Effect of Six Decades of Selective Breeding on Soybean Protein Composition and Quality:  A Biochemical and Molecular Analysis

• Published in: Journal of agricultural and food chemistry Vol. 54; no. 11; pp. 3916 - 3922
• Main Authors: Mahmoud, Ahmed A, Natarajan, Savithiry S, Bennett, John O, Mawhinney, Thomas P, Wiebold, William J, Krishnan, Hari B
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 31.05.2006
• Subjects: amino acid composition; Amino Acids - analysis; ancestral cultivars; Antigens, Plant; artificial selection; beta-glycinin; Biological and medical sciences; Breeding; cultivars; Electrophoresis, Polyacrylamide Gel; Food industries; food quality; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; genes; genetic improvement; genetic variation; Genotype; Globulins - analysis; Glycine max; Glycine max - chemistry; Glycine max - genetics; glycinin; longitudinal studies; modern cultivars; nucleotide sequences; Nutritive Value; plant breeding; protein composition; protein content; Seed Storage Proteins; seeds; Seeds - chemistry; soy protein; Soybean Proteins - analysis; Soybean Proteins - genetics; soybeans; Storage protein; Biochemical analysis; Genetic variability; protein composition; Genetic diversity; Glycinin; Soybean; protein quality; Glycine max; Grain legume; Leguminosae; Dicotyledones; Quality; Angiospermae; Plant protein; Spermatophyta; Chemical composition; β-Conglycinin
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf060391m

To evaluate the extent of the genetic change and its effects on the seed protein composition of soybean cultivars released during the past 60 years, representative ancestral cultivars and those derived from selective breeding were grown in a side-by-side comparison. Total seed protein content, determined by combustion analysis of nitrogen, revealed a decline in the protein content after decades of selection and breeding. Sodium dodecyl sulfate−polyacrylamide gel electrophoresis comparison of protein profiles of the soybean cultivars indicated that relative expression of most of the seed storage proteins had not varied substantially from the ancestral lines to the present commercial cultivars. There was noticeably less β-subunit of β-conglycinin, a protein devoid of sulfur amino acids, in the modern cultivars represented by Mustang, Pioneer 93B09, and Asgrow 3602. Comparison of the amino acid profiles of soybean seed, a benchmark of the protein's nutritional quality, revealed that the ancestral progenitor, G. soja, was significantly higher in cysteine, glutamic acid, histidine, and arginine than either the ancestral or the modern cultivars. Selective breeding over the past 60 years minimally affected the overall amino acid composition. The degree of divergence in the DNA sequence of the genes encoding glycinin and β-conglycinin in the ancestral and modern cultivars was investigated using Southern hybridization and the polymerase chain reaction. Even though some restriction fragment polymorphisms could be detected, overall, the banding patterns were remarkably similar among the ancestral cultivars and those derived from them, suggesting a high degree of conservation of seed-storage protein genes. The results of our study suggest that selection and breeding for yield during the past 60 years had no major influence on the protein composition, ostensibly because of limited genetic diversity among the parental lines. Keywords: β-Conglycinin; genetic diversity; glycinin; protein composition; protein quality