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Articles 2131 - 2160 of 2597

Full-Text Articles in Agricultural Science

Composting Of Feedlot And Dairy Manure: Compost Characteristics And Impact On Crop Yields, Galen E. Erickson, Terry J. Klopfenstein, Walker Luedtke, Mark Schroeder, Charles A. Francis, Gary Lesoing Jan 2001

Composting Of Feedlot And Dairy Manure: Compost Characteristics And Impact On Crop Yields, Galen E. Erickson, Terry J. Klopfenstein, Walker Luedtke, Mark Schroeder, Charles A. Francis, Gary Lesoing

Nebraska Beef Cattle Reports

Since 1993, approximately 17,600 tons of beef feedlot and dairy compost have been spread on 1,100 acres. Crop yields were measured to determine the impact of a one-time compost application by using no-compost check strips in large-scale production fields. Adding compost to irrigated corn, irrigated soybeans, and dryland corn acres significantly increased yields, with four-year average increases of 2.3, 1.5, and 2.7%, respectively. For all crops measured, the response to compost was greatest the first year following application and declined linearly in subsequent years. The increased yield from compost application offsets spreading costs using average prices for crops.

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Distinctive Hydrocarbons Of The Black Dump Fly, Hydrotaea Aenescens (Diptera: Muscidae), David A. Carlson, Ulrich R. Bernier, Jerome A. Hogsette, Bruce D. Sutton Jan 2001

Distinctive Hydrocarbons Of The Black Dump Fly, Hydrotaea Aenescens (Diptera: Muscidae), David A. Carlson, Ulrich R. Bernier, Jerome A. Hogsette, Bruce D. Sutton

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Hydrotaea aenescens (Wiedemann), the black dump fly, is a potential biological control agent originally from the western hemisphere, now found in many parts of the Palearctic region except for the United Kingdom, where it cannot be imported for any reason. A complication of classical biological control is the problem of strain identification, as one must be able to somehow mark or follow a particular strain that has been introduced into the field or is contemplated for release. Gas chromatographic analysis of the surface hydrocarbons of pooled and individual dump fly adults resulted in reproducible hydrocarbon patterns that differentiated widely distributed …

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Gas Exchange And Photosynthetic Acclimation Over Subambient To Elevated Co2 In A C3-C4 Grassland, Laurel J. Anderson, Hafiz Maherali, Hyrum B. Johnson, H. Wayne Polley, Robert B. Jackson Jan 2001

Gas Exchange And Photosynthetic Acclimation Over Subambient To Elevated Co2 In A C3-C4 Grassland, Laurel J. Anderson, Hafiz Maherali, Hyrum B. Johnson, H. Wayne Polley, Robert B. Jackson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Atmospheric CO2 (Ca) has risen dramatically since preglacial times and is projected to double in the next century. As part of a 4-year study, we examined leaf gas exchange and photosynthetic acclimation in C3 and C4 plants using unique chambers that maintained a continuous Ca gradient from 200 to 550 µmol mol-1 in a natural grassland. Our goals were to characterize linear, nonlinear and threshold responses to increasing Ca from past to future Ca levels. Photosynthesis (A), stomatal conductance (gs), leaf water-use efficiency (A/gs …

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Dis And Distributed Watershed Models I, Jurgen Garbrecht, Fred L. Ogden, Paul A. Debarry, David R. Maidment Jan 2001

Dis And Distributed Watershed Models I, Jurgen Garbrecht, Fred L. Ogden, Paul A. Debarry, David R. Maidment

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The increasing proliferation of spatial data, geographic information systems (GIS), and models for hydrologic applications provide many new investigation opportunities but also present a number of challenges for the uninitiated water resources practitioner. This two-part paper is intended for the practicing engineer who wants to expand into the arena of spatial data and distributed watershed modeling. It provides an integrated overview of the multiple facets of data-GIS-modeling issues and a source of background information for selection and application of GIS in watershed modeling. This first paper addresses selected spatial data issues, data structures and projections, data sources, and information on …

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Automated Gas Sampling System For Laboratory Analysis Of Ch4 And N2O, Spencer L. Arnold, Timothy B. Parkin, John W. Doran, Bahman Eghball, Arvin R. Mosier Jan 2001

