Growing more food, and more nutritious food, for a hungry world is again an urgent challenge. Productivity needs to increase by at least 50 percent.
Excerpted from The Future Postponed, Massachusetts Institute of Technology, 2015
Mary Gehring: Assistant Professor of Biology, and Member of the Whitehead Institute for Biomedical Research
Fifty years ago, rapid population growth in developing countries was outracing global food production, creating the prospect of mass famine in many countries. What forestalled such a tragedy were the agricultural innovations known as the Green Revolution, including the creation of higher yielding varieties of wheat and rice. While world population grew from 3 billion to 5 billion, cereal production in developing countries more than doubled; crop yields grew steadily for several decades. By some estimates, as many as 1 billion people were saved from starvation.
Now the world faces similar but more complex food challenges. Population is expected to grow from 7 billion to 9 billion by 2040, but little arable land remains to be put into production. So productivity needs to increase still further, by at least 50 percent. Moreover, the Green Revolution did not specifically address the nutritional content of the food produced— and today that is critical, because of widespread malnutrition from deficiencies of iron, vitamin A, and other micronutrients. Traditional breeding approaches, and even the kind of genetic engineering that has produced more pest-resistant commercial crops, will not be enough to meet these challenges: more fundamental innovations in plant science—integrating knowledge of genetic, molecular, cellular, biochemical, and physiological factors in plant growth—will be required.
One example of the opportunities for such fundamental innovation comes from research on a non-food plant, Arabidopsis thaliana, which is the “lab mouse” of plant molecular bio- logy research. Recently scientists were seeking to better understand the process by which a plant’s chromosomes—normally, one set each from the male and the female parent—are distributed when a cell divides. They inserted into the plant cells a modified version of the protein that controls chromosome distribution. The resulting plants, when “crossed” or bred to unmodified plants and then treated chemically, had eliminated one set of chromosomes and had instead two copies of a single chromosome set. Such inbred plants usually don’t produce well, but when two different inbred lines are crossed together, the resulting variety is usually very high yield. This phenomena, called hybrid vigor, has been created in a few crops—such as corn—via conventional breeding techniques and is responsible for huge increases in yields, stress tolerance, and other improvements in recent decades. The new “genome elimination” method could make these same improvements possible for crops such as potatoes, cassava, and bananas that have more heterogeneous chromosomes.
Creating golden rice involved adding two new genes to the plant, which increased yield and also enriched the crop in vitamin A. Such self-fortifying crops could address malnutrition far more effectively than traditional methods.
Another research frontier is new methods to protect crops from devastating disease, such as the papaya ringspot virus that almost completely wiped out the Hawaiian papaya crop in the 1990s. What researchers did was develop a crop variety that includes a small portion of genetic material from the virus—in effect, inoculating the crop to make it immune from the disease, much like a flu vaccination protects people. Virtually all Hawaiian and Chinese farmers now grow this resistant papaya. The technique, known as RNA silencing, was initially discovered and understood through basic research into the molecular biology of tobacco and tomato plants, but seems likely to be useful against viral diseases in many crops.
Similarly, Chinese researchers doing basic research on wheat—a grain that provides 20 percent of the calories consumed by humans— developed a strain that is resistant to a widespread fungal disease, powdery mildew. The researchers identified wheat genes that encoded proteins that in turn made the plant more vulnerable to the mildew, then used advanced gene editing tools to delete those genes, creating a more resistant strain of wheat. The task was complicated by the fact that wheat has three similar copies of most of its genes—and so the deletion had to be done in each copy. The result is also an example of using genetic engineering to remove, rather than to add, genes. Since mildew is normally controlled with heavy doses of fungicides, the innovation may eventually both reduce use of such toxic agents and increase yields.
Modifications in a single gene, however, are not enough to increase the efficiency of pho- tosynthesis, improve food nutritional content, or modify plants for biofuel production—these more complex challenges require putting together multiple traits, often from different sources, in a single plant. This will require more basic understanding of plant biology, as well as developing and utilizing new technologies like synthetic chromosomes and advanced genome editing tools that are still in their infancy, and thus will require sustained research. One example of the potential here is golden rice—the creation of which involved adding two new genes to the plant—which is not only high yielding but also produces a crop rich in Vitamin A. Such “self-fortifying” crops, because they incorporate micronutrients in a “bioavailable” form that is accessible to our bodies, could address malnutrition far more effectively than traditional methods of fortifying food or typical over- the-counter supplements. Another possibility may come from efforts to convert C3 plants such as rice into C4 plants that are more efficient at capturing and utilizing the sun’s energy in photosynthesis and perform better under drought and high temperatures—a modification which may require, among other things, changing the architecture of the leaf.
Investment in basic plant-related R&D is already far below that of many other fields of science. Yet the agriculture sector is responsible for more than two million U.S. jobs and is a major source of export earnings.
Capturing these opportunities and training necessary scientific talent cannot be done
with existing resources, as has been amply documented. Not only is federal investment
in plant-related R&D declining, it is already far below the level of investment (as a percentage of U.S. agricultural GNP) of many other fields of science. Yet the agriculture sector is responsible for more than two million U.S. jobs and is a major source of export earnings. Moreover, the USDA research effort effectively ignores fundamental research; the research breakthrough on genome elimination described above could not have been supported by USDA funds, which are narrowly restricted to research on food crops.
In contrast other countries, particularly in Asia, are increasing investments in plant research. The impact of these investment are exemplified by the surge in publication in fundamental plant molecular biology research: 70% of the research published in the leading journal in this field now comes from outside the Unites States, and the entire field has seen a sharp increase in publications from Chinese labs. The U.S. is at clear risk of no longer being a global leader in plant sciences.