Brassica rapa
(field mustard)

Identity

Preferred Scientific Name

• Brassica rapa L.

Preferred Common Name

• field mustard

Other Scientific Names

• Barbarea derchiensis S.S.Ying
• Brassica antiquorum H.Lév
• Brassica asperifolia Lam.
• Brassica brassicata A.Chev.
• Brassica briggsii Varenne
• Brassica campestris L.
• Brassica celerifolia (Tsen & S.H. Lee) Y.Z.Land & T.Y.Cheo
• Brassica chinensis L.
• Brassica cibaria Dierb.
• Brassica colza H.Lév.
• Brassica cyrenaica Spreng.
• Brassica dubiosa L.H.Bailey
• Brassica macrorhiza Gray
• Brassica napella Chaix
• Brassica narinosa L.H.Bailey
• Brassica nipposinica L.H.Bailey
• Brassica oleronensis A.Sav. ex Foucaud
• Brassica parachinensis L.H.Bailey
• Brassica pekinensis (Lour.) Rupr.
• Brassica pekinensis Skeels
• Brassica perfoliata Crantz
• Brassica perviridis (L.H.Bailey) L.H.Bailey
• Brassica petsai (Lour.) L.H.Bailey
• Brassica pseudocolza H.Lév
• Brassica purpuraria (L.H.Bailey) L.H.Bailey
• Brassica quadrivalvis Hook.f. & Thomson
• Brassica rapifera (Metzg.) Dalla Torre & Sarnth.
• Brassica rapoasiatica Sinskaya
• Brassica rapoeuropea Sinskaya
• Brassica saruna Siebold
• Brassica septiceps (L.H.Bailey) L.H.Bailey
• Brassica sphaerorrhiza Gray
• Brassica trilocularis Hook.f. & Thomson
• Brassica trimestris Boenn.
• Brassica tuberosa Salisb.
• Caulanthus sulfureus Payson
• Crucifera rapa E.H.L.Krause
• Napus campestris (L.) Schimp. & Spenn.
• Napus rapa (L.) Schimp. & Spenn.
• Raphanus campestris (L.) Crantz
• Raphanus rapa (L.) Crantz
• Sinapis dichotoma Roxb.
• Sinapis pekinensis Lour.
• Sinapis rapa (L.) Brot.
• Sinapis tuberosa Poir.

International Common Names

• English: Chinese savoy; biennial turnip rape; bird rape; bird’s rape; birdrape mustard; bok choi; bomdong; broad-beak mustard; brown sarson; caisim; caisin; cai-xin; canola; celery cabbage; Chinese cabbage; Chinese mustard; Chinese white cabbage; choisum; choi-sum; colbaga; colza; common turnip; dwarf white stem pak choy; false pak choi; flowering white cabbage; fodder kale; hanover salad; Indian colza; Indian rape; Italian kale; Italian turnip broccoli; komatsuna; leaf rape; mizuna; mustard cabbage; mustard spinach; napa cabbage; nep crops; pakchoi; pak-choi; petsai; pe-tsai; Polish canola; rape; rapini; rosette pak choi; ruvo kale; seven-top turnip; shantung cabbage; Siberian kale; spring turnip rape; stubble turnip; summer turnip rape; Swedish turnip; tat soi; turnip; tyfon; white celery mustard; white turnip; wild mustard; wild rutabaga; wild turnip; winter turnip; winter turnip rape; yellow sarson
• Spanish: col de China; colza; mostaza blanca; nabina; nabo; nabo gallego; repollo chino; yuyo
• French: navet blanc; pakchoï; pétsaï; brocoli chinois; chou Chinois; chou de Chine; chou de Shanghai; chou de shanton; chou-navet; choy sum; moutarde des oiseaux; moutarde épinard; navet; navette d’hiver; navette sauvage; pakchoy; rave; roquette d’orient
• Portuguese: couve Chinesa; couve d’inflorescência; couve da China; couve petsai; nabo; rábano

