Phaseolus angularis

The adzuki bean (Vigna angularis; from azuki (Japanese: アズキ（小豆）); sometimes transliterated as azuki or aduki), or English red mung bean, is an annual vine widely cultivated throughout East Asia for its small (approximately 5 millimetres (0.20 in) long) bean. The cultivars most familiar in Northeast Asia have a uniform red color, but white, black, gray, and variously mottled varieties also are known. Scientists presume Vigna angularis var. nipponensis is the progenitor. The wild ancestor of cultivated adzuki bean is probably Vigna angularis var. nipponensis, which is distributed across Japan, Korea, China, Nepal and Bhutan. Speciation between Vigna angularis var. nipponensis and Vigna angularis var. angularis occurred around 50,000 years ago. Archaeologists estimate it was domesticated around 3000 BC. However, adzuki beans (as well as soybeans) dating from 3000 BC to 2000 BC are indicated to still be largely within the wild size range. Enlarged seeds occurred during the later Bronze Age or Iron Age, periods with plough use. Domestication of adzuki beans resulted in a trade-off between yield and seed size. Cultivated adzuki beans have fewer but longer pods, fewer but larger seeds and a shorter stature, but also a smaller overall seed yield than wild forms. The exact place of domestication is not known; multiple domestication origins in northeast Asia (for example Japan, China, and Korea) have been suggested. In Japan, the adzuki bean was one of the first crops subjected to scientific plant breeding. Important breeding traits are yield, pureness of the bean colour and the maturing time. Separate cultivars with smaller seeds and higher biomass are bred for fodder production and as green manure. Locally adapted cultivars are available in China, Japan, Korea and Taiwan. More than 300 cultivars/landraces/breeding lines are registered in Japan. Moreover, China (Institute of Crop Germplasm Resources (CAAS), Beijing, more than 3700 accessions) and Japan (Tokachi Agricultural Experiment Station, Hokkaido-ken, about 2500 accessions) accommodate large germplasm collections of adzuki bean. Weed forms of adzuki bean frequently occur in Japan. The wide spread of weed forms is due to adaptation to human-disturbed habitats, escapes of old cultivars, and natural establishment from derivatives of hybrids between cultivars and wild forms. In contrast to wild forms, the weed forms of adzuki bean are used as a substitute for the cultivated form and consumed as sweet beans, especially if cultivated adzuki beans are attacked by pests. However, in cultivated gardens the weed form is recognized as contamination and lowers the seed quality of adzuki cultivars. The name adzuki (or azuki) is a transliteration of the native Japanese name. Japanese also has a Chinese loanword, shōzu (小豆), which means 'small bean', its counterpart 'large bean' (大豆, daizu) being the soybean. It is common to write 小豆 in kanji but pronounce it as azuki listen (help·info), an example of jukujikun. In China, the corresponding name (Chinese: 小豆; pinyin: xiǎodòu) still is used in botanical or agricultural parlance, however, in everyday Chinese, the more common terms are hongdou (红豆; hóngdòu) and chidou (赤豆; chìdòu), both meaning 'red bean', because almost all Chinese cultivars are uniformly red. In English-language discussions of Chinese topics, the term 'red bean' often is used (especially in reference to red bean paste), but in other contexts this usage may cause confusion with other beans that also are red. In normal contexts, 'red cowpeas' have been used to refer to this bean. In Korean, adzuki beans are called pat (팥) and it contrasts with kong (콩, 'bean'), rather than being considered a type of it. Kong ('beans') without qualifiers usually means soybeans. In Vietnamese it is called đậu đỏ (literally: red bean). In some parts of India, they are referred to as 'red chori'. In Punjabi it is called ravaa'n and is a common ingredient of chaat. In Marathi, it is known as lal chavali (लाल चवळी), literally meaning 'red cowpea'. In Iraq its name is lūbyā ḥamrāˈ (لوبيا حمراء) meaning 'red cowpeas'. The adzuki bean is mainly cultivated in China (670,000 ha), Japan (60,000 ha), South Korea (25,000 ha) and Taiwan (15,000 ha) (data published 2006). The bean is also grown commercially in the US, South America and India, as well as New Zealand, Kongo and Angola. In Japan, the adzuki bean is the second most important legume after the soy bean; its 1998 annual yield of this crop was around 100,000 tons. With a consumption of about 140,000 t/year (data published 2006), Japan is also the most important importer of adzuki beans. The imports are received from China, Korea, Colombia, Taiwan, US, Thailand and Canada. The bean yields per area spread over a broad range due to differing cultivation intensity. Amounts of 4 to 8 dt/ha are reported, but in Japan and China yields between 20 and 30 dt/ha are reached.