Elevated Palmitate and Stearate Concentrations in the Oil of Low‐Phytate Soybean Lines

Abstract

The combination of low phytate (LP) and low saturated fatty esters in a soybean [Glycine max (L.) Merr] cultivar could improve the availability of inorganic phosphorus (Pi) in livestock rations and improve the nutrition of the oil used in human diets. Previous studies indicated that lines with the Ipal and ipa2 alíeles for LP and the fap7(C1726) and fap3(A22) alíeles for reduced palmitate had greater palmitate plus stéarate (saturate) concentrations than normal-phytate (NP) lines. The objective of our study was to evaluate possible causes of the association between LP and saturate concentration. Lowphytate and NP F3 individuals and their progeny were evaluated from three single-cross populations segregating for Lpa1, tpa1, Lpa2, and ipa2 and homozygous for fap1{C^726) and fap3{A22). The mean palmitate, stéarate, and saturate concentrations of the LP lines were significantly greater than the NP lines in all the populations. The frequency of F3.4 lines with a saturate concentration of <70 g kg"^ averaged across populations was 8% for the LP lines and 74% for the NP lines. The elevated saturates was not attributable to genetic factors linked to Ipal or ipa2 but was associated with a greater concentration of Pi in LP individuals. The apparent relationship between elevated Pi and elevated saturate concentrations would hinder the development of LP cultivars with low saturated fatty esters.

Agronomic and seed traits of soybean lines with genes for aphid resistance, inheritance and mapping of Cowpea mild mottle virus-like resistance in soybean, and fatty ester composition of low-phytate, low-saturate soybean lines

“…Food and Drug Administration, 2009) for labeling as a low-saturate oil. Gill and Fehr (2011) found a low frequency of LP F 3 individuals with a saturate concentration ≤70 g kg -1 in three populations formed by crossing a LP line with reduced saturate concentration to three LS lines. Their hypothesis was that the LP lines with a saturate concentration ≤70 g kg -1 were the result of the accumulation of favorable modifying genes for LS concentration.…”

“…Combining the LP trait with low saturated fatty esters (LS) in the oil would result in added value for both the meal and oil (Dilger and Adeola, 2006;Powers et al, 2006;Fehr, 2007;. Multiple studies have reported a negative association between the concentrations of phytate P and saturated fatty esters (Hulke et al, 2004;Oltmans et al, 2005;Gill and Fehr, 2011). Gill and Fehr (2011) were able to recover a small frequency of LP individuals with <70 g kg -1 saturates, and hypothesized that this was due to the accumulation of favorable modifying genes for reduced saturates.…”

“…Multiple studies have reported a negative association between the concentrations of phytate P and saturated fatty esters (Hulke et al, 2004;Oltmans et al, 2005;Gill and Fehr, 2011). Gill and Fehr (2011) were able to recover a small frequency of LP individuals with <70 g kg -1 saturates, and hypothesized that this was due to the accumulation of favorable modifying genes for reduced saturates. The first low-phytate soybean line with low saturates, A38, was developed at Iowa State Univ.…”

“…A38 was homozygous for the fap1(C1726) and fap3(A22) alleles and had a saturate concentration as low as that of NP,LS cultivars grown in the same environments (data not shown). The LS of A38 may have been due to the accumulation of favorable modifying genes for LS concentration as proposed by Gill and Fehr (2011). However, an alternative hypothesis could be that genes for elevated saturate concentration linked to both lpa1 and lpa2 interact epistatically to cause the elevated saturate concentration in LP lines, similar to the epistatic interaction between lpa1 and lpa2 that result in the LP phenotype.…”

“…Combining the LP trait with low saturated fatty esters (LS) in the oil would result in added value for both the meal and oil (Dilger and Adeola, 2006;Powers et al, 2006;Fehr, 2007;. Three studies have been reported in which the lpa1 and lpa2 alleles for LP were combined with the fap1(C1726) (Erickson et al, 1988) and fap3(A22) (Fehr et al, 1991) alleles for reduced palmitate that are used in LS cultivars currently grown in the United States (Hulke et al, 2004;Spear and Fehr, 2007;Gill and Fehr, 2011). All of the studies found that LP lines had greater palmitate plus stearate (saturate) concentration than normal-phytate (NP) lines.…”