Submitted to: The Plant Genome
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/11/2009
Publication Date: 7/10/2009
Citation: Gillman, J.D., Pantalone, V.R., Bilyeu, K.D. 2009. The Low Phytic Acid Phenotype in Soybean Line CX1834 is Due to Mutations in Two Homologues of the Maize Low Phytic Acid Gene. The Plant Genome. 2(2):179-190. Interpretive Summary: Soybean is an important component of many foods and animal feeds. One nutritional limitation to the use of soybean in animal feeds such as poultry and swine is the presence of a large amount of phytate, a complex of phosphorous and minerals that prevents the uptake of these important nutrients by livestock during feeding. Several soybean mutants exist which have seeds, which are low in phytate and have an increased nutritional phosphate content, but transferring this important trait into commercial soybean varieties has been hampered by its genetically complex nature. The objective of our research was to determine the molecular genetic basis for the low phytate trait in two soybean mutant sources and utilize that information to develop specific molecular marker assays that could be used to accelerate plant breeding and the release of new low phytate soybean cultivars. We discovered three mutations in the two low phytate soybean lines that were closely linked with the low phytate trait in independent experimental populations. We developed molecular markers which are “breeder friendly” so the direct selection of the genes responsible for the low phytate trait can be made. Our discoveries and the development of the molecular marker assays will assist breeders in developing elite soybean varieties with improved nutritional value for animal feeds.
Technical Abstract: Plant seeds accumulate phosphorus in the form of myo-inositol-1,2,3,4,5,6 hexa-kisphosphate, commonly referred to as phytic acid. Phytic acid is found complexed with cationic mineral species in the form of phytate, which is not well digested or absorbed by monogastric species such as humans, poultry and swine. As a result, soybean has an effective deficiency of phosphorus and other minerals, despite high levels of minerals and phosphorus in the seed. Excreted phytate can also contribute to phosphorus contamination of groundwater and eutrophication of freshwater lakes and streams. In maize, a recessive mutation in a conserved region within the low phytic acid 1 (lpa1) gene is responsible for the low phytic acid phenotype. We have identified recessive mutations in two soybean homologs of the maize lpa1 gene in soybean line CX1834, an EMS mutagenized line with a low phytic acid phenotype. In three populations analyzed we identified complete association between homozygosity for mutant alleles of the two lpa1 homologs and the low phytic acid phenotype in soybean. Molecular marker assays were designed that can be used to directly select for the mutant alleles that control the phenotype.