Regional analysis of planting date and cultivar maturity recommendations that improve soybean oil yield and meal protein concentration.

Planting date and cultivar maturity group (MG) are major management factors affecting soybean [Glycine max (L.) Merr.] yield, but their effect on seed oil and protein concentration, and in particular meal protein concentration, is less understood. We quantified changes in seed oil and protein, and estimated meal protein concentration, and total oil and protein yield in response to planting date and cultivar MG ranging from 3 to 6 and across locations comprising a 8.3° range in latitude in the U.S. Midsouth. Our results show that delayed planting date and later cultivar maturity reduced oil concentration, and this was partially associated with a decrease in temperature during the seed fill phase. Thus, optimum cultivar MG recommendations to maximize total oil yield (in kg ha-1) for planting dates in May and June required relatively earlier cultivar MGs than those recommended to maximize seed yield. For planting dates in April, short-season MG 3 cultivars did not increase oil yield compared to full-season MG 4 or 5 cultivars due to a quadratic yield response to planting date at most locations. Planting date and cultivar maturity effects on seed protein concentration were not always consistent with the effects on estimated meal protein concentration after oil extraction. Meal protein concentration decreased with lower temperatures during seed fill, and when the start of seed fill occurred after August 15, but relatively short-season cultivar MGs reduced the risk of low meal protein concentration. Meal protein concentration is a trait of interest for the feed industry that would be beneficial to report in future studies evaluating genetic, management, and environmental effects on seed protein concentration.

Development of soybean experimental lines with enhanced protein and sulfur amino acid content.

Soybean is the preferred protein source for both poultry and swine feed. However, this preferred status is being challenged due to competition from alternative feed ingredients. To overcome this, it becomes necessary for breeders to develop soybean cultivars that contain higher protein and better nutritional composition. In this study, we have developed experimental soybean lines that not only contain significantly higher amounts of protein but also improved sulfur amino acid content. This objective was achieved by crossing a O-acetylserine sulfhydrylase (OASS) overexpressing transgenic soybean line with elevated levels of sulfur amino acid content (CS) with a high protein Korean soybean cultivar (Lee 5). Introgression of high protein and overexpression of OASS was monitored in the experimental lines at each successive generation (F2-F6) by measuring protein content and OASS activity. The average protein content of transgenic CS and Lee 5 seeds were 34.8 % and 44.7 %, while in the experimental soybean lines the protein content ranged from 41.3 %-47.7 %, respectively. HPLC and inductively coupled plasma-mass spectrometry analyses revealed that all the experimental lines developed in this study contained significantly higher amounts of sulfur containing amino acids and elemental sulfur in the seeds. The sulfur amino acid (cysteine + methionine) content of the experimental lines ranged from 1.1 % to 1.26 % while the parents Lee 5 and CS had 0.79 % and 1.1 %, respectively. SDS-PAGE and western blot analysis demonstrated that the accumulation of Bowman-Birk protease inhibitor and lunasin, two sulfur amino acid rich peptides, were elevated in experimental soybean lines. High-resolution 2D-gel electrophoresis and Delta2D gel analysis validated that an overall increase in the different subunits of 7S ß-conglycinin and 11S glycinin were mainly responsible for the observed increase in the total amount of protein in experimental lines.

Environmental Stability of Seed Carbohydrate Profiles in Soybeans Containing Different Alleles of the Raffinose Synthase 2 (RS2) Gene.

Soybean [Glycine max (L.) Merr.] is important for the high protein meal used for livestock feed formulations. Carbohydrates contribute positively or negatively to the potential metabolizable energy in soybean meal. The positive carbohydrate present in soybean meal consists primarily of sucrose, whereas the negative carbohydrate components are the raffinose family of oligosaccharides (RFOs), raffinose and stachyose. Increasing sucrose and decreasing raffinose and stachyose are critical targets to improve soybean. In three recently characterized lines, variant alleles of the soybean raffinose synthase 2 (RS2) gene were associated with increased sucrose and decreased RFOs. The objective of this research was to compare the environmental stability of seed carbohydrates in soybean lines containing wild-type or variant alleles of RS2 utilizing a field location study and a date of planting study. The results define the carbohydrate variation in distinct regional and temporal environments using soybean lines with different alleles of the RS2 gene.

