Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2006
Publication Date: 3/1/2007
Citation: Lorenz, A., Scott, M.P., Lamkey, K.R. 2007. Quantitative determination of phytate and available phosphorus for maize breeding. Crop Science. 47:600-604.
Interpretive Summary: Maize is the main ingredient of animal feed in the US. Most of the phosphorus in maize grain is not nutritionally available to animals because it is contained in a chemical called phytic acid which cannot be digested by animals. Thus, animal diets must be supplemented with phosphorus, and much of the phosphorus from the grain is excreted. The high levels of phosphorus in animal waste is bad for the environment. The objective of this study was to establish the feasability of breeding to make more of the phosphorus in maize nutritionally available to animals. We developed methods to measure both available phosporus and phytic acid and surveyed maize inbreds with these methods. Our results suggest that is should be possible to manipulate phytic acid levels with breeding. This will allow the production of maize varieties with increased available phosphorous and less phytic acid. These varieties will benefit the environment by causing reduced phosphorus pollution from animal waste. In addtion, these varieties will decrease the cost of animal feed by reducing the amount of phosphorus supplementation required. Animal producers and consumers of meat products will benefit from this reduced feed cost.
Technical Abstract: Phytate is the dominant storage form of phosphorus (P) in mature cereal and oil grains. Phosphorus bound in phytate is nutritionally unavailable to monogastric animals and thus contributes to water pollution because it is excreted in the manure. Also, phytate can chelate certain minerals and exacerbate human mineral deficiencies. A rapid, inexpensive method of measuring phytate and available P levels in maize was derived from previously published assays and used to screen 50 inbred lines. Measurements were also taken on grain yield, total P, protein, oil, methionine, lysine, tryptophan, and kernel weight. Field repeatability values for phytate and available P (0.78 and 0.91, respectively) suggest that these traits can be measured with adequate precision using the derived protocols. Correlations among all traits were calculated; the positive phytate:protein correlation commonly reported was also detected in this study. A relationship between phytate and kernel weight indicates that selection for low phytate may result in increased endosperm and kernel size.