Soybean [Glycine max (L.) Merr.] grain with reduced phytate, myo-inositol-1,2,3,4,5,6-hexakisphosphate, and increased inorganic phosphorus (Pi) would be useful for feeding soybean meal to monogastric animals, such as swine and poultry. A low-phytate (LP) soybean meal would increase the availability of phosphorus (P) in their ration (Adeola et al., 2005; Erdman, 1979; Powers et al., 2006; Richert et al., 2009), reduce the cost of supplemental P and synthetic phytase (Cromwell, 2002), and reduce the Pi in their excrement, which could have positive benefits for the environment (Daverede et al., 2004).The study by Hulke et al. (2004) showed that LP BC1F2:4 soybean lines had a higher concentration of palmitate and stearate in their oil compared to normal-phytate (NP) BC1F2:3 lines. All of their backcross lines were homozygous for the fap1(C1726) and fap3(A22) alleles for reduced palmitate. Spear and Fehr (2007) indicated that additional generations of backcrossing to the same recurrent parent used in the study by Hulke et al. (2004) resulted in the same association between the LP trait and elevated palmitate + stearate (saturate) concentration. Hulke et al. (2004) indicated that the elevated saturate concentration of LP lines in their study may have been due to modifiers for elevated saturated fat content that were linked to one or both genes that control the LP trait or that one or both of the genes have a pleiotropic effect on saturate content.The first objective of this study was to determine if the association between the LP trait and elevated saturates continued after multiple generations of breeding and, if so, to evaluate possible causes of the association between LP and saturate concentration. LP and NP F3 individuals and their progeny were evaluated from three single-cross populations segregating for the wild-type and mutant alleles controlling phytate concentration, Lpa1, lpa1, Lpa2, and lpa2. All the individuals in the populations were homozygous for the fap1(C1726) and fap3(A22) alleles for reduced palmitate. The mean palmitate, stearate, 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-1 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 lpa1 or lpa2, 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.The second objective of this study was to determine if there was a relationship between LP and linolenate in lines that were homozygous for three alleles that reduce linolenate concentration. LP and NP F2 individuals and their progeny were evaluated from two three-way cross populations segregating for Lpa1, lpa1, Lpa2, and lpa2 and homozygous for the fan1(A5), fan2(A23), and fan3(A26) alleles for reduced linolenate. The mean linolenate content was not significantly different between the NP and LP types for the two populations. These results indicated that it should be possible to select LP lines with a linolenate concentration similar to commercial low-linolenate cultivars.
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