Chinese cabbage (Brassica rapa ssp. pekinensis) is one of the most important vegetables and widely cultivated in Asia countries including Korea and China. Recently, whole genome sequence and full-length cDNA information of this species became available, which are encouraging genetic studies of this species to characterize agricultural important traits. Orange-colored (Or) cultivar of Chinese cabbage has inner leaves in orange, whereas other cultivars generally cultivated have yellow (Ye)- or white-colored inner leaves. In this study, we investigated phenotypes and carotenoid biosynthesis genes related to color variation in the Or cultivar. Firstly we compared the carotenoid content and composition between the Or and Ye cultivars by HPLC analysis. The inner leaves of Or cultivar contained approximately 9-fold high β-carotene content, whereas content of both lutein and violaxanthin was decreased to less than 30%, compared to Ye cultivar. Or cultivar was segregated with ratio of 3:1 in F2 population derived from crossing between Or and Ye inbred lines, indicating that Or phenotype is controlled by single recessive gene. To identify this gene, we investigated the expression of several genes involved in carotenoid biosynthesis by RT-PCR analysis. Among genes tested, two encoding putative carotenoid isomerase (CRTISO) and phytoene desaturase (PDS) were identified to show different expression between Or and Ye cultivars. Through further analysis of genomic DNA regions of these two genes, we could expect that several mutations such as InDel and base-substitution occurred and then affected expression of these genes in Or cultivar. In this presentation, I will introduce more detailed results for Or cultivars.

Beta-carotene producing transformants were produced in the background of 'Nagdongbyeo', a Japonica rice cultivar. Introgression of the carotenoid locus in the transformant, PAC4-2 into the elite cultivar 'Ilpumbyeo' was started. To initiate a backcrossing program, we surveyed 220 SSR markers and found that 38% of them were polymorphic between 'Ilpumbyeo' as a recurrent parent and the PAC4-2 as a recipient parent. The selection strategy comprising foreground and background selection was employed. First, foreground selection was practiced in BC1, BC2, and BC3 generations using the transgene specific PCR-based marker in addition to visual scoring of the seed color. Marker-based background selection combined with phenotypic selection was employed from BC3F2 to BC3F4 generations. Blast search indicated that the transgene PAC4-2 was located between SSR markers, RM6 and RM482. 240 BC3F3 and 63 BC3F4 lines were evaluated for four agronomic traits including days to heading. Most of the lines were similar to Ilpumbyeo in agronomic traits evaluated. The percentage of PAC4-2 genome ranged from 4% to 21% with a mean of 12.5%, which was higher than the expected for an unselected BC3 backcross population. This could be explained by the fact that two genes for beta-carotene and the stripe virus resistance were targeted in this study. We selected 10 representative BC3F5 lines from 63 BC3F4 lines based on agronomic traits and carotenoids content. The selection strategy would be appropriate for the introgression of beta-carotene gene in a breeding program.