Korean Soybean Research Articles

Effect of different planting times on the quantitative variation of total seed isoflavone content and composition in Korean soybean cultivars (Glycine max (L.) Merr.)

There is great interest in the enhancement of isoflavones as one of the functional ingredients in soybean. This study aimed to investigate the effects of changes in the ecological environment over different planting times on isoflavone content. A total of 28 Korean soybean cultivars were grown at different planting times in late May, mid-June, and early July and their isoflavone content was measured over 2 years (2017 and 2018). Analyses of variance revealed significant effects of genotypes, planting times, years, and their interactions on isoflavone content. The average content of total isoflavone, as well as its component groups of malonylglucoside and aglycon, increased significantly as the seed planting time was delayed from late May to early July. The accumulation of each isoflavone component varied with changes in the planting time. The isoflavone content of the soybean cultivars for soy-sprout and soy-paste and tofu were higher for plantings in early July than for those in late May and/or mid-June, except for the black soybean cultivars. Despite significant correlations of the isoflavone content of the 28 cultivars among the three planting times, the responses of individual cultivars varied in isoflavone content by planting time. When planting was delayed, the time to flowering and maturity was also delayed and the number of days of growth from planting or flowering to maturity decreased; however, this was not related to isoflavone content. When planting was delayed, the temperature during the ripening period from flowering to maturity was lower, which was inversely related to the isoflavone content.

Questionnaire Survey of the Methods Used in Household Doenjang Production in Korea

This study examined the methods used in household doenjang (Korean soybean paste) production. Nine hundred fortythree responses were obtained using a nationwide, questionnaire-based survey (2018-2019) with non-probabilistic snowballing sampling. Consistent with previous studies, the respondents were primarily over the age of 50 years (97.1%) and female (97.9%). In addition to soybeans, the most used ingredients were red pepper (85.8%) and charcoal (85.5%), which most respondents obtained through direct farming (50.4-59.9%). Seasonal production occurred later in the higher latitude regions (Gyeonggi-do, Gangwon-do, Chungcheong-do) (p < 0.01), which have lower average temperatures, and the fermentation period was shorter in the lower latitude regions (Jeolla-do, Gyeongsang-do, Jeju-do) (p < 0.01), which have higher average temperatures. There were no significant regional differences in the season when doenjang was made, with most production occurring during January and February (81.1%). Most respondents (71.3%) made doenjang using homemade meju (soybean block used as a starter) in a traditional way to allow the microorganisms to be naturally inoculated. These results could be used as a basis for future research on topics such as starter development, standardized production, and safety of household doenjang.

Family structure of F5 soybeans lines derived from soybean varieties with the main differences on seed size and maturity traits

Abstract. Kuswantoro H, Artari R, Iswanto R, Imani H. 2020. Family structure of F5 soybeans lines derived from soybean varieties with the main differences in seed size and maturity traits. Biodiversitas 21: 2576-2585. The success of breeding programs depends on the availability of genetic resources with high genetic diversity. Genetic diversity plays a role in relationship between genotypes or within a group of genotypes. Seed size and the days to maturity are the main traits to develop a new superior variety for better seed quality and quantity. The plant materials consisted of eight F5 families originating from a combination of crossbreeding between four Korean soybean varieties (Daehwang, Daemang, Daewon, and Songhak) and two Indonesian soybean varieties (Argomulyo and Lawit). The main traits of four Korean soybean varieties are similar to each other, i.e. large seed size and early maturity. The two Indonesian soybean varieties differ on seed size and maturity. Argomulyo has a large seed size and early maturity, while Lawit has a small seed size and late maturity. Agronomic data, such as days to 50% flowering, days to maturity, days to harvesting, plant height, number of branches, number of reproductive nodes, number of filled pods, number of unfilled pods, seed yield per plant, 100 seeds weight, and seed yield per plot, were analyzed using R programs to form the groups. The grouping was based on principal component analysis. The results showed that the family structure of a cross was determined by the characteristics of the crossed genotypes. The family structures with Argomulyo as male parents were more influenced by 100 seeds weight, while the family structures with Lawit as male parents were more influenced by days to maturity. No family structure was formed with a large seed size on crossing with Lawit as the male parent. In this population, high seed yield as the main target of plant breeding was obtained on crossing of Daemang with Lawit.

