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.

Ginseng (Panax ginseng) is a self-fertilized crop, and all ginseng cultivars developed until now have been bred by pure-line selection. Ginseng has few genetic variations and lacks diversity in genetic resources. To obtain genetic resources with useful traits, mutations must be artificially induced. In this study, indehiscent seeds from ginseng landrace were treated with 20 to 400 Gy of gamma rays for 24 hours to determine the optimal dose for mutation breeding. Results showed no significant differences in seed dehiscence rates among the 0 Gy (control) to 80 Gy groups. However, above 100 Gy, the dehiscence rate sharply decreased as the radiation dose increased. Seed development below 40 Gy was superior to that of control but declined rapidly above 60 Gy. The seedling survival rate decreased significantly at 60 Gy (less than 50% compared to that of the control), and most seeds did not survive above 100 Gy. We observed a significant reduction in the growth of seedlings irradiated above 60 Gy. The above results suggest that a suitable gamma-ray dose for inducing mutagenesis in indehiscent ginseng seeds is 40 Gy.

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.