About 7 billion people live on Earth today and that number is expected to rise to more than 9 billion by 2050. In order to meet that growing population's demand for food, the United Nations Food and Agriculture Organization has estimated that we will need to increase global food production by at least 70 percent.
To make that happen, scientists have come up with a gene editing method that could make the process of photosynthesis more efficient in plants, thus increasing crop yield without increasing agricultural land use. Their technique is detailed in a study published Thursday in the journal Science.
The purpose of the research, which was funded by the Bill and Melinda Gates Foundation, is to generate more sustainable farming practices for subsistence farmers in developing countries in the future.
“[Plants] are not optimized for productivity and that is the key change in thinking that you need to have,” study co-lead author Johannes Kromdijk of the University of Illinois at Urbana-Champaign, tells The Christian Science Monitor. “They are optimized to reproduce, but they are not necessarily optimized to reproduce as much as possible.”
But to meet the demand for food, humans need plants to produce more. This is not the first time that scientists have worked to genetically improve crop yield, says Donald Ort, a professor of plant biology also at the University of Illinois at Urbana-Champaign who was not an author on the paper.
During the green revolution of the 1950s through the 1980s, breeding research improved plants’ ability to intercept radiation. Today the best crops absorb around 90 percent of the light available during the growing season. Scientists also worked to improve the harvest index – the percentage of the above ground dry matter that contributes to food – so that now 50 to 60 percent of that biomass is seeds.
“The other determinant of yield potential is photosynthetic energy conversion efficiency – the efficiency with which the plant can take that intercepted light and turn it into biomass,” Dr. Ort tells the Monitor. “During the first green revolution that was not improved at all, so it seems like if there is gong to be a second green revolution it would have to be driven by improving that process.”
And photosynthesis is frequently an inefficient process.
Direct sunlight can damage important molecules within the plant, so when the sun is particularly bright the plant converts photons into heat in a process called photoprotection – a kind of sunblock that protects the plant from sunburn. However, as a result, the efficiency of the plant's photosynthesis process drops significantly.
While it only takes a few minutes for the plant to react to direct sunlight, it takes hours for it to return to a normal rate of photosynthesis, and in that time the plant loses out on an estimated 20 percent of potential growth and crop yield.
This lag time would not be a problem in the wild, where the only evolutionary pressure is to reproduce enough to pass on genes, but it does raise concerns when the world’s food supply may need to double in 30 to 40 years.
Using tobacco plants, because their genes can be easily modified, the researchers tested what would happen if they sped up the photosynthetic recovery time. By changing just three genes involved in photoprotection, the plants' leaves, stems, and roots all got larger, says Krishna Niyogi, a co-author on the study and professor of plant and microbial biology at University of California Berkeley and researcher at the Lawrence Berkeley National Laboratory.
After being tested in a lab and a greenhouse, the plants were transplanted to a field, where in 22 days they weighed 14 to 20 percent more than unmodified plants.
“None of us care at all about tobacco,” Dr. Kromdijk says. “It is just a health-damaging crop that we really don’t need to improve, but we used it as a quick proof of concept and now we can start with the real interesting stuff by trying to put this technology to use to improve food crops.”
Eventually, the researchers will test the same process on such crops as cassava, rice, and cowpea, which will help farmers in the developing world, particularly across sub-saharan Africa and southeast Asia. If the concept applies to these crops as well, it would allow for more food to be produced without increasing the amount of land dedicated to agricultural production, which is already at its limit in many parts of the world.
There will likely be some social push back from the vocal anti-GMO movement, but Dr. Niyogi says the actual gene manipulation in this highly productive process is fairly minimal.
“In this first proof of concept, we did take the genes of one plant and put them into another plant, but all plants have these three genes,” Niyogi tells the Monitor. “So in the long run, what we can do is just manipulate the genes that are already in the plant and not introduce the genes from another organism.”
And ending hunger, Ort says, also makes for a pretty convincing argument.
“There is the belief that we need to develop these capabilities so that they exist at the time when push comes to shove and we simply don't have enough food and then maybe some of these things get reassessed at that time,” Ort says.