Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2006
Publication Date: 4/25/2006
Citation: Bregitzer, P.P., Raboy, V. 2006. Effects of four independent low-phytate mutations in barley (hordeum vulgare l.)on seed phosphorus characteristics and malting quality. Cereal Chemistry. Crop Sci. 46:1318-1322 (2006) Interpretive Summary: The phosphorus in cereal grains such as barley, and other food crops like soybeans, is mostly stored as a compound, phytate, that is not digestible by non-ruminant animals (such as pigs, poultry, and fish). Consumption of normal cereals grains results in the excretion in the manure of the phosphorus contained in phytate. To achieve optimal animal growth, producers must supplement their rations with phosphorus, which adds to their costs of production. Furthermore, the excreted phosphorus is associated with significant environmental costs, as phosphorus is a major factor in many instances of water pollution. One solution that addresses both these problems is to develop grain that has reduced phytate and elevated available phosphorus. This has been accomplished for barley, wheat, rice, corn, and soybean, and the challenge is now to develop low phytate cultivars that perform well in commercial agriculture. This report documents the results of studying the grain quality characteristics of barley lines containing four different types of genes that increase phosphorus availability and reduce phytate. Grain was produced in both irrigated (non-stressed) and rain-fed (moisture-stressed) environments. Variable increases in available phosphorus were recorded, depending on the type of gene in the grain. Despite the two very different growth environments, the increase in available phosphorus was not affected, nor was the amount of total phosphorus affected by environment. This means that no matter where the low phytate barleys are produced, one can predict how much phosphorus will be available to the animals fed that barley. Malting quality was also measured by this study. Several important characteristics were changed by the low phytate genes, meaning that although low phytate barley may be a superior feed grain, it will not be very useful for the production of malt and malt products.
Technical Abstract: Conversion of the seed phosphorus storage compound phytic acid, which is poorly digested by non-ruminants, to available forms of P will have nutritional and environmental benefits. Low Phytate (LP) barley (Hordeum vulgare L.) cultivars are in development, and their commercialization will be facilitated by understanding their P profiles and malting quality. To study these issues, LP and normal types derived from mutagenized populations of Harrington barley (sets of sib lines homozygous for the wild-type (WT) allele, or for one of four low phytic acid mutations, lpa1-1, lpa2-1, lpa3-1 or M 955), were developed via backcrosses to Harrington. Grain was produced in irrigated and dryland environments. WT phosphorus profiles were similar to Harrington, suggesting that the major variable was the presence or absence of mutant alleles. All mutations conferred increased inorganic P. Total P was reduced for lpa1-1. P profiles were relatively stable across environments, which will facilitate the inclusion of LP barley in animal rations. Utilization of LP cultivars for malting will be difficult, as the LP trait was associated with substantial reductions in diastatic power. All mutations except for lpa2-1 affected malt '-glucan levels which could not be attributed to altered grain '-glucan levels.