Automated Gas Sampling System For Laboratory Analysis Of Ch4 And N2O, Spencer L. Arnold, Timothy B. Parkin, John W. Doran, Bahman Eghball, Arvin R. Mosier

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Analyzing the flux of CH4 and N2O from soil is labor intensive when conventional hand injection techniques are utilized in gas chromatography. An automated gas sampling system was designed and assembled from a prototype developed at the National Soil Tilth Laboratory in Ames, IA. The sampler was evaluated for accuracy and precision when attached to a Varian 3700 gas chromatograph configured with flame ionization and electron capture detectors. The automated gas sampling system is easy to operate and provides acceptable results (standards ranging from 1.0–5.0 ppmv CH4 and 0.342–2.0 ppmv N2O had coefficients of …

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Evidence For The Innervation Of Sperm Storage Tubules In The Oviduct Of The Turkey (Meleagris Gallopavo), S. L. Freedman, V. G. Akuffo, M. R. Bakst Jan 2001

Evidence For The Innervation Of Sperm Storage Tubules In The Oviduct Of The Turkey (Meleagris Gallopavo), S. L. Freedman, V. G. Akuffo, M. R. Bakst

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The presence of neural tissue and smooth muscle elements in the vicinity of the oviductal sperm storage tubules at the uterovaginal junction was assessed by several modes of light microscopy. Isolated neurones and small ganglia were identified in the uterovaginal junction of the turkey oviduct. The nerve cell bodies were observed in the tunica mucosa by bright field microscopy. Immunoreactivity against neurofilament antibody and recombinant fragment C of the tetanus toxin reacted with nerve fibres and the nuclei of neurones. Fluorescence microscopy and confocal laser scanning microscopy revealed that nerve fibres continued from the base of the tunica mucosa into …

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Wheat Polyphenol Oxidase: Distribution And Genetic Mapping In Three Inbred Line Populations, Tigst Demeke, Craig F. Morris, Kimberly A. Garland-Campbell, Garrison E. King, James A. Anderson, Hak-Gil Chang Jan 2001

Wheat Polyphenol Oxidase: Distribution And Genetic Mapping In Three Inbred Line Populations, Tigst Demeke, Craig F. Morris, Kimberly A. Garland-Campbell, Garrison E. King, James A. Anderson, Hak-Gil Chang

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The enzyme polyphenol oxidase (PPO) has been implicated in discoloration of Asian noodles. The recombinant inbred line (RIL) populations, M6/‘Opata 85’, NY18/CC, and ND2603/‘Butte 86’ were used to investigate the distribution, chromosome location, and number of loci involved in wheat (Triticum aestivum L.) PPO. PPO activity was measured by means of the substrates L-DOPA (L-3,4-dihydroxyphenyl-alanine) and L-tyrosine. The M6/Opata 85 RIL population had a normal distribution, while the ND2603/Butte 86 RIL population had a bimodal distribution for PPO activity (L-DOPA assay).

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Genomic Regions That Underlie Soybean Seed Isoflavone Content, K. Meksem, V. N. Njiti, W. J. Banz, M. J. Iqbal, My. M. Kassem, David L. Hyten, J. Yuang, T. A. Winters, D. A. Lightfoot Jan 2001

Genomic Regions That Underlie Soybean Seed Isoflavone Content, K. Meksem, V. N. Njiti, W. J. Banz, M. J. Iqbal, My. M. Kassem, David L. Hyten, J. Yuang, T. A. Winters, D. A. Lightfoot

Department of Agronomy and Horticulture: Faculty Publications

Soy products contain isoflavones (genistein, daidzein, and glycitein)that display biological effects when ingested by humans and animals, these effects are species, dose and age dependent. Therefore, the content and quality of isoflavones in soybeans is a key to their biological effect. Our objective was to identify loci that underlie isoflavone content in soybean seeds. The study involved 100 recombinant inbred lines (RIL)fr om the cross of ‘Essex’ by ‘Forrest,’ two cultivars that contrast for isoflavone content. Isoflavone content of seeds fromeach RIL was determined by high performance liquid chromatography (HPLC). The distribution of isoflavone content was continuous and unimodal. The …

