Illustration by J.T. Morrow
Ag lag: Can Science & Good Policy Finally Feed Everyone?
Clashing philosophies have hampered agriculture's efforts to secure the world’s food supply. Can new science turn things around?With the food price spike of 2008 and the global economic recession in the year that followed, a crisis that had been steadily worsening since the mid-1990s suddenly intensified. Last year, for the first time, the number of people who are living in hunger rose above one billion, according to the Food and Agriculture Organization (FAO) of the United Nations.1
Food is the most basic of human needs—and rights. And with the world’s population inexorably climbing toward 9 billion people by 2050—it is currently estimated at 6.8 billion—food security is arguably the greatest challenge facing this generation.
Despite steady global increases in food production, increasing numbers of men, women and children do not have enough to eat to sustain their health and their lives. According to one recent analysis, maternal and child malnutrition are responsible for one third of all child deaths under five years and for eleven percent of the total global disease burden.2 Diets deficient in micronutrients such as iron, vitamin A and zinc directly lead to problems such as anemia, blindness and growth retardation. They also exacerbate vulnerability to infection and diarrhea, major causes of child mortality.
Hunger is not the outcome of a natural catastrophe, it is a man-made phenomenon. According to Olivier de Schutter, the UN’s Special Rapporteur on the Right to Food, “It is something which has its source in policies, decisions made by identifiable actors at precise moments in time.” He describes the lack of food security as a complex, multi-factor problem that is ultimately rooted in poverty, injustice and under-development.
Achieving meaningful progress will require sustained efforts on multiple fronts. Yet debates on how agriculture can or should proceed frequently degenerate into circular either/or arguments over the merits or demerits of biotechnology versus organic or agroecological methods of agricultural production.
Plant science in Europe, in particular, has been badly damaged by the controversies accompanying the emergence of biotechnology-based approaches to agriculture. This has created what Prem Bindraban, director of the International Soil Reference and Information Centre at Wageningen University in The Netherlands, calls an “innovation lag.” It takes around ten years to produce a new crop variety—and it is going to be impossible to make up for the time that has already been lost. “The fact we haven’t invested in agriculture for twenty years is an enormous problem,” he said at a conference on food, sustainability and plant science, hosted by the European Molecular Biology Organization in Heidelberg, Germany, last November. However, there are signs that researchers are again making progress to meet the challenge of food security in the 21st century.
Biotechnology benefits
Clearly there is a role for both biotechnology- and agroecology-based approaches, depending on the context. Indeed, the use of no-till agriculture in conjunction with some biotechnology crops illustrates the scope for integrating the two approaches. “They’re not conflicting at all,” says Matin Qaim, an agricultural and development economist at the University of Goettingen, Germany. Qaim has carried out village-level studies in India, which demonstrate that growing insect-resistant transgenic cotton significantly boosted the incomes of small farmers earning less than $1 per day.3 Small farmers growing genetically modified (GM) insect-resistant white maize in South Africa have also obtained sizeable yield benefits, he says. “This is not to say those examples can be extrapolated to completely different crops or completely different settings,” Qaim says. “India and South Africa are certainly not the poorest countries, and there are many situations where this model is probably not going to work.”
Conventional agriculture using hybrid, non-GM varieties will continue to play a central role in agriculture as well. A flood-tolerant rice hybrid, developed through a collaboration between Pam Ronald at the University of California, Davis, and David Mackill at the International Rice Research Institute, in Manila, The Philippines, exemplifies the advances that have been attained in conventional plant breeding using modern genomics tools. Most rice varieties cannot last beyond three days of complete immersion, and flood-related losses in south and southeast Asia can amount to $1 billion in a given year. Ronald’s group employed molecular cloning methods to pinpoint a trait found in a weedy rice variety, which can withstand up to two weeks of immersion. “People were trying to introduce this trait for 50 years,” Ronald says. “They couldn’t develop lines that the farmers liked.”
Earlier attempts led to the transfer of an excessive genetic payload, which had negative consequences for the resulting cross. Having identified and characterized the trait, Ronald employed a technique called marker-assisted selection to transfer—via conventional breeding methods—a much smaller DNA segment into an agronomically useful strain. It relies on following the inheritance of DNA molecular markers that flank the trait of interest in crossing experiments. The resulting hybrid is now being rolled out to farmers in the region via the public sector seed distribution system. By 2012, the variety is expected to be planted on up to 5 million hectares in Bangladesh alone. Meanwhile, Ronald is working on an enhanced variety with the potential to withstand up to three weeks of immersion.
