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Full-Text Articles in Life Sciences

Breeding For Modified Seed Composition In Soybean: Selection Of Genotypes, Yield Stability, And Environmental Effects, Luciano Miguel Jaureguy Dec 2012

Breeding For Modified Seed Composition In Soybean: Selection Of Genotypes, Yield Stability, And Environmental Effects, Luciano Miguel Jaureguy

Graduate Theses and Dissertations

The development of cultivars with modified seed composition represents an excellent alternative to cope with the world's need for more nutritious food. Understanding the genetic and environmental factors controlling crop seed quality traits is of crucial importance for such an endeavor. The objectives of this study were: a) to evaluate the efficiency of phenotype and marker-assisted selection for low stachyose and low phytate soybean breeding lines, and their yield stability, b) to study the effect of management practices planting date and delayed harvest on soybean seed composition, and c) to study the potential association between soil properties and leaf chemical …


False Smut Of Rice: Histological Analysis Of Infection, Liem Thi Thanh Nguyen Dec 2012

False Smut Of Rice: Histological Analysis Of Infection, Liem Thi Thanh Nguyen

Graduate Theses and Dissertations

False smut of rice, caused by Ustilaginoidea virens (Cooke) Takahashi (Teleomorph: Villosiclava virens), has become a common disease in most major rice growing regions throughout the world. Considerable confusion exists regarding the infection process and the disease cycle. Therefore, a clearer understanding of pathogenesis caused by Ustilaginoidea virens is critical for future efforts to develop genetic and chemical tools to manage false smut in Arkansas and other regions of the world. The overall goal of this research was to clarify the infection process underlying false smut, with emphasis on comparing and contrasting the histological basis of root and foliar infections. …


Evaluation Of The Recombination Efficiencies Of Flp Proteins, Linh Duy Nguyen Dec 2012

Evaluation Of The Recombination Efficiencies Of Flp Proteins, Linh Duy Nguyen

Graduate Theses and Dissertations

Site-specific recombination systems are powerful tools for genetic modification. They have been used to integrate a transgene into a pre-defined locus and to remove marker genes from a transgene locus. Two of the most widely used site-specific recombination systems in plants are the Cre/lox system from the bacteriophage P1 and the FLP/FRT system from the yeast Saccharomyces cerevisiae. The Cre/lox system is well-characterized and is the first choice in application of site-specific recombination system. However, some applications such as marker-free site-specific gene integration require the use of two recombination systems. In addition, the availability of alternative recombination systems can offer …


Meta-Analysis Of Wheat Qtl Regions Associated With Heat And Drought Stress, Marlovi Andrea Acuna Galindo Dec 2012

Meta-Analysis Of Wheat Qtl Regions Associated With Heat And Drought Stress, Marlovi Andrea Acuna Galindo

Graduate Theses and Dissertations

Heat and drought are the two most important environmental constraints to wheat production globally, are often present simultaneously and will become more severe with global climate change. This presents a unique challenge to wheat scientists who must work to develop wheat cultivars that are productive and adapted to future environmental conditions. A number of recent studies have reported quantitative trait loci (QTL) associated with heat and drought tolerance, as well as QTL for stress adaptive traits such as the availability of stem carbohydrates or crop canopy temperature. The objective of this study was to perform a meta-analysis of these QTL …


Long-Term Effects Of Rice Rotation, Tillage, And Fertility On Near-Surface Soil Carbon And Nitrogen Cycling, Jill Marie Motschenbacher Dec 2012

Long-Term Effects Of Rice Rotation, Tillage, And Fertility On Near-Surface Soil Carbon And Nitrogen Cycling, Jill Marie Motschenbacher

Graduate Theses and Dissertations

Rice (Oryza sativa L.)-based cropping systems are different from other row crops due to the flood-irrigation scheme used from about one month after planting to a few weeks prior to harvest. The frequent cycling between anaerobic (i.e., flooding during the growing season) and aerobic (i.e., generally, the remainder of the year) conditions can influence the rate of soil organic matter (SOM) decomposition, which can greatly influence carbon (C) and nitrogen (N) storage and sequestration in the soil over time. Therefore, a study was conducted on a silt-loam soil (fine, smectitic, thermic, Typic Albaqualf) at the Rice Research and Extension Center …


Documentation And Control Of Acetolactate Synthase-Resistant Barnyardgrass (Echinochloa Crus-Galli) In Arkansas Rice, Michael Joshua Wilson Dec 2012

Documentation And Control Of Acetolactate Synthase-Resistant Barnyardgrass (Echinochloa Crus-Galli) In Arkansas Rice, Michael Joshua Wilson

Graduate Theses and Dissertations

Barnyardgrass, the most problematic grass weed of Arkansas rice, was found resistant to propanil in 1990, and since then, it has evolved resistance to quinclorac and clomazone. Barnyardgrass is now believed to have evolved resistance to acetolactate synthase (ALS)-inhibiting herbicides. The goal of this research was to confirm and determine the level of resistance of the putative resistant biotype to the ALS-inhibiting herbicides imazethapyr, bispyribac, and penoxsulam and to develop herbicide programs for controlling ALS-, propanil-, quinclorac-, and clomazone-resistant barnyardgrass. The lethal dose needed to kill 50% of the putative ALS-resistant plants was higher than that of the susceptible biotype …