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Seed Physiology, Production & Technology: Germination, Emergence, And Yield Of 20 Plant-Color, Seed-Color Near-Isogenic Lines Of Grain Sorghum, Jeffrey F. Pedersen, J. J. Toy Jan 2001

Seed Physiology, Production & Technology: Germination, Emergence, And Yield Of 20 Plant-Color, Seed-Color Near-Isogenic Lines Of Grain Sorghum, Jeffrey F. Pedersen, J. J. Toy

Department of Agronomy and Horticulture: Faculty Publications

Although there is growing demand for sorghum [Sorghum bicolor (L.) Moench] with white seed and tan plant color, there is limited information on the overall agronomic fitness of sorghum with these characters. A set of experiments was conducted to evaluate the combined effects of plant color and seed color on sorghum germination, emergence, and agronomic performance. Twenty near-isogenic lines with red seed/tan plant (RT), red seed/purple plant (RP), white seed/ tan plant (WT), white seed/purple plant (WP) phenotypes were tested under field and laboratory conditions. Plant color X seed color interactions were not significant. Purple plant color phenotypes had higher …

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Fallow Versus Wheat Cropping Of Unamendedand Manure-Amended Soils Related To Mycorrhizal Colonization, Yield, And Plant Nutrition Of Dry Bean And Sweet Corn, Brett L. Allen, Von D. Jolley, Charles W. Robbins, Larry L. Freeborn Jan 2001

Fallow Versus Wheat Cropping Of Unamendedand Manure-Amended Soils Related To Mycorrhizal Colonization, Yield, And Plant Nutrition Of Dry Bean And Sweet Corn, Brett L. Allen, Von D. Jolley, Charles W. Robbins, Larry L. Freeborn

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Previous studies reported manure application to eroded Portneuf silt loam soil (Coarse-silty, mixed, superactive, Durinodic Xeric Haplocalcid) improved dry bean (Phaseolus vulgaris L., cv. Viva) yield to levels of topsoil. These yield increases only correlated with whole-plant zinc (Zn) concentration and soil organic matter. This might be related to enhanced arbuscular mycorrhizal (AM) colonization stimulated by manure application. A greenhouse study with dry bean suggested a relationship between manure application, increased AM colonization, and whole-plant Zn uptake, while field studies with wheat (Triticum aestivum L.) and sweet corn (Zea mays L.) did not. To clarify the apparent …

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Methyl-Β-Cyclodextrin: An Alternative Carrier For Intravenous Infusion Of Palmitate During Tracer Studies In Swine (Sus Scrofa Domestica), Diane Wray-Cahen, Thomas J. Caperna, Norman C. Steele Jan 2001

Methyl-Β-Cyclodextrin: An Alternative Carrier For Intravenous Infusion Of Palmitate During Tracer Studies In Swine (Sus Scrofa Domestica), Diane Wray-Cahen, Thomas J. Caperna, Norman C. Steele

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Fatty acid-free albumin has been the standard carrier for intravenous infusion of fatty acids to study in vivo lipid metabolism. However, subjects can have adverse reactions to infusion of albumin. We sought an alternative to albumin as a carrier for intravenous infusion of fatty acids, using the pig as a model. Cyclodextrins are naturally occurring water-soluble molecules that can serve as carriers for lipid-soluble compounds. 13C-palmitate was complexed to either 20% methyl-β-cyclodextrin, 20% 2-hydroxypropyl-β-cyclodextrin, or 5% porcine albumin (isotopic purity of infusates: 99.22±0.06%). 13C-palmitate-albumin was infused under fed conditions and 13C-palmitate-methyl-β-cyclodextrin was infused under fasted and fed …

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Mechanical Barrier For Preventing Climbing By Lesser Mealworm (Coleoptera: Tenebrionidae) And Hide Beetle (Coleoptera: Dermestidae) Larvae In Poultry Houses, Christopher Geden, David Carlson Jan 2001

Mechanical Barrier For Preventing Climbing By Lesser Mealworm (Coleoptera: Tenebrionidae) And Hide Beetle (Coleoptera: Dermestidae) Larvae In Poultry Houses, Christopher Geden, David Carlson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Mechanical barriers consisting of bands of polyethylene terepthalate resin attached to wooden posts by latex caulk adhesive and staples were 100% effective in preventing passage of dispersing lesser mealworm, Alphitobius diaperinus (Panzer), larvae in the laboratory. Barriers continued to be 100% effective after being held in a caged layer poultry house for 3 mo. Polyethylene terepthalate barriers installed on support posts in a pullet house in Brooker, FL, were>92% effective against natural populations of lesser mealworm larvae 6 mo. after installation. The barriers also were >94% effective against natural populations of larvae of the hide beetle, Dermestes maculatus DeGeer, …