It is only when a potentially valuable trait is not available within a species, that plant breeders start to look elsewhere for genes. Ronald’s team is currently in the early stages of a project to develop a transgenic banana variety resistant to a bacterial pathogen called Xanthomonas. “We’re particularly interested in bananas, because there’s a Xanthomonas disease that’s causing a terrible problem in East Africa,” she says. Bananas that are consumed by humans are particularly vulnerable to disease. Because they are reproduced via clonal propagation, they lack genetic diversity. In 1995, Ronald’s group identified a gene in rice that imparts resistance to Xanthomonas, and they recently characterized the molecular mechanism underpinning that resistance.4 It is based on an interaction between a rice pattern recognition receptor called XA21 and a bacterial protein designated AX21 (activator of XA21-mediated immunity). A peptide, derived from AX21, containing just 17 amino acid residues, is enough to promote recognition by the XA21 protein. A transgenic banana variety encoding the same gene could, potentially, impart resistance to Xanthomonas. “We know that the banana pathogen also has that peptide,” says Ronald.
Smart agroecology
Improving agricultural productivity is essential but not, in itself, sufficient to guarantee adequate nutrition for all. Although per capita food availability has been steadily increasing in recent decades, so too has hunger. For each person alive today, according to a recent report by the UK’s Royal Society, there is, in theory, an additional 29 percent more food being produced than in 1960.5
Nevertheless, an absolute increase in food production of about 50 percent is necessary to ensure that there is sufficient food for everyone in the coming decades, according to the same report. The growing demand for animal food products, engendered by rising incomes in emerging economies, and the scale-up of plant-derived biofuels production add further complexity to what is already a difficult equation. And a solution has to be achieved within the constraints imposed by climate change and by the limited availability of land and water.
Massive expansion of current intensive farming practices is not environmentally sustainable. “Agriculture has become a mining activity as a result of the methods of industrial agriculture,” de Schutter says. He frames the problem as: “How to reconcile the need to produce more with the need to do so in ways that raise the incomes of the poorest populations.” For the poorest farmers, he argues that agroecological methods, including intercropping, water conservation, organic fertilizers (such as manure) and locally sourced seeds, offer the best prospect. This is neither a ‘natural’ approach, nor a return to the past. “It’s the science of the 21st century— combining the best agronomy with the best ecology,” he says.
Work underway in Uganda illustrates some of the ideas underlying this approach, but it also highlights the extremely difficult choices facing the country’s farmers.
The International Institute of Tropical Agriculture (IITA), a not-for-profit organization focused on building agricultural capacity in sub-Saharan Africa, is promoting a banana-coffee intercropping system that can increase productivity and boost incomes. The two crops, while they may offer an unlikely combination for the taste buds, are perfect partners in agriculture. Shade-loving coffee trees do not engage in light competition with taller banana trees. The presence of each in a single plot helps to reduce competition from weeds, while the presence of banana trees also improves potassium availability for coffee plants. Data from test plots indicate that coffee yields from monocropped and from intercropped coffee-banana fields are similar. Banana yields are unaffected when grown alongside high-quality Arabica beans, although they decline somewhat when grown alongside Robusta beans. Because coffee yields are not affected, the additional banana production increases the revenue of banana-coffee intercropped fields by 50 to 60 percent compared to monocropped coffee fields.
Easily adopted innovations like this offer considerable scope for bringing real improvements to agricultural productivity in sub-Saharan Africa, the part of the world that is most vulnerable to food insecurity. “Sometimes we don’t need new technologies—we just need existing technologies put together in a smart way,” says Piet van Asten, a Dutch scientist who has been based at the IITA’s Kampala office in Uganda for the last seven years.
Uganda exemplifies the scale of the challenge facing the region. Its rapidly growing population of 30 million is forecast to reach 90 million by 2050. So agricultural output will have to increase three-fold simply to keep pace with that expansion—and it will need to expand even more rapidly if it is to act as an engine for economic growth. “It’s just not possible to avoid agricultural intensification. You have to do that—it’s a path that has to be taken,” says van Asten.
Land constraints have already undermined the use of manure as fertilizer. Traditionally, farmers grew crops near their homes and allowed their livestock to forage on commonly held grazing land or on fallow land during the daytime before they returned in the evening, bringing nutrients for the soil with them. “The problem is these systems have collapsed,” says van Asten. Families, often with five or six children, are now working with plots of less than two hectares. Grazing for cattle has disappeared, while many farmers have been encouraged to produce cash crops for exports. “Nutrient exports (from the soil) have increased, and nutrient imports have decreased,” van Asten says—not a good recipe for increasing yields.
One recent, USAID-funded study by van Asten and Lydia Wairegi, of Makere University, showed that even moderate use of mineral fertilizers could help farmers double their yield of bananas, the most important staple crop in Uganda. Currently, less than five percent of farmers apply fertilizer. “Fertilizer can be extremely profitable if you know what to apply and where to apply it,” van Asten says. But high input costs, price uncertainties (particularly for farmers located a long distance from their main markets), a lack of access to credit and a lack of knowledge about how to use fertilizers correctly are among the factors that discourage the majority from doing so.