Introgression of leginsulin, a cysteine-rich protein, and high-protein trait from an Asian soybean plant introduction genotype into a North American experimental soybean line.

Soybean is an important protein source for both humans and animals. However, soybean proteins are relatively poor in the sulfur-containing amino acids, cysteine and methionine. Improving the content of endogenous proteins rich in sulfur-containing amino acids could enhance the nutritive value of soybean meal. Leginsulin, a cysteine-rich peptide, predominantly accumulates in Asian soybean accessions but not in most North American cultivars. By screening diverse soybean accessions from the USDA Soybean Germplasm Collection, we were able to identify one plant introduction, PI 427138, as a high-protein line with relatively high amounts of both elemental sulfur and leginsulin. We introgressed these desirable traits from PI 427138 into an experimental line with the aim of improving the overall protein content and quality of seed proteins. Biochemical characterization of inbred progenies from the cross of LD00-3309 with PI 427138 grown at six locations revealed stable ingression of high protein, high elemental sulfur, and high leginsulin accumulation. Comparison of soybean seed proteins resolved by high-resolution 2-D gel electrophoresis in combination with Delta2D image analysis software revealed preferential accumulation of a few glycinin subunits contributed to the increased protein content in the introgressed lines. Amino acid analysis revealed that even though the leginsulin introgressed lines had higher protein, leginsulin, and elemental sulfur, the overall concentration of sulfur-containing amino acids was not significantly altered when compared with the parental lines. The experimental soybean lines developed during this study (Leg-3, Leg-7, and Leg-8) lack A5, A4, and B3 glycinin subunits and could be utilized in breeding programs to develop high-quality tofu cultivars.

Climate-induced reduction in US-wide soybean yields underpinned by region- and in-season-specific responses.

The United States is one of the largest soybean exporters in the world. Production is concentrated in the upper Midwest(1). Much of this region is not irrigated, rendering soybean production systems in the area highly sensitive to in-season variations in weather. Although the influence of in-season weather trends on the yields of crops such as soybean, wheat and maize has been explored in several countries(2-6), the potentially confounding influence of genetic improvements on yields has been overlooked. Here we assess the effect of in-season weather trends on soybean yields in the United States between 1994 and 2013, using field trial data, meteorological data and information on crop management practices, including the adoption of new cultivars. We show that in-season temperature trends had a greater impact on soybean yields than in-season precipitation trends over the measurement period. Averaging across the United States, we show that soybean yields fell by around 2.4% for every 1 °C rise in growing season temperature. However, the response varied significantly among individual states, ranging from -22% to +9%, and also with the month of the year in which the warming occurred. We estimate that year-to-year changes in precipitation and temperature combined suppressed the US average yield gain by around 30% over the measurement period, leading to a loss of US$11 billion. Our data highlight the importance of developing location-specific adaptation strategies for climate change based on early-, mid- and late-growing season climate trends.

Effect of six decades of selective breeding on soybean protein composition and quality: a biochemical and molecular analysis.

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 beta-subunit of beta-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 beta-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.

Positional effect on protein and oil content and composition of soybeans.

Soybean (Glycine max [L.] Merr.) protein and oil qualities, with respect to monogastric nutrition, have been linked to the relative abundance of specific protein subunits and fatty acids, respectively. An analysis of field-grown soybean seeds by near-infrared spectroscopy revealed significant differences in their protein and oil contents as a function of nodal position. Seed proteins from the plant apex were high in protein and low in oil content, while those from the basal region exhibited an opposite pattern of accumulation. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of total seed proteins revealed that the beta-subunit of beta-conglycinin content was 4-fold higher in seeds from the apical nodes than in seeds from basal nodes. The glycinin A3 polypeptide content gradually increased in successively lower nodes from the top of the plant. Its accumulation was drastically reduced when nitrogen was applied at specific growth stages. Exogenous nitrogen did not alter the pattern of beta-subunit accumulation, but accrual of the acidic and basic polypeptides of glycinin was diminished. The remaining seed storage protein components were not influenced by nodal position or nitrogen application. Gas chromatographic analysis of fatty acids indicated that only oleic (18:0) and linoleic (18:2) acids showed variability in accumulation at different nodes. Neither the abundance nor the distribution of the fatty acids was altered by nitrogen application.