Historical trend on seed amino acid concentration does not follow protein changes in soybeans

Abstract

Soybean [Glycine max (L.) Merr.] is the most important oilseed crop for animal industry due to its high protein concentration and high relative abundance of essential and non-essential amino acids (AAs). However, the selection for high-yielding genotypes has reduced seed protein concentration over time, and little is known about its impact on AAs. The aim of this research was to determine the genetic shifts of seed composition for 18 AAs in 13 soybean genotypes released between 1980 and 2014. Additionally, we tested the effect of nitrogen (N) fertilization on protein and AAs trends. Soybean genotypes were grown in field conditions during two seasons under a control (0 N) and a N-fertilized treatment receiving 670 kg N ha−1. Seed yield increased 50% and protein decreased 1.2% comparing the oldest and newest genotypes. The application of N fertilizer did not significantly affect protein and AAs concentrations. Leucine, proline, cysteine, and tryptophan concentrations were not influenced by genotype. The other AAs concentrations showed linear rates of decrease over time ranging from − 0.021 to − 0.001 g kg−1 year−1. The shifts of 11 AAs (some essentials such as lysine, tryptophan, and threonine) displayed a relative-to-protein increasing concentration. These results provide a quantitative assessment of the trade-off between yield improvement and seed AAs concentrations and will enable future genetic yield gain without overlooking seed nutritional value.

May mineral composition trigger or limit the protein content in soybean (Glycine max (L.) Merrill) seeds? Insights from a survey on 95 varieties cultivated in Brazil

“…Nevertheless, several pieces of evidence suggest that higher productivity neither boosted the content nor quality of protein of soybean seeds, since a negative correlation between yield and the protein content has been often reported (Assefa et al, 2018; de Borja Reis et al, 2020; Mello Filho et al, 2004). A recent study conducted with 26 soybean cultivars released over the last 50 years in southern Brazil revealed that the yield has increased at a rate of 45.9 kg ha−1 year -1 whereas the protein content has decreased by 0.84 g kg−1 year -1 , respectively (Umburanas et al, 2022).…”

“…As these figures are affected by environmental conditions and crop management practices (Assefa et al, 2019; de Borja Reis et al, 2020), one should expect that the protein content in soybean seeds might surely be influenced by their elemental composition. In this scenario, direct relationships were observed between protein content and the sulphur concentration (p = 0.5), as well as zinc, copper (p > 0.1-0.2), and manganese concentration in the probed soybean seeds (Fig.…”

“…Besides this downward trend in protein content, no significant changes in the amino acid composition were observed in a field trial exploring the soybean genotypes released between 1980 and 2014 in the United States (de Borja Reis et al, 2020). Thus, a change in amino acid profile would indicate an imbalance in the protein fractions, i.e ., those from the albumin, globulin, glutelin, and prolamin families (Makeri et al, 2017), which has not been observed.…”

“…In this context, although several strategies have been successfully explored for increasing the agricultural productivity of soybean crops, a major fraction did not focus on improving the quality of soybean seeds, such as the content or quality of soybean proteins, leading to a significant reduction on the protein content as a function of the higher outputs per unit of area (de Borja Reis et al 2020; Umburanas et al 2022). Overcoming this outline relies on understanding the physiological mechanisms that promote or hinder protein synthesis in soybeans seeds.…”

Vertical Canopy Profile and the Impact of Branches on Soybean Seed Composition

“…Changing the yield allocation among canopy portions could be manipulated by plant breeding and management practices. For instance, enhanced branching in modern genotypes could be related to stable LAA concentration despite protein decay over the last 40 years (de Borja Reis et al, 2020 ). Future research must consider to study the branching process (initiation, progress rate and duration, dry matter, and harvest index) as a potential moderator of soybean seed composition, plausibly benefitting human nutrition with improved AA profile and oil concentration.…”