Oryza sativa

O. sativa has an erect stalk stem that grows tall, with a smooth surface. The leaf is lanceolate, long, and grows from a ligule long. Image:Kerbau Jawa.jpg|Water buffalo ploughing a rice paddyfield, Java File:Jumli Marshi Oryza sativa Rice.jpg|Jumli Marshi, brown rice from Nepal File:Niyamgiri rice.jpg|Traditional rice of Niyamgiri Hills, India File:Medicinal Rice.jpg|From Chhattisgarh File:Koeh-232.jpg| File:RiceStemcs400x1.jpg|Stem cross section magnified 400 times == Taxonomy ==

Oryza sativa contains two major subspecies: the sticky, short-grained japonica or sinica 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, 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. Glaszmann (1987) used isozymes to sort O. sativa into six groups: japonica, aromatic, indica, aus, rayada, and ashina. Garris et al. (2004) used simple sequence repeats to sort O. sativa into five groups: temperate japonica, 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. Etymology The generic name Oryza is a classical Latin word for rice, while the specific epithet sativa means "cultivated". == Genetics ==

/ is a gene that regulates the overall architecture/growth habit of the plant. Some of its epialleles increase rice yield. An accurate and usable simple sequence repeat marker set was developed and used to generate a high-density map. Other molecular breeding tools have produced rice blast resistant cultivars. 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. , 15 R genes have been cloned and characterized. == See also ==