Abstract
Soybean is rich in various functional components such as isoflavones, saponins, tocopherols and sterols that are beneficial to human health. However, the contents of some of these components such as α-tocopherol (α-Toc) and lutein are relatively low in the seeds. Therefore, genetic manipulation to enhance the α-Toc and lutein contents is an important breeding objective in soybean. Recently, we have successfully identified soybean varieties and wild strains with high α-Toc and lutein contents, respectively. In the present investigation, we made a cross between a soybean variety with a high α-Toc content thereafter referred to as a high α-Toc soybean variety, Keszthelyi A.S. (female parent), and a wild soybean strain with a high lutein content thereafter referred to as a high lutein wild soybean strain, B09092 (pollen parent). We analyzed the α-Toc and lutein contents of the F2 seed and F2-plant (F3 seeds) populations by a single-pass method for extraction and quantification, using high performance liquid chromatography (HPLC). The α-Toc content of the F2 seeds ranged from 1.0 to 6.0 mg/100 g meal, whereas that of the high α-Toc parent, var. Keszthelyi A.S. varied from 4.27 to 6.43 mg/100 g meal, and that of the wild soybean parent, B09092 ranged from 1.74 to 2.30 mg/100 g meal. The lutein content of the F2 seeds ranged from 0.1 to 4.0 mg/100 g meal, while that of the var. Keszthelyi A.S. from 0.19 to 0.42 mg/100 g meal, and that of the high lutein parent, B09092 from 2.48 to 3.50 mg/100 g meal. Broad-sense heritability for the α-Toc and lutein contents in the F2 seeds was estimated to be 0.598 and 0.656, respectively. In the F2-plants (F3 seeds), the broad-sense heritabilities were 0.693 for the α-Toc content and 0.824 for the lutein content, respectively. The heritabilities in a narrow sense for the α-Toc and lutein contents in the F2 seeds were 0.598 and 0.413, respectively. In the F2-plants (F3 seeds), the estimates were 0.693 and 0.718, respectively. The results suggested that both high α-Toc and lutein contents are highly heritable. A significant positive correlation was observed between the α-Toc and lutein contents both in the F2 seeds (r = 0.420, P < 0.01) and in the F2-plants (F3 seeds) (r = 0.228, P < 0.01). In addition, a significant positive genetic correlation was observed between the α-Toc and lutein traits in the F2-plants (F3 seeds) (rG = 0.311, P < 0.01). No correlation was observed between the 100-kernel weight and lutein content in the F2-plants (F3 seeds). Likewise no correlation was obtained between the 100-kernel weight and α-Toc content. These results indicate that it is possible to simultaneously select individuals among the progenies with high contents of lutein and α-Toc without decreasing the kernel weight of the seeds.
