Genetic architecture of protein and oil content in soybean seed and meal.

Soybean is grown primarily for the protein and oil extracted from its seed and its value is influenced by these components. The objective of this study was to map marker-trait associations (MTAs) for the concentration of seed protein, oil, and meal protein using the soybean nested association mapping (SoyNAM) population. The composition traits were evaluated on seed harvested from over 5000 inbred lines of the SoyNAM population grown in 10 field locations across 3 years. Estimated heritabilities were at least 0.85 for all three traits. The genotyping of lines with single nucleotide polymorphism markers resulted in the identification of 107 MTAs for the three traits. When MTAs for the three traits that mapped within 5 cM intervals were binned together, the MTAs were mapped to 64 intervals on 19 of the 20 soybean chromosomes. The majority of the MTA effects were small and of the 107 MTAs, 37 were for protein content, 39 for meal protein, and 31 for oil content. For cases where a protein and oil MTAs mapped to the same interval, most (94%) significant effects were opposite for the two traits, consistent with the negative correlation between these traits. A coexpression analysis identified candidate genes linked to MTAs and 18 candidate genes were identified. The large number of small effect MTAs for the composition traits suggest that genomic prediction would be more effective in improving these traits than marker-assisted selection.

Field-Based Scoring of Soybean Iron Deficiency Chlorosis Using RGB Imaging and Statistical Learning.

Iron deficiency chlorosis (IDC) is an abiotic stress in soybean that can cause significant biomass and yield reduction. IDC is characterized by stunted growth and yellowing and interveinal chlorosis of early trifoliate leaves. Scoring IDC severity in the field is conventionally done by visual assessment. The goal of this study was to investigate the usefulness of Red Green Blue (RGB) images of soybean plots captured under the field condition for IDC scoring. A total of 64 soybean lines with four replicates were planted in 6 fields over 2 years. Visual scoring (referred to as Field Score, or FS) was conducted at V3-V4 growth stage; and concurrently RGB images of the field plots were recorded with a high-throughput field phenotyping platform. A second set of IDC scores was done on the plot images (displayed on a computer screen) consistently by one person in the office (referred to as Office Score, or OS). Plot images were then processed to remove weeds and extract six color features, which were used to train computer-based IDC scoring models (referred to as Computer Score, or CS) using linear discriminant analysis (LDA) and support vector machine (SVM). The results showed that, in the fields where severe IDC symptoms were present, FS and OS were strongly positively correlated with each other, and both of them were strongly negatively correlated with yield. CS could satisfactorily predict IDC scores when evaluated using FS and OS as the reference (overall classification accuracy > 81%). SVM models appeared to outperform LDA models; and the SVM model trained to predict IDC OS gave the highest prediction accuracy. It was anticipated that coupling RGB imaging from the high-throughput field phenotyping platform with real-time image processing and IDC CS models would lead to a more rapid, cost-effective, and objective scoring pipeline for soybean IDC field screening and breeding.

Multi-Population Selective Genotyping to Identify Soybean [Glycine max (L.) Merr.] Seed Protein and Oil QTLs.

Plant breeders continually generate ever-higher yielding cultivars, but also want to improve seed constituent value, which is mainly protein and oil, in soybean [Glycine max (L.) Merr.]. Identification of genetic loci governing those two traits would facilitate that effort. Though genome-wide association offers one such approach, selective genotyping of multiple biparental populations offers a complementary alternative, and was evaluated here, using 48 F2:3 populations (n = âˆ¼224 plants) created by mating 48 high protein germplasm accessions to cultivars of similar maturity, but with normal seed protein content. All F2:3 progeny were phenotyped for seed protein and oil, but only 22 high and 22 low extreme progeny in each F2:3 phenotypic distribution were genotyped with a 1536-SNP chip (ca 450 bimorphic SNPs detected per mating). A significant quantitative trait locus (QTL) on one or more chromosomes was detected for protein in 35 (73%), and for oil in 25 (52%), of the 48 matings, and these QTL exhibited additive effects of ≥ 4 g kg(-1) and R(2) values of 0.07 or more. These results demonstrated that a multiple-population selective genotyping strategy, when focused on matings between parental phenotype extremes, can be used successfully to identify germplasm accessions possessing large-effect QTL alleles. Such accessions would be of interest to breeders to serve as parental donors of those alleles in cultivar development programs, though 17 of the 48 accessions were not unique in terms of SNP genotype, indicating that diversity among high protein accessions in the germplasm collection is less than what might ordinarily be assumed.

