A black soybean cultivar ‘Gyeongheukcheong’ was developed by Gyeongsangbuk-do Agricultural Research and Extension Services. ‘Gyeongheukcheong’ was selected from a cross between ‘RCS640’ and ‘Geomjeongsaeol’ in 2011. The cultivar was evaluated in multiple performance and yield trials in seven locations from 2017 to 2019. ‘Gyeongheukcheong’ has a gray pubescence, light brown pod, and dark green cotyledon, whereas ‘Cheongja 3’ has a brown pubescence, brown pod, and light green cotyledon. The seed weight and maturity of ‘Gyeongheukcheong’ was similar to that of ‘Chungja 3’. ‘Gyeongheukcheong’ was resistant to soybean mosaic virus (strain G6H), moderately resistant to bacterial pustule (caused by Xanthomonas axonopodis pv. glycines), and resistant to root rot. Total chlorophyll content (sum of chlorophyll a and b) in the green cotyledon of ‘Gyeongheukcheong’ was 48.0 μg/g, which was higher than that of ‘Cheongja 3’ (30.1 μg/g). The regional yield trial showed that ‘Gyeongheukcheong’ had a similar or significantly higher average yield than ‘Chungja 3’ in locations with single (similar) and double (19% higher) cropping systems, respectively. ‘Gyeongheukcheong’ represents a consumer-friendly black soybean with dark green cotyledons and high yield potential (Registration No. 9065).

A black soybean cultivar, “Saebaram” with green cotyledons, was developed and released by the Gyeongsangbuk-do Agricultural Research and Extension Services (GBARS) in 2019. It was developed from a single cross between “Seonheuk” and “RCS640” in 2011. The preliminary yield trial and advanced yield trial were conducted at GBARS from 2015 to 2016. The regional yield trial (RYT) was conducted in seven locations from 2017 to 2019 in Korea. “Saebaram” had purple flowers, grey pubescence, light brown pods, a black seed coat, an ellipse seed shape, and a large seed size (42.8 g/100 seeds). The seed size was significantly larger than that of the check cultivar “Cheongja 3” (36.2 g/100 seeds). Moreover, it was moderately resistant to bacterial pustule (caused by Xanthomonas axonopodis pv. glycines) and soybean mosaic virus (strain G6H). “Saebaram” had dark green cotyledons, whereas “Cheongja 3” had light green cotyledons. The total chlorophyll contents (chlorophyll a and chlorophyll b) in the green cotyledons of “Saebaram” and “Cheongja 3” were 76.1 μg/g and 30.1 μg/g, respectively. Furthermore, the RYT showed that “Saebaram” had 287 kg/10a, which was 10% higher than that of “Cheongja 3” (261 kg/10a). This black soybean cultivar with improved yield, large-size seeds, and dark green cotyledons is expected to have a high commercial value for Korean farmers (Registration No. 9155).

Understanding plant morphological and seed characteristics is an essential step for the utilization of genetic resources to improve targeted traits in soybean breeding programs. The purpose of this study was to evaluate the agronomic traits and seed pigments of 469 black soybean germplasms with green cotyledons to identify useful resources using multivariate analyses, correlation, principal component analysis (PCA), and cluster analyses. The results showed that the range of flowering days from planting were 37.7-71.5 days, harvesting days from planting were 112.3-153.0 days, plant height was 49.6-151.6 cm, and 100-seed weight was 9.1-49.3 g. According to the correlation analyses with agronomic traits, flowering and harvesting days were positively correlated with the plant height, number of nodes, and number of branches. Additionally, it was found that the chlorophyll a and total chlorophyll content had the greatest effect on the green color of the cotyledon. Based on the PCA, 13 quantitative traits were compressed into three components. The first three principal components accounted for 82.5% of the total variance. In this study, black soybean germplasms with green cotyledons were divided into four clusters by the K-means cluster analysis (non-hierarchical procedure), based on the PCA. The cluster analysis showed that chlorophyll a and plant height had a significant effect on the clustering of the black soybean germplasms used in this study. This study provides opportunities to easily select useful genetic resources for the development of new black soybean cultivars.

A black soybean cultivar called ‘Noksim’ was developed using pedigree selection by crossing ‘Ilpumgeomjeong’ (SLSB87-3 × YS558) and ‘PI547426’. A p reliminary y ield t rial (PYT), advanced y ield t rial (AYT), and regional y ield t rial (RYT) were conducted in t hree regions. ‘Noksim’ has a determinate growth habit, purple flowers, and spherical seeds. In the regional yield trial, the flowering and maturity dates of ‘Noksim’ were August 4 and October 13, respectively, and its 100-seed weight was 26.5 g, which was lower than that of ‘Chungja 3’ (36.5 g). Additionally, ‘Noksim’ showed resistance to lodging, soybean mosaic virus (SMV), bacterial blight, and pod shattering. In terms of the seed quality, the chlorophyll content of ‘Noksim’ was 71.19%, which was higher than that of ‘Chungja 3’ (50.78%), and its total anthocy anin c ontent w as 2 5.17 m g/100g, w hich w as t hree t imes more than t hat of ‘Chungja 3’. The mean y ield o f ‘Noksim’ i n RYT was 2.35 ton/ha, which was 18% greater than that of ‘Chungja 3’. ‘Noksim’ is suitable for cooking with rice and soy products such as soymilk because of its high brix degree (35 Brix) after cooking with rice, as well as its soymilk yield (71.2%). Overall, ‘Noksim’ has dark green cotyledons with a black seed coat that is preferred by consumers, and its early maturity with pod shattering resistance results in an increased seed yield. (Registration No. 7734).

