Isoflavone contents in soybean seeds are affected by both genetic and environmental factors. Correlation analysis between these factors and isoflavone contents are considered as valuable inputs when breeding improved soybean cultivars. In this study, the seeds of 49 soybean accessions grown in Korea were grouped as black, yellow, green, yellowish-green, pale yellow, and green with a black spot based on their seed coat colors. The contents of 12 isoflavones were analyzed and the association between isoflavone content and seed coat color was determined. The accessions were also grouped as early, intermediate, and late-maturing based on their days to maturity. Out of the 12 isoflavones, 11 were found in 2 accessions, 9 in 18 accessions, 8 in 11 accessions, 7 in another 11 accessions, and 6 in 7 accessions. The total isoflavone content (TIC) in black, yellow, green, yellowish-green, pale yellow, and green with black spot soybeans was in the ranges 2.110 ~ 5.777, 2.487 ~ 4.733, 2.185 ~ 4.413, 2.681 ~ 4.065, 1.827 ~ 4.085, and 3.376 ~ 4.133 ㎎/g, respectively. The average TIC was highest in green with black spot soybeans (3.616 ㎎/g), and lowest in pale yellow soybeans (2.875 ㎎/g). Besides, the average TIC was lowest in early maturing accessions compared to late- and intermediate-maturing accessions. TIC was strongly correlated to malonylgenistin (r = 0.91) and malonyldaidzin (r = 0.78) contents, and poorly correlated to glycitein (r = 0.04) and malonylglycitin (r = 0.18) contents. Also, days to maturity showed strong correlation with malonylgenistin (r = 0.47) content and TIC (r = 0.38). The principal component analysis outlined accessions with high TIC and diverse isoflavones along the first and second components, respectively. The results of the present study depicted that green soybeans with a black spot could be sources of high TIC. Furthermore, late-maturing accessions with diverse isoflavones in their seeds could be useful in future agricultural systems in Korea.

Abstract
Introduction
Materials and Methods
    Chemicals and reagents
    Plant materials
    Extraction of isoflavones
    Identification and quantification of isoflavones
    Statistical analysis
Results and Discussion
    Plant properties and seed characters
    Identification of isoflavones
    Quantification of isoflavones
    Comparison of isoflavone contents and seed coat colors
    Comparison of isoflavone contents and days to maturity(DtM)
    Principal component and correlation analysis
References

• Yu-Mi Choi(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Hyemyeong Yoon(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Sukyeung Lee(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Ho-Cheol Ko(Rural Development Administration)
• Myoung-Jae Shin(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Myung-Chul Lee(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Sejong Oh(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration)
• Kebede Taye Desta(National Agrobiodiversity Center, National Institute of Agricultural Sciences, Rural Development Administration/Department of Applied Chemistry, Adama Science and Technology University) Corresponding author