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Illinois long-term selection strains of maize (Zea mays L.) have been useful for identifying genomic regions controlling kernel oil, protein, and starch concentrations. To identify kernel trait quantitative trait loci (QTL) in a genetic background more relevant to practical breeding, 150 B[C.sub.1]-derived [S.sub.1] lines (B[C.sub.1][S.sub.1]s) were produced from Illinois High Oil and recurrent parent B73. Oil, protein, and starch were measured in B[C.sub.1][S.sub.1]s and in Mo17-topcross hybrids (TCs). Kernel mass of B[C.sub.1][S.sub.1]s and grain yield of TCs were also determined. Starch was positively correlated with mass in B[C.sub.1][S.sub.1]s ([r.sub.p] = 0.67**, [alpha] [less than or equal to] 0.01) and with yield in TCs ([r.sub.p] = 0.59**). Oil was negatively correlated with mass in B[C.sub.1][S.sub.1]s ([r.sub.p] = -0.29**) and with yield in TCs ([r.sub.p] = -0.30**). Oil was negatively correlated with starch in B[C.sub.1][S.sub.1]s ([r.sub.p] = -0.75**) and TCs ([r.sub.p] = -0.66**). A genetic map with length = 1486 cM was created with 110 markers. Multiple regression models with QTL detected by composite interval mapping (CIM) explained 46.9, 45.2, 44,3, and 17.7% of phenotypic variance for oil, protein, starch, and mass, respectively, in B[C.sub.1][S.sub.1]s and 17.5, 22.9, 40.1, and 28.7% for oil, protein, starch, and yield, respectively, in TCs. A 22 cM-interval on chromosome 6 in B[C.sub.1][S.sub.1]s included oil, protein, and starch QTL, including a QTL explaining 36.7% of the B[C.sub.1][S.sub.1] phenotypic variation for oil. No yield QTL were detected in this region. Introgression of this QTL into breeding lines might increase oil while maintaining yield.

Maize (Zea mays L.) produces high-quality oil valued for oxidative stability and low concentrations of saturated fatty acids. The nutritional value of maize oil could be improved by increasing the concentration of oleic acid, a 'heart-friendly' monounsaturated fatty acid. To identify quantitative trait loci (QTL) for the major fatty acids constituting oil from maize kernels, we produced 150 backcross1-derived [S.sub.1] (B[C.sub.1][S.sub.1]) lines from donor parent, Illinois High Oil (IHO), and recurrent parent, B73. There was a positive phenotypic correlation between oil and oleic acid ([r.sub.p] = 0.47**, [alpha] [less than or equal to] 0.01) and negative correlations between oil and linoleic acid ([r.sub.p] = -0.46**), and between oleic and linoleic acids ([r.sub.p] = -0.99**). Multiple regression models with QTL detected by composite interval mapping (CIM) on a genetic map with length = 1486 cM, explained 15.4, 41.6, 51.0, 59.6, and 47.9% of the phenotypic variation for palmitic, stearic, oleic, linoleic, and linolenic acids, respectively. A 6-cM interval on chromosome 6 (bin 6.04) includes QTL for stearic, oleic, linoleic, and linolenic acids, explains 10.9 to 39.6% of the variation for these fatty acids, and is 10 to 16 cM from QTL for oil. Another region on chromosome 6 (bin 6.01) includes QTL for oleic and linoleic acids and was epistatic with the QTL in bin 6.04. One or both of these two QTL regions on chromosome 6 may be responsible for fatty acid variation previously attributed to linoleic acid1.

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 [F.sub.1]R[M.sub.7][S.sub.2] 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.

To identify and characterize quantitative trait loci (QTL) affecting oil, protein and starch concentration in the corn (Zea mays L.) kernel, plants from Generation 70 of the Illinois High Oil (IHO) and Illinois Low Oil (ILO) populations, previously developed by divergent selection for kernel oil concentration, were crossed. The cross was random mated 10 generations and selfed two generations to develop 500 F1RM10S2 lines. The lines per se and their testcross progenies were evaluated at three locations with two replications for 2 yr. Genotypes were evaluated using 479 SNP markers on a bulk of kernels from each line. Since the parent plants used to make the original cross were not available for genotyping, a multivariable optimization procedure was developed to estimate parental population parameters required for QTL mapping. Simple interval mapping was performed with software specially developed to account for the complex mating structure and the fact that the initial cross was made between populations. Correlations and signs of QTL effects suggest development of high oil-high starch lines would be difficult but that it should be possible to develop high oil-high protein lines. The identification of a large number of QTL (at least 40 each for oil, protein, and starch) with small effects has implications for breeding for improved corn chemical composition. Abbreviations: IHO, Illinois High Oil; ILO, Illinois Low Oil; RM, random mating., THE ILLINOIS long-term selection experiment is a classic illustration of efficacy of selection for chemical composition in the corn kernel. Initiated in 1896 with the objective of changing kernel composition [...]

In one of the longest-running experiments in biology, researchers at the University of Illinois have selected for altered composition of the maize kernel since 1896. Here we use an association study to infer the genetic basis of dramatic changes that occurred in response to selection for changes in oil concentration. The study population was produced by a cross between the high- and low-selection lines at generation 70, followed by 10 generations of random mating and the derivation of 500 lines by selfing. These lines were genotyped for 488 genetic markers and the oil concentration was evaluated in replicated field trials. Three methods of analysis were tested in simulations for ability to detect quantitative trait loci (QTL). The most effective method was model selection in multiple regression. This method detected ~50 QTL accounting for ~50% of the genetic variance, suggesting that >50 QTL are involved. The QTL effect estimates are small and largely additive. About 20% of the QTL have negative effects (i.e., not predicted by the parental difference), which is consistent with hitchhiking and small population size during selection. The large number of QTL detected accounts for the smooth and sustained response to selection throughout the twentieth century.

