Soybean (Glycine max L. Merr.) is one of the most important crops in the world. Its major content of vegetable oil made it widely used for human consumption and several food industries. To investigate the variation in seed fatty acid composition of soybeans from different origins, a set of 633 soybean accessions originated from four diverse germplasm collections—including China, United States of America (USA), Japan, and Russia—were grown in three locations, Beijing, Anhui, and Hainan for two years. The results showed significant differences (P < 0.001) among the four germplasm origins for all fatty acid contents investigated. Higher levels, on average, of palmitic acid (PA) and linolenic acid (LNA) were observed in Russian germplasm (12.31% and 8.15%, respectively), whereas higher levels of stearic acid (SA) and oleic acid (OA) were observed in Chinese germplasm (3.95% and 21.95%, respectively). The highest level of linoleic acid (LA) was noticed in the USA germplasm accessions (56.34%). The largest variation in fatty acid composition was found in LNA, while a large variation was observed between Chinese and USA germplasms for LA level. Maturity group (MG) significantly (P < 0.0001) affected all fatty acids and higher levels of PA, SA, and OA were observed in early maturing accessions, while higher levels of LA and LNA were observed in late maturing accessions. The trends of fatty acids concentrations with different MG in this study further provide an evidence of the importance of MG in breeding for such soybean seed components. Collectively, the unique accessions identified in this study can be used to strengthen the soybean breeding programs for meeting various human nutrition patterns around the globe.

In order to ensure an ongoing and long-term breeding progress of soybean, stable sources of major quality traits across multi-environments need to be identified. Here, a panel of 135 soybean genotypes was tested in three different Chinese environments, including Beijing, Anhui, and Hainan during the 2017 and 2018 growing seasons to identify stable genotypes for cultivation under varying environmental conditions. The weighted average of absolute scores biplot (WAASB) for the best linear unbiased predictions of the genotype-environment interaction and multi-trait stability index (MTSI) were utilized to determine the stability of the soybeans for seven seed composition traits viz; protein content, oil content, and five fatty acids (palmitic, stearic, oleic, linoleic, and linolenic acids). Based on the WAASB index, the following genotypes were identified as stable genotypes for some specific traits; ZDD12828 and ZDD12832 for protein content, WDD01583 and WDD03025 for oil content, ZDD23040 for palmitic acid, WDD00033 for stearic acid, ZDD23822 for oleic acid, ZDD11183 for linoleic acid, and ZDD08489 for linolenic acid. Furthermore, based on MTSI at a selection intensity of 10%, 14 soybean genotypes were selected for their average performance and stability. Overall, the MTSI was shown to be a powerful and simple tool for identifying superior genotypes in terms of both performance and stability, hence, identifying stable soybean genotypes for future breeding programs of quality traits.

Soybean contains nutritional bioactive compounds, including carotenoids associated with human health benefits. Carotenoids are applicable in pharmaceuticals/nutreceuticals, cosmetic, and mainly food industries. However, an efficient and accurate method for carotenoid and chlorophyll detection and quantification has not yet been developed and validated for soybean seeds. The need for a rapid and reliable analysis method has become increasingly important. Thus, this study was initiated to develop and validate a simple, rapid, and selective reversed-phase high-performance liquid chromatographic (RP-HPLC) method for the simultaneous determination of lutein, zeaxanthin, α-carotene, β–carotene, β–cryptoxanthin, and chlorophyll–a and –b in soybean flour sample (100.00 mg) extracted using ethanol-acetone (1:1) solvents at a volume of 1.50 mL. Interestingly, the effective separation technique was achieved using the mobile phases of methyl tert-butyl ether, methanol containing 10 mM ammonium acetate, and water delivered at a 0.90 mL min⁻¹ flow rate through a C₃₀YMC Carotenoid (250 × 4.6 mm I.D., S-5 µm) column coupled with a UV-VIS detector set at 450 nm. The detector response was linear from 0.05–30.00 μg mL⁻¹ with a coefficient of determination (R²) of 0.9993–0.9999. The validated method was sensitive with a detection limit (LOD) of 0.0051–0.0300 μg mL⁻¹ and 0.0155–0.0909 μg mL⁻¹ for the quantification limit (LOQ). The recovery values were from 83.12–106.58%, and the repeatability precision ranged from 1.25–4.20% and 0.15–0.81% for the method and system, respectively. The method showed adequate precision with a relative standard deviation smaller than 3.00%. This method was also found to be applicable for profiling carotenoids and chlorophylls in other legumes. In summary, this method was successfully implemented for qualitative and quantitative determination of major carotenoids and chlorophylls in soybean and other legume seeds, which are beneficial to food industry and quality breeding programs to meet human nutrition demands globally.

