Phytic acid and inorganic phosphate composition in soybean lines with independent IPK1 mutations

Authors: VINCENT, JENNIFER - University Of Missouri; STACEY, MINVILUZ - University Of Missouri; STACEY, GARY - University Of Missouri; Bilyeu, Kristin

Submitted to: The Plant Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/20/2014
Publication Date: 3/13/2015
Publication URL: http://handle.nal.usda.gov/10113/61210
Citation: Vincent, J.A., Stacey, M., Stacey, G., Bilyeu, K.D. 2015. Phytic acid and inorganic phosphate composition in soybean lines with independent IPK1 mutations. The Plant Genome. 8(1). Available https://dl.sciencesocieties.org/publications/tpg/pdfs/8/1/plantgenome2014.10.0077.

Interpretive Summary: Soybean seeds contain a large amount of phosphorus in a storage molecule termed phytic acid (PA). PA is considered an anti-nutritional factor because it prevents essential nutrients such as phosphorus and minerals from being nutritionally available in soybean-based feeds. Interest in reducing PA has increased greatly over the years and several low PA soybean lines have been discovered; however, many of these lines have inadequate germination and emergence. Our objective was to investigate novel strategies to reduce PA levels with conventional breeding methods. We determined that a unique combination of two mutant genes could drastically reduce seed PA levels and still maintain acceptable germination and emergence. The impact of this research is the generation of new genetic resources for low PA soybeans that can be utilized for soybean breeding and variety development.

Technical Abstract: Soybean [Glycine max (L.) Merr] seeds contain a large amount of phosphorus (P), which is stored as phytic acid (PA). PA is indigestible by nonruminent livestock and considered an anti-nutritional factor because PA chelates divalent cations and prevents the uptake of essential nutrients. Interest in reducing PA has increased greatly over the years and several low PA soybean lines have been discovered; however, many of these lines have inadequate germination and emergence. Previous research identified and characterized the gamma irradiated soybean line, ZC-2, which contained a 50% reduction in PA and was found to have excellent germination and emergence. The low PA phenotype was a result of a mutation in a gene orthologous to inositol pentakisphosphate 2-kinase (IPK1; Glyma14g07880, Glycine max v1.1), which is responsible for phosphorylating inositol pentakisphosphate into PA. Our objective was to reduce PA levels by more than 50% with conventional breeding methods. Our own fast neutron irradiated line, FN38, has a large deletion that includes an independent gene homologous to IPK1 (Glyma06g03310, Glycine max v1.1. Characterization of PA and inorganic phosphate (Pi) levels for the soybean lines containing the chromosome 6 deletion showed no differences compared to wild-type lines. In order to determine if we could further reduce PA, we conducted genetic research to combine the IPK1 mutations from FN38 and ZC-2 to conduct a phenotype and genotype association analysis. Lines containing both IPK1 mutations increased Pi and decreased PA statistically more than either parental genotype.