Natural Variation of Seed Tocopherol Composition in Diverse World Soybean Accessions from Maturity Group 0 to VI Grown in China

Abstract

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.

Origin, Maturity Group and Seed Coat Color Influence Carotenoid and Chlorophyll Concentrations in Soybean Seeds

“…The same pattern was also observed in lutein, where a decreasing trend of lutein towards late MGs was observed, implying that early matured soybeans accumulate more lutein, which might be attributed to climatic conditions and lutein accumulation pattern in short-season soybean genotypes, which are naturally originated and distributed in high-latitude regions. This concurs with the study of Ghosh et al [ 23 ], who reported that early MG soybean accessions, originated and distributed in high-latitude regions, contained high levels of soybean seed nutritional compositions, including tocopherols.…”

“…As shown in Figure S3 , individual chlorophylls, zeaxanthin and β-carotene contents did not show significant responses to MGs, indicating that these components are not more sensitive to the day of maturity. Most importantly, alongside the effects of MGs on the biochemical responses of the targeted pigments, cultivation year had a significant contribution to the contents of carotenoids and chlorophylls ( Table S3 ), implying that seasonal changes can influence the carotenoid and chlorophyll concentrations and the profile of soybeans of different MGs, which is supported by similar reports on soybean isoflavone [ 16 ] and tocopherol [ 23 ]. Additionally, the MG by year interaction had significant effect ( p < 0.001) on lutein, total carotenoids and chlorophylls, which is in consonance with the earlier study on soybean seed nutritional characteristics [ 21 ].…”

“…Some studies have investigated the influence of geographical origins in various nutritional components (including isoflavones, protein, oil, fatty acids, tocopherols and folates) of soybean varieties [ 12 , 13 , 18 , 19 , 20 , 21 ]. Similarly, other recent studies evaluated soybean accessions of different origins and maturity groups for their nutritional quality attributes such as isoflavone [ 21 ], fatty acid compositions [ 22 ] and tocopherols [ 23 ] and found variation among genotypes and between MGs. Moreover, several soybean genotypes with different seed colors have previously been used for evaluating and improving seed chemical compositions such as isoflavone, fatty acids, carbohydrates, protein and oil [ 17 ].…”

Identification of Genomic Loci and Candidate Genes Related to Seed Tocopherol Content in Soybean

“…The current results suggest that cultivars are more reliable resources for the accumulation of tocopherols relative to landraces [41]. Moreover, soybean cultivars are largely developed by targeting high oil content for the oilseed industry by soybean breeders, which indirectly increases the tocopherol content in seeds of soybean cultivars since total tocopherol has a significantly positive correlation with oil [41][42][43]. Thus, breeding for enhanced oil content might have influenced the tocopherol content in the cultivars used in this experiment.…”

Comparison of nutritional composition between plant-based drinks and cow’s milk

“…As expected, the vitamin E contents of most plant-based beverages were higher than those of cow’s milk, with the soy and almond drinks providing the highest contributions to the RDA for this vitamin reaching up to 47% of RDA ( Supplementary Table 7 ). Both almond and soy are naturally high in vitamin E ( 34 , 67 ). The vitamin E concentrations in the rice, oat, and spelt drinks might have benefited from the addition of sunflower oil that is known to be naturally rich in vitamin E ( 34 ).…”