Effects Of Environment And Genotype On Charcoal Rot Development On Soybeans, Micah Diane Doubledee Aug 2012

Effects Of Environment And Genotype On Charcoal Rot Development On Soybeans, Micah Diane Doubledee

Graduate Theses and Dissertations

Charcoal rot of soybean, caused by the soilborne fungus Macrophomina phaseolina (Tassi) Goid, is a disease associated with high soil temperature and low soil moisture. Above-ground symptoms, which can be difficult to distinguish from drought symptoms, include low vigor, dead leaves that remain attached to the plant, early senescence and yield loss. Irrigation limits damage, but does not prevent colonization of the tissue by the pathogen. No soybean line is immune to M. phaseolina, but a few lines may have moderate resistance. The objectives of this research were to 1) determine the effects of genotype and drought on the development …


Market Analysis Of Fresh Berries In The United States, Kristina Sobekova Aug 2012

Market Analysis Of Fresh Berries In The United States, Kristina Sobekova

Graduate Theses and Dissertations

This thesis contains a market analysis of fresh berries in United States. Specifically, it addresses strawberry, blueberry, blackberry and raspberry markets during 2008-2011. A double log model and the Almost Ideal Demand model are used to gain insight into the demand side of the market. An equilibrium displacement model is used to develop suggestions for producers and decision makers. The results demonstrate that retail demand for berry crops is elastic and that the different berries are substitutes for one another. The equilibrium displacement model is used to predict producer surplus changes to industry wide efforts aimed at both production efficiencies …


Multifunctionality In U.S. Rice Production: A Logit Analysis In Farmers Participation, Juan Tur Cardona May 2012

Multifunctionality In U.S. Rice Production: A Logit Analysis In Farmers Participation, Juan Tur Cardona

Graduate Theses and Dissertations

Multifunctional agriculture is particularly fundamental to some working lands conservation policies and programs, such as the Environmental Quality Incentive Program (EQIP), Conservation Security Program (CSP) and Wildlife Habitat Incentive Program (WHIP). Farmers can also be engaged in providing recreational and agri-tourism services such as hunting, fishing, bird-watching, farm tours, petting zoos and hospitality services. Using the Agricultural Resource Management Survey (ARMS) we analyze factors associated with participation in conservation, recreation and agri-tourism activities as a function of farm structure, farm financial measures, production practices, and socio-demographic characteristics of the farm operator. To estimate the functional relationships we estimate a binary …


Herbicide Resistance Mechanism(S) In Italian Ryegrass (Lolium Perenne Ssp. Multiflorum) Populations In The Southern United States, Reiofeli Algodon Salas May 2012

Herbicide Resistance Mechanism(S) In Italian Ryegrass (Lolium Perenne Ssp. Multiflorum) Populations In The Southern United States, Reiofeli Algodon Salas

Graduate Theses and Dissertations

Italian ryegrass is a principal weed problem in wheat production fields in the Southern US. Resistance to herbicides diclofop, mesosulfuron, and pinoxaden among ryegrass populations has been reported. Glyphosate-resistant Italian ryegrass populations were identified in Desha County, Arkansas. This research aimed to 1) determine resistance patterns to ACCase (diclofop and pinoxaden) and ALS (imazamox, mesosulfuron, and pyroxsulam) herbicides among Italian ryegrass populations from the southern US; 2) determine if cytochrome P450-mediated enhanced herbicide metabolism contributed to resistance; and 3) elucidate the resistance mechanism to glyphosate in four Arkansas populations (Des03, Des05, Des14, and D8). For objective 1, 30 accessions from …


Identification And Confirmation Of Ssr Markers And Qtl For Seed Calcium Content And Hardness Of Soybean, Moldir Orazaly May 2012

Identification And Confirmation Of Ssr Markers And Qtl For Seed Calcium Content And Hardness Of Soybean, Moldir Orazaly

Graduate Theses and Dissertations

The health benefits and the nutritional values of soyfood products have expanded the demand for food-grade soybean varieties. For whole soyfood products such as natto, small seeded varieties with proper texture are essential. Seed calcium content and hardness are main factors in determining the seed texture. Utilizing molecular markers associated with quantitative trait loci (QTL) for marker assisted selection (MAS) has been an efficient technique for breeders. To find molecular markers associated with a trait is an initial step. The confirmation of QTL in different environments and in different genetic backgrounds is important for MAS. The objectives of this research …


Cotton Response To High Temperature Stress During Reproductive Development, Justin B. Phillips May 2012

Cotton Response To High Temperature Stress During Reproductive Development, Justin B. Phillips

Graduate Theses and Dissertations

Temperature is a primary controller of the rate of plant growth, developmental events, and fruit maturation. Increased temperatures from global climate change are projected to cause substantial losses in crop productivity by the end of the twenty-first century. Elevated temperatures affect all stages of cotton development, but the crop seems to be particularly sensitive to adverse temperatures during reproductive development. In Arkansas, temperature stress is considered to be one of the main factors affecting cotton yield. Environmental stress during floral development is a major reason for the disparity between actual and potential yields. Field and growth chamber studies were conducted …