Abstract
A linkage map of carrot (Daucus carota L.) was developed in order to study reproductive traits. The F2 mapping population derived from an initial cross between a yellow leaf (yel) chlorophyll mutant and a compressed lamina (cola) mutant with unique flower defects of the sporophytic parts of male and female organs. The genetic map has a total length of 781 cM and included 285 loci. The length of the nine linkage groups (LGs) ranged between 65 and 145 cM. All LGs have been anchored to the reference map. The objective of this study was the generation of a well-saturated linkage map of D. carota. Mapping of the cola-locus associated with flower development and fertility was successfully demonstrated. Two MADS-box genes (DcMADS3, DcMADS5) with prominent roles in flowering and reproduction as well as three additional genes (DcAOX2a, DcAOX2b, DcCHS2) with further importance for male reproduction were assigned to different loci that did not co-segregate with the cola-locus.
Highlights
Carrot is the second most economically valuable vegetable in the European Union and is of worldwide significance
The phenotype class II is highly similar to the wildtype, but the chlorophyll biosynthesis is dramatically delayed resulting in yellowish leaves
We have identified sequence polymorphisms for DcMADS3 and DcMADS5 as well as DcAOX2a, DcAOX2b, and DcCHS2 (Table 1) and mapped them to search for co-localization with the COLA-gene
Summary
Carrot is the second most economically valuable vegetable in the European Union and is of worldwide significance. Daucus carota is a typical biannual diploid (2n = 2x = 18) outcrossing species with a relatively small genome estimated as 473 Mb. Carrot chromosomes are small but morphologically distinguishable (Schrader et al, 2003). To facilitate genetic characterization by improved mapping studies, several tools have been made available in recent years. This includes a deep coverage BAC library (Cavagnaro et al, 2009), assignment of linkage groups (LGs) to chromosomes by fluorescence in situ hybridization (Iovene et al, 2011) and de novo assembly of the carrot transcriptome (Iorizzo et al, 2011) and opens advanced perspectives for carrot research and breeding
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