What is C4 Rice?

Courtesy: C4 Website

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Published on Tuesday, 04 December 2012 10:37

Background

Agriculture is the indispensable base of human society and the nature and productivity of agriculture is determined by land, water, climate, management and agricultural research. Only 29% of the earth’s surface is land and only a little over a third of that is suitable for agriculture; the rest is ice, desert, forest or mountain and is unsuitable for farming. More simply stated, only 10% of the surface of the earth has topographical and climatic conditions suitable for producing the food requirements of human beings. Today, 75% of the world’s 6.6 billion people live in the developing world where most of the world’s existing poverty is concentrated.

Currently, about a billion people live on less than a dollar a day and spend half their income on food; 854 million people are hungry and each day about 25,000 people die from hunger-related causes. Sixty percent of the world’s population lives in Asia, where each hectare of land used for rice production currently provides food for 27 people, but by 2050 that land will have to support at least 43 people. Nonetheless, the area for rice cultivation is continually being reduced by expansion of cities and industries, to say nothing of soil degradation. Climate change will likely result in more extreme variations in weather and cause adverse shifts in the world’s existing climatic patterns. Water scarcity will grow; the increasing demand for biofuels will result in competition between grain for fuel and grain for food resulting in price increases. Furthermore, more than 75% of the world's people will live in cities, the populations of which will need to be largely supported by a continuous chain of intensive food production and delivery.

All of these adverse factors are growing now, at a time when the growth in rice production has slowed as efficient farmers have approached yield limits. Research shows that current maximum rice yields are close to a fundamental yield barrier shaped by the efficiency of solar energy conversion.

How will the required increases in yield be achieved? Solar energy captured in photosynthesis over the duration of a crop gives it the capacity to grow. There is now a growing body of scientific opinion, that the only way to achieve the rice harvests needed for the future is to change the biophysical structure of the rice plant, making it a much more efficient user of energy from the sun. Plants use solar radiation to grow—to develop leaves, roots, stems, flowers, and seeds in a process known as photosynthesis. Rice has what is known as a C3 photosynthetic pathway, less efficient than that of maize, which has a C4 pathway. Taking a lesson from evolution and converting a plant from C3 to C4 would involve a rearrangement of cellular structures within the leaves and more efficient expression of various enzymes related to the photosynthetic process. However, all the components for C4 photosynthesis already exist in the rice plant, but they are distributed differently and are not as active.

Roadmap

Research Grant from the Bill & Melinda Gates Foundation (BMGF)

The costs of the project were estimated to be about $5m per year. In October 2008, The Bill & Melinda Gates Foundation awarded IRRI a grant of $11.1M to begin research on the first 3 year phase of the C4 Rice Project.