Phosphorus fractions in developing seeds of four low phytate barley (Hordeum vulgare L.) genotypes

Low phytic acid (lpa) crops have reductions in the amount of seed phytic acid (myo-inositol hexakisphosphate, InsP(6)) and increases in inorganic phosphorus (Pi) with little change to the amount of total seed P In this study, four barley lpa genotypes (lpa1-2, lpa2-1, lpa3-1, and M955), backcross wild-type (wt) sib-selections, and original parental line 'Harrington' were grown in the field over 2 yr. Developing seed was harvested once a week for 3 wk and then again at physiological maturity, and the seeds assayed for levels of total P, Pi, and phytic acid P Total phosphorus concentration showed no consistent differences between the lpa genotypes and Harrington. Inorganic P declined during development in the wt genotypes; however in lpa genotypes, inorganic P declined during the first few weeks of development, and then increased from 24 d to maturity. Phytic acid concentration increased steadily during development for the wt lines and barley lpa1-1 and lpa2-1, although the increase was much slower in the lpa lines. The lpa3-1 and M955 had very little InsP6 accumulation until later in development, with little to no increase in the amount of phytic acid in mature seed of M955 compared to the developing seeds of lpa3-1. This information is useful in understanding timing of phosphorus accumulation in seeds, as well as the nature of the low phytic acid mutation in seed development.