Morphological and Biochemical Variation in Carrot Genetic Resources Grown under Open Field Conditions: The Selection of Functional Genotypes for a Breeding Program

Carrot (Daucus carota), one of the most economically important root vegetables, shows a wide range of morphological and biochemical diversity. However, there is a lack of simultaneous systematic study regarding the biochemical composition and morphological characteristics in carrot genetic resources, which is crucial for crop improvement. For this reason, the morphological characteristics, carotenoids, and free sugar content of 180 carrot genetic resources grown in open field conditions from March to June 2020 were accessed to select the lines for a potential breeding program. Altogether, 15 qualitative and 4 quantitative agronomical characteristics were evaluated and grouped into four categories based on root color (orange, yellow, white, and purple). Three carotenoids (lutein, α-carotene, and β-carotene) and three free sugars (fructose, glucose, and sucrose) were also analyzed. The results revealed wide genetic variation in both qualitative and quantitative traits. Most of the genetic resources were orange (n = 142), followed by white (n = 16), yellow (n = 14), and purple (n = 8). Carotenoid profile and content were highly dependent on root color and showed wide genetic variability, while sugar content and profile were independent of the root color. Alpha- and β- carotene were the major carotenoids in orange carrots representing 43.3 and 41.0% of total carotenoids. In contrast, lutein was most dominant in other colored carrots (79.7–98.6% of total carotenoids). In most of the genetic resources, sucrose was the most dominant free sugar, followed by glucose and fructose. The results of this study showed that some genetic resources elevated carotenoid and sugar content. The morphological and biochemical diversity observed in this study might be useful for improving the agronomic traits and biochemical content of carrot lines for breeding programs.