Together with maize and wheat, rice supplies more than 42% of the calories of the global human diet. 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 subspecies: 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 8,200 and 13,500 years ago and expanded to South, East and Southeast Asia. Asian rice reached Lower Mesopotamia, Greece and the Mediterranean in the late centuries BC. From here, 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 and 3,000 years ago in the Upper Niger River. African rice was introduced to the American continent during the 17th century through the slave trade.
Rice is conserved as botanical seeds. Genesys contains information for more than 200,000 rice accessions, with nearly 65,500 landraces. The largest rice collections are held by [The International Rice Research Institute] (https://www.genesys-pgr.org/wiews/PHL001), followed by [USDA genebanks] (https://www.genesys-pgr.org/explore?page=1&filter=%7B%22institute.country.iso3%22%3A%5B%22USA%22%5D%2C%22crops%22%3A%5B%22rice%22%5D%7D&results=50) and [AfricaRice] (https://www.genesys-pgr.org/wiews/CIV033).
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 AfricaRice, CIAT, CIRAD, IRD and JIRCAS.