Abstract
Cultivated carrot is thought to have been domesticated from a wild species, and various phenotypes developed through human domestication and selection over the past several centuries. Little is known about the genomic contribution of wild species to the phenotypes of present-day cultivars, although several studies have focused on identifying genetic loci that contribute to the morphology of storage roots. A backcross inbred line (BIL) population derived from a cross between the wild species Daucus carota ssp. carota “Songzi” and the orange cultivar “Amsterdam forcing” was developed. The morphological features in the BIL population became more diverse after several generations of selfing BC2F1 plants. Only few lines retained features of wild parent. Genomic resequencing of the two parental lines and the BILs resulted in 3,223,651 single nucleotide polymorphisms (SNPs), and 13,445 bin markers were generated using a sliding window approach. We constructed a genetic map with 2027 bins containing 154,776 SNPs; the total genetic distance was 1436.43 cM and the average interval between the bins was 0.71 cm. Five stable QTLs related to root length, root shoulder width, dry material content of root, and ratio of root shoulder width to root middle width were consistently detected on chromosome 2 in both years and explained 23.4–66.9% of the phenotypic variance. The effects of introgressed genomic segments from the wild species on the storage root are reported and will enable the identification of functional genes that control root morphological traits in carrot.
Highlights
Wild carrot (Daucus carota L. ssp. carota) is a widespread weedy species that is distributed in Europe, Southwest and Central Asia, North Africa, North and South America [1,2], and found from Afghanistan to the Mediterranean area [3]
Some morphological traits of the F1 hybrid such as leaf number, white root, conical shape, deep lateral root scars, rough skin, and annual growth habit were clearly inherited from the wild species (Ws) parent [34], but other traits showed obvious heterosis, such as maximum leaf length (MLL) and root length (RL) (Figure 1A,D)
The cultivated carrots differ in many morphological characters compared to the wild species, including increased size and variation in root shape, loss of lateral root branching, increased carotenoid and anthocyanin contents, and a biennial growth habit [42]
Summary
Wild carrot (Daucus carota L. ssp. carota) is a widespread weedy species that is distributed in Europe, Southwest and Central Asia, North Africa, North and South America [1,2], and found from Afghanistan to the Mediterranean area [3]. Sativus) can be regarded as early ancestral types from approximately 1100 years ago [4,5], the red or purple-red cultivars are recorded from about 440 years ago [6], and orange cultivars are not reliably reported until the sixteenth century in Europe [7]. Recent molecular evidence suggested that wild species have made significant contributions to carrot evolution and domestication [4,5,6,8,9,10]. An open question is to what extent the genome segments originating from wild carrot species affect phenotypes in the cultivars. Little is known about the roles that wild species have played in the domestication of carrot
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