vol 8, issue 5

Scientists to help African farmers

20 May 2013
By Abi Grogan
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An African farmer with a new strain of rice

New strains of rice including Nerica (pictured) have increased yields in Africa by varying success rates

Harvesting rice

Current efforts are focused on wiping out rice blast fungus and improving crop yield

A scientist with Nerica rice

Scientists are breeding ‘miracle rice’ Nerica with new strains to improve resistance to disease

Around half of all crops fail in Africa. In response, laboratories across the world are applying advanced scientific methods to provide a viable way of making cereal crops more robust.

"Working within this field is not about starvation. It's about poverty, education and food security and creating steps out of poverty." These are the kinds of words that are often found in the voiceovers of fundraising advertisements for charitable aid organisations. Nick Talbot, however, is not a charity worker; he is vice chancellor at a cutting-edge agricultural research facility at the University of Exeter, and, more importantly, he is a scientist.

While aid-funding from charities such as Unicef and Oxfam is clearly a necessary intervention, small-scale farmers in Africa are unlikely to achieve food security unless the aid supplies – particularly supplies of seed – are biologically resilient enough to meet their needs.

Currently half of all crop harvests fail in Africa. This is partly due to soil quality, heat, lack of water and lack of access to biological stimulants such as fertiliser. Scientists and chemical engineers believe that the key to achieving food security in some of the poorest parts of the world is improving the productivity of the source from which food is grown: the seed.

Making rice sustainable

Rice is a staple dietary component of 70 per cent of the world's poorest people. It is the productivity of this vital cereal that Talbot and other scientists around the world are attempting to rebalance.

Nigeria is the world's biggest importer of rice. This is a surprising statistic considering the country has enough arable land and water supplies to provide food security for its own population. Well-irrigated land produces a higher yield of crop, which is why rice grows so well in thoroughly irrigated rice-paddies in regions such as rural China.

Irrigated land allows drought-stricken regions to be farmed by facilitating water supply to crops, which represents a colossal engineering challenge in itself. The stumbling block for Africa as a continent is that it occupies land spanning a hugely diverse range of climes, from rainforest and woodland to savannah and desert. Over 70 per cent of African-grown rice is grown in two remaining eco-systems: naturally rain-fed uplands and rain-fed lowlands, where crops must withstand not only punishing droughts, but also severe flooding and extreme temperatures.

In an attempt to increase the yield of crops in this unpredictable environment, scientists at the Africa Rice Centre developed a superior, durable strain of rice called Nerica, which has increased the amount of rice grown in Africa by 5 per cent. Nerica was achieved by interbreeding strains of locally occurring of rice that demonstarted resilience to varying criteria with a commercially adapted strain, producing a hybrid with a higher yield, taller stems and slight increase in protein content.

The hybrid was met with a mixed reception, with some regions experiencing increase in yield while others experienced none at all. At its peak, South Africa experienced a 16 per cent increase in rice production, while western and eastern Africa experienced 5 and 7 per cent increase respectively. Proven results of the heat and drought tolerance of Nerica rice is still very limited, though the strain was produced mostly for use in the dry uplands, a region which traditionally produces a relatively meagre one tonne per hectare, compared with six tonnes per hectare for irrigated land. Nerica has, however, achieved success in the form of poster-boy Uganda, who turned the seed into a successful cash-crop, converting the country from importer to exporter.

Inheriting resistance

Although the rate of rice grown has increased thanks to the integration of Nerica, net demand for it is still steadily rising too. So while more rice is being grown in Africa, even more is being imported.

Even with the benefits of hybrid strains grown in well-irrigated rice paddies, the quantity of harvestable crops produced in Africa is still worryingly sparse: as low as 20-30 per cent of those sown in some regions. This is mostly due to Africa's primary nemesis ' plant disease and fungus often destroys entire harvests and consigns generations of farmers to poverty.

Africa's most serious agricultural bacteria epidemic is rice blast fungus, which destroys enough rice to feed 60'million people per year. While south-east Asia and South America are the biggest casualties of the fungus, sub-Saharan African stock has also been seriously affected, hampering the region's ability to decrease its total rice importation and become self-sufficient.

The University of Exeter, in collaboration with world-leading agricultural specialists the University of Arkansas, Ohio State University and Cornell University in New York, are engineering rice strains that are genetically resilient to rice blast. Talbot is coordinating the research project, which is currently still in its early stages.

"At the moment, rice blast is a very serious situation. It is leading to losses of 50-80 per cent of yield which is not uncommon in certain parts of sub-Saharan Africa. If there is a rice blast outburst it will just decimate entire fields," says Talbot.

"Our research's success would enable rice blast resistance to be more commonly deployed in Africa, because unfortunately most of the [rice crops] grown in Africa are culpable to the disease, even Nerica rice strains. What we would like to do is take these high-yielding Nerica lines and introduce rice-blast resistance into their genetic make-up."

Talbot's team has been monitoring pathogen population of the fungus in crop harvests in problem areas, including Kenya, Uganda and Burkina Faso. Isotopes gathered in the region are scanned against all known resistance genes worldwide in order to find a match against the fungus strains found in Africa. The genes with resistant characteristics are then identified and integrated into the genetic makeup of Nerica lines of rice. Talbot wants to deploy around three to four main resistance genes in each isolate, meaning the strains should be rice-blast resistant for future generations.