Local Common Names

• : latok
• Afghanistan: shalgham
• Australia: wombok
• Azerbaijan: turp
• Bolivia: k’ita mostacilla; k’ita nabo; navo
• Brazil: couve-chinesa-petsai; couve-repolho-da-china; nabo-selvagem; nabo-silvestre
• Bulgaria: repitsa
• Cambodia: Pe-chhaay; Spéi khiew
• Canada: Annual turnip rape; Argentine canola; Polish rape
• China: bai cai; bo leng jie; da ge cai; man jing; qing cai; qing cai pak choi; sui choi; ta ke cai; taatsai; wang sheng cai; xi yang you cai; xiqo you cai; yun tai; ze cai hua; ze tai cai; zi cai tai
• Colombia: mostaza silvestre; alpiste
• Denmark: höstoe; knakaal; majroe
• Ecuador: nabo chino
• Finland: pakchoi; pe-tsai; pinaattikiinankaali; rapsi
• Germany: Chinakohl; Chinesischer senf-kohl; Herbstrübe; Kohlrübe; Mairübe; Pakchoi; Rübsaat; Rübsen; Schnittkohl; Speiserübe; Steckrübe; Stoppelrübe; Wasserrübe; Weiße Rübe; Wruke
• Haiti: chou; navet
• India: an-tam; chalgom; grunjanakam; kalamohare; kali sarson; katusneha; nalla avalu; salgam; sarisan; sarsapa; sarson; shalgam; shaljam; sherasa; tantubha; tori; toria
• Indonesia: caisin; paksoi; pecai; sawi hijau; sawi kembang; sawi putih
• Italy: broccoletto; cime di rapa; colza; navete; navone; rapa; rapaccio; ravizzone
• Japan: hakusai; kabu; kabuna; kisaragina; kyona; mibuna; mizuna; natane; shakushina; taasai; taisi; turnip greens
• Laos: kaas chiin
• Malaysia: kobis cina; pak choi; petsai; sawi bunga; sawi puhit
• Mexico: flor de nabo; huachelai; mostacilla; mostaza; nabo de campo; nabo de canarios; nabo silvestre; pata de cuervo; semilla para pájaros; vaina
• Moldova: turneps
• Nepal: gante mula; salgam
• Netherlands: chinesekool; koolzaad
• New Caledonia: navet
• New Zealand: won bok; wong bok
• Norway: kålrot
• Pakistan: gonglu; shaljam
• Papua New Guinea: kapis
• Philippines: Chinese cabbage; dagawan; pechai baguio; pechay; wombok
• Poland: brukiew
• Portugal: couve nabiça de grelo; couve nabo; couve nabo branca; nabo redondo; turnepo
• Russian Federation: brjukva; kapusta kitajskaja; kapusta polevaya; kol’za; raps; repa; superitsa; surepica; turneps
• Spain: berza campía; berza silvestre; cabeza de nabo; carola; colinabo; grela; grelo; naba; nabicol; nabilla; nabina; nabiza; nabo forrajero; nabo galego; nabo gallego; nabo largo; nabo redondo; nabos; nap rodó; nap-i-col; raba
• Sweden: åkerkål; kohlraps; raps; rofraps; rofva; rova
• Thailand: phakkat-kheokwangtung; hong-how; hong-tae; phakkat-khaokwangtung; phakkat-khaopli; phakkat-khaoyai; phakkwangtung
• Turkey: chordal
• UK: Chinese leaf
• Ukraine: kapusta polova; ripa
• USA: asian greens; California peppergrass; common mustard; forage turnip; Japanese mustard; mibuna; mizuna; potherb mustard; rape mustard; summer turnip; turnip rape
• Vietnam: cari bawsc kinh; cari bej trawsng; cari ngojt; cari thiaf

Summary of Invasiveness

Brassica rapa is an annual to biennial herb that is widely cultivated as a vegetable or oilseed crop. It has escaped and become weedy or invasive in cultivated fields and disturbed areas. In Oceania it is listed as an invasive in Australia, Fiji, New Caledonia and New Zealand. In North America it is listed as invasive in some areas of Canada and the USA. In USA, seed use is restricted in Arizona and Michigan. It is also listed as invasive in Cuba, Mexico, Nicaragua, Chile, Ecuador and Peru. 

There is limited information available about its invasiveness and how it affects habitats, but it has been reported that the species can displace desirable vegetation if not properly managed. In California, USA it establishes in disturbed areas and forms dense stands that can displace native vegetation. In Mexico, although B. rapa is a frequent species in disturbed areas, there are no conclusive data about its negative impact on natural habitats. Its low stature prevents B. rapa from shading other species, and as most of its growth occurs during the winter months and the rainy season it avoids competition with many native species.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Plantae
•         Phylum: Spermatophyta
•             Subphylum: Angiospermae
•                 Class: Dicotyledonae
•                     Order: Capparidales
•                         Family: Brassicaceae
•                             Genus: Brassica
•                                 Species: Brassica rapa

Notes on Taxonomy and Nomenclature

The Brassicaceae, known as the mustard family, is composed of about 3740 species within 325 genera (Koch et al., 2012; Kiefer et al., 2014; Koch et al., 2018). It includes many economically important species, mostly in the genus Brassica, with some species being among the oldest cultivated plants. Brassica is the biggest genus of the family, providing oils, vegetables and condiments as well as being used as a fodder (PFAF, 2018).

