alfa which is used to treat Gaucher's disease. In the laboratory, transgenic plants have been modified to increase photosynthesis (currently about 2% at most plants versus the theoretic potential of 9–10%). This is possible by changing the rubisco enzyme (i.e. changing C3 plants into C4 plants), by placing the rubisco in a carboxysome, by adding CO2 pumps in the cell wall, by changing the leaf form/size. Plants have been engineered to exhibit bioluminescence that may become a sustainable alternative to electric lighting.
Cisgenic
Cisgenic plants are made using genes found within the same species or a closely related one, where conventional plant breeding can occur. Some breeders and scientists argue that cisgenic modification is useful for plants that are difficult to crossbreed by conventional means (such as potatoes), and that plants in the cisgenic category should not require the same regulatory scrutiny as transgenics.
Subgenic
Genetically modified plants can also be developed using gene knockdown or gene knockout
to alter the genetic makeup of a plant without incorporating genes from
other plants. In 2014, Chinese researcher Gao Caixia filed patents on
the creation of a strain of wheat that is resistant to powdery mildew.
The strain lacks genes that encode proteins that repress defenses
against the mildew. The researchers deleted all three copies of the
genes from wheat's hexaploid genome. Gao used the TALENs and CRISPR gene editing tools without adding or changing any other genes. No field trials were immediately planned. The CRISPR technique has also been used by Penn State researcher Yinong Yang to modify white button mushrooms (Agaricus bisporus) to be non-browning, and by DuPont Pioneer to make a new variety of corn.
Multiple trait integration
With multiple trait integration, several new traits may be integrated into a new crop.
Economics
GM food's economic value to farmers is one of its major benefits, including in developing nations.
A 2010 study found that Bt corn provided economic benefits of $6.9
billion over the previous 14 years in five Midwestern states. The
majority ($4.3 billion) accrued to farmers producing non-Bt corn. This
was attributed to European corn borer populations reduced by exposure to
Bt corn, leaving fewer to attack conventional corn nearby.
Agriculture economists calculated that "world surplus [increased by]
$240.3 million for 1996. Of this total, the largest share (59%) went to
U.S. farmers. Seed company Monsanto received the next largest share
(21%), followed by US consumers (9%), the rest of the world (6%), and
the germplasm supplier, Delta & Pine Land Company of Mississippi (5%)."
According to the International Service for the Acquisition of Agri-biotech Applications
(ISAAA), in 2014 approximately 18 million farmers grew biotech crops in
28 countries; about 94% of the farmers were resource-poor in developing
countries. 53% of the global biotech crop area of 181.5 million
hectares was grown in 20 developing countries.
PG Economics comprehensive 2012 study concluded that GM crops increased
farm incomes worldwide by $14 billion in 2010, with over half this
total going to farmers in developing countries.
Critics challenged the claimed benefits to farmers over the prevalence of biased observers and by the absence of randomized controlled trials.
The main Bt crop grown by small farmers in developing countries is
cotton. A 2006 review of Bt cotton findings by agricultural economists
concluded, "the overall balance sheet, though promising, is mixed.
Economic returns are highly variable over years, farm type, and
geographical location".
In 2013 the European Academies Science Advisory Council (EASAC)
asked the EU to allow the development of agricultural GM technologies to
enable more sustainable agriculture, by employing fewer land, water,
and nutrient resources. EASAC also criticizes the EU's "time-consuming
and expensive regulatory framework" and said that the EU had fallen
behind in the adoption of GM technologies.
Participants in agriculture business markets include seed
companies, agrochemical companies, distributors, farmers, grain
elevators and universities that develop new crops/traits and whose
agricultural extensions advise farmers on best practices.
According to a 2012 review based on data from the late 1990s and early
2000s, much of the GM crop grown each year is used for livestock feed
and increased demand for meat leads to increased demand for GM feed
crops.
Feed grain usage as a percentage of total crop production is 70% for
corn and more than 90% of oil seed meals such as soybeans. About 65
million metric tons of GM corn grains and about 70 million metric tons
of soybean meals derived from GM soybean become feed.
In 2014 the global value of biotech seed was US$15.7 billion;
US$11.3 billion (72%) was in industrial countries and US$4.4 billion
(28%) was in the developing countries. In 2009, Monsanto had $7.3 billion in sales of seeds and from licensing its technology; DuPont, through its Pioneer subsidiary, was the next biggest company in that market. As of 2009, the overall Roundup line of products including the GM seeds represented about 50% of Monsanto's business.
