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1

Electronic Resource

Selection for Early Flowering Results in Simultaneous Selection for Reduced Nuclear DNA Content in Maize (1994)

Rayburn, A. Lane. ; Dudley, J. W. ; Biradar, D. P.

Oxford, UK : Blackwell Publishing Ltd

Plant breeding 112 (1994), S. 0

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ISSN: 1439-0523

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Several studies have indicated a possible link between genome size and earliness in maize. In this study, an original maize population, South African photo-period insensitive maize composite II (C0) and several selected generations were analyzed for days to flowering, plant height, ear height, and yield. The selection criterion was earliness. Over six cycles of selection a 14-day decrease in days to flowering was obtained with no significant reduction in grain yield. In the initial population (C0) and the most advanced selection (C6) 101 plants were analyzed for nuclear DNA content. A significant decrease in the mean nuclear DNA content of the C0 population (102 AU) was observed with respect to the C0 population (105 AU). This reduction was the result of a decrease in frequency of plants in the C6 population with large genome sizes. Therefore it was concluded that selection for earliness resulted in selection against plants with large genome sizes. Hence, the nucleotype of a maize plant can be modified by selection such as early flowering time.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1439-0523.1994.tb00690.x

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2

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Measurements of second- and third-order nonlinear polarizabilities for HF and HCl (1985)

Dudley, J. W. ; Ward, J. F.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 82 (1985), S. 4673-4677

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Measurements of second- and third-order nonlinear polarizabilities (hyperpolarizabilities) for HF and HCl using dc electric-field-induced second-harmonic generation are presented: χ(3)(parallel)(HF)=70(10)×10−39 esu/mol, χ(2)(parallel) (HF)=−4.70(41)×10−32 esu/mol, χ(3)(parallel)(HCl)= 347(15)×10−39 esu/mol, χ(2)(parallel)(HCl)= −4.22(50)×10−32 esu/mol. In the case of HF this allows a critical comparison with theory. HF has fewer electrons than any polar molecule previously studied experimentally and the small size of HF has made it an attractive candidate for theoretical investigation. Christiansen and McCullough have used numerical Hartree–Fock techniques to establish generally accepted criteria for basis set selection; and Bartlett and Purvis have applied to HF the most elaborate technique applied so far to the calculation of any molecular hyperpolarizability (CHF SDQ-MBPT[4]). Experimental corrections and uncertainties are carefully considered as are several other factors relevant to a comparison of these experimental and theoretical data. The theoretical results are about a factor of 2 smaller than the experimental data and none of the factors considered seems to offer a resolution of this discrepancy.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.448726

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3

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Theory for identification of marker locus-QTL associations in population by line crosses (1992)

Dudley, J. W.

Springer

Theoretical and applied genetics 85 (1992), S. 101-104

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ISSN: 1432-2242

Keywords: Marker assisted selection ; RFLP ; QTL ; Quantitative genetics ; Corn breeding

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The objective of this paper is to present genetic theory demonstrating the conditions under which it should be possible to identify molecular marker-quantitative trait locus (QTL) associations in crosses of random-mating populations to inbreds. Using as an example the cross of a corn (Zea mays L.) population to an inbred, the expected disequilibrium for testcross and per se performance of F2, F3, BC1 (to the inbred) and recombinant inbred generations was derived for cases where a marker allele is linked to an unfavorable QTL allele in the inbred and where the marker allele is linked to a favorable QTL allele in the inbred. Disequilibrium in segregating generations was shown to be a function of disequilibrium in the parent population, the frequency of marker and QTL alleles in the parent population, and the recombination distance between the marker and the QTL. To maximize the opportunity to identify a favorable QTL the following procedures are suggested: (1) Select marker loci with alleles in the parent population which are not present in the inbred. (2) Select populations known to have favorable QTL alleles not present in the inbred. (3) Use as many marker loci as possible to enhance the probability of tight linkage between the marker and the QTL.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00223850

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4

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Use of RFLP markers to search for alleles in a maize population for improvement of an elite hybrid (1992)

Zehr, B. E. ; Dudley, J. W. ; Chojecki, J. ; [et al.]