Variability of Phytochemicals by Breeding Year, Usage and Seed Size of Korean Soybean (Glycine max (L.) Merrill) Varieties

The interest in phytochemicals from crops has grown in recent years, with soybean, as a functional crop, having great potential for providing a high level of nutrition. Therefore, the aim of this study was to evaluate phytochemicals from Korean soybean varieties, and to provide the basic information necessary for targeted breeding of soybean. The seeds of 172 soybean varieties were collected from various domestic institutes, and their phytochemicals were analyzed and compared based on agronomic characteristics (color, size, usage, etc.) using cluster analysis. We found that the soybean varieties contained relatively higher levels of the following phytochemicals: lutein (3 var., &gt;7.0 μg g−1 seed), tocopherols (26 var., &gt;300 μg g−1 seed), and phytosterols (33 var., &gt;1000 μg g−1 seed). Overall, phytochemical levels were higher in varieties released since 2000 and with small-sized seeds (&lt;12 g, 100-seed weight). The distribution of phytochemicals varied according to the usage (cooking, sauce, sprouts, etc.), even though the highest levels of each phytochemical were mainly observed in sprouts. The cluster analysis using three main components classified the varieties into five groups. Of them, group III showed relatively higher tocopherols, group IV had relatively higher lutein, and group I had relatively higher phytosterols. Jonam and Manpoong (group I) were observed in varieties high in phytochemicals. Overall, some Korean soybean varieties were found to have relatively higher levels of phytochemicals compared to those reported in previous studies of other origins. In conclusion, our findings suggest that some varieties might provide suitable breeding material for target-centered improvement of soybean varieties, and a comparison between different origins is necessary for providing better knowledge for soybean breeding.

Genetic Diversity Patterns and Discrimination of 172 Korean Soybean (Glycine max (L.) Merrill) Varieties Based on SSR Analysis

The soybean development goal in Korea has changed over time, but the pattern of genetic diversity in modern varieties has not yet been well characterized. In this study, 20 simple sequence repeat (SSR) markers are shown to generate a total of 344 alleles, where the number of alleles ranges from 7 to 29, with an average of 17.2 per locus, and the polymorphism informative content (PIC) values range from 0.6799 to 0.9318, with an average of 0.8675. Five different clusters are classified using the unweighted pair group mean arithmetic (UPGMA) method. The genetic distance between clusters I and V (0.3382) is the farthest, and that between clusters III and IV (0.0819) is the closest. The genetic distance between all pairings of groups, according to the time period of their release, is lowest (0.1909) between varieties developed in the 1990s and those from 2000 onward, and highest (0.5731) between varieties developed in the 1980s and those from 2000 onward. Model-based structure analysis revealed the presence of three sub-populations and 17 admixtures in the Korean soybean varieties. All 172 Korean soybean varieties were tested for discrimination using six SSR markers. The numbers of varieties that were clustered in each step are as follows: 7 (4.1%) in step 1 (Sat_076), 73 (42.4%) in step 2 (Sat_417), 69 (40.1%) in step 3 (Sat_043), 13 (7.6%) in step 4 (Satt197), 8 (4.6%) in step 5 (Satt434), and 2 (1.2%) in step 6 (Satt179). These results, based on the analysis of genetic resources, can contribute to the creation of a core collection for soybean conservation and breeding, as well as to the development of future varieties with useful traits.

Quality Characteristics of Tofu Made from Korean Soybean Cultivars

Quality Characteristics of Tofu Made from Korean Soybean Cultivars

Discrimination of Cultivated Regions of Soybeans (Glycine max) Based on Multivariate Data Analysis of Volatile Metabolite Profiles.

