Putative Second-Site Mutations in the Barley Low Phytic Acid 1-1 (lpa 1-1) Genetic Background Further Reduce Seed Total Phosphorus
Beverly L. Agesa | Victor Raboy | Paul J. A. Withers | Katherine A. Steele
Inefficient crop phosphorus (P) use impacts global food security and P fertilizer use can be environmentally harmful. Lines homozygous for barley (<i>Hordeum vulgare</i> L.) <i>low phytic acid 1-1</i> (<i>lpa 1-1</i>) have yields equivalent to the wild type but ~15% less seed Total P (TP). The objective here was to identify second-site mutations in the <i>lpa1-1</i> background that condition a further reduction in seed TP, again with little impact on yield. A chemically mutagenized population was derived from <i>lpa 1-1</i> and screened to identify lines with seed TP reductions greater than 15% (as compared with wild-type) but with seed weights per plant within 80% of wild-type. Three M<sub>4</sub> lines were selected and evaluated in a greenhouse pot experiment. Plants were grown to maturity either on a soil with low soil P fertility (16 to 25 mg Olsen P L<sup>−1</sup>; Soil P Index 1) or with that soil supplemented (36 kg P ha<sup>−1</sup>) to provide optimal available soil P. Mean seed P reduction across the three lines and two soil P levels was 28%, a near doubling of the <i>lpa1-1</i> seed Total P reduction. When grown with optimal soil available P, no impact of these putative mutations on grain yield was observed. These findings suggest that the three <i>lpa 1-1</i>-derived mutant lines carry second-site mutations conferring substantially (~17%) greater decreases in seed TP than that conferred by <i>lpa 1-1</i>. If the putative mutations are confirmed to be heritable and to have negligible impact on yield, they could be used in breeding P-efficient barley cultivars as a step towards reducing regional and global P demand.
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