A yellow soybean cultivar called ‘Hipro’ was developed using the single seed descent (SSD) method by crossing ‘Saedanbaek’ (SS92414 ×MD87L) and ‘Daepung’ (Baekwon × Sinpaldal2). A preliminary yield trial (PYT), advanced yield trial (AYT), and regional yield trial (RYT) were conducted in three regions. ‘Hipro’ has a determinate growth habit, white flowers, and a spherical seed shape. In the regional yield trial, the flowering and maturity dates of ‘Hipro’ were August 4 and October 17, respectively, and the 100-seed weight was 22.2 g, which was lower than that of Daewon (26 g). Additionally, ‘Hipro’ showed resistance to lodging, soybean mosaic virus (SMV), bacterial blight, and pod shattering. The seed protein content of ‘Hipro’, which was of particular interest in this study, was 53.9%, which was higher than that of ‘Daepung’ (41.5%), and the total amino acid content without tryptophan was 43.6%, 19% higher than that of ‘Daepung’. The mean yield of ‘Hipro’ in RYT was 2.23 ton/ha, which was 91.3% of the yield of ‘Daewon’. However, ‘Hipro’ showed an 11% higher yield than Daewon in Paju. As a result of the tofu characteristic test, 'Hipro' is suitable for making soy milk and tofu due to its high solid content (12.67 Brix) and protein content (13.68%) and high yield (325%) of tofu. Overall, ‘Hipro’ had high protein content, excellent processing quality for tofu and soy milk, and strong resistance to disease and pod shattering that will greatly contribute to the consumption of soybeans in Korea. (Registration No. 7735).

Soybean has a high protein content in both its hay and seed. Studies have shown that the mixed cropping of corn and soybean improved forage yield and quality. The objective of this study was to select soybean germplasm suitable for mixed cropping with corn on the same row to produce better forage yield and quality. Eleven soybean lines selected from previous evaluations were used in this study. Soybeans were planted with corn on the same row at 10 cm intervals. The planting rate in hills was one corn plant and three soybean plants. The fertilization and time of forage harvest were based on the recommendations for forage corn production. The results showed that in corn–soybean mixed cropping, the forage yield increased by about 19%, the silage protein content increased by 1%–2%, the percentage of acid detergent fibers and neutral detergent fibers decreased, the total digestible nutrients increased, and the acetic acid content decreased. Therefore, the selected soybean lines were suitable for mixed cropping with corn to produce high quality forage and/or as breeding material for the development of forage soybean varieties. Based on this study, we suggest that the agronomic traits of soybean needed for mixed cropping with corn on the same row for forage are as follows: soybean should 1) have the ability to grow well under the corn canopy, 2) have lodging tolerance for ease of mechanical forage harvest, 3) develop to the full pod stage at the time of harvest for increased protein content, and 4) have no adverse effects on corn growth to maintain a high forage yield.

This study was carried out to evaluate the oil contents and fatty acid compositions of 379 soybean germplasm accessions which is composed of 128 Korean, 214 Chinese and 37 USA accessions, and to select useful resources for the development of high oil content and quality fatty acid varieties in soybean. Korean and Chinese germplasm accessions were obtained from the National Agrobiodiversity Center, National Academy of Agricultural Science, Rural Development Administration, and USA accessions from the Plant Genetics and Breeding Laboratory of Kyungpook National University, Korea. The oil content ranges from 12.7~26.0% with an average of 19.1% among accessions. The average contents and ranges of palmitic and stearic acid, saturated fatty acids (SFA), were 10.6% with a range of 4.1~18.1% and 2.9% with a range of 1.9~ 12.7% respectively, while those of oleic, linoleic and linolenic acid, unsaturated fatty acids (USFA), were 28.2% with a range of 15.3~56%, 51.2% with a range of 24.4~68% and 7.1% with a range of 3.4~11.1% respectively. The average linoleic(ω -6)/linolenic(ω-3) acid ratio was 7.5 ranging from 3.8~17, and the average SFA and USFA contents were 13.5% ranging from 6.7~21.7% and 86.5% ranging 78.3~93.4% respectively. Accessions with better essential properties were selected as useful resources for the development of high oil content and quality fatty acid varieties. Three accessions, Suinong 14, Dongnong 434 and Dongnong 46 from China contain oil higher than 25.0%, while five accessions including KLG 12073 and KLG 12074 from USA, Jilin 14 from China, Kwangan and Bongeui from Korea contain oleic acid higher than 50%. Eight accessions including KLG12083 and KLG12081 from USA contain linoleic acid higher than 60%. Seven accessions including KLG 12093 and KLG12096 from USA contain linolenic acid lower than 4%. Five accessions, KLG12074 and KLG12073 from USA, Kwangan and Bongeui from Korea, and Dongnong 47 from China were low linoleic acid(ω-6)/linolenic(ω-3) ratio resources with lower than 4.5.