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Japonica rice (Oryza sativa subsp. japonica), sometimes called sinica rice, is one of the two major domestic types of Asian rice varieties. Japonica rice is extensively cultivated and consumed in East Asia, whereas in most other regions indica rice is the dominant type of rice. Japonica rice originated from Central China, where it was first domesticated along the Yangtze River basin approximately 9,500 to 6,000 years ago.^[1]^[2]^[3]

Characteristics

Japonica rice grains are rounder, thicker, and harder, compared to longer, thinner, and fluffier indica rice grains. Japonica rice is also stickier due to the higher content of amylopectin, whereas indica rice starch consists of less amylopectin and more amylose.^[4] Japonica rice plants are shorter than indica rice plants.^{[citation needed]}

Genetics

Japonica has a large amount of waxy protein and a low amount of the non-waxy type.^[5]^: 12–13 Non-waxy rice proteins are produced by four alleles, each producing one of four protein subtypes.^[5]^: 12–13 Japonica is the only source of Type III, shares Type IV with only javanica, and lacks Type I and Type II.^[5]^: 12–13

Classification

Japonica rice can be classified into three subgroups, 'temperate japonica',^[6] 'tropical japonica' (also known as 'javanica', Oryza sativa subsp. javanica [ja]),^[7]^[8] and 'aromatic'.^[9] Temperate japonica is cultivated in East Asia (China, Japan, Korea, Vietnam, and Taiwan), while tropical japonica is in Indonesia, Madagascar, and also the Americas where it was brought to with slave trade.^[10]