Brassica rapa is one of the oldest Brassicaceae domesticated for oil production, as a vegetable and as a fodder (PROTA, 2018). The species exhibits high levels of morphological variation, with a long history of breeding and selection (Lou et al., 2007). Several infraspecific classifications have been proposed; more than 140 names appear in The Plant List (2013). Some of the morphotypes most common in cultivation include oilseed (B. rapa subsp. oleifera (rape), B. rapa subsp. dichotoma (brown sarson or toria) and B. rapa subsp. trilocularis, (yellow sarson)), leafy vegetables (B. rapa subsp. pekinensis (Chinese cabbage), B. rapa subsp. chinensis (pakchoi) and B. rapa subsp. nipposinica (mizuna)), root vegetables (Brassica rapa subsp. rapa (turnip)), and fodder crops (Guo et al., 2014).

In the 18th century the turnip and the oilseed-producing morphotypes were described as two different species by Linnaeus who named them B. rapa and B. campestris (PROTA, 2018). Metzger united the two species under B. rapa (Flora of China, 2018). Of the synonyms listed for B. rapa in The Plant List (2013), B. amplexicaulis, B. japonica, B. musifolia, B. polymorpha and Raphanus chinensis are illegitimate names; B. lutea is an invalid name and Sinapis communis and S. glauca are unresolved names.

Description

The following description is from PROTA (2018):

Erect, annual to biennial herb up to 1.5 m tall, with stout taproot, sometimes partly swollen (turnip); stem branched. Leaves arranged spirally but in a basal rosette during the vegetative stage; stipules absent; lower leaves more or less petiolate, pinnately parted with 1-5 pairs of small lateral lobes and large terminal lobe up to 90 cm × 35 cm, crenate, toothed, sinuate or entire, usually hairy; stem leaves pinnately parted to simple, clasping at base, glabrous, glaucous. Inflorescence a terminal umbel-like raceme up to 60 cm long, with open flowers overtopping the buds, elongating in fruit. Flowers bisexual, regular, 4-merous; pedicel up to 3 cm long, ascending; sepals 5-8 mm long, spreading, yellow-green; petals obovate, 0.5-1 cm long, clawed, bright yellow; stamens 6; ovary superior, cylindrical, 2-celled, stigma globose. Fruit a linear silique 4-10 cm × 2-4 mm, with a tapering beak 0.5-3 cm long, dehiscent, up to 30-seeded. Seeds globose, 1-1.5 mm in diameter, finely reticulate, dark brown. Seedling with epigeal germination, with a taproot and lateral roots; hypocotyl c. 5 cm long, epicotyl 2-4 mm long; cotyledons with petiole c. 2 cm long, blade cordate, 1-1.5 cm long, cuneate at base, notched at apex.

Plant Type

Distribution

The native range of B. rapa is difficult to ascertain due to its widespread cultivation and naturalization since ancient times (Kell, 2011). The species is present on all continents, being most common in temperate areas and at higher elevations in subtropical areas (See Distribution Table for details; Kell, 2011; Acevedo-Rodríguez and Strong, 2012; Euro+Med, 2018; Flora do Brasil, 2018; Flora of China Editorial Committee, 2018; Flora of North America Editorial Committee, 2018; India Biodiversity Portal, 2018; New York Botanical Garden, 2018; Missouri Botanical Garden, 2018; PIER, 2018; PROTA, 2018; USDA-ARS, 2018). Its distribution is also uncertain for some countries that have common names listed for B. rapa, without clear reports on whether the species is in cultivation or only being sold in markets.

There are some discrepancies about the native distribution of B. rapa. The species has been suggested as originating in Europe (Encyclopedia of Life, 2018), Eurasia (PIER, 2018), or from the eastern Mediterranean to Pakistan and China (PROTA, 2018). For some of the countries in Europe and Asia various resources list the species as both native or introduced, as being data deficient, as of uncertain origin or as doubtfully native (Kell, 2011; Encyclopedia of Life, 2018; Euro+Med, 2018). It is also reported as only being present in cultivation in some countries (PIER, 2018; USDA-ARS, 2018).

