Genetic Architecture of the High Inorganic Phosphate Phenotype Derived from a Low Phytate Mutant in Winter Wheat (Triticum aestivum L.)

Authors: VENEGAS, JORGE - Pairwise; Guttieri, Mary; Boehm Jr, Jeffrey; GRAYBOSCH, ROBERT - Retired ARS Employee; Bai, Guihua; St Amand, Paul; Palmer, Nathan - Nate; HUSSAIN, WASEEM - University Of Nebraska; BLECHA, SARAH - University Of Nebraska; BAENZIGER, PETER - University Of Nebraska

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2022
Publication Date: 3/17/2022
Citation: Venegas, J., Guttieri, M.J., Boehm Jr, J.D., Graybosch, R.A., Bai, G., St. Amand, P.C., Palmer, N.A., Hussain, W., Blecha, S., Baenziger, P. 2022. Genetic architecture of the high inorganic phosphate phenotype derived from a low phytate mutant in winter wheat (Triticum aestivum L.). Crop Science. https://doi.org/10.1002/csc2.20738.
DOI: https://doi.org/10.1002/csc2.20738

Interpretive Summary: Phytic acid is the primary storage form of phosphorus in wheat grain. Unfortunately, phytic acid has low digestibility in humans and other non-ruminant animals like pigs and chickens. Phytic acid also reduces the bioavailability of minerals such as iron and zinc. Reducing grain phytic acid concentration and increasing the concentration of nutritionally available inorganic phosphorus in the grain could have benefits for human nutrition and could reduce phosphorus pollution associated with animal waste. Previous research identified a low phytic acid wheat mutant that could be used to improve the nutritional quality of wheat. This study characterized the inheritance of this high inorganic phosphorus/low phytic acid phosphorus trait using next generation sequencing tools. Two regions of the wheat genome work together to increase the inorganic phosphorus concentration in grain. These regions of the genome include genes that encode enzymes in the phytic acid biosynthetic pathway. High throughput, breeder-friendly molecular markers were developed to support breeding for improved nutritional quality in wheat by decreasing phytate concentrations.

Technical Abstract: Phytic acid (myo-inositol 1,2,3,4,5,6-hexakisphosphate) in grains and legumes reduces bioavailability and absorption of minerals in the gut via chelation of divalent minerals such as iron and zinc. In wheat (Triticum aestivum L.), a low phytate mutant (lpa1-1), developed by ethyl methanesulfonate (EMS) mutagenesis, has been reported to reduce phytate in wheat grain by up to 35% and to elevate free inorganic phosphate (Pi). Little is known about the genetic architecture conditioning this high Pi phenotype in wheat. Inheritance of the high Pi phenotype was evaluated in three segregating populations developed with the lpa1-1 derivative A02568WS-A-12-10 as a common parent. Distinct genotypic classes were not identified in these populations. Therefore, to identify quantitative trait loci (QTLs) and develop molecular markers for the high Pi phenotype, 171 recombinant inbred lines (RILs) from a winter wheat cross ‘Danby’ × A02568WS-A-12-10 were phenotyped for Pi concentration and genotyped by reduced-representation sequencing. A total of 1,246 non-redundant, high quality single nucleotide polymorphisms (SNPs) were used to construct a linkage map spanning 3,272 cM. Two major effect QTLs were identified on chromosomes 4D and 5A, accounting for 23% and 33% of the total phenotypic variation, respectively. Multiple interval mapping (MIM) identified synergistic additive × additive epistasis between these QTLs, and the full MIM model accounted for 54% of the phenotypic variation in grain Pi. Ten candidate genes were identified within or in close proximity to the genomic locations of the two QTLs, five of which encode proteins within the inositol phosphate metabolism pathway which produces phytate. Site-specific marker assays were developed for marker-assisted breeding for the high Pi phenotype.