Skip to main content
ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #362937

Research Project: Exploiting Genetic Diversity through Genomics, Plant Physiology, and Plant Breeding to Increase Competitiveness of U.S. Soybeans in Global Markets

Location: Soybean and Nitrogen Fixation Research

Title: Increased nitrogen fixation and remobilization may increase seed protein without a yield penalty in a soybean introgression line

item Locke, Anna

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2020
Publication Date: 10/28/2020
Citation: Locke, A.M., Ramirez, M.E. 2020. Increased nitrogen fixation and remobilization may increase seed protein without a yield penalty in a soybean introgression line. Journal of Crop Improvement.

Interpretive Summary: As soybean yields have increased over time, seed protein content has decreased. Few soybean varieties break this negative relationship, but a soybean line called Benning hi-pro has been developed that breaks this negative association. Nitrogen supply into the seed typically limits seed protein. We compared nitrogen fluxes in Benning hi-pro and its lower protein parent, Benning, to determine the source of the nitrogen that gives Benning hi-pro its higher seed protein content. Field and growth chamber experiments showed that Benning hi-pro has greater nitrogen fixation capacity and greater remobilization of nitrogen from vegetative tissues during seed fill. However, these traits were only observed in certain environments, suggesting that the genetic differences between Benning and Benning hi-pro do not directly alter nitrogen fixation or nitrogen remobilization.

Technical Abstract: The development of soybean varieties with higher seed protein content has been hindered by a negative correlation between protein content and yield. Benning hi-pro, a genotype that breaks this tradeoff, was recently developed by introgression of a high protein allele on chromosome 20 into a high yielding parent. Because seed protein is thought to be limited by N, field and growth chamber experiments were performed to identify the N flux(es) that enable Benning hi-pro’s increased seed protein without a yield penalty. When the N source was completely controlled in growth chambers, Benning hi-pro was occasionally able to fix more N than its recurrent parent, but this response depended on the strain of the rhizobia symbiont and was not observed at all developmental stages. In the field, Benning hi-pro remobilized N from its leaves at a higher rate relative to C during seed fill, but this response was only observed in one of the two years studied. The high protein allele and surrounding region of chromosome 20 present in Benning hi-pro increases its potential for N fixation and N remobilization from vegetative tissue, but those phenotypes are not consistently expressed and may depend on environmental and sink control.