Based on linguistic and historical research, Ignatov et al. (2010) suggest that B. rapa was first domesticated in the West-Central Asia region and subsequently spread across Europe and East Asia as a result of migrations of farmers from the area of Central Asia and Asia Minor. Dixon (2006) suggests that the species originated in the Mediterranean region. Molecular and taxonomic research by Guo et al. (2014) supports the theory that the Mediterranean region is the centre of origin of B. rapa, with centres of diversity in east Asia and along ancient trade routes, and recent migrations to the New World.

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

The long history of B. rapa cultivation, the discrepancies about its native distribution and the great variety of cultivars known make it difficult to provide a clear history of its introduction and spread (PROTA, 2018). It is likely the domestication of B. rapa occurred following the advent of written history (approximately 3,500 BCE). Demographic modelling suggests a series of domestication events occurring in B. rapa between 2400 and 4100 years ago, starting in Europe and Central Asia and continuing east, which is validated by written records from the region (Qi et al., 2017). There are references to ‘oilseed rape’ and ‘mustard’ in Indian Sanskrit writings of 2000 to 1500 BCE, and in Greek, Roman and Chinese writings of 500 to 200 BCE (Canadian Food Inspection Agency, 2018). B. rapa is also mentioned as occurring during the empire of Alexander the Great (356-323 BCE); from where the species is believed to have spread to South-East Asia and Africa via trade routes (PROTA, 2018). Dixon (2006) suggests that B. rapa originated in the Mediterranean; spreading to into Europe, northwards to Scandinavia, eastwards to Germany, and eventually towards Asia. He also suggests that the species reached China via Mongolia and was introduced to Japan via either China or Siberia. In Europe commercial plantings of rapeseed are recorded in the Netherlands as early as the 16th century (Canadian Food Inspection Agency, 2018). The species is known from the New World since the 1800s (New York Botanical Garden, 2018).

Introductions

Risk of Introduction

Brassica rapa is an annual to biennial herb, cultivated worldwide, and mostly adapted to temperate climates (PROTA, 2018). It is reported in some areas as an escape from cultivation, but without many details given (Young-Mathews, 2012; Vibrans, 2018). Although it does not grow well in the lowlands of tropical areas, there is a potential increase in the risk of introduction into these areas as research is done to expand its range of cultivation (Young-Mathews, 2012; PROTA, 2018). Climate change is a threat to crop production worldwide and research is being done to develop crops tolerant to heat, drought and extreme weather (Guo et al., 2014).

Habitat

Brassica rapa is cultivated and also has naturalized in disturbed habitats in temperate areas and tropical highlands (PIER, 2018; PROTA, 2018). It is reported as occurring in croplands, weedy fields, roadsides, gravelly areas along railroads, waste areas, pastures, open forests, orchards, gardens and riverbanks (Kell, 2011; Flora of North America Editorial Committee, 2018; India Biodiversity Portal, 2018; PIER, 2018; PROTA, 2018; Missouri Botanical Garden, 2018; Useful Tropical Plants, 2018).

Habitat List

Hosts/Species Affected

Brassica rapa is a weed in crop fields, including garlic, alfalfa, rice, oats, peanuts, coffee, pumpkin, sugarcane, barley, peas, cauliflower, beans, chickpeas, sunflower, lentils, maize, apples, nopal cactus, potatoes, sorghum, tomato and vanilla, among others (Vibrans, 2018). It is also a contaminant of grains (Missouri Botanical Garden, 2018).

Brassica rapa is listed as being a host of various phytoplasmas that affect important crops and are transmitted by phloem tapping insects (Casati et al., 2016). B. rapa can hybridise and form fertile progeny with B. napus, creating a potential route for transgenes introduced into either species to enter the wild (Young-Mathews, 2012; Vibrans, 2018). It is also reported as impoverishing and drying up soils (Vibrans, 2018).

Host Plants and Other Plants Affected

Biology and Ecology

Genetics

Brassica rapa contains high levels of phenotypic diversity contributing to several cultivars that are important crops worldwide (PROTA, 2018). Population genetic analysis found strong support for five subpopulations within B. rapa that reflect both morphology and geography: European turnip and oilseed cultivars; Asian turnip and oilseed cultivars; yellow and brown sarson (B. rapa subsp. trilocularis and ssp. dichotoma); Chinese cabbage; and pakchoi, choi sum and tatsoi (Bird et al., 2017). In Europe, oilseed forms were selected from the turnip type from about the 14th century, when more oil production was needed in some areas (Guo et al., 2014), which explains the oilseed and turnip morphotypes being present in the same subpopulation.