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Hymenopteran Pupal Parasitoids Recovered From House Fly And Stable Fly (Diptera: Muscidae) Pupae Collected On Livestock Facilities In Southern And Eastern Hungary, Jerome A. Hogsette, Róbert Farkas, Csaba Thuróczy Jan 2001

Hymenopteran Pupal Parasitoids Recovered From House Fly And Stable Fly (Diptera: Muscidae) Pupae Collected On Livestock Facilities In Southern And Eastern Hungary, Jerome A. Hogsette, Róbert Farkas, Csaba Thuróczy

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

This field survey, the second noting the occurrence and diversity of filth fly pupal parasitoid fauna in Hungary, was performed on beef and dairy feedlots and swine facilities in the southern and eastern parts of the country. The filth flies Musca domestica L. And Stomoxys calcitrans (L.) Were the two most commonly parasitized hosts. The three species of Spalangia recovered, in decreasing order of abundance, were S. Cameroni Perkins, S. Nigroaenea Curtis, and S. Endius Walker. Pachycrepoideus vindemiae Rondani, Trichomalopsis sp., two apparently undetermined Diapriidae spp. And one apparently undetermined Brachycera sp. Are believed to be new country records.

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Grain Color Stability And Classification Of Hard White Wheat In The U.S., C. J. Peterson, D. R. Shelton, T. J. Martin, R. G. Sears, E. Williams, R. A. Graybosch Jan 2001

Grain Color Stability And Classification Of Hard White Wheat In The U.S., C. J. Peterson, D. R. Shelton, T. J. Martin, R. G. Sears, E. Williams, R. A. Graybosch

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Variability in grain color of hard white wheat was investigated in cultivars grown over two years in Nebraska and Kansas and related to variation observed in grain hardness, kernel weight, kernel size, and protein content and to color of ground meal and flour. Grain color was scored subjectively, through visual evaluation, and objectively through use of a colorimeter. Of the 543 hard white wheat samples examined by USDA-GIPSA grain inspectors, 15.5% were scored as visually darker than the 1990 grain color standard established as a minimum for hard white wheat classification. The remaining samples were scored as having grain color …

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Assessing Site Vulnerability To Phosphorus Loss In An Agricultural Watershed, Andrew N. Sharpley, Richard W. Mcdowell, Jennifer L. Weld, Peter J. A. Kleinman Jan 2001

Assessing Site Vulnerability To Phosphorus Loss In An Agricultural Watershed, Andrew N. Sharpley, Richard W. Mcdowell, Jennifer L. Weld, Peter J. A. Kleinman

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A P index was developed as a tool to rank agricultural fields on the basis of P loss vulnerability, helping to target remedial P management options within watersheds. We evaluated two approaches, a soil P threshold and components of a P index, by comparing site vulnerability estimates derived from these two approaches with measured runoff P losses in an agricultural watershed in Pennsylvania. Rainfall–surface runoff simulations (70 mm h-1 for 30 min) were conducted on 57 sites representing the full range of soil P concentrations and management conditions found in the watershed. Each site was comprised of two, abutting …

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History, Current Status, And Collaborative Researchprojects For Bemisia Tabaci, M. R. V. Oliveira, T. J. Henneberry, P. Anderson Jan 2001

History, Current Status, And Collaborative Researchprojects For Bemisia Tabaci, M. R. V. Oliveira, T. J. Henneberry, P. Anderson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Bemisia tabaci was described over 100 years ago and has since become one of the most important pests worldwide in subtropical and tropical agriculture as well as in greenhouse production systems. It adapts easily to new host plants and geographical regions and has now been reported from all global continents except Antarctica. In the last decade, international transport of plant material and people have contributed to geographical spread. B. tabaci has been recorded from more than 600 plant species and there may be many additional hosts not yet formally documented. Biotypes have been identified in different areas of the world …

