Genetic Variation for Modifiers Controlling Reduced Saturated Fatty Acid Content in Soybean

Soybean [Glycine max (L.) Merr.] oils with reduced palmitic acid concentrations should comply with U.S. Food and Drug Administration (FDA) regulations for vegetable oils with lower saturated fatty acid contents. This study was designed to investigate the genetic basis for reduced palmitic and stearic acid contents in the seed oil of reduced palmitic acid germplasm, N87-2122-4. Crosses between N87-2122-4 and Midwest-adapted cultivars, Kenwood and P9273, revealed frequencies of reduced and normal palmitic acid among F₂ progeny consistent with segregation at a single major locus. There was a large phenotypic variation (15–30 g kg⁻¹) for paimitic acid content measured on progeny homozygous for either reduced or normal palmitic acid alleles, however. Repeatability of this variation was examined in 87 reduced and normal palmitic F₅:₇ lines randomly sampled from each cross. Reduced palmitic acid lines ranged between 54 and 72 g kg⁻¹, and normal palmitic acid lines between 90 and 119 g kg⁻¹ for both crosses. No line produced significantly less palmitic acid than N87-2122-4 but ≈ 55% of the reduced palmitic acid lines were significantly greater (P < 0.01). The large genotypic ranges observed for both F₂ and F₅:₇ generations may be explained by an undetermined number of genetic modifiers associated with the major palmitic acid locus. Across both populations, the major reduced palmitic acid allele was associated with a 15% reduction in stearic acid content. However, genetic correlations for palmitic and stearic acid contents among lines homozygous for the major palmitic acid alleles were nonsignificant (rg = −0.30–0.18), enabling simultaneous selection of inbred lines producing both reduced palmitic and stearic acid contents. High narrow-sense heritabilities (>80%) for palmitic and stearic acid contents suggest that total saturates may be reduced by selection in few environments for major and modifier genes controlling reduced palmitic acid content. Cooperative investigations of the USDA-ARS, and North Carolina Agric. Res. Serv., Raleigh, NC. Mention of propriety products are included for the benefit of the reader and do not imply endorsement by the USDA or North Carolina State University.