The Role of Genetically Modified Crops in Attaining Food Security in the Developing World

New genetically modified crops that could help developing countries attain food security are in the pipeline, but resistance to their introduction is preventing many from reaching the poor.

A genetically modified eggplant, at right, is more resistant to disease and pests. Image Credit: D M Hautea, University of the Philippines Los Banos

Plant diseases and pests not found in other parts of the world can be found in developing countries. These, as well as adverse climate conditions such as drought, can severely hinder crop production, potentially resulting in a lack of food security.

This paper discusses how to combat these problems with genetic modification (GM). Unfortunately, resistance to the introduction of GM crops is preventing many such crops from being planted, and preventing resource-poor farmers from producing food much more cheaply.

In a recent paper from Purdue University (Mahaffey et al., 2016), the authors considered the economic and environmental impacts of a global GM crop ban. They predict that global cropland would have to increase by 3.1 million hectares to implement a ban, with 2.5 million coming from pasture land and the balance (0.6 million) from global forest loss. One of the main problems with such land-use conversion is that when forest or pastures are converted much of the carbon that has been sequestered over the years is released into the atmosphere. Mahaffey et al. estimate that the total emissions due to land use conversion would be the equivalent of about 0.9 billion tons of carbon dioxide (CO2).

This, however, paints a worst-case scenario. The following provides examples of GM crops in the pipeline that could make a difference for food-insecure people in the developing world.

Bananas resistant to bacterial wilt and nematodes

Genetically modified bananas resistant to bacterial wilt are shown on the left (image A), while Non-GM bananas are shown on the right. Image Credit: L. Tripathi, International Institute for Tropical Agriculture

Banana and plantain are widely cultivated in the Great Lakes region of Africa (GLA) and provide the staple food in this region which comprises Kenya, Tanzania, Uganda, Burundi, Rwanda and the eastern part of the Democratic Republic of Congo. It is also an important source of cash income (FAO, 2014). Banana Xanthomonas wilt (BXW), caused by the bacterium Xanthamonas campestris, threatens the livelihoods of millions of farmers in the GLA. Crop devastation can be extreme and rapid. Prospects for developing varieties with resistance to BXW through conventional breeding are poor as no source of germplasm exhibiting resistance has been identified. Therefore, scientists at the International Institute for Tropical Agriculture (IITA) in Uganda and Kenya have turned to a transgenic approach.

Using genes obtained from the sweet pepper, BXW-resistant GM bananas, artificially infected with X. campestris, have been tested in confined field trials in Uganda. All non-GM control plants died while the majority of the GM lines had a significantly higher resistance, with some showing 100 percent resistance (Tripathi et al. 2014).

Insect resistant brinjals and cowpeas

GM insect-resistant maize and cotton, expressing the Bt gene, obtained from the insect Bacillus thuringiensis, have been grown for many years in countries such as the United States, South Africa and India. Now scientists are turning their attention to insect problems in other crops of greater importance to the developing world, including brinjals and cowpea.

Brinjals, eggplants or talong, as they are known in the Philippines, are one of the most important vegetable crops grown there and in Bangladesh, but they are plagued by the fruit and shoot borer (FSB) caterpillar. Farmers spray between 20 and 70 times over the growing season, sometimes every second day. Residues from their application can be found in farm soil and in harvested fruit. Bt brinjals do not require insecticide spraying since the Bt protein provides 95-100 percent control by itself (Hautea et al., 2016).

Greenpeace and other anti-GMO groups won a court action in the Philippines in early 2016 preventing the cultivation of Bt talong. However, in July the Supreme Court reversed this order. The technology proponents must now submit further evidence on the food and feed safety of the product. It is hoped that this process should not take very long as the cry1Ac gene has already received regulatory approval by the Philippine authorities for use in GM soybean and cotton. As a last requirement Bt talong must be registered with the Fertilizer and Pesticide Authority. Once these conditions have been satisfied farmers in that part of the world should be able to benefit from the economic, environmental and health benefits from this crop (Javier, 2016). Naturally farmers will only buy the seeds if they provide economic benefits.

