Grain quality traits of maize such as protein, oil, starch, and kernel size and density are essential for various end-uses; feed for animals, food for humans, and raw materials for industry. Kernel pigments like anthocyanins and carotenoids have numerous nutritional functions in animals and human beings. Increasing the levels of these compositional traits and pigments in kernels should increase the nutritional quality of maize.
An investigation of protein content and its relationship with kernel physical traits and identification of quantitative trait loci (QTL) underlying these traits was conducted in a population arising from a cross between a low protein temperate dent inbred (B73) and a high protein tropical flint breeding line (H140). The QTL associated with these traits were determined by selective genotyping and the correlations among kernel traits were calculated. A preliminarily examination of QTL associated with oil and starch was also undertaken. Kernel pigment content of representative Arido-American land race maize accessions was evaluated and relationships between pigments, protein, and oil contents were determined. Reciprocal effects when high and low pigment containing progenies were crossed also were examined.
Multiple regression analysis detected QTL for protein, density, and 100-kernel weight that explained 38 to 71%, 15 to 42%, 27 to 64% of phenotypic variation, respectively. Initial findings for oil and starch suggested that the QTL explained 13 to 64% and 38 to 80% of phenotypic variation, respectively. Starch content was negatively correlated with protein and oil, and these correlations were consistent across environments. Starch content was negatively correlated with kernel density and protein content was also negatively correlated with 100-kernel weight. Protein content and kernel density were positively correlated. Our results indicate that certain desirable trait combinations may be easily selected, whereas other combinations will be much more difficult due to negative associations between them.
Orange and yellow colored kernels contained large amounts of carotenoids and blue and purple colored kernels contained high anthocyanin concentrations. It was concluded that the Arido-American germplasm generally does not possess high carotenoid content, but does display high anthocyanin content which may provide health and nutritional benefits to those who consume it. Phenotypic correlations between carotenoid and oil content, and between carotenoid and protein content, were not consistent across populations, suggesting that simultaneous enhancement of these traits may be difficult in some populations. Carotenoids in reciprocal crosses were intermediate between the parents, or were more affected by the female parent, suggesting a dosage effect. Anthocyanin content of reciprocal crosses was not significantly different from that of their female parents, indicating a strong maternal effect. The selected high anthocyanin progenies from Arido-American grermplasm may serve as a germplasm resource for development of high anthocyanin temperate maize.