Identification and Characterization of a Low Phytic Acid Wheat

crease the absorption of essential micronutrients such as Ca (Kies, 1985), Fe (Brune et al., 1992), and Zn Phytic acid (myo-inositol-1,2,3,4,5,6-hexakisphosphate, or Ins P6) (Sandström et al., 1987). Phytate forms chelates with is the most abundant storage form of P in seeds, yet indigestible by humans and nonruminant livestock. A wheat (Triticum aestivum L.) these divalent minerals, which reduces bioavailability mutant is described herein with greatly reduced seed phytic acid P to humans (Jacobsen and Slotfeldt-Ellingsen, 1983). In but little change in seed total P, similar to lpa1-type mutants described developing countries, flatbreads may be prepared from in other grain species. One nonlethal mutant from 562 ethyl-methanewhole-wheat flour or high (≈95%) extraction flour. The sulfonate (EMS) mutagenized M2 lines was identified with a high phytate in wheat grain is found predominantly in the inorganic phosphate (HIP) phenotype and designated Js-12-LPA. aleurone layer, which remains attached to the pericarp Js-12-LPA homozygotes produced seed in which phytic acid P repreduring milling and therefore is concentrated in the bran sented 48.2% of seed total P, in contrast to 74.7% of seed total P in fraction. Although phytate decreases in proportion to nonmutant or wild-type control, Js-12-WT. The inorganic portion of fermentation time, in chapati bread, the phytate concenseed P was increased from 9.1% in Js-12-WT to 50.1% in Js-12-LPA, tration was only 18 to 24% lower than the concentration with little effect on total seed P. Weight distributions among milling fractions were similar for the Js-12-LPA and Js-12-WT genotypes. in the whole-wheat flour from which it was prepared The low phytic acid trait altered the distribution of total P within (Anjum et al., 2002). The phytate concentration in chathe kernel, increasing the P content of the central endosperm and pati breads was sixto nine-fold higher than in breads decreasing the P content of the bran. The low phytic acid trait deprepared from straight-grade flour. However, mineral creased the phytic acid concentration in the bran by 43% and increased concentrations generally were significantly higher in the inorganic P concentration in the bran nearly four-fold. Inheritance whole-grain flour than in straight-grade flour, which data of F2 and F4:6 families was inconsistent with a single-gene mutation might offset the effect of phytate on human nutrition. and suggests the involvement of two or more genes. This low phytic Human bioavailability studies will be necessary to conacid wheat mutant is a genetic resource for studying the biology of firm this hypothesis. seed phytic acid metabolism and wheat quality improvement. Nonlethal recessive mutations that decrease seed phytic acid concentration have been isolated in maize (Zea mays L.; Raboy and Gerbasi, 1996; Raboy et al., 2000), M is ubiquibarley (Hordeum vulgare L.; Larson et al., 1998; Rastous in eukaryotic cells, where it is typically the mussen and Hatzack, 1998), rice (Oryza sativa L.; Larmost abundant inositol phosphate (Ins P) (Sasakawa et son et al., 2000), and soybean [Glycine max (L.) Merr.; al., 1995). First observed as an abundant P-containing Hitz et al., 2002; Wilcox et al., 2000]. These low phytic compound in seeds, Ins P6 in plant species is thus reacid (lpa) mutants affect the partitioning of P into phytic ferred to as “phytic acid” in agronomic literature (Cosacid, inorganic phosphorus (Pi), and Ins P’s with five or grove, 1980). Applied interest in seed phytic acid is fewer P esters (Raboy, 2002). The lpa mutations are the result of its role in human and livestock nutritional divided into two groups, designated lpa1 and lpa2. Phyquality, as well as P management in integrated agricultic acid P reductions in lpa1 mutants are counterbaltural production systems. According to Shears (2001) anced by molar-equivalent increases in Pi. In contrast, and Raboy (1997), Ins P6 is a major pool in both P and phytic acid P reductions in lpa2 mutants are counterbalIns P metabolism. Phytic acid P typically represents anced by increases in both Pi and non-Ins P6 Ins P’s from 65 to 85% of seed total P and 90% of free Ins (Ins P’s of lower phosphorylation). The isolation and polyphosphates (Raboy, 1997). Trace levels ( 10% of characterization of seed P and Ins P phenotype of a total Ins P) of Ins tris-, tetrakis-, and pentakisphosphates heritable wheat lpa1-like mutant is described here. (Ins P’s with three, four, or five phosphomonoesters, respectively), as well as pyrophosphate-containing Ins P’s more highly phosphorylated than Ins P6, also are observed MATERIALS AND METHODS in mature, wild-type seeds (Dorsch et al., 2003). Mutant Isolation In humans, diets high in phytate can significantly deSeed of the breeding line A95631S-Js-12 was mutagenized with 2% EMS. A95631S-Js-12 has the pedigree ‘Kanto 79’/ M. Guttieri, D. Bowen, and E. Souza, Univ. of Idaho, Aberdeen 2*IDO488. IDO488 is a soft white spring wheat breeding line Research and Extension Center, P.O. Box 870, Aberdeen, ID 83210; with the pedigree PI 294994/4*‘Centennial’. M1 plants were J. Dorsch, BASF Corp., Research Triangle Park, NC 27709; V. Raboy, grown in the greenhouse. Approximately 50% of the M1 seeds USDA-ARS Small Grains and Potato Research Unit, P.O. Box 607, either did not germinate or senesced without setting seed. An Aberdeen, ID 83210; J. Dorsch is a former postdoctoral fellow of the USDA-ARS. Research supported by the Idaho Agric. Exp. Stn. M2 row was planted in the field from each of 562 M1 greenProject IDA1222, Manuscript no. 3725. Received 1 May 2003. *Corresponding author (esouza@uidaho.edu). Abbreviations: AACC, American Association of Cereal Chemistry; EMS, ethyl-methanesulfonate; HIP, high inorganic phosphate; Ins P, Published in Crop Sci. 44:418–424 (2004). Crop Science Society of America inositol phosphate; Ins P6, myo-inositol-1,2,3,4,5,6-hexakisphosphate; lpa, low phytic acid; Pi, inorganic phosphorus. 677 S. Segoe Rd., Madison, WI 53711 USA