GM sweet potato to “feed countless people in Africa”

Claims

In 2003 Florence Wambugu, a Monsanto-trained scientist who is the founder and CEO of Africa Harvest Biotech Foundation International,¹ gave an interview to Canada’s National Post about a GM sweet potato that she had developed to resist the feathery mottle virus. Wambugu claimed, “The modified sweet potato seeds should be able to produce 10 tonnes of vegetables per hectare compared with a natural Kenyan crop that yields four tonnes per hectare.” ²

The Toronto Globe & Mail repeated the same figures: “Dr Wambugu’s modified sweet potato… can increase yields from four tonnes per hectare to 10 tonnes.” ⁹

In the previous year, 2002, an article in Forbes magazine titled “Millions served” had claimed that the GM sweet potato had doubled yields and was already being used to “feed” Kenya. The article declared, “While the West debates the ethics of genetically modified food, Florence Wambugu is using it to feed her country.” ¹⁰

Forbes called the GM sweet potato “a breakthrough 25 years in the making”. It said, “Now halfway through field trials, the results are astonishing. The sweet potato is sub-Saharan Africa’s first genetically modified crop, and its yields so far are double that of the regular plant. Potatoes are bigger and richer in colour, indicating they’ve retained more nutritional value. On a continent where population growth outstrips food supply growth by 1% a year, Wambugu’s modified sweet potato offers tangible hope. According to the World Bank, biotech crops could increase food production in the developing world by 25%.”

According to a report in Kenya’s Daily Nation, “The modified potato was launched in Kenya, in 2001 by US special envoy, Dr Andrew Young, who had flown into the country for the occasion.” ¹¹

In 2003 Wambugu published a paper on the GM sweet potato in Nutrition Reviews, the official journal of the International Life Sciences Institute,¹² which concluded, “Even small improvements in crop yield, owing to this new [GM] technology, will feed countless people in Africa.”

She wrote, “Assuming the SPFMV [sweet potato feathery mottle virus] protection results in only a 15% average increase in yield, the total gain from the improved sweet potato would be 1.8 million tons per year. With a subsistence growers’ value of about $275 per ton, in Africa, virus-tolerant sweet potato could potentially be worth an additional $495 million a year to Africa. More importantly, the extra 1.8 million tons would supply half of the dietary needs of about 10 million people, with no additional production costs.” ³

In a report published in 2003, the Nuffield Council on Bioethics said the project “could prevent dramatic and frequent reductions in yield of one of the major food crops of many poor people in Africa.” ¹³

Africa Harvest Biotech Foundation International

Africa Harvest Biotech Foundation International has been funded by the Bill & Melinda Gates Foundation¹⁴ and has counted the agricultural industry association CropLife among its partners and funders.¹⁵ CropLife’s member companies include the large agricultural biotech and chemical companies BASF, Bayer, Corteva, and Syngenta.¹⁶

According to Aaron deGrassi, then of the Institute of Development Studies, University of Sussex,¹⁷ the GM sweet potato project was funded by the Kenyan Agricultural Research Institute (KARI) and Monsanto, with additional funding from USAID and the World Bank.⁶

Results

The results of the GM sweet potato project were reported in Kenya’s Daily Nation in January 2004 under the headline, “GM technology fails local potatoes”. The article said, “Trials to develop a virus-resistant sweet potato through biotechnology have failed. US biotechnology, imported three years ago, has failed to improve Kenya’s sweet potato.” ⁴ The failure was also reported by New Scientist.¹⁸

According to the Daily Nation, “Investigations on the transgenic crop, by KARI’s [Kenyan Agricultural Research Institute] Biotechnology Centre, say the technology has failed to produce a virus-resistant strain.”

The Daily Nation article continued, “’There is no demonstrated advantage arising from genetic transformation using the initial gene construct,’ says a report by researchers Dr Francis Nang’ayo and Dr Ben Odhiambo.

“The transgenic potato was imported from Monsanto in the US to Kenya for tests. The initial genetic engineering work was done at the Monsanto laboratories, using virus-resistant technologies. In a nine-year study, Monsanto had developed a coat protein responsible for virus resistance, and donated it to KARI, royalty free, to use in its sweet potato improvement programme.

“‘The transgenic material did not quite withstand virus challenge in the field,’ says the report, doubting whether the gene expression was adequate or it failed to address the diversity of virus in this region or just that the gene construct was inappropriate. Actually, the report indicates that during the trials non-transgenic crops used as control yielded much more tuber compared to the trangenics. ‘All lines tested were susceptible to viral attacks.’” ⁴

The project seems to have been abandoned.

