• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.2
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• pp.89-101
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• 2019

The variation of content of 12 soybean seed isoflavone components was determined in the aglycone, glucoside, malonylglucoside and acetylglucoside groups of 44 Korean soybean cultivars grown in 2016 as well as in 2017. The total isoflavone content of the 44 cultivars averaged at $2935.4{\mu}g/g$ and was in the range of 950.6 to $5226.3{\mu}g/g$ for two years. Malonylglucoside group averaged at $2437.2{\mu}g/g$ with the highest proportion of isoflavone composition (83.0%). Significant differences were observed between cultivars, years and their interactions for both the total isoflavone and each composition group contents (P < 0.0001); however, no year-wise differences were observed for daidzein and genistin. The broad-sense heritability ($h^2$) within the set of 44 Korean soybean cultivars was as high as 0.93 for the total isoflavone content and was in the range of 0.8-0.92 for each composition group of isoflavone except for acetylglucoside. The total isoflavone content in cultivar group for soy-sprout was higher ($3850.4{\mu}g/g$) than that for the other cultivar groups of soy-paste and tofu ($3082.8{\mu}g/g$), black or green soybean cooked with rice ($2345.8{\mu}g/g$), and early maturity group ($1298.6{\mu}g/g$). The total isoflavone content of 'Sowonkong', a soybean cultivar for soy-sprout, was the highest ($5226.3{\mu}g/g$). In the cultivar group for soy-paste and tofu, the average isoflavone contents of 'Daepung', 'Daepung2ho', 'Saegeum', 'Uram', and 'Jinpung' were higher than $4000{\mu}g/g$. With the exception of small seeded cultivars with low isoflavone contents such as 'Sohwang' and 'Socheongja', the seed size and total isoflavone content were significantly negatively correlated in 2016 and 2017, respectively ($r=-0.47^{**}$ and $-0.49^{**}$). The number of days of growth from flowering to maturity did not affect the variations observed in isoflavone content.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.3
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• pp.239-247
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• 2018

Soybean produces three major types of isoflavones, daidzein, genistein, and glycitein aglycones and their glucosides and malonylglucosides. It has been known that malonylated glucosides are rapidly converted to their corresponding aglycones due to the unstable thermolabile glucoside malonates; therefore, the analytical study of malonylated glucosides has been insufficient. In this study, we analyzed the malonylglucoside content in soybean seeds. Isoflavone analysis of three soybean cultivars revealed that 81.5~90.0% of the total isoflavones were malonylglucosides, whereas aglycones were rarely detected. Moreover, the total isoflavone content increased during a 5-day germination period where growth regulators and coumaric acid treatments tended to yield higher isoflavone content than the normal germination treatment, however the differences were not significant; notably, the isoflavone accumulation trend continued with additional germination days. The content of malonylglucoside was higher than that of other isoflavones, which was 83.7~86.6% of the total isoflavone content in seeds with a 3-day germination period. Furthermore, isoflavones were significantly accumulated in the hypocotyl of seedlings with a 5-day germination period. The content of isoflavone in the hypocotyl of the Pungsannamul-kong was 10,240 ug/g when treated with coumaric acid, which was considerably higher than that of other cultivars and treatments. Additionally, soybean seeds heated at $60^{\circ}C$ for 1 hour produced higher isoflavone content than non-heated soybean seeds. Our results show that it is possible to increase the isoflavone content in soybean seeds through various treatments.