Genetic Analysis of Corn Kernel Chemical Composition in the Random Mated 7 Generation of the Cross of Generations 70 of IHP × ILP

Abstract

To identify and characterize quantitative trait loci (QTL) affecting kernel weight and concentrations of protein, oil, and starch in the corn (Zea mays L.) kernel, plants from generations 70 of the Illinois High Protein (IHP) and Illinois Low Protein (ILP) strains, previously developed by divergent selection for kernel protein concentration, were crossed. The cross was random mated (RM) seven generations and selfed twice to develop 500 F1RM7S2 lines. The lines per se were evaluated at three locations with two replications for 2 yr and testcrosses were evaluated at three locations in 1 yr. Genotypes were evaluated using 499 SNP markers on DNA from a bulk of leaf tissue from each line. As the parent plants used to make the original cross were not available for genotyping, previously reported multivariable and modified simple interval mapping (SIM) procedures were used. SIM identified more significant regions for all traits than did single marker analysis. Correlations and signs of QTL effects suggest development of high protein–high starch lines would be difficult but that it should be possible to develop high protein–high oil lines with minimal effects on kernel weight. The identification of a large number of QTL (at least 40 each for oil, protein, starch, and kernel weight) with small effects agrees in general with earlier estimates based on quantitative genetic theory and has implications for breeding strategies for improved corn kernel quality traits.

Discrimination of maize inbreds for kernel quality traits and fatty acid composition by a multivariate technique

“…Of the genotypes located in the direction pointed by above-mentioned vectors, A619 and RSSSC appeared in different locations in different year graphs for oil content (Figure 2a and c), indicating the presence of year x genotype interaction. The well known negative association between the protein and oil ratios reported by others (DUDLEY et al, 2007) in maize is clearly visible in HE plots. Similarly, year x genotype interaction came up due to the variation caused by A680 for ash and RSSSC for moisture contents (Figure 2a and c).…”

“…If a positive correlation exists between two variables, the vectors head similar directions, while they show diverse directions in the case of a negative correlation. The length of the related vector indicates how well the variation for that trait can be explained in two-dimensional space (FRIENDLY, 2006b). In other words, the longer a vector is, the better interpretation is possible about the variable it represents.…”

“…As a result of the studies to enhance oil and protein concentration, lines have been developed containing as high as 220 g kg (Illinois High Protein) protein (DUDLEY; LAMBERT, 1992). The main quality traits of the kernel, protein and oil, also possess some quality criteria of their own.…”

“…Jellum (1970) determined large ranges of oleic (16-64%) and linoleic (19-71%) acids and reported a negative correlation between them in a study with 788 maize strains. Dunlap et al (1995a) evaluated 20 maize populations collected from US, Chile, Argentina and Uruguay for their fatty acid compositions, and reported ranges of 6.3-18.2% for palmitic acid, 0.9-4.5% for stearic acid, 18.5-46.1% for oleic acid, 36.6-66.8% for linoleic acid, 0.0-2.0% for linolenic acid, and 0.0-1.4% for arachidic acid. In another study by the same researchers using 418 hybrids and 98 inbreds 6.7-16.5% palmitic; 0.7-6.6% stearic, 16.2-43.8% oleic, 39.5-69.5% linoleic, and 0.0-3.7% linolenic acid values were reported (DUNLAP et al, 1995b).…”

“…Dunlap et al (1995a) evaluated 20 maize populations collected from US, Chile, Argentina and Uruguay for their fatty acid compositions, and reported ranges of 6.3-18.2% for palmitic acid, 0.9-4.5% for stearic acid, 18.5-46.1% for oleic acid, 36.6-66.8% for linoleic acid, 0.0-2.0% for linolenic acid, and 0.0-1.4% for arachidic acid. In another study by the same researchers using 418 hybrids and 98 inbreds 6.7-16.5% palmitic; 0.7-6.6% stearic, 16.2-43.8% oleic, 39.5-69.5% linoleic, and 0.0-3.7% linolenic acid values were reported (DUNLAP et al, 1995b). It may be inferred that, genetic resources existed in Zea mays species should be screened and characterized for their quality traits to determine objectives and possibilities of use in quality breeding.…”