Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/6/2008
Publication Date: 9/23/2008
Citation: Scott, M.P., Darrigues, A., Stahly, T., Lamkey, K. 2008. Recurrent Selection to Control Grain Methionine Content and Improve Nutritional Value of Maize. Crop Science. 48:1705-1713. Interpretive Summary: Much of the livestock and poultry feed in the US is based on corn. Because corn does not meet the requirements of these animals for the essentail amino acid methionine, supplements must be added to balance the diet. These supplements increase the cost of meat production. Corn with increased levels of methionine would require less supplementation and would allow meat to be produced with reduced cost. Plant breeders have used transgenes and mutants to alter amino acids. We demonstrated that methionine content can be controlled using recurrent selection and these compositional changes result in an altered feed efficiency in a rat feeding trial. This illustrates the utility of recurrent selection as an additional tool with which to improve amino acid balance. This work facilitates the development corn with improved nutritional quality, benefitting meat producers and consumers of meat products.
Technical Abstract: Methionine is an essential amino acid that is limiting in maize-based diets. The objective of this work was to determine if we could alter methionine content in random-mated maize populations by recurrent selection for grain methionine content. In one study, we developed two populations by selecting for high or low grain methionine content for three generations starting from the random-mated maize population BS11. The resulting populations were shown to differ significantly in their methionine content. Grain from these populations was used to formulate diets for a rat feeding trial. Rats fed the diet containing corn selected for high methionine had higher feed efficiency than rats fed the diet containing corn selected for low methionine. In a second study, we carried out three cycles of recurrent selection for high or low grain methionine content starting with two random-mated maize populations, BS11 and BS31. We evaluated each cycle of selection in a field trial to determine the impact on selection on plant and grain traits. Methionine content was significantly correlated with the cycle of selection, with methionine content changing on average 0.004 g/100 g grain per cycle. Other grain traits including grain weight, protein, oil and starch content did not exhibit significant correlations with cycle of selection. Comparison of the amino acid content of the third cycle of selection for high methionine to the third cycle of selection for low methionine indicated that selection was extremely precise, with methionine being the only amino acid with a significant selection effect.