Some patents on GM traits have expired, allowing the legal
development of generic strains that include these traits. For example,
generic glyphosate-tolerant GM soybean is now available. Another impact
is that traits developed by one vendor can be added to another vendor's
proprietary strains, potentially increasing product choice and
competition. The patent on the first type of Roundup Ready crop that Monsanto produced (soybeans) expired in 2014 and the first harvest of off-patent soybeans occurs in the spring of 2015.
Monsanto has broadly licensed the patent to other seed companies that
include the glyphosate resistance trait in their seed products. About 150 companies have licensed the technology, including Syngenta and DuPont Pioneer.
Yield
In 2014, the largest review yet concluded that GM crops' effects on farming were positive. The meta-analysis
considered all published English-language examinations of the agronomic
and economic impacts between 1995 and March 2014 for three major GM
crops: soybean, maize, and cotton. The study found that
herbicide-tolerant crops have lower production costs, while for
insect-resistant crops the reduced pesticide use was offset by higher
seed prices, leaving overall production costs about the same.
Yields increased 9% for herbicide tolerance and 25% for insect
resistant varieties. Farmers who adopted GM crops made 69% higher
profits than those who did not. The review found that GM crops help
farmers in developing countries, increasing yields by 14 percentage
points.
The researchers considered some studies that were not
peer-reviewed and a few that did not report sample sizes. They attempted
to correct for publication bias, by considering sources beyond academic journals.
The large data set allowed the study to control for potentially
confounding variables such as fertilizer use. Separately, they concluded
that the funding source did not influence study results.
Traits
GM crops grown today, or under development, have been modified with various traits. These traits include improved shelf life, disease resistance, stress resistance, herbicide resistance, pest resistance, production of useful goods such as biofuel or drugs, and ability to absorb toxins and for use in bioremediation of pollution.
Recently, research and development has been targeted to enhancement of crops that are locally important in developing countries, such as insect-resistant cowpea for Africa and insect-resistant brinjal (eggplant).
Extended shelf life
The first genetically modified crop approved for sale in the U.S. was the FlavrSavr tomato, which had a longer shelf life. First sold in 1994, FlavrSavr tomato production ceased in 1997. It is no longer on the market.
In November 2014, the USDA approved a GM potato that prevents bruising.
In February 2015 Arctic Apples were approved by the USDA, becoming the first genetically modified apple approved for US sale. Gene silencing was used to reduce the expression of polyphenol oxidase (PPO), thus preventing enzymatic browning of the fruit after it has been sliced open. The trait was added to Granny Smith and Golden Delicious varieties. The trait includes a bacterial antibiotic resistance gene that provides resistance to the antibiotic kanamycin.
The genetic engineering involved cultivation in the presence of
kanamycin, which allowed only resistant cultivars to survive. Humans
consuming apples do not acquire kanamycin resistance, per
arcticapple.com. The FDA approved the apples in March 2015.
Improved photosynthesis
Plants use non-photochemical quenching
(NPQ) to protect them from excessive amounts of sunlight. Plants can
switch on the quenching mechanism almost instantaneously but it takes
much longer for it to switch off again. During the time that it is
switched off, the amount of energy that is wasted increases.[citation needed]
A genetic modification in three genes allows to correct this (in a
trial with tobacco plants). As a result, yields were 14-20% higher, in
terms of the weight of the dry leaves harvested. The plants had bigger
leaves, were taller and had more vigorous roots.
Another improvement that can be made on the photosynthesis process (with C3 pathway plants) is on photorespiration. By inserting the C4 pathway into C3 plants, productivity may increase by as much as 50% for cereal crops, such as rice.
Improved nutritional value
Edible oils
Some GM soybeans offer improved oil profiles for processing. Camelina sativa has been modified to produce plants that accumulate high levels of oils similar to fish oils.
Vitamin enrichment
Golden rice, developed by the International Rice Research Institute (IRRI), provides greater amounts of vitamin A targeted at reducing vitamin A deficiency. As of January 2016, golden rice has not yet been grown commercially in any country.
Toxin reduction
A genetically modified cassava under development offers lower cyanogen glucosides and enhanced protein and other nutrients (called BioCassava).
In November 2014, the USDA approved a potato that prevents bruising and produces less acrylamide when fried. They do not employ genes from non-potato species. The trait was added to the Russet Burbank, Ranger Russet and Atlantic varieties.
Stress resistance
Plants have been engineered to tolerate non-biological stressors, such as drought, frost, and high soil salinity. In 2011, Monsanto's DroughtGard maize became the first drought-resistant GM crop to receive US marketing approval.