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Quantitative Trait Loci Associated With Milling And Baking Quality In A Soft X Hard Wheat Cross, Kimberley Garland Campbell, Patrick L. Finney, Christine J. Bergman, Daisy G. Gualberto, James A. Anderson, Michael J. Giroux, Dimuth Siritunga, Jiaqian Zhu, Francois Gendre, Catherine Roué, Aliette Vérel, Mark E. Sorrells Jan 2001

Quantitative Trait Loci Associated With Milling And Baking Quality In A Soft X Hard Wheat Cross, Kimberley Garland Campbell, Patrick L. Finney, Christine J. Bergman, Daisy G. Gualberto, James A. Anderson, Michael J. Giroux, Dimuth Siritunga, Jiaqian Zhu, Francois Gendre, Catherine Roué, Aliette Vérel, Mark E. Sorrells

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Interclass hybridization between soft and hard wheat (Triticum aestivum L.) results in new genetic combinations of potential value.

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Gis And Distributed Watershed Models Ii, Fred L. Ogden, Jurgen Garbrecht, Paul A. Debarry, Lynn E. Johnson Jan 2001

Gis And Distributed Watershed Models Ii, Fred L. Ogden, Jurgen Garbrecht, Paul A. Debarry, Lynn E. Johnson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

This paper presents representative applications and models that can take advantage of spatially distributed data in a geographic information system (GIS) format for watershed analysis and hydrologic modeling purposes. The intention is to inform hydrologic engineers about the current capabilities of GIS, hydrologic analysis modules, and distributed hydrologic models, and to provide an initial guide on implementing GIS for hydrologic modeling. This paper also discusses key implementation issues for individuals and organizations that are considering making the transition to the use of GIS in hydrology. Widespread use of GIS modules and distributed watershed models is inevitable. The controlling factors are …

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Food Webs, Risks Of Alien Enemies And Reform Of Biological Control, D. R. Strong, R.W. Pemberton Jan 2001

Food Webs, Risks Of Alien Enemies And Reform Of Biological Control, D. R. Strong, R.W. Pemberton

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

As ilwasions of alien species mount, biological control will become an increasingly important tool of conservation and agriculture. In an effort to understand indirect interactions in biological control, we review food web ecology in terms of resource competition, trophic cascades, intraguild predation, apparent competition, omnivory and a diverse set of tritrophic interactions. The most inclusive study suggests that food webs in biological control are simpler than in natural communities. Risks to non-target species created by biological control have been studied seriously for only about 20 years, and knowledge of these risks is incomplete. The greatest risks are known to be …

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Innovative 15N Microplot Research Techniques To Study Nitrogen Use Efficiency Under Different Ecosystems, Ronald F. Follett Jan 2001

Innovative 15N Microplot Research Techniques To Study Nitrogen Use Efficiency Under Different Ecosystems, Ronald F. Follett

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Use of labeled 15N techniques can help improve and refine knowledge required to understand the dynamics of the N cycle under agricultural systems. The examples reported in this paper illustrate that, with creativity and careful planning, use of 15N-enriched or depleted fertilizers can be used in many types of N experiments with various crops, cropping systems, and in many types of agroecosystems. The objective is to report examples of a wide range of field studies that researchers can hopefully draw upon to design and utilize N isotope techniques that accomplish the objectives for their own research. Examples of …

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Interlaboratory Comparison Of Soil Phosphorus Extracted By Various Soil Test Methods, Peter J.A. Kleinman, A. N. Sharpley, K. Gartley, W. M. Jarrell, S. Kuo, R. G. Menon, R. Myers, K. R. Reddy, E. O. Skogley Jan 2001

Interlaboratory Comparison Of Soil Phosphorus Extracted By Various Soil Test Methods, Peter J.A. Kleinman, A. N. Sharpley, K. Gartley, W. M. Jarrell, S. Kuo, R. G. Menon, R. Myers, K. R. Reddy, E. O. Skogley

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The widespread use of soil phosphorus (P) data, either in the context of agronomic or environmental management, requires an explicit understanding of potential errors related to soil P testing. This study compares a variety of soil P extraction methods, each performed by 9 separate laboratories on 24 soils from across the United States. Soil clay content ranged from 0 to 47%, pH from 4.2 to 8.6, and Mehlich-3 P concentration from 2 to 205 mg kg-1. Average interlaboratory coefficients of variation (CVs) ranged from 0.11 to 0.22 for solution extracts (Bray-1 P, Fe-strip P, Mehlich-3 P, and Olsen …

