Soybean accessions with increasingly dark seed coats had lower oil content and distinct lipid profiles in a study that combined broad screening with quantitative lipidomics. Among 169 yellow, green, brown and black accessions, yellow seeds had the highest oil content and black seeds the lowest, revealing a negative association between seed coat pigmentation and oil content. The researchers also identified 38 differentially accumulated lipids between common yellow and black soybeans, with these compounds significantly enriched in the sphingolipid metabolism pathway.
The research, published in npj Science of Food, used Soxhlet extraction to measure oil in all 169 soybean accessions. The researchers then selected two representative accessions from each of the four seed color groups for metabolomic analysis and detailed quantitative lipidomic profiling. This design separated the large-scale assessment of oil content from the more intensive molecular comparison, which involved eight accessions. The broader screening established the overall association with pigmentation, while the selected accessions were used to characterize differences in metabolic pathways and individual lipid species.
Quantitative profiling identified 650 lipid species in the eight accessions, divided among five major lipid classes and 26 subclasses. HPLC quantification showed that total lipid content decreased progressively as seed coat pigmentation increased. The differences were mainly associated with changes in triglycerides, phosphatidylethanolamines, phosphatidylcholines and phosphatidylinositols. In the broader metabolomic analysis, lipid subclasses were consistently represented among significantly altered pathways across the four color groups. These measurements show that the observed differences in oil content were accompanied by shifts in the classes and subclasses of lipids present in the seeds.
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