Brassica rapa breeding programmes are currently underway, mainly in Asia and Europe. Some of the targets of the breeding programmes are improving existing cultivars, increasing dry-matter yield and producing tropical hybrids with heat tolerance and resistance to major diseases (Young-Mathews, 2012; PROTA, 2018). B. rapa is closely related to some other Brassica spp. and is sexually compatible with some of them. There is not a strong hybridization barrier between B. napus and B. rapa, and the F1 hybrids can be as fit, or nearly as fit as their parents (Jong and Hesse (2012).

There has been extensive research into the molecular genetics of B. rapa (Cardoza and Stewart Jr, 2004). Among the Brassica species, B. rapa possesses many economically important traits and it is receptive to gene transfer techniques (Mithila and Hall 2013, USDA-ARS, 2018). The species is considered as a good potential gene donor for other Brassicaceae; including cultivars of other Brassica species such as broccoli, Brussels sprout, cabbage and cauliflower (Brassica European Database, 2018). Gene transfer between B. rapa and other Brassica spp. via interspecies introgression and recombination has been used, for example, in the genetic improvement of B. napus and B. juncea, to contribute herbicide resistance and oil quality improvement (Hauser et al., 1998; Qing et al., 2000; Cardoza and Stewart Jr., 2004; Jong and Hesse, 2012). Warwick et al. (2008) report the possible occurrence of gene flow from transgenic B. napus into wild B. rapa populations in Canada. The potential for genes from transgenic crops becoming established in populations of wild relatives and the ecological risks involved is a serious concern that needs to be assessed.

The chromosome number reported for B. rapa is 2n=10 (PROTA, 2018). There are germplasm accessions held at various institutions worldwide (Brassica European Database, 2018; PROTA, 2018; USDA-ARS, 2018). The most recent reference genome for B. rapa, covers 353 Mb of the estimated 442 Mb genome (Zhang et al., 2018).

Reproductive Biology

Brassica rapa is seed propagated (PROTA, 2018). The species is self-incompatible and is insect pollinated by bees and butterflies (Vibrans, 2018; Encyclopedia of Life, 2018; Useful Tropical Plants, 2018). Seeds of most cultivars are reported as having a dormancy period (Young-Mathews, 2012; PROTA, 2018). Some cultivars need a cold, moist period to break dormancy and stimulate germination. Optimum soil temperatures for planting are reported as being between 8°C and 30°C (Young-Mathews, 2012). Seed production is unusual in lowland tropics (PROTA, 2018). Flowering and seed production can be induced by low temperatures and longer days. Seeds can be banked at 20°C for at least 5 years without loss of viability.

Physiology and Phenology

Brassica rapa is reported as flowering between January to September, depending on climate and latitude (Encyclopedia of Life, 2018; Flora of China Editorial Committee, 2018; Flora of North America Editorial Committee, 2018). Size can vary depending on the moisture and soil fertility (Encyclopedia of Life, 2018). High temperatures can cause ‘tip burn’ and prevent head formation. Most cultivars are biennials in temperate areas and will require a cold induction for flower and seed production of about 6 weeks in temperatures below 10°C. Some cultivars can be grown in subtropical and tropical regions year-round for their leaves and tender young inflorescences, with a tendency towards faster bolting during long days.

Longevity

Brassica rapa is reported as an annual or biennial herb (PROTA, 2018). Most cultivars growing in temperate areas are biennials (Encyclopedia of Life, 2018).

Environmental Requirements

Brassica rapa is mostly grown in temperate areas with mean annual temperatures of 5.6-25°C with a mean annual precipitation of 350 to 1600 mm (PIER, 2018). The species survives early frosts, but temperatures below 3.8°C will kill most cultivars. However, some winter-type cultivars can withstand temperatures as low as -12°C (Young-Mathews, 2012).

The species grows in neutral to alkaline soils with a pH of 4.8 to 8.5, preferring well drained loam, clay loam or gravelly soils (Encyclopedia of Life, 2018; India Biodiversity Portal, 2018; PROTA, 2018). It will also grow on sandy soils (Young-Mathews, 2012). Although it prefers full sun and moist to dry conditions, it can grow in semi shaded areas (Young-Mathews, 2012).

Brassica rapa has a high-water requirement but will not tolerate flooding and is sensitive to salinity (PROTA, 2018). The species will tolerate drought conditions, moderate heat and soils with low fertility (Young-Mathews, 2012). Although it is a species best adapted to temperate areas, some cultivars are grown in the tropics, mostly above 800 m altitude (PROTA, 2018).