GM cowpeas have shown themselves less susceptible to the insect pod borer, which can cause 20 to 80 percent crop loss. Image Credit: African Agricultural Technology Foundation

Cowpeas are one of the most important food legume crops in the semi-arid tropics of Africa. They are rich in protein and eaten by about 200 million people. As a legume, the plant fixes atmospheric nitrogen in the soil, and its green leaves also can be eaten. In addition it is relatively drought-tolerant. The crop is often infested with the insect pod borer, Maruca vitrata, which can result in 20 to 80 percent yield loss. As a result, scientists have introduced the Bt gene into cowpeas. Confined field trials of this Pod-Borer Resistant (PBR) cowpea in multi-locations in Nigeria showed nearly complete control of Maruca. Insecticide reduction trials indicated that the PBR cowpeas will require fewer sprays in a season to complement this near-complete control. The PBR varieties are estimated to produce cowpea yields comparable with five insecticide sprays the farmers currently use to control insect pests on this crop. The project recommends combination of the GM cowpea with about two to three insecticide sprays to effectively control other insect pests such as pod sucking bugs, thrips and aphids.

Although the advantages of insect-resistant crops are many, it is important to realize that without careful stewardship insects can and will develop resistance to the Bt toxin as they do to any other insecticide. The answers lie in employing the high-dose/refuge (HDR) management strategy. Crops need to express a sufficiently high dose of Bt proteins in order to kill as many of the target pest population as possible. Along with the high dose expression, a separate non-BT refuge must be planted near the Bt crop. This non-Bt refuge serves as a source for the susceptible adults of the target pest that mate with the few resistant adults that survive on the Bt crop. Any susceptible offspring are then controlled by the high dose of Bt protein expressed in the crop (Gould 2000; Tabashnik et al., 2013). In addition, pyramiding of more than one Bt gene with different modes of action can prevent resistance development (Zhao et al., 2003).

Drought-tolerant maize

In recent years, severe drought has affected many parts of Africa, and with the onset of climate change this situation can only get worse. A partnership called WEMA (Water Efficient Maize for Africa), funded by the Bill and Melinda Gates and Howard Buffet foundations and managed by the African Agricultural Technology Foundation (AATF) has produced GM maize that can tolerate dehydration. The gene being used was derived from the bacterium, Bacillus subtilis. This is being field tested in partner countries in East and Southern Africa, while South Africa deregulated the drought tolerant MON87460 in May 2015 making it the second country after the U.S. to deregulate the trait. Confined field trials in Kenya have recorded 20 to 35 percent higher yields than conventional hybrids under drought-stress and optimum-moisture conditions (Obunyali and Oikeh, 2016).

Virus- resistant maize and cassava

Maize streak virus (MSV) and Cassava mosaic virus (CMV) are two of the most important pathogens of maize and cassava in Africa. Scientists in Africa and elsewhere have used genes derived from those found in the viruses themselves to introduce into these crops. The proteins produced by these genes prevent the viruses from spreading and causing damage in the plants. Trials have shown excellent resistance in glasshouses and the field (Shepherd et al. 2014; Taylor et al., 2012).

Are GM crops safe?

Earlier this year more than 100 Noble laureates signed a letter supporting GM crops. Their letter states: “Scientific and regulatory agencies around the world have repeatedly and consistently found crops and foods improved through biotechnology to be as safe as, if not safer than those derived from any other method of production. There has never been a single confirmed case of a negative health outcome for humans or animals from their consumption. Their environmental impacts have been shown repeatedly to be less damaging to the environment, and a boon to global biodiversity.” (Achenbach, 2016)

GM crops are not a “magic bullet” to improve food security in developing countries. However, this is one technology that has proven to work in many countries, including the U.S., Brazil, Argentina, India, Canada, China, Paraguay, Pakistan and South Africa, and could profitably be used in many others. It would be an indictment on society if opinions held by anti-GMO, well-fed, developed country citizens were to prevent resource poor farmers from testing this technology in their own soil.

