We identified QTL associated with protein and amino acids in a soybean mapping population that was grown in five environments. These QTL could be used in MAS to improve these traits. Soybean, rather than nitrogen-containing forages, is the primary source of quality protein in feed formulations for domestic swine, poultry, and dairy industries. As a sole dietary source of protein, soybean is deficient in the amino acids lysine (Lys), threonine (Thr), methionine (Met), and cysteine (Cys). Increasing these amino acids would benefit the feed industry. The objective of the present study was to identify quantitative trait loci (QTL) associated with crude protein (cp) and amino acids in the 'Benning' × 'Danbaekkong' population. The population was grown in five southern USA environments. Amino acid concentrations as a fraction of cp (Lys/cp, Thr/cp, Met/cp, Cys/cp, and Met + Cys/cp) were determined by near-infrared reflectance spectroscopy. Four QTL associated with the variation in crude protein were detected on chromosomes (Chr) 14, 15, 17, and 20, of which, a QTL on Chr 20 explained 55 % of the phenotypic variation. In the same chromosomal region, QTL for Lys/cp, Thr/cp, Met/cp, Cys/cp and Met + Cys/cp were detected. At these QTL, the Danbaekkong allele resulted in reduced levels of these amino acids and increased protein concentration. Two additional QTL for Lys/cp were detected on Chr 08 and 20, and three QTL for Thr/cp on Chr 01, 09, and 17. Three QTL were identified on Chr 06, 09 and 10 for Met/cp, and one QTL was found for Cys/cp on Chr 10. The study provides information concerning the relationship between crude protein and levels of essential amino acids and may allow for the improvement of these traits in soybean using marker-assisted selection.

The development of superior soybean, Glycine max (L.) Merr., cultivars exhibiting resistance to insects has been hindered due to linkage drag, a common phenomenon when introgressing alleles from exotic germplasm. Simple-sequence repeat (SSR) markers were used previously to map soybean insect resistance (SIR) quantitative trait loci (QTLs) in a'Cobb' X PI 229358 population, and subsequently used to create near-isogenic lines (NILs) with SIR QTL i n a 'Benning' genetic background. SIR QTLs were mapped on linkage groups (LGs) M (SIRQTL-M), G (SIRQTL-G), and H (SIRQTL-H). The objectives of this study were to 1) evaluate linkage drag for seed yield by using Benning-derived NILs selected for SIRQTL-M, SIRQTL-H, and SIRQTL-G; 2) assess the amount of PI 229358 genome surrounding the SIR QTL in each Benning NIL; and 3) evaluate the individual effects these three QTLs on antibiosis and antixenosis to corn earworm, Helicoverpa zea (Boddie), and soybean looper, Pseudoplusia includens (Walker). Yield data collected in five environments indicated that a significant yield reduction is associated with SIRQTL-G compared with NILs without SIR QTL. Overall, there was no yield reduction associated with SIRQTL-M or SIRQTL-H. A significant antixenosis and antibiosis effect was detected for SIRQTL-M in insect feeding assays, with no effect detected in antixenosis or antibiosis assays for SIRQTL-G or SIRQTL-H without the presence of PI 229358 alleles at SIRQTL-M. These results support recent findings concerning these loci.

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Soybean [Glycine max (L.) Merr.] is the one of the world's leading sources of oil and high‐quality protein meal. An understanding of genotype × environment (G × E) interactions associated with crude protein (cp), and amino acids lysine (Lys), threonine (Thr), methionine (Met), and cysteine (Cys) would aid breeders in their selection efforts. The objectives of this study were to determine the impact of G × E interactions on protein and amino acid contents, to assess the optimum number of replications and environments necessary to provide a given level of discrimination among genotypes for crude protein and amino acids, and to evaluate the association of seed yield, maturity, and other agronomic traits with amino acid content. To meet these objectives, 140 F5–derived recombinant inbred lines (RILs) were developed from a cross of ‘Benning’ × ‘Danbaekkong’ and were grown in five field environments across the southern United States. The effects of genotype and G × E interaction were significant for crude protein, Lys/cp, Thr/cp, Met/cp, Cys/cp, and Met + Cys/cp (P ≤ 0.001). The genotypic variance component for crude protein was seven times larger than the G × E variance component. These two components of variance were found to be of similar magnitude for Lys/cp and Cys/cp. The G × E component of variance was slightly higher than the genotypic component for Thr/cp, Met/cp, and Met + Cys/cp. It was determined that the combination of five replications and two environments used in the present study could detect a difference of 2.5% between two genotype means for Lys/cp and Thr/cp. An increased number of plots (environment and replication combinations) would be necessary to detect a 2.5% difference or less between two genotype means for crude protein, Met/cp, Cys/cp, and Met + Cys/cp. Significant correlations were detected between yield and crude protein (r = −0.50), Lys/cp (r = 0.49), and Thr/cp (r = 0.49). Associations of crude protein and amino acids with maturity, seed weight, plant height, and lodging were negligible.