Research: Early promises not fulfilled

A paper published in 1993, describing research on tobacco using the same GM method and transgene type (taken from a potyvirus) that were employed to make the GM sweet potato, was uncompromisingly titled, “Plants that express a potyvirus proteinase gene are resistant to virus infection”. A proteinase is a type of protease that degrades intact proteins.

However, the actual results were less solid than this title implies. The authors said the findings indicated that “some, but not all” of the virus resistance transgenes tested “can be used to confer protection against potyviruses in plants” and “The results also suggest that combinations of viral genes in transgenic plants might improve protection against potyviruses.” ¹⁹ Clearly this was a work in progress.

The results of research to develop a sweet potato resistant to feathery mottle virus using a different transgene – taken from rice and coding for a cysteine proteinase inhibitor, which interferes with virus replication – were published in 2001. The authors (Cipriani et al) reported greenhouse trial results that showed improved resistance against the tested strain of the virus in 18 of the 25 GM sweet potato lines developed. While the authors stated that further research was planned to confirm the resistance,²⁰ no final product was ever commercialised.

Interestingly, Cipriani et al noted in their introduction that conventional breeding in Africa and the US had already been successful in developing sweet potato varieties resistant to the sweet potato feathery mottle virus: “A substantial number of African landraces have resistance to this virus… and most US varieties released during the past 30 years appear to have a high level of tolerance to US strains of the virus.”

So why bother with GM? The reason given by Cipriani et al was greater speed. Conventional breeding, they write, “is time-consuming because of the need to combine the resistance trait with desirable yield and postharvest qualities. The strain specificity of the resistance also limits the deployment of released varieties.” ²⁰

Over two decades later, the supposedly quicker GM approach has still not succeeded, while conventionally bred virus-resistant sweet potatoes continue to be widely available.⁶

A 2009 review of GM virus-resistant plants stated, “very few… have been released for cultivation and none is available yet in developing countries”.²¹ While some limited success has been reported in the past in greenhouse trials of GM feathery mottle virus-resistant plants using a different transgene from that used by Wambugu,²⁰ as of 2025, any successes have not translated to the field.

Companies

Monsanto was the main company that attempted to develop a virus-resistant GM sweet potato.

Patents

It seems probable that the transgene and method that Wambugu and colleagues used to make the GM sweet potato that failed in Kenya (see “Results”, above) were the same as those described in a Monsanto patent filing dated 1996. Monsanto filed the patent for a method for genetically engineering virus-resistant plants, focusing on the largest group of plant viruses, the potyviruses.⁸

The Monsanto patent names sweet potato feathery mottle virus as one of the potyviruses targeted by this genetic engineering application. The patent also covers a wide variety of other potyviruses affecting numerous named crops, including potato, wheat, maize, papaya, soybean, watermelon, tobacco, zucchini, beans, plum, and sugarcane. The method involved introducing a DNA sequence coding for a potyvirus protease (a protease is an enzyme that degrades protein) gene, which was designed to inhibit potyviruses from assembling and infecting the plant. The exact process of conferring virus resistance was “not fully understood” by Monsanto, according to the patent.

The patent was applied for in the US in 2001 but the application had lapsed by 2005 due to non-payment of maintenance fees.

Author and updated research: Claire Robinson. Original research: Jonathan Matthews. Editing: Benny Haerlin, Franziska Achterberg. Scientific reviewer: Dr Jonathan Latham

