In this study, composition and agronomic traits, including yield-related traits, were investigated and compared among 35 Korean landrace germplasm for two years (2019 and 2020). The contents of 12 isoflavones were measured using high-performance liquid chromatography, and agronomic trait data were collected according to the Rural Development Administration criteria. Comparing isoflavone composition between the two years, all isoflavones, except glycitein, were generally higher in 2019. The values of yield-related and major agronomic traits decreased in most accessions in 2020. ANOVA showed highly significant differences (p<0.001) in genotypes, years, and genotype-by-year interaction for all isoflavones, the number of pods per plant, and 100-seed weight. The number of seeds per pod, days to flowering, and days to maturity also showed significant differences among genotypes, as well as between the two years. Correlation analysis revealed that daidzin and genistin were positively correlated with their malonylated form. Malonyl daidzin was also positively correlated with malonyl genistin levels. The accessions with the least variation in the total isoflavone content were IT 153844 (907.5 µg/g, 898.6 µg/g) and IT 252252 (663.2 µg/g, 636.4 µg/g). Some of the evaluated landraces will be a promising genetic source for developing soybean varieties with high levels of environmental stability in isoflavone content and agronomic traits.

In this study, we analyzed the growth characteristics and isoflavone content of 43 soybean varieties highly adaptable to highland areas. The flowering period of each cultivation zone was from July 15 to August 12 at Daewallyeong, from July 18 to August 11 at Jinbu, and from July 23 to August 13 at Gangneung. The accumulated temperature from flowering to maturity was 1,297 °C for Daegwallyeong, 1,391 °C for Jinbu, and 1,685 °C for Gangneung. Forty-three varieties were classified into four utilities; soy sauce and tofu, bean sprouts, cooking with rice, and vegetable and early maturity. The content of isoflavone was highest at 2,579 µg/g in varieties for soy sauce and tofu usage. Five varieties (“Paldalkong,” “Sinpaldal2,” “Ilmikong,” “Sinpaldalkong,” and “Daepung”) cultivated in Daegwallyeong had over 4,000 µg/g of isoflavone. The isoflavone content of the region Daegwallyeong was different at the significance level of 0.1 (p=0.061) compared to Gangneung. There was no significant difference between Gangneung and Jinbu. It is thought that the low temperature of the maturation stage during the growing period affected isoflavone accumulation. The varieties with more than 3,000 µg/g of isoflavone content in Daegwallyeong, Jindu, and Gangneung were “L29,” “Williams82,” “Ilmikong,” and “Daepung.” These were genetically and environmentally stable in isoflavone content. It is expected that this study will be used as basic data for the functional breeding and selection of soybean varieties highly adaptable to a specific region, and to help expand soybean cultivation areas in highlands.

This study was carried out to investigate the variation of 12 isoflavone components among 172 Korean soybean varieties released from 1913 to 2013. Cluster analysis was performed to classify the varieties based on the variation of isoflavone contents. Total isoflavone contents ranged from 206.3 μg/g to 2666.2 μg/g with an average of 837.2 μg/g. By each component, malonylgenistin content ranged from 99.2 μg/g to 1149.1 μg/g with the highest average of 390.0 μg/g, and glycitein content ranged from 0.1 μg/g to 2.4 μg/g with the lowest average of 0.8 μg/g. Among composition groups, the aglycone group contents ranged from 2.2 μg/g to 33.1 μg/g with the lowest average of 10.0 μg/g, and glucoside group contents ranged from 36.9 μg/g to 801.8 μg/g with an average of 202.4 μg/g. The malonylglucoside group contents ranged from 143.6 μg/g to 1796.4 μg/g with the highest average of 599.1 μg/g and acetylglucoside group contents ranged from 3.7 μg/g to 103.9 μg/g with an average of 27.5 μg/g. Varieties with high total isoflavone content were Aga8(2666.2 μg/g), Aga4(2569.3 μg/g), and Aga9(2345.0 μg/g) in bean sprouts group. The low total isoflavone content were observed from Deawang(328.8 μg/g) in soy sauce and paste group, Hanol(599.3 μg/g) in vegetable and early maturity group and Gemjeong1(664.1 μg/g) in cooking with rice group. The first three principal component axises accounted for 89.14% of the total variation observed. Dendrogram constructed using average linkage cluster method revealed that 172 Korean soybean varieties were divided into seven groups with the average distance of 0.8 between groups. The group Ⅰ includes 57.6% of the total varieties, which was the largest group among seven groups, followed by the group Ⅱ that includes 35.5% of the total varieties. However, the other groups were small groups containing less than five varieties. In comparison among the total isoflavone contents according to groups, the highest isoflavone content was observed in group Ⅵ with an average of 2526.9 μg/g, followed by group Ⅳ(1546.6 μg/g) and group Ⅴ(1503.5 μg/g). The others were found to contain low isoflavone content.