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Uneasy Unions: Quality Effects Of Rye Chromatin Transfers To Wheat, Robert A. Graybosch Jan 2001

Uneasy Unions: Quality Effects Of Rye Chromatin Transfers To Wheat, Robert A. Graybosch

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

A number of genes of agronomic importance have been transferred from rye (Seale cereale L.) to its close relative, common bread wheat (Triticum aestivum L). Largely through the production of interspecific chromosomal translocation and substitution lines, rye chromatin now rides within the genome of a large number of wheat breeding lines and cultivars. Rye chromosomal materials have been used to transfer resistance genes to fungal pathogens, especially rusts and powdery mildew, resistance to insect pests, and in some cases, may enhance grain yield, grain yield stability, and grain protein content. Unfortunately, the transfer of some rye chromosomal materials …

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Discovery And Deployment Of Molecular Markers Linked To Fusarium Head Blight Resistance: An Integrated System For Wheat And Barley, David Van Sanford, James Anderson, Kimberly A. Garland-Campbell, Josè Costa, Perry Cregan, Carl Griffey, Patrick Hayes, Richard Ward Jan 2001

Discovery And Deployment Of Molecular Markers Linked To Fusarium Head Blight Resistance: An Integrated System For Wheat And Barley, David Van Sanford, James Anderson, Kimberly A. Garland-Campbell, Josè Costa, Perry Cregan, Carl Griffey, Patrick Hayes, Richard Ward

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.)], is a devastating disease that reduces yield, quality and economic value of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.).

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Net Grassland Carbon Flux Over A Subambient To Superambient Co2 Gradient, P. C. Mielnick, W. A. Dugas, H. B. Johnson, H. W. Polley, J. Sanabria Jan 2001

Net Grassland Carbon Flux Over A Subambient To Superambient Co2 Gradient, P. C. Mielnick, W. A. Dugas, H. B. Johnson, H. W. Polley, J. Sanabria

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Increasing atmospheric CO2 concentrations may have a profound effect on the structure and function of plant communities. A previously grazed, central Texas grassland was exposed to a 200-µmol mol-1 to 550 µmol mol-1 CO2 gradient from March to mid-December in 1998 and 1999 using two, 60-m long, polyethylene-covered chambers built directly onto the site. One chamber was operated at subambient CO2 concentrations (200-360 µmol mol-1 daytime) and the other was regulated at superambient concentrations (360-550 µmol mol-1). Continuous CO2 gradients were maintained in each chamber by photosynthesis during the day and …

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Clear-Sky Albedo Measured At Seven Rangland Sites In Southwest Idaho, Clayton L. Hanson Jan 2001

Clear-Sky Albedo Measured At Seven Rangland Sites In Southwest Idaho, Clayton L. Hanson

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

As a component of the energy budget, albedo is used in the calculation of evapotranspiration in many natural resource and hydrologic models. There are few measurements of albedo over sagebrush-dominated rangelands, so albedo was measured at seven sites on the Reynolds Creek Experimental Watershed in southwest Idaho during 1989–1993. For all sites, the average albedo measured during midday under clear skies was 0.14 during the growing season. Albedo varied from a low of 0.11 during June at the Mountain big sagebrush site to a high of 0.17 at the low-elevation Wyoming big sagebrush site. Albedo varied little between about 2 …

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Research Needs Concerning Non-Target Impacts Of Biological Control Introductions, K.R. Hopper Jan 2001

Research Needs Concerning Non-Target Impacts Of Biological Control Introductions, K.R. Hopper

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Two workshops were held in 1999 on research needs concerning non-target impacts of biological control introductions. One took place on the Internet for 9 months, and the other in Montpellier, France, for 1 day. Altogether, over 200 researchers from over 30 countries participated, representing a wide variety of viewpoints on the issues involved. The deliberations of these workshops are summarized here. Both workshops highlighted the need for retrospective studies to: (i) identify cases of significant non-target impacts; (ii) explore mechanisms involved when such impacts are found; (iii) evaluate the reliability of host-range testing protocols; and (iv) determine whether and under …

