Oryza sativa

Oryza sativa, commonly known as Asian rice, is the plant species most commonly referred to in English as rice. It is the type of farmed rice whose cultivars are most common globally, and was first domesticated in the Yangtze River basin in China 13,500 to 8,200 years ago.
"Oryza sativa" is a grass with a genome consisting of 430Mb across 12 chromosomes. It is renowned for being easy to genetically modify and is a model organism for cereal biology.
Classification.
"Oryza sativa" contains two major subspecies: the sticky, short-grained "japonica or sinica" variety, and the nonsticky, long-grained "" variety. "Japonica" varieties are usually 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" varieties are mainly lowland rices, grown mostly submerged, throughout tropical Asia. Rice occurs in a variety of colors, including white, brown, black, purple, and red rices. Black rice (also known as purple rice) is a range of rice types, some of which are glutinous rice. Varieties include Indonesian black rice and Thai jasmine black rice.
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 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.
Nomenclature and taxonomy.
Rice has been cultivated since ancient times and "oryza" is a classical Latin word for rice. "Sativa" means "cultivated".