The influence of the Or and Carotene Hydroxylase genes on carotenoid accumulation in orange carrots [Daucus carota (L.)].

The Or and CH genes are necessary for the accumulation of high amounts of β-carotene and other carotenoid pigments in carrot roots, in addition to the Y and Y genes. Carrot taproot color results from the accumulation of various carotenoid and anthocyanin pigments. Recently, the Or gene was identified as a candidate gene associated with the accumulation of β-carotene and other provitamin A carotenoids in roots. The specific molecular mechanisms involved with this process, as well as the interactions between Or and the other genes involved in this process are not well understood. In order to better characterize the effect that Or alleles have on conditioning the accumulation of carotenoids in roots, we analyzed an F family fixed homozygous recessive for y and y, derived from a cross between an orange carrot and a white wild carrot, segregating for the two known Or alleles, which we name Or and Or. QTL mapping across three different environments revealed that the accumulation of several carotenoids was associated with the Or allele, with consistent patterns across environments. A second QTL on chromosome 7, harboring a carotene hydroxylase gene homologous to Lut5 in Arabidopsis, was also associated with the accumulation of several carotenoids. Two alleles for this gene, which we name CH and CH, were discovered to be segregating in this population. Our study provides further evidence that Or and CH are likely involved with controlling the accumulation of β-carotene and may be involved with modulating carotenoid flux in carrot, demonstrating that both were important domestication genes in carrot.