Rice (Oryza sativa) is a staple food for nearly half of the world's population. Rice is a member of the grass family, which also includes wheat, corn, sorghum, barley, oats, and rye. Unlike other grains, rice is well adapted to aquatic environments. Rice originated in Southeast Asia, where archeological evidence—including carbon-dated grain imprints in pottery shards—indicates that it was under cultivation at least six thousand years ago. Cultivated rice consists of two subspecies, O. sativa subsp. indica, which is grown in the tropics and subtropics, and O. sativa subsp. japonica, which is grown in temperate regions.

Although rice is grown in 115 countries, over 90 percent of the crop is in Asia. In 1999 world rice area was 153 million hectares (Mha), and total production was 589 million metric tons (Mmt). India had the largest area, 43.0 million hectares, and China was second with 31.7 million hectares. However, yields in China averaged 6.33 metric...