Drought resistance occurs by modifying the plant's genes responsible for the mechanism known as the crassulacean acid metabolism
(CAM), which allows the plants to survive despite low water levels.
This holds promise for water-heavy crops such as rice, wheat, soybeans
and poplar to accelerate their adaptation to water-limited environments. Several salinity tolerance mechanisms have been identified in salt-tolerant crops. For example, rice, canola and tomato crops have been genetically modified to increase their tolerance to salt stress.
Herbicides
Glyphosate
As of 1999, the most prevalent GM trait was glyphosate-tolerance. Glyphosate (the active ingredient in Roundup and other herbicide products) kills plants by interfering with the shikimate pathway in plants, which is essential for the synthesis of the aromatic amino acids phenylalanine, tyrosine, and tryptophan.
The shikimate pathway is not present in animals, which instead obtain
aromatic amino acids from their diet. More specifically, glyphosate
inhibits the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS).
This trait was developed because the herbicides used on grain and
grass crops at the time were highly toxic and not effective against
narrow-leaved weeds. Thus, developing crops that could withstand
spraying with glyphosate would both reduce environmental and health
risks, and give an agricultural edge to the farmer.
Some micro-organisms have a version of EPSPS that is resistant to glyphosate inhibition. One of these was isolated from an Agrobacterium strain CP4 (CP4 EPSPS) that was resistant to glyphosate. The CP4 EPSPS gene was engineered for plant expression by fusing the 5' end of the gene to a chloroplast transit peptide derived from the petunia
EPSPS. This transit peptide was used because it had shown previously an
ability to deliver bacterial EPSPS to the chloroplasts of other plants.
This CP4 EPSPS gene was cloned and transfected into soybeans.
The plasmid used to move the gene into soybeans was PV-GMGTO4. It contained three bacterial genes, two CP4 EPSPS genes, and a gene encoding beta-glucuronidase (GUS) from Escherichia coli as a marker. The DNA was injected into the soybeans using the particle acceleration method. Soybean cultivar A54O3 was used for the transformation.
Bromoxynil
Tobacco plants have been engineered to be resistant to the herbicide bromoxynil.
Glufosinate
Crops have been commercialized that are resistant to the herbicide glufosinate, as well.
Crops engineered for resistance to multiple herbicides to allow farmers
to use a mixed group of two, three, or four different chemicals are
under development to combat growing herbicide resistance.
2,4-D
In October 2014 the US EPA registered Dow's Enlist Duo maize, which is genetically modified to be resistant to both glyphosate and 2,4-D, in six states. Inserting a bacterial aryloxyalkanoate dioxygenase gene, aad1 makes the corn resistant to 2,4-D. The USDA had approved maize and soybeans with the mutation in September 2014.
Dicamba
Monsanto has requested approval for a stacked strain that is tolerant of both glyphosate and dicamba. The request includes plans for avoiding herbicide drift to other crops. Significant damage to other non-resistant crops occurred from dicamba formulations intended to reduce volatilization drifting when sprayed on resistant soybeans in 2017.
The newer dicamba formulation labels specify to not spray when average
wind speeds are above 10–15 miles per hour (16–24 km/h) to avoid
particle drift, average wind speeds below 3 miles per hour (4.8 km/h) to
avoid temperature inversions,
and rain or high temperatures are in the next day forecast. However,
these conditions typically only occur during June and July for a few
hours at a time.
Pest resistance
Insects
Tobacco, corn, rice and some other crops have been engineered to express genes encoding for insecticidal proteins from Bacillus thuringiensis (Bt).
The introduction of Bt crops during the period between 1996 and 2005
has been estimated to have reduced the total volume of insecticide
active ingredient use in the United States by over 100 thousand tons.
This represents a 19.4% reduction in insecticide use.
In the late 1990s, a genetically modified potato that was resistant to the Colorado potato beetle was withdrawn because major buyers rejected it, fearing consumer opposition.
Viruses
Papaya, potatoes, and squash have been engineered to resist viral pathogens such as cucumber mosaic virus which, despite its name, infects a wide variety of plants.
Virus resistant papaya were developed in response to a papaya ringspot virus (PRV) outbreak in Hawaii in the late 1990s. They incorporate PRV DNA. By 2010, 80% of Hawaiian papaya plants were genetically modified.
Potatoes were engineered for resistance to potato leaf roll virus and Potato virus Y in 1998. Poor sales led to their market withdrawal after three years.
