Linkage mapping of two mutations that reduce phytic acid content of barley grain

This study describes the inheritance and linkage map positions of two low phytic acid barley (Hordeum vulgare) mutations, lpa1-1 and lpa2-1, that dramatically reduce grain phytic acid content and increase inorganic seed phosphorus (P). Wide-cross, Fz mapping populations were constructed by mating six-rowed varieties,'Steptoe' and/or 'Morex', with two-rowed 'Harrington' Ipa donor lines homozygous for either lpal-1 or lpa2-1. The barley Ipa1-1 mutation showed normal inheritance patterns, whereas a deficiency of homozygous lpn2-1/lpa2-1 F(2) plants was observed. We identified a codominant, STS-PCR marker (aMSU21) that cosegregated with lpn1-1 in a population of 41 F(2) plants. The aMSU21 marker was then mapped to a locus on barley chromosome 2H, using a North American Barley Genome Mapping Project (NABGMP) doubled haploid population ('Harrington' x 'Morex'). We determined that lpa2-1 is located within a recombination interval of approximately 30 cM between two AFLP markers that were subsequently mapped to barley chromosome 7H by integration with the same NABGMP population. Recent comparative mapping studies indicate conserved genetic map orders of several homologous molecular marker loci in maize and the Triticeae species that also show corresponding linkage to the biochemically similar lpa2 mutations of maize and barley. This observation suggests that barley and maize lpa2 mutations may affect orthologous genes. No such evidence for correspondence of the phenotypically similar lpa1 mutations of barley and maize has been revealed.