Oryza sativa
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Oryza sativa, having the common name Asian cultivated rice,<ref>Template:Cite web</ref> is the much more common of the two rice species cultivated as a cereal, the other species being O. glaberrima, African rice. It was first domesticated in the Yangtze River basin in China 13,500 to 8,200 years ago.<ref name="Normile">Template:Cite journal</ref><ref name="Vaughanetal2008">Template:Cite journal</ref><ref name="harris">Template:Cite book</ref><ref name="Zhang2012">Template:Cite journal</ref>
Oryza sativa belongs to the genus Oryza and the BOP clade in the grass family Poaceae. With a genome consisting of 430Template:NbspMbp across 12 chromosomes, it is renowned for being easy to genetically modify and is a model organism for the study of the biology of cereals and monocots.<ref>Template:Cite journal</ref>
Description
O. sativa has an erect stalk stem that grows Template:Cvt tall, with a smooth surface. The leaf is lanceolate, Template:Cvt long, and grows from a ligule Template:Cvt long.<ref>Template:Cite web</ref>
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Water buffalo ploughing a rice paddyfield, Java -
Jumli Marshi, brown rice from Nepal -
Traditional rice of Niyamgiri Hills, India -
From Chhattisgarh -
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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 Template:Visible anchor rice variety. Japonica was domesticated in the Yangtze Valley 6,000–9,000 years ago,<ref name="Purugganan-Fuller-2009">Template:Cite journal</ref> 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,<ref name="Purugganan-Fuller-2009" /> and its varieties are mainly lowland rices, grown mostly submerged, throughout tropical Asia. Rice grain occurs in a variety of colors, including white, brown, black (purple when cooked), and red.<ref>Oka (1988)</ref><ref>Template:Cite journal</ref>
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.<ref>CECAP, PhilRice and IIRR. 2000. "Highland Rice Production in the Philippine Cordillera."</ref>
Glaszmann (1987) used isozymes to sort O. sativa into six groups: japonica, aromatic, indica, aus, rayada, and ashina.<ref name="Glaszmann 1987">Template:Cite journal</ref>
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.<ref name="Garris Tai Coburn 2004">Template:Cite journal</ref> The Garris scheme has held up against newer analyses as of 2019,<ref name=civan>Template:Cite journal</ref> though one 2014 article argues that rayada is distinct enough to be its own group under japonica.<ref>Template:Cite journal</ref>
Etymology
The generic name Oryza<ref name="oryza-MW">Template:Cite Merriam-Webster</ref> is a classical Latin word for rice, while the specific epithet sativa means "cultivated".<ref name="sativa-dict">Template:Cite Lexico</ref><ref>Template:Cite Merriam-Webster</ref>
Genetics
Template:Visible anchor/Template:Visible anchor is a gene that regulates the overall architecture/growth habit of the plant. Some of its epialleles increase rice yield.<ref name="Stange-et-al-2021">Template:Cite journal</ref> An accurate and usable simple sequence repeat marker set was developed and used to generate a high-density map.<ref name="Rasheed-et-al-2017" /> A multiplex high-throughput marker assisted selection system has been developed but as with other crop HTMAS systems has proven difficult to customize, costly (both directly and for the equipment), and inflexible.<ref name="Rasheed-et-al-2017">Template:Cite journal</ref> Other molecular breeding tools have produced rice blast resistant cultivars.<ref name="Miah-et-al-2012">Template:Cite journal</ref><ref name="Rao-et-al-2014">Template:Cite journal</ref><ref name="Rasheed-et-al-2017" /> DNA microarray has been used to advance understanding of hybrid vigor in rice, QTL sequencing has been used to elucidate seedling vigor, and genome wide association study (GWAS) by whole genome sequencing (WGS) has been used to investigate various agronomic traits.<ref name="Rasheed-et-al-2017" />
In total, 641 copy number variations are known.<ref name="Rasheed-et-al-2017" /> Exome capture often reveals new single nucleotide polymorphisms in rice, due to its large genome and high degree of DNA repetition.<ref name="Rasheed-et-al-2017" />
Resistance to the rice blast fungus Magnaporthe grisea is provided by various resistance genes including Template:Visible anchor, Template:Visible anchor, and Template:Visible anchor.<ref name="Mehta-et-al-2019">Template:Cite book</ref> 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.<ref>Template:Cite journal |Template:Cite journal</ref><ref>Template:Cite journal</ref>
O. sativa has a large number of insect resistance genes specifically for the brown planthopper.<ref name="Wang-Han-2022">Template:Cite journal</ref> Template:As of, 15 R genes have been cloned and characterized.<ref name="Wang-Han-2022" />
See also
- Domesticated plants and animals of Austronesia
- International Code of Nomenclature for Cultivated Plants
- Traceability of genetically modified organisms