Yellow squash that were resistant to at first two, then three
viruses were developed, beginning in the 1990s. The viruses are
watermelon, cucumber and zucchini/courgette yellow mosaic. Squash was
the second GM crop to be approved by US regulators. The trait was later
added to zucchini.
Many strains of corn have been developed in recent years to combat the spread of Maize dwarf mosaic virus,
a costly virus that causes stunted growth which is carried in Johnson
grass and spread by aphid insect vectors. These strands are commercially
available although the resistance is not standard among GM corn
variants.
By-products
Drugs
In 2012, the FDA approved the first plant-produced pharmaceutical, a treatment for Gaucher's Disease. Tobacco plants have been modified to produce therapeutic antibodies.
Biofuel
Algae is under development for use in biofuels. Researchers in Singapore were working on GM jatropha for biofuel production. Syngenta has USDA approval to market a maize trademarked Enogen that has been genetically modified to convert its starch to sugar for ethanol. Some trees have been genetically modified to either have less lignin, or to express lignin with chemically labile bonds. Lignin is the critical limiting factor when using wood to make bio-ethanol because lignin limits the accessibility of cellulose microfibrils to depolymerization by enzymes. Besides with trees, the chemically labile lignin bonds are also very useful for cereal crops such as maize, barley, and oats.
Materials
Companies and labs are working on plants that can be used to make bioplastics. Potatoes that produce industrially useful starches have been developed as well. Oilseed can be modified to produce fatty acids for detergents, substitute fuels and petrochemicals.
Bioremediation
Scientists at the University of York developed a weed (Arabidopsis thaliana) that contains genes from bacteria that could clean TNT and RDX-explosive soil contaminants in 2011. 16 million hectares in the US (1.5% of the total surface) are estimated to be contaminated with TNT and RDX. However A. thaliana was not tough enough for use on military test grounds. Modifications in 2016 included switchgrass and bentgrass.
Genetically modified plants have been used for bioremediation of contaminated soils. Mercury, selenium and organic pollutants such as polychlorinated biphenyls (PCBs).
Marine environments are especially vulnerable since pollution such as oil spills are not containable. In addition to anthropogenic pollution, millions of tons of petroleum
annually enter the marine environment from natural seepages. Despite
its toxicity, a considerable fraction of petroleum oil entering marine
systems is eliminated by the hydrocarbon-degrading activities of
microbial communities. Particularly successful is a recently discovered
group of specialists, the so-called hydrocarbonoclastic bacteria (HCCB) that may offer useful genes.
Asexual reproduction
Crops such as maize
reproduce sexually each year. This randomizes which genes get
propagated to the next generation, meaning that desirable traits can be
lost. To maintain a high-quality crop, some farmers purchase seeds every
year. Typically, the seed company maintains two inbred varieties and crosses them into a hybrid strain that is then sold. Related plants like sorghum and gamma grass are able to perform apomixis,
a form of asexual reproduction that keeps the plant's DNA intact. This
trait is apparently controlled by a single dominant gene, but
traditional breeding has been unsuccessful in creating
asexually-reproducing maize. Genetic engineering offers another route to
this goal. Successful modification would allow farmers to replant
harvested seeds that retain desirable traits, rather than relying on
purchased seed.
Other
Genetic modifications to some crops also exist, which make it easier to process the crop. For instance, the "no tears" onion
prevents the synthesis of lachrymatory factor synthase in onions
(otherwise put, it does not irritate the eyes when the onion is cut.
Also, some crops (such as tomatoes) have been genetic modified to contain no seed at all.
