Crops engineered to use less energy fixing a “photosynthetic glitch” are about 40 percent more productive, according to new research from the University of Illinois and USDA’s Agricultural Research Service published Thursday in Science.
Two years of field trials in tobacco plants resulted in the yield increases, which researchers believe can be replicated in other plants such as soybeans and potatoes. Those plants expend more energy than needed during photosynthesis, causing yield losses of 20 to 50 percent.
The inefficiency arises in certain plants, including most fruits and vegetables, because near the start of the photosynthetic process, the enzyme Rubisco cannot “reliably distinguish” between carbon dioxide and oxygen molecules, a news release on the research said.
“Rubisco grabs oxygen instead of carbon dioxide about 20 percent of the time, resulting in a plant-toxic compound that must be recycled through the process of photorespiration,” which “drastically suppresses their yield potential,” the researchers said.
Yield increases from pesticides, fertilizers, irrigation and mechanization, as well as the adoption of higher-yielding crop varieties, "are now largely optimized for major crops and are unlikely to generate sufficient yield increases" to satisfy demands expected by 2050, the paper said. "However, photosynthetic efficiency remains standing as a determinant of yield potential with the improvement capacity to double crop productivity."
In addition to soybeans and potatoes, other crops that use photorespiration include cowpeas (known as black-eyed peas in the U.S.), rice, tomato and eggplant. Scientists with the Realizing Increased Photosynthetic Efficiency (RIPE) project are working to translate their findings into yield increases for those crops, as well.
“We could feed up to 200 million additional people with the calories lost to photorespiration in the Midwestern U.S. each year,” said principal investigator Donald Ort, a plant science professor at the University of Illinois. “Reclaiming even a portion of these calories across the world would go a long way to meeting the 21st Century’s rapidly expanding food demands – driven by population growth and more affluent high-calorie diets.”
RIPE is funded by the Bill and Melinda Gates Foundation, the Foundation for Food and Agriculture Research, and the United Kingdom’s Department for International Development (DFID).
FFAR told Agri-Pulse "photosynthetic efficiency is a major focus" of its funding dollars. "It’s the space in which there is a large amount of opportunity for improvement."
"In terms of the timeline, it is realistic to say that seeds providing increased photosynthetic efficiency will be available commercially in about 15 years," the group added. "In fact, such seed may be available sooner with the advent of big data and advanced breeding technologies."
The Gates Foundation and DFID “are really excited to get these seeds into the hands of people who need them the most,” said Amanda Cavanagh, a co-author of the paper and Illinois postdoctoral researcher working on the RIPE project. Cowpeas are a popular crop in sub-Saharan Africa because of their affinity for semi-arid soils.
“While it will likely take more than a decade for this technology to be translated into food crops and achieve regulatory approval, RIPE and its sponsors are committed to ensuring that smallholder farmers, particularly in sub-Saharan Africa and Southeast Asia, will have royalty-free access to all of the project’s breakthroughs,” RIPE said in its news release.
Cavanagh said the increased temperatures associated with climate change result in elevated levels of photorespiration. Instead of Rubisco grabbing an oxygen molecule 20 percent of the time, the rate increases to 30 or 40 percent.
Soybeans, for example, would still lose 18 percent of their yield to photorespiration, instead of 36 percent — a big drop, to be sure, but “that’s still quite a few calories,” Cavanagh said.
RIPE researchers have not focused on corn, but recent research at the Boyce Thompson Institute and Cornell has shown how increasing Rubisco can increase corn yield. “Increased Rubisco assists corn’s biological machinery used during photosynthesis to incorporate atmospheric carbon dioxide into carbohydrates,” according to Cornell.
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