Climate

Latitude/Altitude Ranges

Air Temperature

Rainfall

Rainfall Regime

Soil Tolerances

Soil drainage

• free

Soil reaction

• acid
• alkaline
• neutral

Soil texture

• heavy
• light
• medium

Special soil tolerances

• infertile

Natural enemies

Notes on Natural Enemies

Brassica rapa is reported as being attacked by various pests and diseases, especially in tropical areas (Canadian Food Inspection Agency, 2018; Encyclopedia of Life, 2018; PROTA, 2018). Pest problems can be avoided by planting resistant cultivars and using crop rotations (Young-Mathews, 2012).

Means of Movement and Dispersal

Natural Dispersal

The species is reported as being dispersed by autochory (self-dispersal) and anemochory (wind dispersal; India Biodiversity Portal, 2018). Seeds may also be dispersed by water in areas where plants grow along river margins.

Vector Transmission (Biotic)

Brassica rapa is reported as being dispersed by birds and other animals, although no further details are given (Vibrans, 2018; India Biodiversity Portal, 2018).

Accidental Introduction

Brassica rapa has been reported as an escape from cultivation and as growing as a volunteer in crop fields (Young-Mathews, 2012).

Intentional Introduction

Brassica rapa has a long history of cultivation and has been distributed worldwide as a crop (PROTA, 2018).

Pathway Causes

Pathway Vectors

Impact Summary

Economic Impact

Brassica rapa is a weed in cultivated sites, which can lead to a reduction in crop yield (Vibrans, 2018).

Environmental Impact

Impact on Habitats

The seeds of B. rapa can survive in the soil for fifty years or more when deeply buried; seeds closer to the soil surface are not as persistent (Young-Mathews, 2012). The species may become a fire hazard when dry at the end of the growing season (Young-Mathews, 2012).  

Brassica rapa is considered a coloniser of disturbed habitats and a volunteer weed in cultivated land in Canada, possibly outcompeting other species (Canadian Food Inspection Agency, 2018). Despite B. rapa being a frequent to occasional dominant species in disturbed and cultivated sites in Mexico, there is no evidence of negative effects in these habitats (Vibrans,2018). Its low stature does not promote the shading of other species and since most of its growth is during winter and during the rainy season, it avoids competition with other species.

Brassica rapa can hybridise with other Brassica spp., which could lead to gene flow into wild populations, including some from transgenic species (Warwick et al., 2008). Hybridisation between glyphosate-resistant B. napus and B. rapa was reported in Canada. Transgenic hybrids entering the wild might lead to an increase in fitness and invasiveness of B. rapa. More research is needed to understand the ecological implications of transgenic hybrids in natural populations.

Impact on Biodiversity

Roots, leaves and seeds of some B. rapa cultivars can contain high levels of erucic acid and glucosinolates that can irritate digestive tracts or create thyroid problems in animals, especially livestock, if consumed in large quantities (Young-Mathews, 2012). Toxicity symptoms include colic, diarrhoea, anorexia, excessive salivation and thyroid enlargement. Some cultivars have been developed that have lower levels of erucic acid and glucosinolates to make the oil and leaves safer for consumption.

Although no specific impacts over other species and the habitats are reported, disturbances will promote the spread of B. rapa, and it may form dense stands that displace other species (California Invasive Plant Council, 2018).

Social Impact

The oil contained in the seed of some cultivars of this species can be rich in erucic acid, which is toxic to animals. Some cultivars have been selected to have lower levels of erucic acid (Useful Tropical Plants, 2018).

Risk and Impact Factors

• Proved invasive outside its native range
• Has a broad native range
• Highly adaptable to different environments
• Is a habitat generalist
• Pioneering in disturbed areas
• Tolerant of shade
• Fast growing
• Has high reproductive potential
• Has propagules that can remain viable for more than one year
• Has high genetic variability

• Negatively impacts agriculture
• Negatively impacts animal health
• Negatively impacts livelihoods
• Threat to/ loss of native species

• Competition - monopolizing resources
• Pest and disease transmission
• Hybridization
• Poisoning
• Rapid growth

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Difficult to identify/detect as a commodity contaminant
• Difficult/costly to control

Uses

Economic Value

Brassica rapa is one of the oldest Brassicaceae in cultivation (PROTA, 2018). The products of various cultivars are sold in markets worldwide; for example, turnips, Chinese cabbage and pakchoi. The fruits are sold at markets in Mexico as bird food (Vibrans, 2018).