Soybean (Glycine max) is a major crop cultivated in various regions and consumed globally. The formation of volatile compounds in soybeans is influenced by the cultivar as well as environmental factors, such as the climate and soil in the cultivation areas. This study used gas chromatography-mass spectrometry (GC-MS) combined by headspace solid-phase microextraction (HS-SPME) to analyze the volatile compounds of soybeans cultivated in Korea, China, and North America. The multivariate data analysis of partial least square-discriminant analysis (PLS-DA), and hierarchical clustering analysis (HCA) were then applied to GC-MS data sets. The soybeans could be clearly discriminated according to their geographical origins on the PLS-DA score plot. In particular, 25 volatile compounds, including terpenes (limonene, myrcene), esters (ethyl hexanoate, butyl butanoate, butyl prop-2-enoate, butyl acetate, butyl propanoate), aldehydes (nonanal, heptanal, (E)-hex-2-enal, (E)-hept-2-enal, acetaldehyde) were main contributors to the discrimination of soybeans cultivated in China from those cultivated in other regions in the PLS-DA score plot. On the other hand, 15 volatile compounds, such as 2-ethylhexan-1-ol, 2,5-dimethylhexan-2-ol, octanal, and heptanal, were related to Korean soybeans located on the negative PLS 2 axis, whereas 12 volatile compounds, such as oct-1-en-3-ol, heptan-4-ol, butyl butanoate, and butyl acetate, were responsible for North American soybeans. However, the multivariate statistical analysis (PLS-DA) was not able to clearly distinguish soybeans cultivated in Korea, except for those from the Gyeonggi and Kyeongsangbuk provinces.

Variation of Korean Soybean [Glycine max (L.) Merrill] Varieties based on Leaf-Related Characters

Variation of Korean Soybean [Glycine max (L.) Merrill] Varieties based on Leaf-Related Characters

Identification of New Isolates of Phytophthora sojae and the Reactions of Korean Soybean Cultivars Following Hypocotyl Inoculation.

Phytophthora root and stem rot (PRSR) caused by Phytophthora sojae is one of the most destructive diseases of soybean. PRSR recently became an issue as soybean cultivation in paddy fields increased in South Korea. The management of PRSR mainly involves R-gene–mediated resistance, however, little is known about the resistance in Korean cultivars. Major Korean soybean cultivars were investigated for the presence or absence of R-gene–mediated resistance to four P. sojae isolates, two of which were new isolates. Isolate-specific reactions were observed following P. sojae inoculation. Of 21 cultivars, 15–20 cultivars (71.4–95.2%) showed susceptible reaction for each isolate. Ten cultivars were susceptible to all the isolates, and six cultivars were identified to have R-gene–mediated resistance to one or two isolates. The results of this study would provide a framework for the discovery of resistant cultivars, development of new cultivars resistant to P. sojae, and investigation of pathogenic diversity of P. sojae population in South Korea.

Effects of Doenjang, a Traditional Korean Soybean Paste, with High-Salt Diet on Blood Pressure in Sprague-Dawley Rats.

Fermented foods in Korea contain a lot of salt. Although salt is reported to exacerbate health trouble, fermented foods have beneficial effects. We hypothesized that doenjang could reduce blood pressure in Sprague–Dawley (SD) rats fed a high-salt diet. Eighteen SD rats were divided into three groups: normal-salt (NS) group, high-salt (HS) group, and high-salt with doenjang (HSD) group. The salinity of doenjang and saltwater was adjusted to 8% using Mohr’s method. Blood pressure was significantly reduced in the HSD group compared with the HS group. Water intake and urine excretion volume has significantly increased in the HS group compared with the HSD group. The excreted concentrations of urine sodium, urine potassium, and feces potassium significantly increased in the HSD group compared with the HS and NS groups. Renin level was significantly decreased in the HSD group compared to the other groups. These results indicate that eating traditional salty fermented food is not a direct cause of hypertension, and the intake of doenjang in normal healthy animals improved blood pressure.

Korean soybean core collection: Genotypic and phenotypic diversity population structure and genome-wide association study.

