Kiwifruits belong to the genus Actinidia, a group of around 5 to 6 dozen species of climbers in the family Actinidiaceae. They are best known for their edible fruits, although some species are also used as ornamentals, as a source of traditional medicines, and as a stimulant for cats somewhat akin to catnip. The two most commercially important species are A. deliciosa and A. chinensis, both native to China (A. deliciosa grows more in the western, inland, colder areas, whereas A. chinensis grows more in the lowlands in the more eastern provinces towards the coast). Some authors have questioned whether these two taxa should really be treated as distinct species (see Ferguson 2007 and references therein for a discussion of the relationship between these two taxa).
Actinidia deliciosa is a woody vine that may reach 10 m in length. It is dioecious (i.e., individual plants are either male or female). The flowers are white to cream-colored. The fruit is an oval berry (botanically speaking), 55 to 70 mm long, with a light brown skin and green flesh containing many hundreds of tiny black seeds. Although generally grown in warm temperate climates, the species can tolerate a range of conditions. Natural pollen transfer to female plants is sometimes supplemented by spray applications because fruit size is affected by the number of fertilized seeds.
In China, large quantities of kiwifruits are still collected from wild vines. Commercial cultivation of kiwifruit in China started only in the last couple of decades of the 20th century, but by 1998 there were around 45,000 ha of kiwifruit orchards, 75% cultivars of A. deliciosa and 25% cultivars of A, chinensis. Much of the world's commercial stock of A. deliciosa is believed to be derived from stock planted in New Zealand in 1904 (this explains why the common name refers to New Zealand although kiwis are not native there: the name “kiwifruit” was proposed when the fresh fruits were first exported to the United States in 1959 and within a decade had become the accepted name, although in China this fruit is known as "mihoutao", or "monkey peach"). In 1904, Isabel Fraser returned to New Zealand after visiting her missionary sister in China, with kiwifruit seeds. The cultivar 'Hayward', a direct descendant of those first seeds, is now the mainstay of kiwifruit industries throughout the world. (Ferguson 2004, 2007)
The very first commercial kiwifruit orchard was in production by about 1930, but a significant international market for kiwis did not develop until the late 1970s. Kiwis are now grown in Italy, Chile, France, and the United States, among other countries. In 2004, China, Italy, New Zealand, and China accounted for around 80% of the world's commercial kiwifruit production. Today, Italy produces more kiwifruit than any other country with the possible exception of China, and Italy and New Zealand are the largest exporters. The first kiwifruit orchards were established in Italy only 40 years ago, but by 2007 they occupied 26,700 ha and produced 400,000 to 500 000 metric tons of fruit each year. As elsewhere, most Italian kiwifruit plantings are of the cultivar 'Hayward' but there are now orchards of several new cultivars, including yellow-fleshed kiwifruit. The international kiwifruit industry of today, with more than 120,000 ha of orchards planted and with annual production exceeding 1.35 million metric tons of fresh fruit, is based on A. deliciosa and A. chinensis, but a third species, A. arguta, may soon be established as a commercial crop. Most of the Italian kiwifruit crop is consumed within Italy or in other countries of the European Union, whereas most of New Zealand's crop is exported long distances. Ferguson (2007) provided a thorough review of kiwifruit domestication and breeding.
Kiwis contain around 10% total sugars (mainly glucose and fructose) and are rich in vitamin C (most of which remains even after months in storage). Citric acid is the main constituent organic acid.
(Vaughan and Geissler 1997; Huang and Ferguson 2001; Ferguson 2007; Mabberley 2008; Testolin and Ferguson 2009)
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