Koji orange (''Citrus leiocarpa''), also called smooth-fruited orange in English, bingyul in Korean, 光橘 (Guang ju), 柑子 (Gan zi), and 日本土柑 (Ri ben tu gan) in Chinese, and コウジ (Kōji) in Japanese, is a ''

Citrus ''Citrus'' is a genus of flowering plant, flowering trees and shrubs in the rue family, Rutaceae. Plants in the genus produce citrus fruits, including important crops such as Orange (fruit), oranges, Lemon, lemons, grapefruits, pomelos, and lim ...

'' species native to

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

Distribution

Besides

, it is grown in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

, and other parts of East Asia including

South Korea South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korea, Korean Peninsula and sharing a Korean Demilitarized Zone, land border with North Korea. Its western border is formed ...

and

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

Description

The fruit is oblate in shape, slightly ribbed, bright orange in color, very small, and very seedy, and for the latter two reasons it is not grown for commercial use. It ripens from October through November and has been cultivated since at least 1900. It may be

monoembryonic Monoembryony is the emergence of one and only one seedling from a seed. A seed giving two or more seedlings is polyembryonic Polyembryony is the phenomenon of two or more embryos developing from a single fertilized egg. Due to the embryos resulting ...

. The tree is densely branched and has a broad crown and a short, straight trunk. The leaves are dark green and elliptical in shape.

Genetics

''Citrus leiocarpa'' is inferred to be a hybrid between a koji-type species (seed parent) and the

tachibana orange The tachibana orange (''Citrus tachibana,'' or ''Citrus reticulata tachibana'') is a variety of mandarin orange, a citrus fruit. They grow wild in the forests of Japan and are referred to in the poetry of the early Japanese and Ryukyu Islands ki ...

(pollen parent, ''Citrus tachibana''). Its genotype matches with that of the

komikan Komikan (from the Mapuche kom ikan "to eat all") is a two-player abstract strategy board game of the Mapuches (known by the Spaniards as the Araucanians) from Chile and Argentina. The same game is also played by the Incas under the name Tapta ...

and toukan varieties.

Varieties

''Citrus leiocarpa'' f. ''monoembryota'', a

form Form is the shape, visual appearance, or configuration of an object. In a wider sense, the form is the way something happens. Form also refers to: *Form (document), a document (printed or electronic) with spaces in which to write or enter data ...

of ''Citrus leiocarpa'', was described by Chozaburo Tanaka. Once believed to be a mutation of the koji orange, it has been revealed that it is a hybrid between koji (pollen parent) and

kishu The , sometimes called ''Kishu Inu'' or ''Kishu dog'', is a Japanese breed of dog. It is descended from ancient medium-sized breeds and named after the Kishu region, now Mie Prefecture and Wakayama Prefecture. It was designated a living nati ...

(seed parent). In Chinese, it is called 駿河柑子 (Jun he gan zi) and is called スルガユコウ (Suruga yukō) and 駿河柚柑 (Suruga yukō) in Japanese.

Taxonomy

It is treated as a synonym of ''

Citrus aurantium Bitter orange, Seville orange, bigarade orange, or marmalade orange is the citrus tree ''Citrus'' × ''aurantium'' and its fruit. It is native to Southeast Asia and has been spread by humans to many parts of the world. It is probably a cross bet ...

'' in taxonomy.

References