A core collection is a subset that represents genetic diversity of the total collection. Soybean (Glycine max (L.) Merr.) is one of major food and feed crops. It is the world’s most cultivated annual herbaceous legume. Constructing a core collection for soybean could play a pivotal role in conserving and utilizing its genetic variability for research and breeding programs. To construct and evaluate a Korean soybean core collection, genotypic and phenotypic data as well as population structure, were analyzed. The Korean soybean core collection consisted of 430 accessions selected from 2,872 collections based on Affymetrix Axiom® 180k SoyaSNP array data. The core collection represented 99% of genotypic diversity of the total collection. Analysis of population structure clustered the core collection into five subpopulations. Accessions from South Korea and North Korea were distributed across five subpopulations. Analysis of molecular variance indicated that only 2.01% of genetic variation could be explained by geographic origins while 16.18% of genetic variation was accounted for by subpopulations. Genome-wide association study (GWAS) for days to flowering, flower color, pubescent color, and growth habit confirmed that the core collection had the same genetic diversity for tested traits as the total collection. The Korean soybean core collection was constructed based on genotypic information of the 180k SNP data. Size and phenotypic diversity of the core collection accounted for approximately 14.9% and 18.1% of the total collection, respectively. GWAS of core and total collections successfully confirmed loci associated with tested traits. Consequently, the present study showed that the Korean soybean core collection could provide fundamental and practical material and information for both soybean genetic research and breeding programs.

Simultaneous Determination of Twenty Mycotoxins in the Korean Soybean Paste Doenjang by LC-MS/MS with Immunoaffinity Cleanup.

Doenjang, a Korean fermented soybean paste, is vulnerable to contamination by mycotoxins because it is directly exposed to environmental microbiota during fermentation. A method that simultaneously determines 20 mycotoxins in doenjang, including aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEN), and fumonisins (FBs) with an immunoaffinity column cleanup was optimized and validated in doenjang using LC-MS/MS. The method showed good performance in the analysis of 20 mycotoxins in doenjang with good linearity (R2 > 0.999), intra- and inter-day precision (<16%), recovery (72–112%), matrix effect (87–104%), and measurement uncertainty (<42%). The validated method was applied to investigate mycotoxin contamination levels in commercial and homemade doenjang. The mycotoxins that frequently contaminated doenjang were AFs, OTA, ZEN, and FBs and the average contamination level and number of co-occurring mycotoxins in homemade doenjang were higher than those in commercially produced doenjang.

Toxicological evaluation of lotus, ginkgo, and garlic tailored fermented Korean soybean paste (Doenjang) for biogenic amines, aflatoxins, and microbial hazards

The present study aimed to develop a consortium of nutritive fermented food products, supplemented with phytochemicals, with reduced toxicological contents. We developed new flavored Doenjang products (protein rich) fermented with lotus, ginkgo, and garlic plant extract-based Meju (termed as EMD) as the starter culture and by using traditional Meju (termed as TMD), where these plant extracts were added later during the fermentation process. Fermented Doenjang samples were analyzed for reduced levels of biogenic amines (BAs), aflatoxins, and microbial hazards, (including Bacillus cereus) as well as for their nutritive contents and antioxidant potential, after varying periods of fermentation (0, 3, 6, 9 and 12 months). All Doenjang samples prepared using plant extracts and their mixtures (1% and 10%) showed desired reduction in B. cereus counts, BAs, aflatoxins, and other foodborne pathogens as well as showed potent antioxidant abilities, including phenolic/flavonoid contents. Based on the higher efficiency in reducing various toxicants, Ginkgo biloba leaf extract added TMD samples were selected for the development of Doenjang products as an innovative approach, with great potential to improve the quality and safety of soybean fermented products in the Korean market, offering enhanced health benefits and reduced risks of toxicity.

Quantitative Variation of Total Seed Isoflavone and its Compositions in Korean Soybean Cultivars (Glycine max (L.) Merr.)

Quantitative Variation of Total Seed Isoflavone and its Compositions in Korean Soybean Cultivars (Glycine max (L.) Merr.)

