Brassica rapa subsp.oleifera is anoilseed commonly known asturnip rape,field mustard,bird's rape, andkeblock.[2][3][4][5][6][7]Rapeseed oil is a general term for oil from someBrassica species. Food grade oil made from the seed of low-erucic acid Canadian-developed strains is also calledcanola oil, while non-food oil is calledcolza oil.[2] Canola oil can be sourced fromBrassica rapa andBrassica napus, which are commonly grown in Canada, andBrassica juncea, which is less common.[8]
The geographic and genetic origins ofB. rapa have been difficult to identify due to its long history of human cultivation. It is found in most parts of the world, and has returned to the wild many times as aferal plant orweed.
Genetic sequencing and environmental modelling have indicated that ancestralB. rapa likely originated 4000 to 6000 years ago in theHindu Kush area of Central Asia, and had three sets ofchromosomes, providing the genetic potential for a diversity of form, flavour, and growth. Domestication has produced modern vegetables and oil-seed crops, all with two sets of chromosomes.[9][10]
Oilseedsubspecies (subsp.oleifera) ofBrassica rapa may have been domesticated several times from theMediterranean toIndia, starting as early as 2000 BC.[11] There are descriptions ofB. rapa vegetables in Indian and Chinese documents from around 1000 BC.[9]
Edible turnips were possibly first cultivated in northern Europe, and were an important food inancient Rome.[11] The turnip then spread east to China, and reached Japan by 700 AD.[11]
In the 18th century, the turnip and the oilseed-producing variants were thought to be different species byCarl Linnaeus, who named themB. rapa andB. campestris. Twentieth-century taxonomists found that the plants werecross fertile and thus belonged to the same species. Since the turnip had been named first by Linnaeus, the nameBrassica rapa was adopted.[12]
Many butterflies, including thesmall white, feed from and pollinate theB. rapa flowers.
The young leaves are a commonleaf vegetable and can be eaten raw; older leaves are typically cooked. The taproot and seeds can also be eaten raw, although the seeds contain an oil[which?] that can cause irritation for some people.[13]
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