Orange Is the New Yellow: Cracking the Genetic Code Controlling Beta-Carotene Accumulation in Carrot

In the human body, provitamin A carotenoids are converted into vitamin A, which is critical for maintaining healthy vision, immune response, and cellular communication and differentiation. Orange carrots (Daucus carota L.) are one of the most concentrated naturally occurring vegetable sources of provitamin A carotenoids, particularly rich in beta-carotene. Despite high concentrations of beta-carotene in carrot, little is known regarding the genetic regulation of this trait. Here we present our work utilizing Genotyping-by-Sequencing and HPLC to map beta-carotene accumulation, in an F4 mapping population. A localized region on the distal arm of Chromosome 7 (~1Mb) was found to be significantly associated with beta-carotene. To further narrow the list of candidate genes within this region we conducted an RNA-Sequencing experiment using orange and yellow pigmented roots. Within the genomic area of interest, 14 genes were found to be differentially expressed. Co-dominant markers have been created for several candidate genes and are being applied in the breeding program to screen germplasm for beta-carotene accumulation. Fine-mapping using advanced generation mapping populations and an association panel is currently underway to further characterize the genetic regulation of beta-carotene accumulation in carrot.