Purification and characterization of thermostable l-asparaginase from Bacillus amyloliquefaciens MKSE in Korean soybean paste

This study aimed to produce and characterize thermostable l-asparaginase from Bacillus amyloliquefaciens MKSE, a newly screened strain from Korean fermented soybean paste. The isolated MKSE was identified by its morphological, biochemical, and physiological properties and 16S rRNA sequence. Its l-asparaginase II-like gene was expressed in Escherichia coli BL21 (DE3), by using the pET-28a (+) vector. The produced l-asparaginase (specific activity of 4.75 IU/mg) was purified by a one-step procedure, using nickel-affinity chromatography, and its molecular weight of 38.2 kDa was determined by gel electrophoresis. Its optimum pH and temperature were 8.5 and 65 °C, respectively. The enzyme was highly stable in the pH range of 3.0–11.0 for 6 h incubation, and the enzyme retained about 57% of its activity at 95 °C for 6 h. Its activity was activated in the presence of Mn2+, Mg2+, and Fe2+ while it was inhibited by Zn2+, Cu2+, PMSF, and SDS. Its Km was 1.5 mM, and its Vmax was 136.3 IU/mg. The results of this study reveal that MKSE l-asparaginase has a great potential to be used in various industries, due to its stability at high temperature and over a wide pH range.

Highly geographical specificity of metabolomic traits among Korean domestic soybeans (Glycine max)

Classification and characterization of agricultural products at molecular levels are important but often impractical with genotyping, particularly for soybeans that have numerous types of variety and landraces. Alternatively, metabolic signature, a determinant for nutritional value, can be the good molecular indicator, which reflects cultivation region-dependent factors such as climate and soil.Accordingly, we analyzed the integrative metabolic profiles of Korean soybeans cultivated in 7 different provinces (representative production areas), and explored the potential association with geographic traits. A total of 210 primary and secondary metabolites were profiled using gas-chromatography time-of-flight mass spectrometry (GC-TOF MS) and liquid-chromatography Orbitrap mass spectrometry (LC-Orbitrap MS). Despite the partial heterogeneity of the soybean varieties, the metabolomic phenotypic analysis based on multivariate statistics inferred the chemical compositional characteristics was primarily governed by the regional specificity. The OPLS-DA model proposed biomarker cluster re-composed with 5 metabolites (tryptophan, malonylgenistin, malonyldaidzin, N-acetylornithine, and allysine) (AUCs = 0.870–1.0). The most distinctive metabolic profiles were identified with the soybeans of Gunsan (middle-western coast) and Daegu (east-southern inland area), which were best characterized by the highest contents of isoflavones and amino acids, respectively. Further interrogation on geographic data suggested the combinatorial association of region-specific metabolic features with general soil texture and climate traits (total rainfall and average annual temperature).

Primary structure and characterization of a protease from Bacillus amyloliquefaciens isolated from meju, a traditional Korean soybean fermentation starter

Abstract Bacillus amyloliquefaciens FSE-68 isolated from a Korean soybean fermentation starter (meju) produces a distinct alkaline protease, alkaline serine-protease (APR68). The primary structure of APR68 was Determined using a combination of tryptic peptide mapping by LC/ESI-MS/MS analysis and DNA sequencing. The APR68 gene is closely (96.2% identical) related to the gene encoding the B. amyloliquefaciens alkaline protease (also known as subtilisin BPN’). The APR68 gene encodes a 30-amino acid signal peptide, a 77-amino acid propeptide, and a 275-amino acid mature protein with a molecular weight of 27,447 Da. The protein sequence of APR68 differs from that of subtilisin BPN’ by six amino acids (Phe-21, Val-79, Gly-161, Asn-181, Ser-194 and Ala-260). Among the six amino acids, Val-79 is near a calcium-binding pocket of APR68 and alters its calcium-binding properties. The protease activity of APR68 was more stable than that of subtilisin BPN’ in 2 mM EDTA, and its activity increased by 10.1% in 10 mM CaCl2. These results demonstrate the effect of specific amino acid replacements on calcium ion affinity. The APR68 is a good candidate for application under chelating conditions.

