Regulation of seed protein concentration in soybean by supra-optimal nitrogen supply.

Nakasathien, S. and Israel, D.W. and Wilson, R.F. and Kwanyuen, P. (2000) Regulation of seed protein concentration in soybean by supra-optimal nitrogen supply. Crop Science, 40 (5). pp. 1277-1284.

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The physiological and biochemical basis for increased seed protein concentrations (SPC) observed in restriction-index, recurrent-selection breeding programmes with soyabean (Glycine max) are poorly understood. The hypothesis that soyabean SPC is regulated by the supply of nitrogenous substrates available to the seed was evaluated. Effects of supra-optimal external N on seed storage protein accumulation, amino acid concentration and composition in leaves and seeds at R5, and levels of specific storage protein subunits were measured. Genotypes with different SPC (NC 107, normal; N87-984-16, intermediate; and NC 111, high) were grown in controlled-environment chambers and supplied with 30 mM N as NH4NO3 from V5 to maturity or from R5 to maturity. Control plants received 10 mM N throughout the growth cycle. Relative to control, supra-optimal N increased SPC of NC 107 and N87-984-16 by an average of 28%. Greater enhancement of protein accumulation than of dry matter accumulation in the seed resulted in SPCs of 460 to 470 g kg-1, which are appreciably higher than concentrations reported for these cultivars grown in the field and outdoor pot culture. Supra-optimal N also increased SPC of the high protein line (NC 111) by 15%, but this increase resulted entirely from a decrease in yield. Supra-optimal N supplied to NC 107 and N87-984-16 from V5 until R5 increased total free amino acid concentrations in seeds and leaves at R5 by an average of 21 and 46%, respectively. Enhanced accumulation of the β subunit of β-conglycinin, which does not contain methionine and cysteine, accounted for the increase in SPC. While enhanced N availability increased the SPC of a normal protein line into the high range, availability of sulfur amino acids in the developing seed determined which storage protein subunits were synthesized from the extra N.

Item Type: Article
Additional Information: The authors thank Mary Sue Lane, Bill Novitzky, Beverly Taylor, and Jessica Hutchison for their excellent technical support. We are grateful to Dr. Judy Thomas and the staff of the Southeastern Plant Environment Laboratories at North Carolina State University for their assistance in use of growth chambers. Our appreciation is also extended to Drs. J.W.Burton for providing seeds of soybean varieties, C. Arellano for statistical consultation, and C.D. Raper, R.E. Dewey, and colR. J. Volk for helpful suggestions during the preparation of this manuscript.
Uncontrolled Keywords: Seed Protein concentrations, Soybean, Supra-Optimal Nitrogen Supply
Author Affiliation: USDA-ARS, Dep. of Crop Science, North Carolina State University, USA.
Subjects: Plant Protection
Crop Improvement
Divisions: Other Crops
Depositing User: Mr Arbind Seth
Date Deposited: 10 Dec 2012 04:46
Last Modified: 10 Dec 2012 04:46
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