Crops
Herbicide tolerance
| Crop | Use | Countries approved in | First approved | Notes |
|---|---|---|---|---|
| Alfalfa | Animal feed | US | 2005 | Approval withdrawn in 2007 then re-approved in 2011 |
| Canola | Cooking oil
Margarine
Emulsifiers in packaged foods |
Australia | 2003 |
|
| Canada | 1995 |
| ||
| US | 1995 |
| ||
| Cotton | Fiber Cottonseed oil Animal feed |
Argentina | 2001 |
|
| Australia | 2002 |
| ||
| Brazil | 2008 |
| ||
| Colombia | 2004 |
| ||
| Costa Rica | 2008 |
| ||
| Mexico | 2000 |
| ||
| Paraguay | 2013 |
| ||
| South Africa | 2000 |
| ||
| US | 1994 |
| ||
| Maize | Animal feed
high-fructose corn syrup
corn starch |
Argentina | 1998 |
|
| Brazil | 2007 |
| ||
| Canada | 1996 |
| ||
| Colombia | 2007 |
| ||
| Cuba | 2011 |
| ||
| European Union | 1998 | Grown in Portugal, Spain, Czech Republic, Slovakia and Romania | ||
| Honduras | 2001 |
| ||
| Paraguay | 2012 |
| ||
| Philippines | 2002 |
| ||
| South Africa | 2002 |
| ||
| US | 1995 |
| ||
| Uruguay | 2003 |
| ||
| Soybean | Animal feed
Soybean oil
|
Argentina | 1996 |
|
| Bolivia | 2005 |
| ||
| Brazil | 1998 |
| ||
| Canada | 1995 |
| ||
| Chile | 2007 |
| ||
| Costa Rica | 2001 |
| ||
| Mexico | 1996 |
| ||
| Paraguay | 2004 |
| ||
| South Africa | 2001 |
| ||
| US | 1993 |
| ||
| Uruguay | 1996 |
| ||
| Sugar Beet | Food | Canada | 2001 |
|
| US | 1998 | Commercialized 2007, production blocked 2010, resumed 2011. |
Insect resistance
| Crop | Use | Countries approved in | First approved | Notes |
|---|---|---|---|---|
| Cotton | Fiber Cottonseed oil Animal feed |
Argentina | 1998 |
|
| Australia | 2003 |
| ||
| Brazil | 2005 |
| ||
| Burkina Faso | 2009 |
| ||
| China | 1997 |
| ||
| Colombia | 2003 |
| ||
| Costa Rica | 2008 |
| ||
| India | 2002 | Largest producer of Bt cotton | ||
| Mexico | 1996 |
| ||
| Myanmar | 2006 |
| ||
| Pakistan | 2010 |
| ||
| Paraguay | 2007 |
| ||
| South Africa | 1997 |
| ||
| Sudan | 2012 |
| ||
| US | 1995 |
| ||
| Eggplant | Food | Bangladesh | 2013 | 12 ha planted on 120 farms in 2014 |
| Maize | Animal feed
high-fructose corn syrup
corn starch |
Argentina | 1998 |
|
| Brazil | 2005 |
| ||
| Colombia | 2003 |
| ||
| Mexico | 1996 | Center of origin for maize | ||
| Paraguay | 2007 |
| ||
| Philippines | 2002 |
| ||
| South Africa | 1997 |
| ||
| Uruguay | 2003 |
| ||
| US | 1995 |
| ||
| Poplar | Tree | China | 1998 | 543 ha of bt poplar planted in 2014 |
Other modified traits
| Crop | Use | Trait | Countries approved in | First approved | Notes |
|---|---|---|---|---|---|
| Canola | Cooking oil
Margarine
Emulsifiers in packaged foods |
High laurate canola | Canada | 1996 |
|
| US | 1994 |
| |||
| Phytase production | US | 1998 |
| ||
| Carnation | Ornamental | Delayed senescence | Australia | 1995 |
|
| Norway | 1998 |
| |||
| Modified flower colour | Australia | 1995 |
| ||
| Colombia | 2000 | In 2014 4 ha were grown in greenhouses for export | |||
| European Union | 1998 | Two events expired 2008, another approved 2007 | |||
| Japan | 2004 |
| |||
| Malaysia | 2012 | For ornamental purposes | |||
| Norway | 1997 |
| |||
| Maize | Animal feed
high-fructose corn syrup
corn starch |
Increased lysine | Canada | 2006 |
|
| US | 2006 |
| |||
| Drought tolerance | Canada | 2010 |
| ||
| US | 2011 |
| |||
| Papaya | Food | Virus resistance | China | 2006 |
|
| US | 1996 | Mostly grown in Hawaii | |||
| Petunia | Ornamental | Modified flower color | China | 1997 |
|
| Potato | Food | Virus resistance | Canada | 1999 |
|
| US | 1997 |
| |||
| Industrial | Modified starch | US | 2014 |
| |
| Rose | Ornamental | Modified flower colour | Australia | 2009 | Surrendered renewal |
| Colombia | 2010 | Greenhouse cultivation for export only. | |||
| Japan | 2008 |
| |||
| US | 2011 |
| |||
| Soybean | Animal feed
Soybean oil
|
Increased oleic acid production | Argentina | 2015 |
|
| Canada | 2000 |
| |||
| US | 1997 |
| |||
| Stearidonic acid production | Canada | 2011 |
| ||
| US | 2011 |
| |||
| Squash | Food | Virus resistance | US | 1994 |
|
| Sugar Cane | Food | Drought tolerance | Indonesia | 2013 | Environmental certificate only |
| Tobacco | Cigarettes | Nicotine reduction | US | 2002 |
|
Development
The
number of USDA-approved field releases for testing grew from 4 in 1985
to 1,194 in 2002 and averaged around 800 per year thereafter. The number
of sites per release and the number of gene constructs (ways that the
gene of interest is packaged together with other elements) – have
rapidly increased since 2005. Releases with agronomic properties (such
as drought resistance) jumped from 1,043 in 2005 to 5,190 in 2013. As of
September 2013, about 7,800 releases had been approved for corn, more
than 2,200 for soybeans, more than 1,100 for cotton, and about 900 for
potatoes. Releases were approved for herbicide tolerance (6,772
releases), insect resistance (4,809), product quality such as flavor or
nutrition (4,896), agronomic properties like drought resistance (5,190),
and virus/fungal resistance (2,616). The institutions with the most
authorized field releases include Monsanto with 6,782, Pioneer/DuPont
with 1,405, Syngenta with 565, and USDA’s Agricultural Research Service
with 370. As of September 2013 USDA had received proposals for releasing
GM rice, squash, plum, rose, tobacco, flax, and chicory.
