Together with maize and wheat, rice supplies more than 42% of the calories of the human diet globally. It is grown in both tropical and temperate regions, in both rainfed and irrigated systems. Two Oryza species are cultivated: O. sativa, grown worldwide, and O. glaberrima, grown mainly in West Africa but also in small pockets in Latin America.
Asian rice (O. sativa) contains two groups: japonica, grown in cooler zones of the tropics and temperate zones; and indica, grown in tropical and subtropical regions. It was domesticated in China between 8200-13500 BP and expanded to South, East and Southeast Asia. Asian rice reached Lower Mesopotamia, Greece and the Mediterranean in the late centuries BC. From there, it gradually spread to southern Europe. Portuguese and Spanish settlers introduced rice to the New World during the Columbian Exchange.
On the other hand, African rice (O. glaberrima) was first domesticated between 2,000-3,000 BP in the Upper Niger River. African rice was introduced to the American continent during the 17th century through the slave trade.
According to the global strategy for the conservation of rice genetic resources, there are more than 500,000 rice accessions in the world. The six largest rice genebanks conserve together 70% of the world holding, and they are all located in Asia.
Rice is conserved as botanical seeds. Genesys contains information on more than 200,000 rice accessions, with including nearly 65,500 landraces. The largest rice collections are held by The International Rice Research Institute (IRRI), followed by USDA-ARS genebanks and AfricaRice.
RICE, the CGIAR Research Program on Rice, is working on high-yielding and biofortified varieties, and technologies to reduce the environmental footprint associated with the crop. Partners in this research program are the Africa Rice Center (AfricaRice), the International Center for Tropical Agriculture (CIAT), the French Agricultural Centre Research Center for International Development (CIRAD), the French Research Institute for Development (IRD) and the Japan International Center for Agricultural Sciences (JIRCAS).