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Defeating nematode worms with GM bananas
Training and technology transfer among benefits of SARID project.
5 October 2011
Researchers in the UK and Africa are using genetic modification (GM) technologies to make banana and plantain (Musa species) crops resistant to attack from nematode worms. The work uses the GM approach because bananas and plantain crops are sterile, and most breeding techniques cannot be applied for rapid crop improvement.
Ripe for improvement: young GM banana plantlets tended by African scientists.
Image: Hugh Roderick
The project, funded by BBSRC and DfID, is also driving local development. African scientists are closely involved in learning and adapting new and existing techniques that can be used on other non-GM crops to help meet regional and global food security challenges.
Bananas and plantains are together the fourth most widely produced food crop in Africa by quantity (ref 1) and as a calorie-rich staple, support the highest density of people per unit area of crop (about 2x rice, 5x maize and 8x sorghum) (ref 2). They are cheaper to produce than other staples such as rice and maize and as such are a vital food for 100M Africans, including very many low-income families in the poorest areas on the continent where child undernutrition is particularly prevalent.
Musa crops are attacked by a variety of pests and pathogens, including nematode worms that cause estimated yield losses of up to 50-70% in sub-Saharan Africa (ref 3), and damage levels have increased in recent decades in the Great Lakes region of East Africa.
Nematodes cause annual losses to crops estimated at US$125Bn a year and banana is the most severely nematode damaged crop worldwide (ref 4). Nematode control in Uganda would provide an estimated benefit of more than US$250M over 30 years with equal benefits to poor producers and consumers (ref 5).
Dr Leena Tripathi examining a diseased banana plant in the field. Image: IITA
Commercial plantations use pesticides to control nematodes but these can be environmentally damaging and cause health problems for agricultural workers. Moreover, these chemicals are too expensive for small-scale subsistence farmers in Africa where losses are most acutely felt.
No sex please, we're bananas
Hence, there is a pressing need to control nematodes but bananas are very difficult to improve by conventional plant breeding techniques because they are sterile.
A banana plantation in Uganda. Image: IITA
Professor Howard Atkinson from the University of Leeds' Africa College says most important plantain and banana types are propagated vegetatively to make new plantlets because they do not produce pollen and so can't fertilise other plantain/banana types. "Consequently they are sexually isolated from other banana varieties," he says. "So even if natural resistance genes are found in other banana types they cannot be improved readily by crossing."
Atkinson says that that biotechnological (GM) methods offer the most rapid way to provide nematode resistance into susceptible banana types because the approach is not dependent on the plant being fertile. Furthermore, the sterility and the lack of pollen of any new GM varieties means there is no risk of transferring new genes to other plants.
Funded under the Sustainable Agricultural Research for International Development (SARID) programme (see 'Sustainable agriculture overseas'), the project has demonstrated that two safe technologies developed in the UK for potatoes (using funding from BBSRC) can control the nematodes and eliminate the yield losses they impose in plantain.
The initial technology was developed at the University of Leeds and the novel genes transferred into plantain by colleagues led by Dr Leena Tripathi at the International Institute of Tropical Agriculture (IITA). "Leeds and IITA together have shown that the technology is effective and a GM field trial is now planned for 2012," says Atkinson, who adds that if trials are successful uptake could be rapid as the majority of banana consumers in Africa live in countries that favour deployment of [GM] plant biotechnology.
A novel fish-eye camera system can monitor plant growth. Image: Elvis Mbiru
Part of the work involved developing a digital camera based system to measure the impact of nematode population size on plantain and banana canopy growth. The method used a fisheye lens at ground level to record the leaf area index (the extent that leaves cover the camera image, see picture). Previous methods have required the time-consuming destruction of banana roots to extract nematode populations at several points throughout a trial or measurement of banana plants or roots by hand. "Quite laborious, particularly for 9ft cooking banana varieties," says Atkinson. "In contrast, the camera system allows the rapid measurement of the entire banana canopy."
Howard Atkinson and team at the tissue culture facility in Uganda. Image: James Kawuma
All areas of work have involved training of African-based scientists who have worked alongside researchers in Leeds. Most training has been in laboratory techniques required for the development of GM technology. African scientists have been trained in techniques to show the new gene is present and expressing in plantains; methods required to measure nematode multiplication on the crop; and in the use of the canopy growth camera system.
Dr Leena Tripathi, a plant biotechnologist at the principal research partner IITA, says the project was an effective way to transfer technology to Africa and national partners. "Many young African scientists were trained at University of Leeds as well as IITA," she says. "About 10 Africans were trained on this project - six at Leeds and four at IITA."
The relationship between the University of Leeds and IITA may extend into additional projects. "We are looking to trial the banana plants in countries across Africa and also to move our GM technology into other neglected African crops that suffer severe nematode damage," says Atkinson. "IITA are particularly concerned about nematode damage to yams, another important food security crop in Africa. Such projects require the combination of Leeds GM anti-nematode expertise and IITA's expertise in African crops."
Sustainable agriculture overseas
Bananas and plantain are a very important staple crop in Africa. Image: IITA
The SARID programme (Sustainable Agricultural Research for International Development) aims to support relevant high-quality basic and strategic biological and biotechnological research in crop science and sustainable agriculture that has the potential to contribute to the achievement of the Millennium Development Goals, and which will establish productive partnerships between scientists in the UK and developing countries.
12 projects conducted over five years are funded from a pot of £7.5M and DfID are the main co-funders. The project involves 32 collaborations between UK universities and institutions across the globe, and other research initiatives include reducing arsenic levels in rice, tackling pests and pathogens of bananas, coconuts, kale, cabbage and sweet potatoes, as well as efforts against pests such as invasive nematodes and the African witchweed menace.
- FAO Stats (external link)
- Farming systems and Poverty: 2 Sub-Saharan Africa (external link)
- Strategies for resistance to nematodes in Musa spp
- Sasser J.N., Freckman D.W. (1987) A world perspective on Nematology: the role of the society. Pages 7-14 in J.A. Veech and D.W. Dickson (eds) Vistas on Nematology. Society of Nematologists, Hyattsville, Maryland. 509p
- IFPRI An Economic Assessment of Banana Genetic Improvement and Innovation in the Lake Victoria Region of Uganda and Tanzania (external link)
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