Farming practices
Resistance
Bacillus thuringiensis
Constant exposure to a toxin creates evolutionary pressure for pests resistant to that toxin. Over-reliance on glyphosate
and a reduction in the diversity of weed management practices allowed
the spread of glyphosate resistance in 14 weed species in the US, and in soybeans.
To reduce resistance to Bacillus thuringiensis
(Bt) crops, the 1996 commercialization of transgenic cotton and maize
came with a management strategy to prevent insects from becoming
resistant. Insect resistance management plans are mandatory for Bt
crops. The aim is to encourage a large population of pests so that any
(recessive) resistance genes are diluted within the population.
Resistance lowers evolutionary fitness in the absence of the stressor,
Bt. In refuges, non-resistant strains outcompete resistant ones.
With sufficiently high levels of transgene expression, nearly all
of the heterozygotes (S/s), i.e., the largest segment of the pest
population carrying a resistance allele, will be killed before
maturation, thus preventing transmission of the resistance gene to their
progeny.
Refuges (i. e., fields of nontransgenic plants) adjacent to transgenic
fields increases the likelihood that homozygous resistant (s/s)
individuals and any surviving heterozygotes will mate with susceptible
(S/S) individuals from the refuge, instead of with other individuals
carrying the resistance allele. As a result, the resistance gene
frequency in the population remains lower.
Complicating factors can affect the success of the
high-dose/refuge strategy. For example, if the temperature is not ideal,
thermal stress can lower Bt toxin production and leave the plant more
susceptible. More importantly, reduced late-season expression has been
documented, possibly resulting from DNA methylation of the promoter.
The success of the high-dose/refuge strategy has successfully
maintained the value of Bt crops. This success has depended on factors
independent of management strategy, including low initial resistance
allele frequencies, fitness costs associated with resistance, and the
abundance of non-Bt host plants outside the refuges.
Companies that produce Bt seed are introducing strains with
multiple Bt proteins. Monsanto did this with Bt cotton in India, where
the product was rapidly adopted.
Monsanto has also; in an attempt to simplify the process of
implementing refuges in fields to comply with Insect Resistance
Management(IRM) policies and prevent irresponsible planting practices;
begun marketing seed bags with a set proportion of refuge
(non-transgenic) seeds mixed in with the Bt seeds being sold. Coined
"Refuge-In-a-Bag" (RIB), this practice is intended to increase farmer
compliance with refuge requirements and reduce additional labor needed
at planting from having separate Bt and refuge seed bags on hand. This strategy is likely to reduce the likelihood of Bt-resistance occurring for corn rootworm, but may increase the risk of resistance for lepidopteran corn pests, such as European corn borer.
Increased concerns for resistance with seed mixtures include partially
resistant larvae on a Bt plant being able to move to a susceptible plant
to survive or cross pollination of refuge pollen on to Bt plants that
can lower the amount of Bt expressed in kernels for ear feeding insects.
Herbicide resistance
Best management practices
(BMPs) to control weeds may help delay resistance. BMPs include
applying multiple herbicides with different modes of action, rotating
crops, planting weed-free seed, scouting fields routinely, cleaning
equipment to reduce the transmission of weeds to other fields, and
maintaining field borders.
