ABSTRACT
With the advent of plant transformation technology, metabolic engineering for oilseed fatty acids has become possible, and the transgenic plant oils represent some of the fi rst successes in design of modifi ed plant products. Directed gene down-regulation strategies enabled the specifi c tailoring of common fatty acids in several oilseed crops. In addition, transfer of novel fatty acid biosynthetic genes from noncommercial plants has allowed production of novel oil compositions in oilseed crops. These and future endeavors aim to produce seeds higher in oil content as well as containing new oils that are more stable, healthier for humans, and also that can serve as a renewable source of industrial commodities. Large-scale new industrial uses of engineered plant oils are on the horizon but will require a better understanding of factors that limit the accumulation of unusual fatty acid structures in seeds. Yellow seed coat color is one of the most important traits of Brassica napus. Effi cient selection of the yellow-seed trait is one of the most important objectives in oilseed rape breeding, improving the oilseed quality characteristics of lower fi ber content and higher protein and oil contents. Two recombinant inbred line (RIL) populations (RIL-1 and RIL-2) were analyzed for two years at two locations (Fu et al., 2007). Four hundred and twenty SSR, RAPD, and SRAP marker loci covering 1744 cM were mapped in 26 linkage groups of RIL-1, while 265 loci covering 1135 cM were mapped in 20 linkage groups of RIL-2. A total of 19 QTLs were
detected in the two populations. A major QTL was detected adjacent to the same marker (EM11ME20/200) in both maps in both years. This major QTL could explain 53.71, 39.34, 42.42, 30.18, 24.86, and 15.08 percent of phenotypic variation in six combinations (location × year × population). BLASTn analysis of sequences of the markers fl anking the major QTL revealed that the homologous region corresponding to this major QTL is anchored between genes At5g4440 and At5g49640 of Arabidopsis thaliana chromosome 5 (AtC5). Based on the comparative genomic analysis, the bifunctional gene TT10 is nearest to the homologoue of EM11ME20/200 on AtC5 and can be considered an important candidate gene for the major QTL identifi ed here. Besides providing an effective strategy for markerassisted selection of the yellow-seed trait in B. napus, the results also provide important clues for cloning of the candidate gene corresponding to this major QTL. With the black-seeded ‘Youyan 2’ as male and the yellow-seeded GH06 as female parents, respectively, F2 population of 132 individuals was obtained (Liu et al., 2006). A linkage map was constructed with 164 markers including 125 AFLP, 37 SSR, 1 RAPD and 1 SCAR markers distributed over 19 linkage groups covering approximately 2,549.8 cM with an average spacing of 15.55 cM. Two loci located on the 5th and 19th groups were detected for the trait of seed coat color based on the linkage group using multiple interval mapping method and explained 46% and 30.9% of the phenotypic variation, respectively.
