Response of Low Seed Phytic Acid Soybeans to Increases in External Phosphorus Supply

Abstract

Commercialization of soybean [Glycine max (L.) Merr.] varieties with low seed phytic acid will depend on the stability of the trait when grown in soils with a wide range of P availabilities and on the impact of altered P composition on seed protein and oil concentrations. Impacts of deficient (0.05 mmol L−1) to excessive (0.9 to 1.2 mmol L−1) levels of external P on seed P composition of normal and low phytic acid lines and of altered seed P composition on seed protein and oil synthesis were evaluated. Soybean lines homozygous recessive (pha/pha) at one of two loci with genes that condition the low seed phytic acid trait had the same greater‐than‐threefold increase in phytic acid in response to increasing external P as their normal phytic acid parent, ‘AGS Prichard‐RR’ (Pha/Pha). This supports the conclusion from previous inheritance studies that the low seed phytic acid trait in CX1834‐1‐2 is controlled by epistatic interaction between two independent recessive genes. The seed phytic acid concentration in the low phytic acid line G03PHY‐443 (derived from CX1834‐1‐2) was <2 g phytic acid P kg−1 dry wt. when grown under deficient to excessive external P. As the P supply increased, seed inorganic P concentrations for this line increased from 0.8 to 4.0 g kg−1 dry wt., compared to an increase of 0.2 to 0.6 g kg−1 dry wt. for the normal phytic acid lines. Seed protein and oil concentrations did not differ significantly between normal and low phytic acid lines. These results support continued development of varieties with low seed phytic acid and high yields.