Springer

Theoretical and applied genetics 83 (1992), S. 903-911

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ISSN: 1432-2242

Keywords: Zea mays L. ; RFLPs ; Quantitative traits ; Favorable alleles ; Epistasis

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary Molecular markers can be used to detect alleles in donor genetic material for improvement of existing cultivars or hybrids. DNA restriction fragment length polymorphisms (RFLPs) were used as markers to search for favorable alleles at quantitative trait loci in the maize (Zea mays L.) population BS11(FR)C7 which were not in the hybrid ‘FRB73 x FRMo17.’ Thirty-four RFLP markers were used to determine RFLP ‘fingerprints’ for 220 [BS11(FR)C7 x FRMo17] F2 individuals; multiple morphs (bands) were observed at most markers. Statistical associations between RFLPs and trait expression in F2 x FRB73 progeny were found for grain yield, stalk and root lodging, plant and ear height, maturity, and seven grain yield component traits. Associations were found using linear contrasts among RFLP marker classes to estimate trait effects. Estimated effects for grain yield ranged from 213 to 538 kg ha-1, 3.0–7.5% of the experimental mean, respectively. RFLP markers with greatest probability of association with grain yield were NPI234 (short arm of chromosome 1) and UMC16 (long arm of chromosome 3). Digenic epistasis appeared to be important in grain yield expression, as indicated by a 12% increase in the proportion of genotypic variation accounted for when significant di-marker interactions were added to a linear model, including all markers individually associated with grain yield. The majority of interactions associated with grain yield involved markers NPI234 and UMC21 (long arm of chromosome 6). Many RFLP markers were associated with multiple traits. At some markers, the same bands were associated with favorable effects for stalk lodging, grain yield, and yield components. RFLP bands unique to BS11(FR)C7 showed associations favorable over those from FRMo17 for at least one marker in all but one trait. The results of this study will be useful in future RFLP marker-assisted selection programs aimed at developing lines for improved performance in combination with FRB73.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00226714

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5

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Some practical considerations for using RFLP markers to aid in selection during inbreeding of maize (1992)

Zehr, B. E. ; Dudley, J. W. ; Chojecki, J.

Springer

Theoretical and applied genetics 84 (1992), S. 704-708

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ISSN: 1432-2242

Keywords: Zea mays L ; RFLPs ; Marker-based selection ; RFLP-QTL associations ; Favorable marker genotypes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary If molecular markers are to be routinely used in maize (Zea mays L.) breeding for selection of quantitative trait loci (QTL), then consistent marker-trait associations across breeding populations are needed, as are efficient methods for weighting information from different markers. Given 15 restriction fragment length polymorphism (RFLP) markers associated with grain yield in testcrosses of 220 [BS11(FR)C7 x FRMol7] F2 individuals to FRB73, separate weighting schemes were attempted in order to maximize the frequency of favorable marker genotypes associated with increased grain yield in selected F2 individuals and F2:S4 Unes. The following principles were apparent: (1) Differential weighting among markers, in addition to weighting individual marker genotypes on the basis of associated mean effects, should be emphasized when using markers to select in breeding populations. This is due to limited population sizes that can readily be handled. (2) Relatively few markers may need to be used to screen segregating populations (e.g., F2) of limited size for loci affecting complex traits, such as combining ability for grain yield, assuming prior knowledge of marker-QTL associations. Markers given greatest weight (largest estimates of associated effects) will determine most selections. (3) When marker-based selection is among individuals at higher levels of inbreeding (e.g., S4) within selected families, more markers need to be used in screening because those associated with relatively small effects have an increased chance of affecting selection. These results suggest a qualitative approach for utilizing RFLP markers to aid in selection of complex traits in commercial hybrid maize breeding programs. Commercial research programs produce thousands of crosses each year aimed at inbred line development. Discovery of molecular markers with consistent QTL associations across breeding populations and close QTL linkages would allow for rapid screening of new F2 populations at a few key markers. Early elimination of individuals with undesirable genotypes would reduce the extent of hybrid performance testing necessary during later stages of inbreeding.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00224172

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6

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Quantitative trait loci influencing protein and starch concentration in the Illinois Long Term Selection maize strains (1993)

Goldman, I. L. ; Rocheford, T. R. ; Dudley, J. W.