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Innovative Remote Sensing Techniques To Increase Nitrogen Use Efficiency Of Corn, Walter C. Bausch, Kenan Diker Jan 2001

Innovative Remote Sensing Techniques To Increase Nitrogen Use Efficiency Of Corn, Walter C. Bausch, Kenan Diker

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Nitrogen (N) fertilizer recommendations made without adequate knowledge of the N supply capability of a soil can lead to inefficient use of N. Proper crediting of N from manure and legumes as well as mineralization of N from organic matter is difficult. Remote sensing techniques that use the crop to indicate its N status show considerable promise for improving N management. Objectives of this paper were twofold: 1) to compare the N Reflectance Index (NRI) calculated from ground-based radiometer measurements acquired over irrigated corn (Zea mays L.) at a nadir view (0 °) and an oblique view (75 °) …

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Oxidative Metabolism In Plant/Bacteria Interactions: Characterization Of The Oxygen Uptake Response Of Bacteria, C. Jacyn Baker, Norton Mock, Kenneth L. Deahl, Bryan Bailey, Daniel P. Roberts Jan 2001

Oxidative Metabolism In Plant/Bacteria Interactions: Characterization Of The Oxygen Uptake Response Of Bacteria, C. Jacyn Baker, Norton Mock, Kenneth L. Deahl, Bryan Bailey, Daniel P. Roberts

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

An increase in oxygen uptake has been previously described in plant cell suspensions treated with bacteria or bacterial elicitors. These studies, regarding oxygen uptake, have all been undertaken from the perspective of the host plant cell reacting to the invading pathogen. In contrast, here we describe and characterize an increase in oxygen uptake by bacterial cells in response to plant suspensions or autoclaved plant cell filtrates. Autoclaved plant cell filtrates stimulated bacterial oxygen uptake by as much as sevenfold within a few minutes after addition. This oxygen uptake response was proportional to both the concentration of the plant cell filtrate …

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Oxidative Metabolism In Plant/Bacteria Interactions: Characterization Of A Unique Oxygen Uptake Response Of Potato Suspension Cells, C. Jacyn Baker, E. W. Orlandi, Kenneth L. Deahl Jan 2001

Oxidative Metabolism In Plant/Bacteria Interactions: Characterization Of A Unique Oxygen Uptake Response Of Potato Suspension Cells, C. Jacyn Baker, E. W. Orlandi, Kenneth L. Deahl

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Plant suspension cells have been shown to respond to bacteria or microbial elicitors by producing active oxygen as well as increasing oxygen uptake. Here we characterize a unique two stage oxygen uptake response of potato suspension cells to heat-killed bacteria. Stage 1 occurred within minutes after the addition of heat-killed bacteria; the potato suspension cells responded with a rapid increase in oxygen uptake and reached a steady state approximately 50 % greater than the initial basal rate. Stage 2 began 20-30 min after this new steady state was achieved and was characterized by a slow increase in the oxygen uptake …

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Induction Of Defense Responses In Tobacco By The Protein Nep1 From Fusarium Oxysporum, James C. Jennings, Patricia C. Apel-Birkhold, Norton M. Mock, C. Jacyn Baker, James D. Anderson, Bryan A. Bailey Jan 2001

Induction Of Defense Responses In Tobacco By The Protein Nep1 From Fusarium Oxysporum, James C. Jennings, Patricia C. Apel-Birkhold, Norton M. Mock, C. Jacyn Baker, James D. Anderson, Bryan A. Bailey

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Fusarium oxysporum produces a 24-kDa protein, Nep1, which induces necrosis and ethylene production in leaves of many dicot plant species. Detached Nicotiana tabacum L. cv. Xanthi leaves respond with concentration-dependent necrosis after infiltration with Nep1 or when Nep1 is taken up by the vascular tissue. This response follows the induction of ethylene biosynthesis and accumulation of ACC synthase and ACC oxidase transcripts. Pretreating the leaves with 100 µl/l ethylene prior to elicitation enhanced Nep1-induced ethylene production. Nep1 (208 nM) causes extensive necrosis of mature tobacco leaf tissue when applied to Xanthi tobacco as a foliar spray (129 ml/m2). …

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