Tocopherols are a class of fat soluble antioxidant vitamin compounds present in maize (Zea mays L.) that provide health and economic benefits, which potentially could be captured by both producers and consumers to add value to the grain. α-Tocopherol, δ-tocopherol, and γ-tocopherol are the most abundant isomers present in maize. α-Tocopherol has the highest biological activity for the tocopherols; however, γ-tocopherol is generally present in much higher concentrations than the other tocopherols in maize kernels. The objectives of this research were to determine levels of tocopherol isomers in maize kernels from two related maize mapping populations and to map quantitative trait loci (QTL) controlling accumulation of tocopherol isomers. Two sets of materials were assayed in this research, a (W64a x A632) [F.sub.2:4] mapping population and testcross progeny with AE335. Molecular markers were evaluated on the [F.sub.2:4] mapping population and a linkage map created. Each population was analyzed by high performance liquid chromatography (HPLC) for α, δ, and γ-tocopherol. Composite interval mapping (CIM) identified QTL for individual tocopherols and total tocopherols, notably on chromosomes 1 and 5. The ratio of α-/γ-tocopherol was analyzed to identify QTL influencing the conversion of γ-tocopherol to α-tocopherol. The QTL associated with the largest percentage of phenotypic variation in the study was detected on chromosome 5 for ratio (α/γ) tocopherol. The QTL identified in this study have potential for use in a marker assisted selection program to facilitate increasing levels and ratios of tocopherols in maize grain., VITAMIN E describes eight naturally occurring compounds possessing α-tocopherol activity (Bramley et al., 2000; Eitenmiller, 1997). The eight compounds can be divided into two distinct groups, tocopherols and tocotrienols. The [...]

Corn (Zea mays L.) germplasm ownership methods are unwieldy and limit progress. Agronomic performance in hybrids better identifies inbreds for distinctness, i.e., independent varieties (IVs) or for dependency, i.e. essentially derived varieties (EDVs) than do molecular methods alone. Our objectives were to assess hybrid agronomic performance of some popular, closely related inbreds on the basis of molecular methods, and to offer thoughts on developing inbreds and on germplasm ownership. Significant agronomic differences were detected between the following: two hybrids in the same genetic group on the basis of 21 isozymic loci; two closely related inbreds (B73 and LH119) with 88.6% (62/70) RFLP (restriction fragment length polymorphism) similarity; and two closely related inbreds (Mo17 and LH51) with 88.2% (60/68) RFLP similarity. We suggest raising dependency standards for patenting inbreds to 90% or more, allowing the right to use and also paying a small royalty for only 5 yr on EDVs to the owner of the IV, and maintaining a research exemption to provide elite inbreds for developing new inbreds and experimental hybrids to all breeders. This will help maintain genetic gain for corn grain yield and serve the common good., IN THIS STUDY, we provide extensive, true-to-life, seed company data and information about hybrids to illustrate the point that a high degree of relationship between inbreds or hybrids based on [...]

The Illinois Long Term Selection Strains offer a unique opportunity to investigate the quantitative genetic basis of kernel chemical traits. This study was conducted to determine the number and magnitude of quantitative trait loci (QTL) influencing kernel oil concentration and kernel weight in a maize (Zea mays L.) population derived from a cross of Illinois High Protein (IHP) x Illinois Low Protein (ILP). The parental strains had been divergently selected for protein concentration for 76 cycles, yet varied in oil concentration from 29 g [kg.sup.-1] (ILP) to 54 g [kg.sup.-1] (IHP) and in 300 kernel weight from 76.5 g (ILP) to 41.1 g (IHP). One hundred polymorphic RFLP loci spaced throughout the maize genome were scored in a segregating population of 100 [S.sub.1] families. Kernel oil concentration and kernel weight were obtained from replicated field trials grown during 1990 and 1991. Significant (P < 0.05 level) QTL associations of 25 marker loci on 13 chromosome arms with oil concentration and 18 marker loci on 10 chromosome arms with kernel weight were identified. These results demonstrate the effectiveness of identification of QTL for oil concentration in strains divergently selected for protein concentration for 76 cycles. Clusters of two or more marker loci in the same chromosomal region were significantly associated with oil concentration at four different chromosomal locations and with kernel weight at four chromosomal locations. The detection of relatively few clusters of marker loci associated with genomic regions controlling oil concentration suggests the development of high oil maize germplasm via RFLP marker-assisted selection may be feasible.

US maize yield has increased eight-fold in the past 80 years, with half of the gain attributed to selection by breeders. During this time, changes in maize leaf angle and size have altered plant architecture, allowing more efficient light capture as planting density has increased. Through a genome-wide association study (GWAS) of the maize nested association mapping panel, we determined the genetic basis of important leaf architecture traits and identified some of the key genes. Overall, we demonstrate that the genetic architecture of the leaf traits is dominated by small effects, with little epistasis, environmental interaction or pleiotropy. In particular, GWAS results show that variations at the liguleless genes have contributed to more upright leaves. These results demonstrate that the use of GWAS with specially designed mapping populations is effective in uncovering the basis of key agronomic traits. [ABSTRACT FROM AUTHOR]