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Soybean [Glycine max (L.) Merr.] is the primary source of meal used in animal feed in the U.S. However, few studies have been conducted to evaluate genomic regions controlling amino acid composition is soybean. Designing soybean seed compositions that will benefit animal production is essential. The objective of this study was to identify genomic regions controlling essential and non-essential amino acid composition in soybean seed proteins. To achieve this objective, 282 F5:9 recombinant inbred lines (RILs) developed from a cross of Essex × Williams 82 were used. Ground soybean seed samples were analyzed for amino acids and statistically significant differences (p < 0.05) were found among genotypes in the population for all amino acid concentrations. The Universal Soy Linkage Panel (USLP) 1.0 of 1,536 single nucleotide polymorphism (SNP) DNA markers were used to genotype the 282 RILs and identify 480 useful genetic markers. The software R/qtl was used to identify candidate quantitative trait loci (QTL), which were validated using R/MQM. A total of ten QTL were detected on chromosomes 5, 7, 9, 10, 13 and 20 that explained 5 to 14% of the total phenotypic variation for a particular amino acid. Using SNPs from the USLP 1.0 to detect QTL for amino acids in soybean provides additional information to select genotypes with enhanced amino acid profiles that will benefit animal production.

SummarySoybean (Glycine max (L.) Merr.) salicylic acid methyl transferase (GmSAMT1) catalyses the conversion of salicylic acid to methyl salicylate. Prior results showed that when GmSAMT1 was overexpressed in transgenic soybean hairy roots, resistance is conferred against soybean cyst nematode (SCN), Heterodera glycines Ichinohe. In this study, we produced transgenic soybean overexpressing GmSAMT1 and characterized their response to various SCN races. Transgenic plants conferred a significant reduction in the development of SCN HG type 1.2.5.7 (race 2), HG type 0 (race 3) and HG type 2.5.7 (race 5). Among transgenic lines, GmSAMT1 expression in roots was positively associated with SCN resistance. In some transgenic lines, there was a significant decrease in salicylic acid titer relative to control plants. No significant seed yield differences were observed between transgenics and control soybean plants grown in one greenhouse with 22 °C day/night temperature, whereas transgenic soybean had higher yield than controls grown a warmer greenhouse (27 °C day/23 °C night) temperature. In a 1‐year field experiment in Knoxville, TN, there was no significant difference in seed yield between the transgenic and nontransgenic soybean under conditions with negligible SCN infection. We hypothesize that GmSAMT1 expression affects salicylic acid biosynthesis, which, in turn, attenuates SCN development, without negative consequences to soybean yield or other morphological traits. Thus, we conclude that GmSAMT1 overexpression confers broad resistance to multiple SCN races, which would be potentially applicable to commercial production.

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