The most controversial form of crop biotechnology is the production of Genetically Modified (GM) or Engineered (GE) crops. This involves the introduction of a gene or gene sequence into an organism to achieve a specific result. For example, crop varieties can be engineered to express a bacterial gene that controls certain insect pests, reducing the need for harmful synthetic pesticides.
The potentially useful gene is isolated, using a naturally occurring enzyme, in one plant (it can be another crop variety or species or a plant from the wild). It is then transferred into the cell of a desirable crop variety, either by using a naturally occurring bacterium (Agrobacterium tumefacians) that infects plants or by coating gold particles with gene and shooting the particles into the crop plant with a gene gun. It is customary for millions of cells to be treated. Those with the new gene are identified by means of a marker. The transformed cells are then cultured and grown into whole plants and tested in greenhouses to ensure that the transferred gene functions properly. Not all transgenic plants will express the trait or gene product well, but once the trait is stable it can be bred using conventional plant breeding methods into cultivars with adaptation to the environmental conditions where the crop is produced.
The great advantage of recombinant DNA technology is that new combinations of genes are determined beforehand and, with skill and care, are precisely achieved. The process is also much quicker than conventional hybridisation and the sources of genetic material are much larger and less restricted by geographic or biological boundaries. As a result the plant breeder is no longer limited by the genetic variation that arises in traditional breeding programmes.
Some of the most valuable applications lie in the conferment of resistance to bacterial and virus diseases and to insect pests. Resistance to viruses can be achieved by transferring to plants certain viral genes that interfere with the normal replication of the virus thereby inhibiting the spread of infection. The technique has been used against several important viruses: rice stripe virus, alfalfa mosaic virus, and potato leafroll virus.
Breeding for insect pest resistance has benefited from transferring genes that code for the toxins produced by a bacterium, Bacillus thuringiensis (Bt), particularly to protect against the caterpillars of moths such as cotton bollworms, but has also been found useful in the control of stemborers for maize and rice. A further potential for Bt is to gain control of the diamondback moth, a devastating pest of cabbages, cauliflower, kale, mustard, and other brassica crops that are important sources of nutrition across Asia and Africa. GE has also been used against crop pathogens. One of the first and most successful genetically modified crops was a papaya with resistance to ringspot virus. Another example includes the development of bananas resistant to wilt in Uganda.Contribution to Sustainable Intensification
Genetic engineering has great potential for Sustainable Intensification and the transformation of the agricultural sector. New plant varieties and animal breeds could deliver higher yields but also greater tolerance and adaptability to worsening global conditions such as increasing drought, salinity and chemical toxicity. Developments in animal feeds and feeding practices are improving animal nutrition and reducing environmental waste while biotechnology is helping diagnose and treat a range of plant and animal diseases. Resistance to bacterial and viral diseases and to insect pests could, once conferred, provide huge savings in terms of crop losses and potentially lessen agriculture’s dependence on chemical inputs such as fungicides and pesticides. Achieving these targets is a tall order but the potential benefits are considerable. This is why building desirable characteristics – high yields coupled with stability and resilience – into the seed is so attractive. The seed, in a sense, can be a ‘package of desirable and appropriate technologies.’ It is in this respect that the new genetics, in the form of biotechnology, becomes so relevant.
Genetically modified (GM) crops are the fastest adopted crop technology in the world. The number of hectares planted with GM crops has increased more than 100-fold from 1.7 million hectares in 1996 to a record 181.5 million hectares in 2014, planted by 18 million farmers in 28 countries. Although to date most of the products of biotechnology have been developed in the global north, with limited application in the south, this is changing and more and more GM crops designed to reduce hunger and malnutrition, adapt to climate change and protect scarce natural resources are being developed and adopted.
Notably, Bangladesh approved Bt brinjal (eggplant or aubergine) for the first time on 30 October 2013. Less than 100 days after approval, smallholder farmers commercialized Bt brinjal on 22 January 2014. Other advancements in 2014 include the approval of Innate™ potato in the US that has lower levels of acrylamide, a potential carcinogen in humans, and suffers less wastage from bruising. As potato is the fourth most important food staple in the world, this variety has the potential to significantly increase availability. Also approved in the US was an alfalfa containing up to 22% less lignin, leading to higher digestibility and productivity. Further, plantings of the first GM drought tolerant maize in the US, increased from 50,000 hectares in 2013 to 275,000 hectares in 2014 reflecting high acceptance by US farmers.
In South Africa, 2.7 million hectares are planted with GM maize, soybean and cotton; in Burkina Faso, 0.5 million hectares are planted with Bt cotton; and in Sudan about 90,000 hectares are planted with Bt cotton. An additional seven African countries – Cameroon, Egypt, Ghana, Kenya, Malawi, Nigeria, and Uganda – have conducted field trials on the following broad range of staple crops: rice, maize, wheat, sorghum, bananas, cassava, and sweet potato. The Water Efficient Maize for Africa (WEMA) project is expected to deliver its first GM stacked drought tolerant maize with insect control (Bt) in South Africa as early as 2017, followed by Kenya and Uganda, and then by Mozambique and Tanzania, subject to regulatory approval.
The barriers faced by farmers in accessing genetically modified (GM) crops include, for example, the low level of development of domestic seed companies that can produce crops suitable to developing countries environments, preferences and needs. Biotechnology research is occurring in some African countries, notably researchers in Uganda are using GM to control the Xanthomonas banana wilt. By transferring two genes from green peppers, scientists were able to grow highly resistant bananas whilst scientists at the Institute for Agricultural Research at Nigeria’s Ahmadu Bello University have developed a pest-resistant, transgenic blackeyed pea variety using insecticide genes from the Bacillus thuringiensis (Bt) bacterium.
