ARS | Publication request: Soybean seed phenol, lignin, and isoflavones partitioning as affected by seed node position and genotype differences

Submitted to: Food and Nutrition Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 9, 2012
Publication Date: April 1, 2012
Citation: Bellaloui, N. 2012. Soybean seed phenol, lignin, and isoflavones partitioning as affected by seed node position and genotype differences. Food and Nutrition Sciences. 3:447-454.

Interpretive Summary: Phenolic compounds (phenol, lignin, and isoflavones) are natural products produced by plants. They are present in leaves, roots, and seed, and essential for disease resistance. Phenolic compounds have health benefits for humans. Therefore, understanding the factors controlling the production and distribution of phenolic compounds within soybean is important . In a study to evaluate the level and within plant distribution of phenolic compounds in different soybean genotypes at seed-fill, seed phenolic compounds (phenol, lignin, and isoflavones dadzein, genistein, and glycitein) were higher at the bottom of the plant than at the top of the plant. This trend was observed in DT 97-4290, Stressland, and Hutcheson genotypes, but not in Tracy-M genotype. Also, this trend was more obvious for daidzein and genistein isoflavones than for glycitein. The maximum phenolic compounds were recorded just as the soybean plant reached maturity. This trend cannot be generalized in soybean genotypes because cultivar Tracy-M, maturity group VI, did not follow the same trend as those of maturity group IV and V. Breeding for higher levels of phenolics would benefit human health, increase nutritional value of soybean meal, and also protect plants against diseases.

Technical Abstract: Factors controlling the production and partitioning of seed phenolics within soybean are not understood. Understanding these factors may justify selection for higher levels of seed phenolics because of their beneficial impact on human health and soybean defense against diseases. The objective of this research was to investigate the partitioning of seed phenolics (phenol, lignin, and isoflavones) along the main stem of soybean genotypes. A repeated greenhouse experiment was conducted on different soybean genotypes of different maturity and different stem architecture (determinant and indeterminate). Genotypes were DT 97-4290, maturity group (MG) IV; Stressland, MG IV; Hutcheson, MG V; and Tracy-M, MG VI. Seed were harvested from top and bottom nodes at seed-fill stage (R6) and physiological maturity stage (R8). At R6, seed phenolic compounds (phenol, lignin, and isoflavones daidzein, genistein, and glycitein) were greater in the bottom seed than the top seed. This trend was observed in DT 97-4290, Tracy-M, and Hutcheson, but not in Stressland. Also, this trend was more obvious with daidzein and genistein isoflavones than glycitein. The maximum phenolic compounds were recorded at R8. The higher phenolic compounds concentration in bottom seed than in top seed was accompanied by higher cell wall boron (B) percentage and lower total B in bottom seed. The current research demonstrated that phenolic compounds partitioned differently between the top and bottom seed nodes. This trend cannot be generalized in soybean genotypes unless enough germplasm is tested. The partitioning of higher phenolic compounds concentration along the main stem would allow for single seed selection in the breeding program for higher levels of phenolic compounds and for accurate measurements of seed phenolics in breeding lines. The association of B trend with phenolic compound trend may suggest B involvement in phenolic metabolism, and support the structural role of B. Breeding for higher levels of phenolics, especially isoflavones, would benefit human health, provide higher nutritional value of soy meal, and increase plant disease resistance.