Soybeans (Glycine max (L.) Merr.) with black seed coats and green cotyledons are rich in anthocyanins and chlorophylls known as functional nutrients, antioxidants and compounds with anticarcinogenic properties. Understanding the genetic diversity of germplasm is important to determine effective strategies for improving the economic traits of these soybeans. We aimed to analyze the genetic diversity of 470 soybean accessions by 6K single nucleotide polymorphic loci to determine genetic architecture of the soybeans with black seed coats and green cotyledons. We found soybeans with black seed coats and green cotyledons showed narrow genetic variability in South Korea. The genotypic frequency of the d1d2 and psbM variants for green cotyledon indicated that soybean collections from Korea were intermingled with soybean accessions from Japan and China. Regarding the chlorophyll content, the nuclear gene variant pair d1d2 produced significantly higher chlorophyll a content than that of chloroplast genome psbM variants. Among the soybean accessions in this study, flower color plays an important role in the anthocyanin composition of seed coats. We provide 36 accessions as a core collection representing 99.5% of the genetic diversity from the total accessions used in this study to show potential as useful breeding materials for cultivars with black seed coats and green cotyledons.

The yield of soybean (Glycine max (L.) Merr.) is based on several components, such as the number of plants per unit area, pod number per plant, number of nodes, and seed weight. Additionally, the hundred-seed weight (HSW) is an important component affecting soybean yield. The HSW trait can determine soy products meant for human consumption. In this study, we conducted genome-wide association studies with 470 accessions of black seed coats with green cotyledons and applied an online tool with publicly available genome sequencing data. The objective of the study was to identify the genomic regions in the soybean genome associated with seed weight and to identify the candidate genes in linkage disequilibrium blocks where the most significant SNPs were located. This study identified significant SNPs for seed weight on chromosomes 2 and 16. Furthermore, this study indicated that GmCYP78A57 (Glyma.02G119600) encoded a cytochrome P450 monooxygenase may be a possible candidate gene for controlling the seed size in soybean. We assumed that another gene on chromosome 16 may play the important role of a small additive genetic effect to reduce seed size along with GmCYP78A57. An online tool was used to identify 12 allelic variations of GmCYP78A57 with publicly available genomic sequence data. The HSW of 45 accessions having a missense mutation from the Germplasm Resources Information Network ranged from 4.4 to 17.6 g. In addition, 19 accessions were shown to be less than 10.0 g of HSW. This information can provide for the development of molecular markers to use in soybean breeding programs to release new cultivars with increased or decreased seed weight.

The demand for black soybeans (Glycine max (L.) Merr.) with green cotyledons is increasing because of their health benefits. Therefore, it is important to understand the genetic diversity of black soybean germplasms and to develop a new soybean cultivar. This study aimed to evaluate genetic diversity among 469 black soybean germplasms with green cotyledons based on seed composition traits. Twenty seed composition traits were analyzed to conduct correlation analysis, principal component analysis (PCA), and cluster analysis, which indicated that black soybean germplasms were divided into four clusters. Black soybean germplasms in cluster 1 had higher crude fat, lutein, chlorophyll a, chlorophyll b, and total chlorophyll contents, but lower cyanidin-3-glucoside content than those in clusters 2 and 3. However, germplasms in clusters 2 and 3 had the highest cyanidin-3-glucoside content. Moreover, germplasms in cluster 1 had significantly higher palmitic acid content than those in clusters 2 and 3. Germplasms in clusters 2 and 3 had relatively high α-linolenic acid content. Germplasms in cluster 4 had the highest oleic acid content. This study highlights the genetic diversity of black soybean germplasms with different seed composition traits, and the results of this study can be beneficial for soybean breeding programs, enabling them to develop new black soybean cultivars with green cotyledons and improved seed composition traits.

Ji Yun Lee, Chang Ki Son, Jeong Suk Bae, Hyeon Tae Cho, Hong Jib Choi, Jeong-Dong Lee, and Hyun Jo. Korean J. Breed. Sci. 2022;54:453-60. https://doi.org/10.9787/KJBS.2022.54.4.453

Ji Yun Lee, Chang Ki Son, Jeong Suk Bae, Hyeon Tae Cho, Hong Jib Choi, Jeong-Dong Lee, and Hyun Jo. Korean J. Breed. Sci. 2022;54:461-8. https://doi.org/10.9787/KJBS.2022.54.4.461