Other challenges such as underdeveloped national regulation and biosafety laws, the prohibition of GM crops within trading partner countries, a lack of capacity in developing new gene sequences in-country, low public funding of biotech research and issues of intellectual property and technology ownership have also been identified. Additionally, farmers may be reluctant to adopt GM varieties due to distrust of the technology among local consumers or perceived exploitation by transnational seed companies, despite the fact that development of new GM technologies in Africa is dominated by the public sector. For example, the African Agricultural Technology Foundation (AATF), an African based and led organisation, is assisting national agricultural research organisations to test and develop new appropriate GM crops, using donated genes from organisations such as the International Wheat and Maize Improvement Center (CIMMYT) and international seed companies such as Monsanto.
Only 3 countries in Africa currently grow genetically modified (GM) crops – South Africa, Burkina Faso, and Sudan, where the major crop grown is cotton. However many other African countries are engaged in contained field trials of a variety of GM food crops. For example at the Ugandan National Agricultural Research Organisation (NARO) trials include water efficient maize varieties, bananas resistant to a new bacterial wilt disease, and various engineered rice plants.
The benefits of genetic engineering go beyond the economic. In many instances the use of harmful pesticides is reduced. Recently, a meta-analysis covering the use of GM crops over the last 20 years looking at GM soybean, maize and cotton concluded “on average GM technology adoption has reduced chemical pesticide use 37%, increased crop yields by 22% and increased farmer profits by 68%.” The study also found that yield gains and pesticide reductions are largest for insect-resistant crops and yield and profit gains are highest in developing countries.
Moreover there are direct or indirect benefits for nutrition security. A study in India found that each hectare of GM cotton significantly increased farmer income and in turn increased total calorie consumption by 74 kcal per adult per day. Most significant was the reduction in child malnutrition. The households consumed more nutritious foods reflecting the potential of GM crops to contribute to food security in certain locations.
Since World War II, the common approach to pest, pathogen and weed problems has been to spray crops with synthetic pesticides. These compounds pose several problems: 1) they may be harmful to human health; 2) they may be damaging to wildlife in the environment; 3) they may be costly and ineffective at controlling pests; and 4) they can elevate minor pests to the extent that they are more destructive than the pests originally targeted. One solution to these challenges is to put resistance to pests into the seed. It is by far the easiest – and often cheapest – approach.
The bacterium Bacillus thuringiensis (Bt) that occurs naturally and is widespread in soil, when transferred to cotton, has been effective in controlling the bollworm. Farmers in the United States are also regularly growing maize and potatoes containing the Bt gene. Bt has also been transferred to rice and maize to control stem borers, an important pest in developing countries. A further potential for Bt is to gain control of the diamondback moth, a devastating pest of cabbages, cauliflower, kale, mustard, and other brassica crops that are important sources of nutrition across Asia and Africa. GE has also been used against crop pathogens. One of the first and most successful genetically modified crops was a papaya with resistance to ringspot virus. Another example includes the development of bananas resistant to wilt in Uganda.
Inevitably, the use of the Bt gene and other similar bacterium, like synthetic chemical insecticides, leads to selection for resistance. Resistance to Bt has been found in a number of insect species in laboratory experiments. The first in field example of Bt resistance by the cotton bollworm and corn earworm were found in the US states of Arkansas and Mississippi in 2003-2004 and a second case was confirmed in India in 2009. One approach to slowing resistance is to set up refuges of host plants without Bt genes with the expectation that the rare resistant insects will mate with susceptible pests from the refuges. There are also a number of different toxins produced by different Bt genes that can be used to produce crops ‘stacked’ with 2 different toxins, reducing the likelihood significantly that resistance could be built to both toxins simultaneously.
Ingredients produced from genetically modified (GM) crops are found in thousands of products and consumed worldwide with no legitimate evidence of harm to human health or the environment. GM cultivars have experienced wide and growing acceptance amongst farmers globally. Between 1996 and 2014, the acreage devoted to genetically modified crops increased 100-fold from 1.7 million hectares in 1996 to 181.5 million hectares in 2014.
Nevertheless, the safety of agricultural biotechnology to human health and the environment is fiercely contested. Opponents emphasize the potential for harm to occur and justify banning GM crops in Europe based on the ‘precautionary principle.’ Their concerns include the potential for cross-pollination of GM crops with sexually compatible wild relatives that could lead to the development of invasive weed species; destroying beneficial organisms above and below ground; enabling the emergence of ‘superbugs’ resistant to pesticides; increasing the use of chemical pesticides; and introducing new food allergens. It is important to note that these are regularly occurring risks with the introduction of any new plant species regardless of the breeding method employed.
The body of scientific evidence concluding that GM foods are safe to eat and do not pose environmental risks is wide. Findings from the International Council of Scientists that analysed a selection of approximately 50 science-based reviews concluded that “currently available genetically modified foods are safe to eat,” and “there is no evidence of any deleterious environmental effects having occurred from the trait/species combinations currently available.” The United Nations Food and Agriculture Organization (FAO) supported the same consensus in addition to recommending the extension of biotechnology to the developing world. Similarly, the Royal Society and British Medical Association found no adverse health effects of consuming genetically modified foods. These findings supported the conclusions of earlier studies by the European Union Research Directorate a compendium of 81 scientific studies conducted by more than 400 research teams did not show “any new risks to human health or the environment, beyond the usual uncertainties of conventional plant breeding.” Likewise, the Organization for Economic Cooperation and Development in Europe (OECD) and the Nuffield Council on Bioethics did not find that genetically modified foods posed a health risk.