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Image of Daucus carota subsp. sativus (Hoffm.) Schübl. & Martens
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Daucus carota subsp. sativus (Hoffm.) Schübl. & Martens

Brief Summary

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Various forms of wild carrot (usually treated as different subspecies and/or varieties of Daucus carota), occur as natives across much of western Asia and Europe. Their pale roots are small and have an unpleasant taste. In contrast, Daucus carota sativus, the domesticated carrot, which was already mentioned in classical texts two millenia ago, has enlarged roots which can taste quite sweet. The domesticated carrot arose in the Near East, in the region between Afghanistan and Turkey. In its early form, it had dark purple roots that were often branched. Orange, carotene-colored forms developed later and are illustrated in a Byzantine herbal from 512 A.D. In the 17th century, carrots were developed in the Netherlands with denser orange carotene pigment and these were the progenitors of the modern cultivated carrot (Vaughan and Geissler 1997). These orange forms soon replaced the purple ones in Europe and the Mediterranean. Carrots are eaten both raw and cooked and are used in both savory and sweet dishes. In Asia, they are often preserved in jams and syrups. (Sanderson 2005)

The domesticated carrot (Daucus carota sativus) is easily recognized by its highly pigmented, fleshy, edible, brittle roots. In wild carrots, fresh roots are flexible and fibrous (brittle and not fibrous in domesticated forms), the transition from shoot to storage organ is indistinct externally (the storage organ--the "carrot"--is abruptly expanded in domesticated forms), rosette foliage is often prostrate (usually conspicuously erect in domesticated forms), and umbels often have one or several purple central flowers (rarely in domesticated forms). Cultivated carrots with white roots are occasionally encountered, but relative to wild carrots these roots are palatable and brittle and are unbranched.

Within the subspecies D. c. sativus, two varieties are sometimes recognized: The "Western Carrot" (variety sativus) and the "Eastern Carrot" (variety atrorubens). The Western Carrot may have orange, yellow, or white storage organs and is best characterized by yellowish-green highly dissected foliage that mostly lacks pubescence. The Western Carrot is grown around the world and with the exception of Asia is the main variety cultivated. The Eastern Carrot usually has purple and/or yellow storage organs. Occasionally, roots are reddish or yellowish-orange. The Eastern Carrot is characterized by grayish-green (glaucous) and only moderately dissected foliage that is moderately pubescent. The Eastern Carrot is common only in Asia, but it has been introduced elsewhere. Although one might expect the interesting colors of this variety to confer commercial value in Western markets at least as a novelty, the fact that the pigments are water soluble, like those of beets, seems to have limited its appeal in the West (but see Surles et al. 2004). Furthermore, these carrots may be more susceptible to decay. It is important to realize that this varietal taxonomy is somewhat artificial. For example, in Asia, where there has been considerable genetic mixing between these forms, plants with intermediate characteristics are commonly encountered. Some of these varietal hybrids have even found commercial success in the West. (IPGRI 1998)

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Comprehensive Description

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Various forms of wild carrot (usually treated as different subspecies and/or varieties of Daucus carota), occur as natives across much of western Asia and Europe. Their pale roots are small and have an unpleasant taste. In contrast, Daucus carota sativus, the domesticated carrot, which was already mentioned in classical texts two millenia ago, has enlarged roots which can taste quite sweet. The domesticated carrot arose in the Near East, in the region between Afghanistan and Turkey. In its early form, it had dark purple roots that were often branched. Orange, carotene-colored forms developed later and are illustrated in a Byzantine herbal from 512 A.D. By the 17th century, the orange forms had replaced the purple ones in Europe and the Mediterranean. Carrots are eaten both raw and cooked and are used in both savory and sweet dishes. In Asia, they are often preserved in jams and syrups. (Sanderson 2005)

The cultivated carrot is believed to have originated in Afghanistan from forms with roots colored purple by anthocyanins (as well as yellow mutants lacking anthocyanins). These forms spread to the west and east, reaching Asia Minor around the 10th or 11th centuries, Arab-occupied Spain in the 12th century, continental northwestern Europe in the 14th century, England in the 15th century, China in the 14th century, and Japan in the 17th century. Before and during the 16th century, carrots in northwestern Europe were purple or yellow with long roots. The yellow roots were often preferred because they did not release anthocyanins during cooking. In the 17th century, carrots were developed in the Netherlands with denser orange carotene pigment and these were the progenitors of the modern cultivated carrot. Carrots are well known as an excellent source of provitamin A and contain around 7% sugar (glucose, fructose, sucrose) (the nutritional and health value and potential of carrots are reviewed by Arscott and Tanumihardjo 2010 and the influence of carrot genetic background on the content of various nutrients was studied by Nicolle et al. 2004; for additional information about the health benefits of different carrot pigments, see this page at the USDA Agricultural Research Service). The inflorescence is a terminal umbel (a broad, flat inflorescence) of small white flowers, with the umbel subtended by bracts. (Vaughan and Geissler 1997)