The most widely planted GM crops are designed to tolerate herbicides.
By 2006 some weed populations had evolved to tolerate some of the same
herbicides. Palmer amaranth
is a weed that competes with cotton. A native of the southwestern US,
it traveled east and was first found resistant to glyphosate in 2006,
less than 10 years after GM cotton was introduced.
Plant protection
Farmers
generally use less insecticide when they plant Bt-resistant crops.
Insecticide use on corn farms declined from 0.21 pound per planted acre
in 1995 to 0.02 pound in 2010. This is consistent with the decline in European corn borer
populations as a direct result of Bt corn and cotton. The establishment
of minimum refuge requirements helped delay the evolution of Bt
resistance. However, resistance appears to be developing to some Bt
traits in some areas.
Tillage
By leaving at least 30% of crop residue on the soil surface from harvest through planting, conservation tillage
reduces soil erosion from wind and water, increases water retention,
and reduces soil degradation as well as water and chemical runoff. In
addition, conservation tillage reduces the carbon footprint of
agriculture.
A 2014 review covering 12 states from 1996 to 2006, found that a 1%
increase in herbicde-tolerant (HT) soybean adoption leads to a 0.21%
increase in conservation tillage and a 0.3% decrease in quality-adjusted
herbicide use.
Regulation
The regulation of genetic engineering concerns the approaches taken
by governments to assess and manage the risks associated with the
development and release of genetically modified crops. There are
differences in the regulation of GM crops between countries, with some
of the most marked differences occurring between the US and Europe.
Regulation varies in a given country depending on the intended use of
each product. For example, a crop not intended for food use is generally
not reviewed by authorities responsible for food safety.
Production
In
2013, GM crops were planted in 27 countries; 19 were developing
countries and 8 were developed countries. 2013 was the second year in
which developing countries grew a majority (54%) of the total GM
harvest. 18 million farmers grew GM crops; around 90% were small-holding
farmers in developing countries.
| Country | 2013– GM planted area (million hectares) | Biotech crops |
|---|---|---|
| US | 70.1 | Maize, Soybean, Cotton, Canola, Sugarbeet, Alfalfa, Papaya, Squash |
| Brazil | 40.3 | Soybean, Maize, Cotton |
| Argentina | 24.4 | Soybean, Maize, Cotton |
| India | 11.0 | Cotton |
| Canada | 10.8 | Canola, Maize, Soybean, Sugarbeet |
| Total | 175.2 | ---- |
The United States Department of Agriculture (USDA) reports every year on the total area of GM crop varieties planted in the United States. According to National Agricultural Statistics Service,
the states published in these tables represent 81–86 percent of all
corn planted area, 88–90 percent of all soybean planted area, and 81–93
percent of all upland cotton planted area (depending on the year).
Global estimates are produced by the International Service for the Acquisition of Agri-biotech Applications (ISAAA) and can be found in their annual reports, "Global Status of Commercialized Transgenic Crops".
Farmers have widely adopted GM technology (see figure). Between
1996 and 2013, the total surface area of land cultivated with GM crops
increased by a factor of 100, from 17,000 square kilometers (4,200,000
acres) to 1,750,000 km2 (432 million acres). 10% of the world's arable land was planted with GM crops in 2010.
As of 2011, 11 different transgenic crops were grown commercially on
395 million acres (160 million hectares) in 29 countries such as the US,
Brazil, Argentina, India, Canada, China, Paraguay, Pakistan, South
Africa, Uruguay, Bolivia, Australia, Philippines, Myanmar, Burkina Faso,
Mexico and Spain.
One of the key reasons for this widespread adoption is the perceived
economic benefit the technology brings to farmers. For example, the
system of planting glyphosate-resistant seed and then applying
glyphosate once plants emerged provided farmers with the opportunity to
dramatically increase the yield from a given plot of land, since this
allowed them to plant rows closer together. Without it, farmers had to
plant rows far enough apart to control post-emergent weeds with
mechanical tillage.
Likewise, using Bt seeds means that farmers do not have to purchase
insecticides, and then invest time, fuel, and equipment in applying
them. However critics have disputed whether yields are higher and
whether chemical use is less, with GM crops.
Land
area used for genetically modified crops by country (1996–2009), in
millions of hectares. In 2011, the land area used was 160 million
hectares, or 1.6 million square kilometers.
In the US, by 2014, 94% of the planted area of soybeans, 96% of cotton and 93% of corn were genetically modified varieties.
