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Oryza sativa, having the common name Asian cultivated rice, is the much more common of the two rice species cultivated as a cereal, the other species being Oryza glaberrima, African rice. It was first domesticated in the Yangtze River basin in China 13,500 to 8,200 years ago.
Oryza sativa belongs to the genus Oryza and the BOP clade in the grass family Poaceae. With a genome consisting of 430megabase across 12 , it is renowned for being easy to genetically modify and is a model organism for the study of the biology of and Monocotyledon.
Oryza sativa contains two major subspecies: the sticky, short-grained Japonica rice variety, and the nonsticky, long-grained rice variety. Japonica was domesticated in the Yangtze Valley 6,000–9,000 years ago, and its varieties can be cultivated in dry fields (it is cultivated mainly submerged in Japan), in temperate East Asia, upland areas of Southeast Asia, and high elevations in South Asia, while indica was domesticated around the Ganges 4,500–8,500 years ago, and its varieties are mainly lowland rices, grown mostly submerged, throughout tropical Asia. Rice grain occurs in a variety of colors, including White rice, Brown rice, Black rice (purple when cooked), and Red rice.Oka (1988)
A third subspecies, which is broad-grained and thrives under tropical conditions, was identified based on morphology and initially called javanica, but is now known as tropical japonica. Examples of this variety include the medium-grain 'Tinawon' and 'Unoy' cultivars, which are grown in the high-elevation rice terraces of the Central Cordillera Mountains of northern Luzon, Philippines.CECAP, PhilRice and IIRR. 2000. "Highland Rice Production in the Philippine Cordillera."
Glaszmann (1987) used to sort O. sativa into six groups: Japonica rice, aromatic, indica, aus, rayada, and ashina.
Garris et al. (2004) used simple sequence repeats to sort O. sativa into five groups: Japonica rice, tropical japonica and aromatic comprise the japonica varieties, while indica and aus comprise the indica varieties. The Garris scheme has held up against newer analyses as of 2019, though one 2014 article argues that rayada is distinct enough to be its own group under japonica.
In total, 641 copy number variations are known. Exome capture often reveals new single nucleotide polymorphisms in rice, due to its large genome and high degree of DNA repetition.
Resistance to the rice blast fungus Magnaporthe grisea is provided by various resistance genes including , , and . (2025). 9783030207274, Springer. ISBN 9783030207274 O. sativa uses the plant hormones abscisic acid and salicylic acid to regulate immune responses. Salicylic acid broadly stimulates, and abscisic acid suppresses, immunity to M. grisea; success depends on the balance between their levels.
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O. sativa has a large number of insect resistance genes specifically for the brown planthopper. , 15 have been cloned and characterized.
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