The domesticated carrot (Daucus carota sativus) is easily recognized by its highly pigmented, fleshy, edible, brittle roots. In wild carrots, fresh roots are flexible and fibrous (brittle and not fibrous in domesticated forms), the transition from shoot to storage organ is indistinct externally (the storage organ--the "carrot"--is abruptly expanded in domesticated forms), rosette foliage is often prostrate (usually conspicuously erect in domesticated forms), and umbels often have one or several purple central flowers (rarely in domesticated forms). Cultivated carrots with white roots are occasionally encountered, but relative to wild carrots these roots are palatable and brittle and are unbranched. Within the subspecies D. c. sativus, two varieties are sometimes recognized: The "Western Carrot" (variety sativus) and the "Eastern Carrot" (variety atrorubens). The Western Carrot may have orange, yellow, or white storage organs and is best characterized by yellowish-green highly dissected foliage (ultimate segments linear-lanceolate to linear, penultimate segments cleft more than two thirds toward the midrib) that mostly lacks pubescence (fewer than 50 hairs per square millimeter on either abaxial petiole or abaxial leaflets). The Western Carrot is grown around the world and with the exception of Asia is the main variety cultivated. The Eastern Carrot usually has purple and/or yellow storage organs. Occasionally, roots are reddish or yellowish-orange. The Eastern Carrot is characterized by grayish-green (glaucous) and only moderately dissected foliage (ultimate segments lanceolate to ovate, penultimate segments cleft less than two thirds toward the midrib) which is moderately pubescent (more than 50 hairs per square millimeter on either abaxial petiole or abaxial leaflets). The Eastern Carrot is common only in Asia, but it has been introduced elsewhere. Although one might expect the interesting colors of this variety to confer commercial value in Western markets at least as a novelty, the fact that the pigments are water soluble, like those of beets, seems to have limited its appeal in the West (but see Surles et al. 2004). Furthermore, these carrots may be more susceptible to decay. It is important to realize that this varietal taxonomy is somewhat artificial. For example, in Asia, where there has been considerable genetic mixing between these forms, plants with intermediate characteristics are commonly encountered. Some of these varietal hybrids have even found commercial success in the West. (IPGRI 1998)

As one of the most popular vegetables worldwide and the main source of dietary provitamin A, the cultivated carrot has increasingly become a focus for the development of genetically modified forms. Genetically modified (GM) carrots have already been developed that have antifungal activities, herbicide and salt tolerance, and increased nutritional benefits. (Rong et al. 2010 and references therein) They have even been used for the production of drugs (Luchakivskaya et al. 2011 and references therein). Although as of 2010, none of these GM varieties were yet in commercial production (Rong et al. 2010), commercial trials seem likely and with this in mind, Rong et al. used microsatellite marker analysis to explore the fine-scale genetic structure, mating, and gene dispersal in wild carrot. They found high rates of outcrossing and long-distance pollen dispersal among wild carrots, suggesting that the likelihood of transgene flow among carrot populations is high (previous work by other researchers has shown that cultivated and wild carrots interbreed freely). They note that if such transgenes have positive fitness effects on wild carrots, they could easily spread within and between wild populations via pollen dispersal. Magnussen and Hauser (2007), using AFLP markers, found genetic evidence of hybridization between cultivated and wild carrots in wild populations growing in proximity to carrot fields in Denmark. They also found evidence that continued hybridization and introgression has made wild populations close to carrot fields at least somewhat more similar genetically to cultivars than are wild populations farther away from carrot fields. Rong et al. suggest that the fitness of specific transgenes in F1 hybrids and subsequent backcrossing generations in wild carrot populations needs to be assessed to determine whether the risks of transgene introgression are indeed relatively high in carrot.

Clotault et al. (2010) studied the variation in genes incolved in the synthesis of carotenoids in carrots. They examined seven candidate genes involved in the carotenoid biosynthesis pathway in 48 individual plants, each one from a different carrot cultivar (cultivars were chosen to represent a wide range of root colors). Analysis of these genes, along with 17 putatively neutral microsatellite markers, showed moderate genetic differentiation between cultivars originating from the West and the East (no such structure had been evident in previous molecular genetic analyses using various types of markers) (Clotault et al. 2010 and references therein). The carrot is believed to originate in Afghanistan before the 900s, as this area is described as the primary center of greatest carrot diversity, with Turkey proposed as a secondary centre of origin. The first cultivated carrots had purple or yellow roots. Carrot cultivation spread to Spain in the 1100s via the Middle East and North Africa. In Europe, breeding efforts produced a wide variety of cultivars. White and orange-colored carrots were first described in Western Europe in the early 1600s. At the same time, the Asian carrot was developed from the Afghan type and a red type appeared in China and India around the 1700s. Carotenoid composition determines the white, yellow, orange or red root color in the carrot. (Clotault et al. 2010 and references therein)

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Distribution

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The domesticated carrot (D. carota sativus) is grown around the world. Wild carrot (D. carota carota), also known as Queen Anne’s lace, is native to temperate regions of Europe and western Asia, and has been introduced into America, New Zealand, Australia and Japan (Rong et al. 2010 and references therein).

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Risk Statement

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Umehara et al. (2005) showed that wild and cultivated carrots can produce vigorous hybrid offspring and developed genetic markers that could be useful in tracing introgression of genes from cultivated carrots into wild populations. Such introgression is of particular concern in considering the possible risks of genes inserted into cultivated varieties escaping into wild populations and creating "superweeds" or other problems.

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Uses

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Carrots and other vegetables can be used in ways most people have never even thought of, e.g., as musical instruments, as seen and heard here.

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Shapiro, Leo
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