A more powerful and efficient engine for rice: the C3-C4 challenge

Los Baños, Philippines – A major international scientific effort was launched last week to develop and use a radical new approach to boost rice production and avoid potential rice shortages, or even future famine.

Scientists have been working on different aspects of the approach since the early 1990s. But new knowledge generated by the sequencing of the rice genome is allowing researchers for the first time to discuss how they might work together to completely reconfigure what’s known as the engine of rice production, the plant’s photosynthetic system.

“If you think of the rice plant as a car, what we were talking about is really supercharging the engine,” said IRRI crop ecologist John Sheehy, convener of a workshop on C4 Rice – Supercharging the Rice Engine, held at the Philippines-based International Rice Research Institute (IRRI) on 17-21 July. “The photosynthetic process is the engine of growth for the rice plant, so, if we can improve that, then the whole plant benefits.”

“If we continue with the car analogy, the Green Revolution of the 1960s and 1970s, which resulted in high-yielding semidwarf rice varieties, focused on providing a new, more compact body for the rice plant,” Dr. Sheehy added. “But we have never really got under the hood and tried to improve the engine, or the photosynthetic efficiency, of the rice plant. It’s going to be an enormously complex and difficult challenge, but we think that with all the new knowledge we have about the rice plant it can be done.”

Many of the world’s leading experts on photosynthesis attended the five-day workshop. They were warned that unless global rice production continues to increase steadily—despite fewer resources such as land, labor, and capital—millions of people could fall backward into poverty. More than 3 billion people depend on rice as their main food source each day, including most of the world’s poor.

“Frankly, we have almost exhausted the traditional methods of increasing rice production, especially considering the environmental challenges we face such as climate change,” IRRI Director General Robert Zeigler said. “This generation must work to assure food security not only for ourselves, but for future generations as well. We must find and develop big new ideas to help us further increase rice production while using less land, labor, and water.”

To meet this important challenge, scientists at the workshop focused on enhancing the rice plant’s photosynthetic efficiency, or what’s known scientifically as converting rice from a C3 plant to a C4 plant, where the “C” refers to the carbon captured by photosynthesis for growth. To do this, C4 plants—such as maize—use solar energy more effectively for growth.

Dr. Sheehy compared the potential impact of successfully transforming rice from a C3 to a C4 plant as even greater than the production of the semidwarf rice plants that sparked the Green Revolution. “If we can successfully develop a C4 rice plant, the implications and potential impact will be huge—it’s one of the great scientific challenges facing people working in the plant sciences.”

The experts at the workshop suggested that it will probably take another three to four years to achieve the “proof-of-concept” needed before an international consortium of scientists will have assembled the tools and materials to begin constructing the prototypes of a C4 rice plant. It will be another 10–15 years after that before the first varieties are available.

“Considering the urgent rice production challenges we face, we must start now on this work—there’s no time to lose,” Dr. Sheehy said.

The International Rice Research Institute (IRRI) is the world’s leading rice research and training center. Based in the Philippines and with offices in 10 other Asian countries, it is an autonomous, nonprofit institution focused on improving the well-being of present and future generations of rice farmers and consumers, particularly those with low incomes, while preserving natural resources. IRRI is one of 15 centers funded through the Consultative Group on International Agricultural Research (CGIAR), an association of public and private donor agencies. Please visit the CGIAR website (www.cgiar.org) for more information.

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