The oils from B. rapa seeds are used as cooking oil, industrial lubricant, lamp oil, for soap making and for biodiesel production (Young-Mathews, 2012; Canadian Food Inspection Agency, 2018; Vibrans, 2018; PROTA, 2018). Since the Second World War, rapeseed oil production in Europe and Canada has increased. China, India, Europe and Canada are now the top producers, with potential for the crop to be successfully grown in USA, South America and Australia (Canadian Food Inspection Agency, 2018). Although much of commercial production of rapeseed oil used for cooking comes from B. napus (as Canola oil), some of the production still comes from B. rapa.

Social Benefit

Brassica rapa is widely cultivated for its roots, leaves, seed oil and as a fodder (PFAF, 2018). The flowers of some varieties are also consumed. The taproot (turnip), the leaves and flowers are used as a vegetable, boiled, fried, pickled or eaten raw as salads (PROTA, 2018). The species is especially popular in Europe and Asia. In Europe, some cultivars are important as fodder crop. Per 100 g edible portion, B. rapa leaves contain the following: 95 g water, 1.2 g protein, 0.2 g fat, 2.2 g carbohydrates, 0.5 g fibre, 49 mg Ca, 0.7 mg Fe, 0.9 mg vitamin A and 38 mg vitamin C. It is low in energy value, about 65 kJ/100 g (PROTA, 2018).

Although much of the rapeseed oil production now from B. napus, B. rapa is still also cultivated for its oil, mainly for human consumption and for lamp oil (PROTA, 2018; USDA-ARS, 2018).

Brassica rapa leaves, seeds and stems are used ethnobotanically for cancer treatments and in Chinese traditional medicine (India Biodiversity Portal, 2018). The seeds are used as a poultice for burns (PFAF, 2018). Leaf and root extracts of B. rapa have antibacterial and antifungal properties (India Biodiversity Portal, 2018; PROTA, 2018). Extracts of the plant are also used as insecticide against aphids, red spider mites and flies (PFAF, 2018).

Researchers at the University of Wisconsin-Madison (USA) have selectively bred a subspecies of B. rapa, known as Rapid Cycling Brassica rapa, which has an extremely short life cycle, to be used a model organism in education and plant studies (Wisconsin Fast Plants, 2018). This variety is quite small, easy to grow, produces flowers two weeks after planting, and has a rapid seed maturation with no seed dormancy (Daugherty and Musgrave, 1994). Research done using B. rapa include studies into plant physiology, reproduction, conservation, evolution, crop domestication and molecular and population genetics (Demchik and Day, 1996; Kleier et al., 1998, Wise et al., 2002; Cardoza and Stewart Jr, 2004; Lou et al., 2007; Waller et al., 2008; Mithila and Hall, 2013, Franks et al., 2016, Cheng et al., 2016).

Brassica rapa is also an important gene source for other Brassicaceae; for example, the species has provided genes for disease resistance for B. napus (USDA-ARS, 2018).

Environmental Services

Brassica rapa flowers attract bees and butterflies, who visit them for the pollen and nectar. Some insects, including beetles and butterflies are reported as feeding on Brassica species. The seeds are eaten by various birds and the foliage can be eaten in limited amounts by livestock and other herbivores (Encyclopedia of Life, 2018). The species is also reported as being used for soil improvement (USDA-ARS, 2018).

Brassica rapa is used as a winter annual or a rotational cover crop in vegetable, speciality crop and row crop production. It has the potential to prevent erosion, suppress weeds and pests, alleviate soil compaction, and scavenge nutrients. When used as a cover crop, plants should be eliminated before or at full bloom to avoid seed set and volunteers in subsequent crops. Cultivars with larger roots have been a popular forage crop for livestock in Europe and Asia for at least 600 years. Forage turnip is a useful crop for extending the fall grazing season for dairy cows and other livestock (Young-Mathews, 2012)

Uses List

Animal feed, fodder, forage

• Fodder/animal feed
• Forage
• Invertebrate food

Environmental

• Amenity
• Erosion control or dune stabilization
• Soil improvement
• Wildlife habitat