Soil fertility, a major constraint on agricultural productivity, has generally received insufficient attention from international aid organizations. “Soil fertility is never an immediate problem,” he says. Donors can more easily assess the impact of introducing new varieties, in order to justify their spending programs. “For soil, it’s more difficult. It’s a grey area,” he says.
The seeds of hope
In those regions where high-tech, intensive agriculture holds sway, existing methods for boosting productivity appear to be reaching some kind of limit.
Rising demand is outstripping whatever increases in yield can be obtained through normal plant breeding. The two biotechnology applications that have been most widely deployed— for insect resistance and herbicide tolerance—do not improve the intrinsic yield of the transgenic crop varieties into which they have been introduced. They are protective traits, designed to minimize the gap between a crop’s theoretical yield and the actual yield obtained at harvest time.
But fundamental plant science research is opening up two new avenues of exploration that, in time, may lead to totally new ways of developing high-yielding crop varieties.
Dani Zamir, of the Hebrew University of Jerusalem, in Rehovot, Israel, is homing in on the molecular mechanisms underpinning heterosis—or hybrid vigor. This biological phenomenon has played a fundamental role in modern agricultural production since the first corn hybrids were introduced to the U.S. Corn Belt in the 1930s.
“Heterosis contributes—depending on the crop—about 20 to 50 percent of the yield,” he says. “It’s the major force in global food security.” Yet how it does so has largely remained an enigma. Plant breeders have successfully exploited the phenomenon through trial and error, producing hybrid crosses from genetically distant parents that have superior yields to offspring produced naturally, through open pollination. Hybrid vigor is quickly lost, however, as traits of agronomic interest genetically segregate. Farmers planting hybrid varieties have to purchase new seed every year.
“Now it’s time to revisit the question, with the new tools of genetics and biology, and find out what are the genes that are driving the process,” says Zamir. “Once we understand the genes that drive heterosis then we will be able to maximize the effect.” Zamir and his team recently reported on a series of experimental crosses between domesticated tomato plants, which had been subject to random mutagenesis, and wild species.6 Six of the resulting hybrids demonstrated spectacular yield increases. Five of the genes are as yet uncharacterized, but they segregated in a Mendelian fashion, Zamir says. A sixth is linked with the hypothesized florigen gene, which controls flowering. “We were able to show unequivocally [that] heterosis is derived from or driven by a single gene that increases yield by about 50 percent,” he says. “I think it opens the door to accelerating heterosis research.”
Another recent study, which neatly complements the findings in heterosis. could also have a profound impact on crop science.7
Jean-Philippe Vielle-Calzada and his team at the Center for Research and Advanced Studies of the National Polytechnic Institute (Cinvestav) in Irapuato, Mexico, together with colleagues in the U.S. and France, have shown that they can induce cells present in the ovule of Arabidopsis to form gametes, or sex cells, that contain the plant’s full genetic complement. The process mimics apomixis, a form of asexual reproduction found in many plant species, but not in the world’s main food crops.
“It’s the equivalent of Dolly [the cloned sheep] in terms of the outcome,” says Vielle-Calzada. The seed does not undergo fertilization but develops into a plant that is an exact replica of its mother.
Arabidopsis, widely used as a model organism in plant science, does not reproduce via apomixis. It relies on sexual reproduction, involving fertilization of a female egg cell by a male sperm cell. But by disrupting the normal process of female gamete cell formation, Vielle-Calzada and colleagues were able to produce multiple gametic cells that had not undergone meiosis, the cell division process that normally leads to the formation of gametes containing half the normal number of chromosomes. They did so by mutating a gene encoding a protein called Argonaute 9. “This is completely unexpected,” says Vielle-Calzada. “In its natural context, Argonaute 9 is mainly silencing—inactivating—transposons.” (Transposons are sequences of DNA that can move around the genome.)
Although the apomitic gametes that resulted were not capable of undergoing embryonic development into fully fledged plants, Vielle-Calzada predicts that the introduction of a fully functioning apomixis process to Arabidopsis is only three to five years away. If this can be replicated in food crops, the implications for agriculture would be enormous. “Any plant in which you take advantage of heterosis would benefit tremendously from apomixis,” he says. “The advantage of apomixis is it will allow you to genetically fix F1 hybrids by making them perpetuable.”
Apomixis would allow farmers to save hybrid seed, from year to year, a practice that has been completely off the agenda up to now. “It’s completely subversive from the seed company point of view,” says Vielle-Calzada. Ensuring that this kind of technology would be widely—and freely—disseminated has already been the subject of the ‘Bellagio Apomixis Declaration’ more than a decade ago.
This is typical of the sensitive context that science must negotiate if it is to make significant contributions to improving food security. Even though it is virtually impossible to predict which technologies and which processes will underpin global agriculture 40 years from now, as de Schutter notes, “It all depends on the choices we make now. There is no time to lose.”
Photo: Illustration by J.T. Morrow