Jennifer A. Thomson is emeritus professor in the Department of Molecular and Cell Biology at University of Cape Town in South Africa. Thomson is also the president of the Organization for Women in Science for the Developing World.

 

References

Achenbach J. 2016. 107 Nobel laureates sign letter blasting Greenpeace over GMOs. The Washington Post, 30 June.

Ainembabazi JH, Tripathi L, Rusike J, Abdoulaye T, Manyong V. 2015. Ex-ante economic impact assessment of genetically modified banana resistant to Xanthomonas wilt in the Great Lakes Region of Africa. PLoS ONE 10(9):e0138998. DOI:10.1371/journal.pone.0138998

FAO. 2014. Statistical database of the Food and Agricultural Organization of the United Nations,

FAO. Available: http://faostat3.fao.org.  Accessed 21 August 2016
Gould F (2000) Testing Bt refuge strategies in the field. Nature Biotechnology 18, 266-267

Hautea DM, Taylo LD, Masanga APL, Sison MLJ, Narciso JO, Quilloy RB, Hautea RA, Shotkoski FA, Shelton AM. 2016. Field performance of Bt eggplants (Solanum melongena L.) in the Philippines: Cry1Ac expression and control of the eggplant fruit and shoot borer (Leucinodes orbonalis Guenée). PLoS ONE 11(6):e0157498. Doi:10.1371/journal.pone.0157498.

Javier E. 2016. Bt talong case: not quite a total victory but at least the science can go on. Manila Bulletin 31 July.

Mahaffey H, Taheripour F, Tyner WE. 2016. Evaluating the economic and environmental impacts of a global GMO ban.  Journal of Environmental Protection 7, 1522-1546

Obunyali O, Oikeh SO (editors). 2016 Proceedings of the 8th Water Efficient Maize for Africa (WEMA) Project Review and Planning Meeting, 8-11 February, 2016, Ramada Resort Hotel, Dar es Saleem, Tanzania. The African Agricultural Technology Foundation (AATF)

Shepherd DN, Dugdale B, Martin DP, Versani A, Lakay FM, Bezuidenhout ME, Monjane AL, Thomson JA, Dale J, Rybicki EP. 2014. Inducible resistance to Maize streak virus. PLOS One. 9:e105932.

Tabashnik BE, Brévault T and Carriére Y (2013) Insect resistance to Bt crops: lessons from the first billion acres. Nature Biotechnology 31, 510-521

Taylor NJ, Halsey M, Gaitan-Solis E, Anderson P, Gichuki S, Miano D, Bua A, Alicia T, Fauquet CM. 2012. The VIRCA project: virus resistant cassava for Africa. GM Crops Food. 3:93-103

Thomson JA. 2015. Prospects for the utilization of genetically modified crops in Africa. Can. J. Plant Pathol. 37:152-159

Tripathi L, Tripathi JN, Kiggundu A, Korie S, Shotkoski F, Tushemereirwe WK. 2014. Field trial of Xanthomonas wilt disease-resistant bananas in East Africa. Nat. Biotechnol. 32:868-870

Tripathi L, Babirye A, Roderick H, Tripathi JN, Changa C, Urwin PE, Tushemereirwe WK, Coyne D, Atkinson HJ. 2015. Field resistance of transgenic plantain to nematodes has potential for future African food security. Sci. Rep. 5, 8127; DOI:10.1038/srep08127

Zhao J-Z, Cao J, Li Y, Collins HL, Roush RT, Earle ED and Shelton AM. (2003) Transgenic plants expressing two Bacillus thuringiensis toxins delay insect resistance evolution. Nature Biotechnology 21, 1493-1497

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