Fuels

• Biofuels

General

• Laboratory use
• Research model

Genetic importance

• Gene source

Human food and beverage

• Oil/fat
• Root crop
• Vegetable

Materials

• Oils
• Pesticide

Medicinal, pharmaceutical

• Traditional/folklore

Similarities to Other Species/Conditions

Brassica rapa can be distinguished from other Brassica species by its glaucous gray-blue or gray-green foliage and its clasping alternate leaves. B. napus is similar but has bigger petals (10-14 mm) than B. rapa (7-11 mm) (Vibrans, 2018). Brassica species can be confused with Diplotaxis, which have flattened fruits with biseriate seeds. The fruits in Brassica are terete or 4-angled and the seeds are uniseriate. Sinapis is also similar but fruits are prominently 3-7 veined, while Brassica seeds have only one prominent vein or are obscurely veined. Brassica can also be confused with Sisybrium which has 6-160 ovules per ovary and fruits with a prominent midvein and 3 conspicuous lateral veins. Brassica has 4-46 ovules per ovary and fruits with obscure lateral veins (Flora of China Editorial Committee, 2018).

Prevention and Control

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Physical/Mechanical Control

Brassica rapa should be mowed or manually removed before seeds maturation. Using fire to manage the species is not recommended (Young-Mathews, 2012).

Chemical Control

Brassica rapa is susceptible to 2,4-D, MCPA, dicamba, bromoxynil, diuron, simazine, terbacil, glyphosate, chlorsulfuron, metsulfuron methyl and triclopyr (Vibrans, 2018). Some B. rapa cultivars have become resistant to glyphosate and the triazine family of herbicides (Young-Mathews, 2012; Canadian Food Inspection Agency, 2018).

Gaps in Knowledge/Research Needs

More research is needed into the invasiveness of B. rapa and the effect it has on habitats and native species. Since the species is known to hybridize with other Brassica species, information about the effects of genes transferred to B. rapa wild populations is needed.

References

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Distribution References

Acevedo-Rodríguez P, Strong M T, 2012. Catalogue of the Seed Plants of the West Indies. Washington, DC, USA: Smithsonian Institution. 1192 pp. http://botany.si.edu/Antilles/WestIndies/catalog.htm

CABI, Undated. CABI Compendium: Status as determined by CABI editor. Wallingford, UK: CABI

California Invasive Plant Council, 2018. Brassica rapa Plant Assessment Form., California, USA: CAL-IPC. https://www.cal-ipc.org/plants/paf/brassica-rapa-plant-assessment-form/

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Missouri Botanical Garden, 2018. Tropicos database. In: Tropicos database. St. Louis, Missouri, USA: Missouri Botanical Garden. http://www.tropicos.org/

New York Botanical Garden, 2018. The C. Starr Virtual Herbarium. In: The C. Starr Virtual Herbarium. New York, USA: New York Botanical Garden. http://sweetgum.nybg.org/science/vh/

Oviedo Prieto R, Herrera Oliver P, Caluff M G, et al, 2012. National list of invasive and potentially invasive plants in the Republic of Cuba - 2011. (Lista nacional de especies de plantas invasoras y potencialmente invasoras en la República de Cuba - 2011). Bissea: Boletín sobre Conservación de Plantas del Jardín Botánico Nacional de Cuba. 6 (Special Issue No. 1), 22-96.

PIER, 2018. Pacific Islands Ecosystems at Risk. In: Pacific Islands Ecosystems at Risk. Honolulu, Hawaii, USA: HEAR, University of Hawaii. http://www.hear.org/pier/index.html

Press J R, Shrestha K K, Sutton D A, 2000. Annotated checklist of the flowering plants of Nepal. [ed. by Press J R, Shrestha K K, Sutton D A]. London, UK: Natural History Museum Publications. x + 430 pp.

PROTA, 2018. PROTA4U web database. In: PROTA4U web database. Wageningen and Nairobi, Netherlands\Kenya: Plant Resources of Tropical Africa. https://www.prota4u.org/database/

Smithsonian Museum of Natural History, 2019. Smithsonian Museum of Natural History Botany Collections. In: Smithsonian Museum of Natural History Botany Collections. Washington, DC, USA: Smithsonian Museum of Natural History. http://collections.nmnh.si.edu/search/botany/

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Vibrans H, 2018. Weeds of Mexico. (Malezas de México.). In: Malezas de México. http://www.conabio.gob.mx/malezasdemexico/2inicio/home-malezas-mexico.htm

Virtual Herbaria Austria, 2018. Virtual Herbaria Austria. In: Virtual Herbaria Austria. Vienna, Austria: University of Vienna. http://herbarium.univie.ac.at/index.htm

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Links to Websites

Contributors

25/06/18 Original text by:

Jeanine Vélez-Gavilán, UPR-RUM, Mayagüez, Puerto Rico

Distribution Maps