Soybean (Glycine max (L.) Merrill) seeds are abundant in physiologically active metabolites, including carotenoids and chlorophylls, and are used as an affordable source of functional foods that promote and maintain human health. The distribution and variation of soybean seed metabolites are influenced by plant genetic characteristics and environmental factors. Here, we investigated the effects of germplasm origin, genotype, seed coat color and maturity group (MG) on the concentration variation of carotenoid and chlorophyll components in 408 soybean germplasm accessions collected from China, Japan, the USA and Russia. The results showed that genotype, germplasm origin, seed color, and MG were significant variation sources of carotenoid and chlorophyll contents in soybean seeds. The total carotenoids showed about a 25-fold variation among the soybean germplasms, with an overall mean of 12.04 µg g⁻¹. Russian soybeans yielded 1.3-fold higher total carotenoids compared with Chinese and Japanese soybeans. Similarly, the total chlorophylls were substantially increased in Russian soybeans compared to the others. Soybeans with black seed coat color contained abundant concentrations of carotenoids, with mainly lutein (19.98 µg g⁻¹), β-carotene (0.64 µg g⁻¹) and total carotenoids (21.04 µg g⁻¹). Concentrations of lutein, total carotenoids and chlorophylls generally decreased in late MG soybeans. Overall, our results demonstrate that soybean is an excellent dietary source of carotenoids, which strongly depend on genetic factors, germplasm origin, MG and seed coat color. Thus, this study suggests that soybean breeders should consider these factors along with environmental factors in developing carotenoid-rich cultivars and related functional food resources.

Tocopherols are natural antioxidants that increase the stability of fat-containing foods and are well known for their health benefits. To investigate the variation in seed tocopherol composition of soybeans from different origins, 493 soybean accessions from different countries (China, USA, Japan, and Russia) belonging to 7 maturity groups (MG 0–VI) were grown in 2 locations (Beijing and Hainan Provinces of China) for 2 years (2017 and 2018). The results showed that significant differences (p < 0.001) were observed among the accessions and origins for individual and total tocopherol contents. The total tocopherol content ranged from 118.92 μg g⁻¹ to 344.02 μg g⁻¹. Accessions from the USA had the highest average concentration of γ- and total tocopherols (152.92 and 238.21 μg g⁻¹, respectively), whereas a higher level of α-tocopherol (12.82 μg g⁻¹) was observed in the Russian accessions. The maturity group of the accession significantly (p < 0.001) influenced all tocopherol components, and higher levels of α-, γ-, and total tocopherols were observed in early maturing accessions, while late-maturing accessions exhibited higher levels of δ-tocopherol. The inclination of tocopherol concentrations with various MGs provided further evidence of the significance of MG in soybean breeding for seed tocopherol components. Furthermore, the correlation between the seed tocopherol components and geographical factors revealed that α-, γ-, and total tocopherols had significant positive correlations with latitude, while δ-tocopherol showed an opposite trend. The elite accessions with high and stable tocopherol concentrations determined could be used to develop functional foods, industrial materials, and breeding lines to improve tocopherol composition in soybean seeds.

Distinctness, uniformity and stability (DUS) testing of cultivars through morphological descriptors is an important and compulsory part of soybean breeding. Molecular markers are usually more effective and accurate in describing the genetic features for the identification and purity assessment of cultivars. In the present study, we assessed the distinctness and uniformity of five soybean cultivars using both single nucleotide polymorphism (SNP) markers developed by specific-locus amplified fragment sequencing (SLAF-seq) technology, and simple sequence repeat (SSR) markers. The phylogenetic tree and principal component analysis (PCA) from both the SLAF-seq and SSR methods showed a clear distinction among cultivars Zhonghuang 18, Zhonghuang 68 and Zhonghuang 35, while no clear distinction was observed between cultivars Zhonghuang 13 and Hedou 13. Using the SLAF-seq method, we determined the proportion of homozygous loci for the five soybean cultivars. The heterozygosity of each individual plant was estimated for the assessment of cultivar purity and the purity levels of the five soybean cultivars ranged from 91.89% to 93.96%. To further validate the applicability of the SLAF-seq approach for distinctness testing, we used the SNP information of 150 soybean cultivars with different origins. The cultivars were also distinguished clearly. Taken together, SLAF-seq can be used as an accurate and reliable method in the assessment of the distinctness and uniformity of soybean cultivars.