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1. LinkedIn, Dr Florence Wambugu, PhD, DSc. Accessed 18 Oct 2023. https://www.linkedin.com/in/dr-florence-wambugu-phd-dsc-39b3b6105/?originalSubdomain=ke [↩][↩]
2. Lackner C (2003). GM crops touted to fight poverty. National Post, 28 Jun. Archived by Lobbywatch: https://web.archive.org/web/20041028102132/http://www.lobbywatch.org/archive2.asp?arcid=1016[↩][↩]
3. Wambugu FM (2003). Development and transfer of genetically modified virus-resistant sweet potato for subsistence farmers in Kenya. Nutr. Rev. 61(6 Pt 2):S110–3. doi: 10.1301/nr.2003.jun.S110-S113. https://pubmed.ncbi.nlm.nih.gov/12908741/[↩][↩]
4. Gathura G (2004). GM technology fails local potatoes. The Daily Nation (Kenya). 29 Jan. Archived by Lobbywatch and Wayback Machine: https://web.archive.org/web/20150324023702/http://www.lobbywatch.org/archive2.asp?arcid=2481[↩][↩][↩]
5. Cipriani G et al (2001). Transgene expression of rice cysteine proteinase inhibitors for the development of resistance against sweetpotato feathery mottle virus. In: International Potato Center (2001). Scientist and farmer partners in research for the 21st century: CIP Program Report 1999-2000: 267–271. https://cgspace.cgiar.org/handle/10568/109461[↩]
6. deGrassi A (2003). Genetically modified crops and sustainable poverty alleviation in Sub-Saharan Africa: An assessment of current evidence. Third World Network – Africa. https://grain.org/en/article/2706-genetically-modified-crops-and-sustainable-poverty-alleviation-in-sub-saharan-africa-an-assessment-of-current-evidence[↩][↩][↩]
7. Ngailo S et al (2013). Sweet potato breeding for resistance to sweet potato virus disease and improved yield: progresses and challenges. African Journal of Agricultural Research 8:3202-3215. DOI:10.5897/AJAR12.1991. https://www.researchgate.net/publication/256086449_Sweet_potato_breeding_for_resistance_to_sweet_potato_virus_disease_and_improved_yield_progresses_and_challenges[↩]
8. US Patent No. US5589612A. Virus resistant plants transformed with a PVY protease gene. Patent lapsed 2005. https://worldwide.espacenet.com/patent/search/family/025429333/publication/US5589612A?q=US5589612A [↩][↩]
9. Wente M (2003), Breaking the food chains. Globe & Mail, 5 Jul. Archived by Wayback Machine: https://web.archive.org/web/20040925082606/http://www.spcottawa.on.ca/ofsc/breaking_the_food_chains.html[↩]
10. Cook LJ (2002), “Millions served: Florence Wambugu feeds her country with food others have the luxury to avoid”. Forbes magazine, 23 Dec. Archived by Wayback Machine: https://web.archive.org/web/20050405133626/http://www.forbes.com/forbes/2002/1223/302_print.html [↩]
11. Gathura G (2004). GM technology fails local potatoes. The Daily Nation (Kenya). 29 Jan. Archived by Lobbywatch: https://web.archive.org/web/20050219231938/http://www.lobbywatch.org/archive2.asp?arcid=2481 [↩]
12. The International Life Sciences Institute (ILSI) is a food industry-funded organisation that presents itself as a scientific research body. A peer-reviewed article on ILSI (Sarah Steele et al (2020). Pushing partnerships: corporate influence on research and policy via the International Life Sciences Institute. Public Health Nutrition, 18 May. https://www.cambridge.org/core/journals/public-health-nutrition/article/pushing-partnerships-corporate-influence-on-research-and-policy-via-the-international-life-sciences-institute/C42EDA188F5E66983D80C8A44E90AB21) concluded that ILSI “promotes industry positions” and that it has “sought to exploit the credibility of scientists and academics to bolster industry positions and promote industry-devised content in its meetings, journal and other activities. ILSI also actively seeks to marginalise unfavourable positions.”[↩]
13. Nuffield Council on Bioethics (2003). The use of GM crops in developing countries. Dec. https://www.nuffieldbioethics.org/publications/gm-crops-in-developing-countries[↩]
14. Bill & Melinda Gates Foundation (2025). Africa Harvest Biotech Foundation International. https://www.gatesfoundation.org/about/committed-grants?q=Africa%20Harvest%20Biotech%20Foundation%20International#committed_grants Accessed 20 Aug 2024.[↩]
15. Africa Harvest Annual Report 2010. Published 2011. https://www.sourcewatch.org/images/d/d2/Africa_Harvest_Annual_Report_2010.pdf[↩]
16. CropLife. Our member companies. Accessed 18 October 2023. https://croplife.org/who-we-are/#our_members[↩]
17. He subsequently changed his name to Aharon deGrassi and his report can also be found under that name. https://www.sjsu.edu/people/aharon.degrassi/[↩]
18. New Scientist (2004). Monsanto failure. 7 Feb. https://www.newscientist.com/article/mg18124330-700-monsanto-failure/  The full text is archived by Lobbywatch: https://www.lobbywatch.org/archive2.asp?arcid=2561 [↩]
19. Maiti IB et al (1993). Plants that express a potyvirus proteinase gene are resistant to virus infection. Proc Natl Acad Sci USA 90(13): 6110–6114. doi: 10.1073/pnas.90.13.6110. https://www.pnas.org/doi/pdf/10.1073/pnas.90.13.6110 [↩]
20. Cipriani G et al (2001). Transgene expression of rice cysteine proteinase inhibitors for the development of resistance against sweetpotato feathery mottle virus. In: International Potato Center (2001). Scientist and farmer partners in research for the 21^st century: CIP Program Report 1999-2000: 267–271. https://cgspace.cgiar.org/handle/10568/109461[↩][↩][↩]
21. Reddy DVR et al (2009). Chapter 6 – Genetically Engineered Virus-Resistant Plants in Developing Countries: Current Status and Future Prospects. In: Advances in Virus Research Vol 75: 185–220. https://www.sciencedirect.com/science/article/abs/pii/S006535270907506X [↩]