Effects of four independent low-phytate mutations on barley agronomic performance

The seed phosphorus storage compound phytic acid (myo-inositol-1,2,3,4,5,6-heakisphosphate) is poorly utilized by nonruminant animals. Low Phytate (LP) crops, in which reductions of phytate are accompanied by increases in nutritionally available P, are in development and their utility will be enhanced by competitive agronomic performance. To assess the performance of LP barley (Hordeum vulgare L.), sets of sib lines that are homozygous wild type (WT), or homozygous for one of four independent low phytic acid mutations (lpa1-1, lpa2-1, lpa3-1, and M955), were developed via backcrosses to Harrington. The WT sibsets performed similarly to the Harrington parent, suggesting that the major variable in these experiments was the presence or absence of the LP alleles. Under irrigation, M955, which has an extreme reduction in phytate, was associated with reduced yield and percentage plump kernels; all mutations except lpa2-1 were associated with reduced test weight. In rain-fed locations, all mutations were associated with reduced test weight and percentage plump kernels, and all except lpa1-1 were associated with reduced yield. These results suggest that one component of yield loss in LP types is reduced stress tolerance. The performance of the lpa1-1 mutation, which appears to be aleurone specific, suggests a potential strategy to avoid this source of yield loss: the use of genotypes where the desirable effect is limited to a target tissue, in this case the aleurone layer.