Genetically modified soybeans carried herbicide-tolerant traits only,
but maize and cotton carried both herbicide tolerance and insect
protection traits (the latter largely Bt protein).
These constitute "input-traits" that are aimed to financially benefit
the producers, but may have indirect environmental benefits and cost
benefits to consumers. The Grocery Manufacturers of America estimated in
2003 that 70–75% of all processed foods in the U.S. contained a GM
ingredient.
Europe grows relatively few genetically engineered crops with the exception of Spain, where one fifth of maize is genetically engineered, and smaller amounts in five other countries. The EU had a 'de facto' ban on the approval of new GM crops, from 1999 until 2004. GM crops are now regulated by the EU. In 2015, genetically engineered crops are banned in 38 countries worldwide, 19 of them in Europe. Developing countries grew 54 percent of genetically engineered crops in 2013.
In recent years GM crops expanded rapidly in developing countries. In 2013 approximately 18 million farmers grew 54% of worldwide GM crops in developing countries. 2013's largest increase was in Brazil (403,000 km2 versus 368,000 km2 in 2012). GM cotton began growing in India in 2002, reaching 110,000 km2 in 2013.
According to the 2013 ISAAA brief: "...a total of 36 countries
(35 + EU-28) have granted regulatory approvals for biotech crops for
food and/or feed use and for environmental release or planting since
1994... a total of 2,833 regulatory approvals involving 27 GM crops and
336 GM events (NB: an "event" is a specific genetic modification in a
specific species) have been issued by authorities, of which 1,321 are
for food use (direct use or processing), 918 for feed use (direct use or
processing) and 599 for environmental release or planting. Japan has
the largest number (198), followed by the U.S.A. (165, not including
"stacked" events), Canada (146), Mexico (131), South Korea (103),
Australia (93), New Zealand (83), European Union (71 including approvals
that have expired or under renewal process), Philippines (68), Taiwan
(65), Colombia (59), China (55) and South Africa (52). Maize has the
largest number (130 events in 27 countries), followed by cotton (49
events in 22 countries), potato (31 events in 10 countries), canola (30
events in 12 countries) and soybean (27 events in 26 countries).
Controversy
Direct genetic engineering has been controversial since its
introduction. Most, but not all of the controversies are over GM foods
rather than crops per se. GM foods are the subject of protests,
vandalism, referenda, legislation, court action
and scientific disputes. The controversies involve consumers,
biotechnology companies, governmental regulators, non-governmental
organizations and scientists.
Opponents have objected to GM crops on multiple grounds including
environmental impacts, food safety, whether GM crops are needed to
address food needs, whether they are sufficiently accessible to farmers
in developing countries and concerns over subjecting crops to intellectual property
law. Secondary issues include labeling, the behavior of government
regulators, the effects of pesticide use and pesticide tolerance.
A significant environmental concern about using genetically
modified crops is possible cross-breeding with related crops, giving
them advantages over naturally occurring varieties. One example is a
glyphosate-resistant rice crop that crossbreeds with a weedy relative,
giving the weed a competitive advantage. The transgenic hybrid had
higher rates of photosynthesis, more shoots and flowers, and more seeds
than the non-transgenic hybrids. This demonstrates the possibility of ecosystem damage by GM crop usage.
There is a scientific consensus that currently available food derived from GM crops poses no greater risk to human health than conventional food, but that each GM food needs to be tested on a case-by-case basis before introduction. Nonetheless, members of the public are much less likely than scientists to perceive GM foods as safe.
The legal and regulatory status of GM foods varies by country, with
some nations banning or restricting them, and others permitting them
with widely differing degrees of regulation.
No reports of ill effects from GM food have been documented in the human population. GM crop labeling is required in many countries, although the United States Food and Drug Administration does not, nor does it distinguish between approved GM and non-GM foods.
The United States enacted a law that requires labeling regulations to
be issued by July 2018. It allows indirect disclosure such as with a
phone number, bar code, or web site.
Advocacy groups such as Center for Food Safety, Union of Concerned Scientists, Greenpeace and the World Wildlife Fund
claim that risks related to GM food have not been adequately examined
and managed, that GM crops are not sufficiently tested and should be
labelled, and that regulatory authorities and scientific bodies are too
closely tied to industry. Some studies have claimed that genetically modified crops can cause harm;
a 2016 review that reanalyzed the data from six of these studies found
that their statistical methodologies were flawed and did not demonstrate
harm, and said that conclusions about GM crop safety should be drawn
from "the totality of the evidence... instead of far-fetched evidence
from single studies".
