Genetic Structure and Domestication of Carrot

Human manipulation of wild progenitors during crop domestication has led to the foundation of modern agriculture ( Zohary and Hopf, 2000 ; Glémin and Bataillon, 2009 ). A common suite of traits including loss of seed shattering, dormancy, and branching are often selected during the domestication process and referred to as the “domestication syndrome” ( Zohary and Hopf, 2000 ). After primary traits have been selected and fi xed, the process of domestication often has directed more attention to quality traits such as color, shape, and fl avor, and physiological traits contributing to uniformity ( Doebley et al., 2006 ). Studies analyzing the genetic structure of wild and cultivated crops, in combination with archeological and historical evidence, have provided insight into the geographic and temporal details of domestication to reveal where, when, and how many times a crop was domesticated ( Meyer et al., 2012 ). To date, the majority of domestication studies has focused on staple food crops with little attention toward root vegetables ( Meyer et al., 2012 ). Cultivated carrot ( Daucus carota L. subsp. sativus L.) is a common vegetable with a well-known and widely distributed weedy progenitor, wild carrot or Queen Anne’s lace ( D. carota subsp. carota ). Carrot is the most widely grown crop of the family Apiaceae (Umbelliferae), cultivated on 1.2 M hectares globally (carrot and turnip as aggregate data) ( FAO, 2011 ), of which 34 000 hectares of carrots are produced in US with an estimated annual crop value of $758 M ( USDA, National Agricultural Statistics Service, 2011 ). Wild carrot occurs widely across temperate regions of the globe. The time frame and geographic region(s) of the fi rst cultivation of carrots are unclear. Vavilov (1992 , pp. 337–340) identifi ed Asia Minor (eastern Turkey) and the inner Asiatic regions as the centers of origin of cultivated carrot and noted Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan, Uzbekistan) as being “the basic center of Asiatic kinds of cultivated carrots” where “wild carrots ... practically invited themselves to be cultivated”. As observed by the presence of carrot seed at prehistoric human habitations 4000 to 5000 yr 1 Manuscript received 8 February 2013; revision accepted 26 March 2013. The authors thank the California Fresh Carrot Marketing Board and the Bejo, Nunhems, Rijk Zwaan, Takii, and Vilmorin seed companies for fi nancial support. D.G. was supported by the Polish National Science Center, project no. N N302 062236 from 2009–2011. 9 Author for correspondence: (e-mail: [email protected])