Quality Protein Maize Germplasm Characterized for Amino Acid Profiles and Endosperm Opacity

Abstract

Quality protein maize (QPM) is improved over normal (non‐QPM) maize in grain concentrations of the essential amino acids lysine and tryptophan. Quality protein maize has a long history as tropical adapted germplasm, but little effort has been made to incorporate temperate or sub‐tropical germplasm for temperate adaptation and interactions between different modifier loci in these backgrounds are poorly understood. A design‐II mating scheme including new temperate and subtropical lines produced 69 hybrids. Large hybrid genetic variation components 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 × environment (G×E) effects. Endosperm opacity had no G×E effects across both Texas and Iowa locations demonstrating stability for this trait. Endosperm opacity primarily followed an additive, midparent trend, with a few hybrids deviating from the trend (36%) suggesting a complex nature of multiple modifier loci across diverse germplasm. The top QPM hybrid outperformed the top commercial hybrid by 35 and 30% for lysine and tryptophan as a proportion of grain, respectively. QPM line Tx832 was a parent of top hybrids for lysine and tryptophan, and the highest noncommercial hybrids for methionine. Minimal correlations with yield and other traits suggest that future breeding should result in QPM hybrids with increasingly competitive yields.

Diversity of Maize Kernels from a Breeding Program for Protein Quality: II. Correlatively Expressed Functional Amino Acids

“…Broad sense heritability estimates for all three amino acids in maize are relatively lower than those for other phytochemicals (Mahan et al, 2014). Nevertheless, there were sufficient levels of variation at the heterotic group and population levels to discriminate between endosperm textures based on amino acid contents (Fig.…”

“…When compared with the original germplasm classification, the CDA results suggested that the ratio between translucent and opaque endosperm may possibly be revised upward from the original 0.613:0.387 to approximately 0.7:0.3, indicating that the breeding program already succeeded in developing populations, and accessions within populations, with the desirable combinations of amino acid content and endosperm texture (Pollak, 2003;Gutierrez-Rojas et al, 2008;Mahan et al, 2014). When compared with the original germplasm classification, the CDA results suggested that the ratio between translucent and opaque endosperm may possibly be revised upward from the original 0.613:0.387 to approximately 0.7:0.3, indicating that the breeding program already succeeded in developing populations, and accessions within populations, with the desirable combinations of amino acid content and endosperm texture (Pollak, 2003;Gutierrez-Rojas et al, 2008;Mahan et al, 2014).…”

“…The extremely small percentage of correct classification (26.0%) of opaque endosperm in CH05015-Mo17 could be attributed to the combined nonsignificant tolerances of the highly correlated LYS and MET in that population. When compared with the original germplasm classification, the CDA results suggested that the ratio between translucent and opaque endosperm may possibly be revised upward from the original 0.613:0.387 to approximately 0.7:0.3, indicating that the breeding program already succeeded in developing populations, and accessions within populations, with the desirable combinations of amino acid content and endosperm texture (Pollak, 2003;Gutierrez-Rojas et al, 2008;Mahan et al, 2014). Also, the results indicated that it is possible to reduce the loss of LYS during conversion from opaque to translucent endosperm and that significantly larger MET and LYS contents can be combined in the maize kernel (Amir, 2010).…”

“…In spite of its long history, and although it was met with mixed success in terms of large-scale production and consumption, breeding, evaluation, and release of maize with high protein quality remains an important objective in developed (Raboy, 2013;Mahan et al, 2014) and developing countries (Prasanna et al, 2001;Tang et al, 2013). A well-designed crossing scheme, based on choice of parents, recurrent selection Newell et al, 2014), and inbreeding for a few generations, may have been critical in shifting frequencies toward more translucent endosperm (~70% of all germplasm accessions on the basis of canonical discriminant analysis; Fig.…”

Fortification of Commercial Nixtamalized Maize (Zea mays L.) with Common Bean (Phaseolus vulgaris L.) Increased the Nutritional and Nutraceutical Content of Tortillas without Modifying Sensory Properties

“…Nixtamalization entails to an increase in maize amino acids bioavailability. Maize is deficient in lysine and tryptophan essential amino acids, resulting in a low nutritional quality protein (Mahan et al 2014). This deficiency has led the attention of research to improve the nutritional value of tortillas by supplementing them with pulses flours among others, however, this supplementation decrease significantly consumers acceptance.…”