Genetic diversity patterns and domestication origin of soybean

Key messageGenotyping data of a comprehensive Korean soybean collection obtained using a large SNP array were used to clarify global distribution patterns of soybean and address the evolutionary history of soybean.Understanding diversity and evolution of a crop is an essential step to implement a strategy to expand its germplasm base for crop improvement research. Accessions intensively collected from Korea, which is a small but central region in the distribution geography of soybean, were genotyped to provide sufficient data to underpin population genetic questions. After removing natural hybrids and duplicated or redundant accessions, we obtained a non-redundant set comprising 1957 domesticated and 1079 wild accessions to perform population structure analyses. Our analysis demonstrates that while wild soybean germplasm will require additional sampling from diverse indigenous areas to expand the germplasm base, the current domesticated soybean germplasm is saturated in terms of genetic diversity. We then showed that our genome-wide polymorphism map enabled us to detect genetic loci underlying flower color, seed-coat color, and domestication syndrome. A representative soybean set consisting of 194 accessions was divided into one domesticated subpopulation and four wild subpopulations that could be traced back to their geographic collection areas. Population genomics analyses suggested that the monophyletic group of domesticated soybeans was likely originated at a Japanese region. The results were further substantiated by a phylogenetic tree constructed from domestication-associated single nucleotide polymorphisms identified in this study.

Growth Characteristics and Biological Responses of Korean Elite Soybean (Glycine max L. Merr.) Cultivars Exposed to Gamma-Rays

The present study was conducted to evaluate the biological responses of soybean irradiated by gamma-rays. Four elite Korean soybean cultivars, Kwangankong, Shinpaldal-2, Shinhwakong, and Ilmikong, were irradiated with 100-400 Gy of gamma-rays. All cultivars showed significant reductions in morphological parameters. Seedling emergence rates of Kwangankong, Shinpaldal-2, Shinhwakong, and Ilmikong decreased by 46%, 31%, 44%, and 43% at 400 Gy, respectively. Plant height and fresh weight decreased with increasing dose. The median reduction dose (RD50) for plant height ranged from 184 to 278 Gy with an average of 212 Gy.The optimal dose of gamma irradiation for inducing mutation in the four elite soybean cultivars was in the range 200-300 Gy. Contents of malonaldehyde (MDA) in the gamma-ray irradiated plants were higher than those in the controls. With the exception of Kwangankong, activities of ascorbate peroxidase (APX) in other cultivars decreased at 100 Gy and started to increase significantly at 200 Gy and Shinhwakong cultivar had highest APX value observed at 300 Gy. No significant changes in peroxidase (POD) activity were observed inthe Kwangankong, Shinpaldal-2, and Shinhwakong, while, POD activity increased with increasing dose in Ilmikong. In addition, gamma-ray treatments elicited a marked reduction in chlorophyll a contents compared to chlorophyll b contents in Kwangankong, Shinpaldal-2, and Ilmikong. Growth characteristics (plant height and fresh weight) were highly negatively (P ＜ 0.01) correlated with the dose of gamma-rays, while the MDA content and APX activities were positively (P ＜ 0.05) correlated with dose.

Discrimination and prediction of the origin of Chinese and Korean soybeans using Fourier transform infrared spectrometry (FT-IR) with multivariate statistical analysis.

The ability to determine the origin of soybeans is an important issue following the inclusion of this information in the labeling of agricultural food products becoming mandatory in South Korea in 2017. This study was carried out to construct a prediction model for discriminating Chinese and Korean soybeans using Fourier-transform infrared (FT-IR) spectroscopy and multivariate statistical analysis. The optimal prediction models for discriminating soybean samples were obtained by selecting appropriate scaling methods, normalization methods, variable influence on projection (VIP) cutoff values, and wave-number regions. The factors for constructing the optimal partial-least-squares regression (PLSR) prediction model were using second derivatives, vector normalization, unit variance scaling, and the 4000–400 cm–1 region (excluding water vapor and carbon dioxide). The PLSR model for discriminating Chinese and Korean soybean samples had the best predictability when a VIP cutoff value was not applied. When Chinese soybean samples were identified, a PLSR model that has the lowest root-mean-square error of the prediction value was obtained using a VIP cutoff value of 1.5. The optimal PLSR prediction model for discriminating Korean soybean samples was also obtained using a VIP cutoff value of 1.5. This is the first study that has combined FT-IR spectroscopy with normalization methods, VIP cutoff values, and selected wave-number regions for discriminating Chinese and Korean soybeans.