Impact de la variation nucléotidique de gènes de la voie de biosynthèse des caroténoïdes sur leur accumulation dans la racine de carotte cultivée

Abstract

Impact of nucleotide variation in carotenoids biosynthesis genes on their accumulation in the cultivated carrot root Due to the carotenoid content, carrot, Daucus carota L., exhibits a great nutritional value and root color variability, obtained by anthropic selection. Still partially known, the genetic determinism of carotenoid content is an important issue for breeding to market segmentation. This work focuses on the identification of genetic factors involved in the root carotenoids accumulation, related with color. An association mapping approach was used to link candidate gene polymorphisms, mostly located in the carotenoid biosynthetic pathway, and carotenoid content and root color variations. The study resolution has been previously evaluated by measuring the extent of linkage disequilibrium. The genetic resources structuration of the species was studied to evaluate the risk of false positives detection when testing for associations. This study was conducted on two populations, a structured panel of lines and an unstructured population. The results highlight the key role of anabolism and catabolism genes in the overall accumulation of carotenoids. In particular, the zeaxanthin epoxidase gene was associated with the β­carotene and total carotenoids content, and may be involved in the yellow or orange color and is probably the underlying gene of the locus Y2. More specifically, lycopene β­cyclases and carotene hydroxylase could be responsible for the accumulation of lycopene and α­carotene, respectively. These results show the complementarity of the populations used to improve the detection of potential associations. Biosynthetic pathway functioning schemes leading to different types of colored carrot are proposed