Effects of voluntary running and soy supplementation on diet-induced metabolic disturbance and inflammation in mice.

We investigated the effects of diet (AIN93G or high-fat), physical activity (sedentary or voluntary running), and protein source (casein or soy protein isolate (SPI)) and their interactions on metabolic disturbance and inflammation in mice. After 14 weeks of feeding, the high-fat diet increased body weight gain by 34.5% (p < 0.01), whereas running reduced weight gain by 30.5% (p < 0.01) compared to their respective AIN93G and sedentary controls; SPI did not affect weight gain. The high-fat diet significantly increased plasma concentrations of insulin, glucose, triglycerides, leptin, and monocyte chemotactic protein-1 (MCP-1); running and SPI significantly reduced these parameters compared to their respective controls. The high-fat diet significantly increased and running significantly reduced plasma plasminogen activator inhibitor-1. A unique finding was that SPI supplementation to the high-fat diet reduced plasma insulin by 11% (p < 0.05), MCP-1 by 21% (p = 0.03), and tumor necrosis factor-α (TNF-α) by 50% (p = 0.05) compared to casein. As adipose tissues produce many adipocytokines, including MCP-1 and TNF-α, that contribute to a state of chronic low grade systemic inflammation and facilitate metabolic disturbance in obesity, further investigations are warranted into the roles of soy protein in reducing the risk of obesity.

Dietary supplementation with high-selenium soy protein reduces pulmonary metastasis of melanoma cells in mice.

The effect of high-selenium (Se) soy protein on pulmonary metastasis of murine B16BL6 melanoma cells was investigated in male C57BL6 mice. Isolated soy proteins (ISP) from soybeans grown with and without Se foliar application during seed development were compared. Five diets were studied, a basal AIN-93G diet or a basal diet containing 10% low-Se ISP, 5% low-Se + 5% high-Se ISP, 10% high-Se ISP, or 10% low-Se ISP supplemented with Se equivalent to that of the 10% high-Se ISP diet. The Se concentrations of the 5 diets were 0.13, 0.13, 1.9, 3.6, and 3.0 microg/g, respectively. Mice were fed the diet for 2 wk before and 2 wk after an i.v. injection of 5 x 10(4) viable cells. At necropsy, the number and size of tumors that had developed in the lungs were determined. In the control group, 13/18 mice exhibited > or = 50 tumors. The numbers of mice with > or = 50 tumors were 8/18, 7/18, 3/18, and 6/17 in the ISP-fed groups, respectively. The differences between the 10% high-Se ISP group, the Se-supplemented 10% low-Se group, and the control were significant (P < 0.05). Dietary supplementation with 10% low-Se ISP significantly decreased the mean number of tumors per group and the tumor size compared with the control. A greater reduction in these variables occurred in mice fed the 10% high-Se ISP diet. The inhibition by the Se-supplemented 10% low-Se ISP diet was similar to that by the 10% high-Se ISP diet. The whole-blood Se concentration was inversely related to the tumor number (R = -0.87, P = 0.052), tumor cross-sectional area (R = -0.91, P < 0.05), and tumor volume (R = -0.93, P < 0.05). These findings suggest that Se is responsible for the greater antimetastatic effect of the high-Se ISP. We conclude that the high-Se soy protein has a greater inhibitory effect than the low-Se soy protein on pulmonary metastasis of melanoma cells in mice.