Springer

Theoretical and applied genetics 87 (1993), S. 217-224

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ISSN: 1432-2242

Keywords: Restriction fragment length polymorphism (RFLP) ; Mapping ; Illinois Long Term Selection Experiment ; Quantitative trait loci (QTL) ; Protein ; Starch ; Zea mays L.

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract A study was initiated to determine the number, chromosomal location, and magnitude of effect of QTL (quantitative trait loci or locus depending on context) controlling protein and starch concentration in the maize (Zea mays L.) kernel. Restriction fragment length polymorphism (RFLP) analysis was performed on 100 F3 families derived from a cross of two strains, Illinois High Protein (IHP), X Illinois Low Protein (ILP), which had been divergently selected for protein concentration for 76 generations as part of the Illinois Long Term Selection Experiment. These families were analyzed for kernel protein and starch in replicated field trials during 1990 and 1991. A series of 90 genomic and cDNA clones distributed throughout the maize genome were chosen for their ability to detect RFLP between IHP and ILP. These clones were hybridized with DNA extracted from the 100 F3 families, revealing 100 polymorphic loci. Single factor analysis of variance revealed significant QTL associations of many loci with both protein and starch concentration (P 〈 0.05 level). Twenty-two loci distributed on 10 chromosome arms were significantly associated with protein concentration, 19 loci on 9 chromosome arms were significantly associated with starch concentration. Sixteen of these loci were significant for both protein and starch concentration. Clusters of 3 or more significant loci were detected on chromosome arms 3L, 5S, and 7L for protein concentration, suggesting the presence of QTL with large effects at these locations. A QTL with large additive effects on protein and starch concentration was detected on chromosome arm 3L. RFLP alleles at this QTL were found to be linked with RFLP alleles at the Shrunken-2 (Sh2) locus, a structural gene encoding the major subunit of the starch synthetic enzyme ADP-glucose pyrophosphorylase. A multiple linear regression model consisting of 6 significant RFLP loci on different chromosomes explained over 64 % of the total variation for kernel protein concentration. Similar results were detected for starch concentration. Thus, several chromosomal regions with large effects may be responsible for a significant portion of the changes in kernel protein and starch concentration in the Illinois Long Term Selection Experiment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00223767

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7

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Linkage disequilibrium in crosses between Illinois maize strains divergently selected for protein percentage (1994)

Dudley, J. W.

Springer

Theoretical and applied genetics 87 (1994), S. 1016-1020

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ISSN: 1432-2242

Keywords: Maize ; Long-term selection ; Quantitative genetics ; Corn breeding ; Protein

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The objectives of this study were two fold: (1) to determine whether divergent selection for kernel protein concentration, which produced the Illinois high protein (IHP), Illinois low protein (ILP), reverse low protein (RLP), and reverse high protein (RHP) maize (Zea mays L.) strains, had generated coupling-phase linkages among genes controlling protein concentration or other traits and (2) to measure the effectiveness of random mating in reducing linkage disequilibrium in segregating generations from crosses between the strains. To achieve these objectives, design III progenies from the F2 and F6 (produced by random mating the F2) from the crosses of IHP × ILP, IHP × RHP, ILP × RLP, and RHP × RLP were evaluated. Estimates of additive variance for percent protein in the crosses of IHP × ILP and ILP × RLP were significantly less in the F6 than in the F2 indicating the presence of coupling-phase linkages in the parents and their breakup by random mating. In addition, a significant reduction in dominance variance for grain yield from the F2 to the F6 in IHP × ILP suggested the presence of repulsion-phase linkages. No other evidence of coupling or repulsion-phase linkages was found for any of the traits measured. These results demonstrate the effectiveness of long-term divergent selection in the development of coupling-phase linkages and of random mating to dissipate linkage disequilibrium.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00225797

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