To improve the oxidative stability of soybean [Glycine max (L.) Merr.] oil, it is desirable to increase the percentage of the monounsaturated fatty ester oleate. By altering the endogenous FAD2-1gene in soybean, oleate concentrations of greater than 750 g kg^-1 can be obtained. From a commercial perspective, it is important to understand the influence of this genetic alteration on agronomic and seed traits, as well as the stability of the increased oleate concentration across a range of environments.

Objective one of my research was to evaluate the influence of the DP-305423-1 high-oleate (HO) transgene on agronomic and seed traits in five populations evaluated across locations in Iowa, Illinois and Ohio during 2011. A total 27 high-oleate, normal-linolenate (HONL) and 27 normal-oleate, normal-linolenate (NONL) F_3:5 lines from each population were evaluated. On average, the HONL lines yielded 4.6% less than the NONL lines, had 25 g kg^-1 greater protein and 13 g kg^-1 lower oil concentration. Of the top 10 yielding lines in each of the five populations, only 12% were HONL. These results suggested it may be difficult to develop HONL lines with seed yield and protein and oil concentration similar to NONL lines.

A second objective of my research was to evaluate the possible influence of undesirable linkage drag near the HO transgene as an explanation for the reduced yield of the HONL lines. All F_3:5 lines were genotyped with a panel of single nucleotide polymorphism (SNP) markers flanking the HO transgene. Of the six HONL lines that had a mean yield not significantly different than the highest yielding NONL line, only one of them had a genetic recombination near the HO transgene. There were other HONL lines whose mean yield was significantly less than the highest yielding NONL line that had a recombination in the genomic region. These results suggest that the reduction in yield of the HONL lines is not a result of linkage drag.

A third objective of my research was to evaluate the environmental stability of the increased oleate concentration in soybean lines homozygous for the DP-305423-1 HO transgene. A set of 15 lines with different combinations of alleles for alter fatty ester concentration, as well as three conventional lines were evaluated across 18 environments during 2010 and 2011. Stability was measured by the range in oleate concentration across environments as well as by regressing the mean oleate for each genotype on an environmental index for each environment. The HONL lines had the lowest mean range in oleate concentrations among environments at 73 g kg^-1 and the lowest mean regression coefficient. These data indicated that the increased oleate concentration in lines homozygous for the DP-305423-1 transgene would be as stable as the oleate concentration of normal-oleate cultivars when produced across multiple environments.