Initially the genes will be integrated by genetically modifying the plant seed to speed up the testing period. This is done by injecting agri-bacteria, which will carry the resistant genes into the seed's genetic makeup. However, when the cultivars are released for commercial sale they will be produced via conventional plant cross-breeding, which can take up to four years. Talbot says: "The reason we want to produce them via conventional plant breeding rather than GM methods is because it makes it easier to release these strains and give them out to farmers commercially than if they were GM, due to regulations."

This cross-breeding will be done with the help of the latest in DNA-sequencing technology, called marker-assisted breeding. An Illumina sequencing machine uses optical tracking and markers to produce millions of DNA sequences very quickly using a fluorescence-based sequencing method, so rapid that throughput can be achieved at a million nucleotides per second.

Technology from less than a decade ago would take ten years to map an entire human genome, but now it can be completed in a number of days. Even more encouraging to local knowledge networks, much of the marker-assisted breeding used to aid the research will be carried out locally by Kenyan university students and professors.

This pilot scheme in Africa will have implications around the globe. The American government is investing in the research in an effort to forego a Brazilian crisis that is now affecting one of the US's biggest agricultural money-spinners: wheat. "Climate change could cause this new strain of wheat blast to spread to more temperate climates," says Talbot. "The worry is that if the disease spreads north into the US it could become a serious problem – one the American government is very worried about."

But Talbot's primary aim is to make sure the crop is made available to those who really need it – African farmers. "This research is being done entirely for humanitarian reasons. If we manage to develop a strain of rice that is not susceptible to rice blast fungus the impact would be enormous. We could change the whole economic system so that it would be more cost effective for more people to grow rice, because there would be more land that could be deployed to grow it."

Nitrogen fixation

While some scientists are researching ways to make agriculture more robust to harsh environmental conditions, others are concentrating on making crops more receptive to it. One crucial aspect of increased yield productivity in developed countries is to stimulate growth using fertilisers.

Fertilisers aid the nitrogen absorption process by adapting the signalling pathways between the plant's roots and the bacteria it is trying to absorb to stimulate growth. But fertiliser is an expensive commodity, and the accomplishment of the farming industry in countries such as China owes its success largely to heavy government subsidisation of fertiliser production plants. Unfortunately, the ozone layer above these regions also owes its deterioration to these subsidies.

Regions such as Africa, with fragmented countries and frequently corrupt political systems, have no access to European-made subsidised fertilisers, which,'coupled with sky-rocketing transport costs, means the price of fertiliser in Africa is three or four times the amount it is in the UK.

Scientists at the John Innes Centre, funded by the Biotechnology and Biological Sciences Research Laboratory, are working in collaboration with the Bill and Melinda Gates Foundation to engineer crops that don't require fertiliser at all. Professor Giles Oldroyd is leading the project focusing on nitrogen fixation, a process that legumes – beans and peas – biologically do very well.

Legumes get their nitrogen fix through a beneficial interaction with nitrogen-fixing bacteria, which resides in specialised organs in the roots, or nodules. Legumes alter the signalling pathway that is present in all plants to allow a larger absorption of nitrates, meaning fertiliser isn't needed. Oldroyd's team is focusing predominantly on the staple crop maize, one of the most widely grown crops in Africa by small holder farmers.

"In contrast to legumes, cereals need a lot of nitrogen to grow but they can't get it biologically from nitrogen fixation meaning they need a lot of fertiliser to flourish," says Oldroyd. "Nitrogen availability is a major limitation to crop productivity in Africa, and the reason that Africa did not experience a Green Revolution."

"As an engineering problem it's actually much simpler than we'd originally thought because this pathway is already present in cereals, we just need to follow the more subtle adaptations that have happened in legumes."

Unlike projects that increase resistant characteristics in cereals – such as rice – cross-breeding a bean plant and a maize plant is biologically impossible, so all of Oldroyd's research will be done through genetic modification, from initial research to commercial cultivars. This nitrogen-fixation does not naturally occur in cereals and, therefore, the DNA of the cereal has to be permanently genetically modified each time.

But despite being genetically modified, Oldroyd's research should not be tarred with the same brush as corporate, mass-produced GM produce that often comes at a cost to consumers in the developing world. One stipulation of the partnership with the Bill and Melinda Gates Foundation is that any commercially viable product to result out from Oldroyd's project should be made available to farmers in the developing world.

"There is no reason why publicly or charity-funded GM commodities cannot come into existence," says Oldroyd. "A good example is golden rice, which is entirely funded by charities and does not come with the corporate cost or control of privately produced stock."

Food security

Oldroyd believes that, provided technologies such as his are successful, food security is on the horizon. "I think if you're going to solve the food security crisis then the best way to do it is to secure the improvement of yields in sub-Saharan Africa. Their yields are 20-30 per cent of what they could be, so if you double or triple yields in this region then you can pretty much solve the food security crisis."

Talbot concurs with his line of thinking, saying the initial success of all of these technologies will be judged by their ability to achieve food security through sustainability. If agriculture in Africa fails, food security is at risk across the world.

Initially the onus must be placed on reducing imports needed to feed a growing population and to stabilise rice production, before attention eventually turns to the rest of the world. "One of the things we want to ensure is that farming is productive," says Talbot. "An awful lot of rice productivity is carried out by women in Africa, and very often the yield of the crop will determine whether a crop will sell at market, which in turn determines whether or not they can send their children to school. With increased productivity, you're now looking at steps out of poverty for whole generations."

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