|Mahan, Adam - Texas A&M University|
|Murray, Seth - Texas A&M University|
|Crosby, Kevin - Texas A&M University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2013
Publication Date: 3/7/2014
Citation: Mahan, A.L., Murray, S.C., Crosby, K., Scott, M.P. 2014. Quality protein maize germplasm characterized for amino acid profiles and endosperm opacity. Crop Science. 54(3):863-872. DOI: 10.2135/cropsci2012.11.0658.
Interpretive Summary: Corn is an important component of food and animal feed, however it's nutritional value is limited by it's content of the essential amino acids lysine and tryptophan. Corn with higher levels of these nutrients called Quality Protein Maize (QPM) has been developed and successfully deployed in tropical regions, however QPM varieties suitable for the United States have not been deployed yet, in part because the experimental QPM varieties suited to the US are relatively uncharacterized. We characterized economically important traits in experimental U.S.-adapted QPM varieties and obtained data that will be useful for developing new QPM varieties for the U.S. Most importantly, we learned that our experimental varieties have higher yields of lysine and tryptophan than commercial check varieties, suggesting that QPM varieties have added value for food and feed markets. Our results benefit plant breeders working on development of QPM varieties. By facilitating the development of new QPM varieties, this work ultimately benefits consumers of corn-based food including meat produced from livestock and poultry raised on corn-based diets.
Technical Abstract: Quality protein maize (QPM) is improved over normal maize in grain concentrations of the essential amino acids lysine and tryptophan. QPM has a long history as tropical adapted germplasm but little effort has been made in temperate and sub-tropical adaptation and it is unknown if different modifier loci might be present. A design-II mating scheme including new temperate and sub-tropical lines produced 69 hybrids. Large hybrid genetic component effects resulted in substantial broad-sense heritability H2 estimates, specifically tryptophan (0.46) and endosperm opacity (0.82). A microbial assay for amino acid estimation proved robust across diverse environments with minimal genotype x environment (GxE) effects. Endosperm opacity had no GxE effects across both Texas and Iowa locations demonstrating stability for this trait. Additionally, endosperm opacity primarily followed an additive, mid-parent trend, with a few hybrids deviating from that trend (36%) suggesting a complex and recessive nature of multiple modifier loci from diverse germplasm. We found hybrid rank changes were observed when amino acid estimates were adjusted for protein content. The top QPM hybrid out yielded the top commercial hybrid by 35 and 30% for lysine and tryptophan, respectively. Minimal correlations with yield and other traits suggest that future breeding may result in QPM hybrids with increasingly competitive yields.