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Full-Text Articles in Life Sciences

The Effects Of Salinity On Pythium Disease Of Rice And Soybean, Terea Jeanette Stetina Dec 2013

The Effects Of Salinity On Pythium Disease Of Rice And Soybean, Terea Jeanette Stetina

Theses and Dissertations

Increasing salinity is an important factor limiting agricultural productivity worldwide. In addition to direct effects on growth and yield, diseases also may be affected. This study characterized the effects of soil salinity on seedling disease of soybean and rice caused by Pythium spp. Controlled environment experiments on soybean used two cultivars which differed in chloride tolerance and soil treated with a CaCl2 solution to create a range of electrical conductivity (EC) levels. For soybean, soil was either not infested or infested with Pythium sylvaticum or P. aphanidermatum (pathogenic to soybean), or P. oligandrum (not pathogenic to soybean). Twenty-one days ...


Long-Term Residue And Water Management Effects On Soil Respiration And Soil Aggregate Stability In A Wheat-Soybean, Double-Crop System In Eastern Arkansas, Sharon Faye Smith Dec 2013

Long-Term Residue And Water Management Effects On Soil Respiration And Soil Aggregate Stability In A Wheat-Soybean, Double-Crop System In Eastern Arkansas, Sharon Faye Smith

Theses and Dissertations

Sustainability in agriculture is paramount to assuring continued production from our most naturally fertile soils. Storing carbon (C) in soil as organic matter through sustainable agricultural management practices can both remove atmospheric C and improve soil quality. The objective of this study was to evaluate the long-term effects of water management (irrigation and dryland), residue management [burn and no-burn, conventional (CT) and no-tillage (NT)] and residue/fertility level (high and low) on soil respiration and aggregate stability in a wheat- (Triticum aestivum L.) soybean [Glycine max (L.) Merr.], double-crop system in a silt-loam soil (Aquic Fraglossudalf) in the Mississippi River ...


Quantitative Trait Loci Associated With Waterlogging Tolerance In A Soft Red Winter Wheat Mapping Population, Diana Carolina Ballesteros Benavides Dec 2013

Quantitative Trait Loci Associated With Waterlogging Tolerance In A Soft Red Winter Wheat Mapping Population, Diana Carolina Ballesteros Benavides

Theses and Dissertations

Waterlogging is caused when water stays superficially in the soil for an extended period of time, creating an anaerobic environment which decreases plant growth and grain yield at maturity. Despite the impact of waterlogging on wheat production both globally and in the southeastern U.S., very little is known about the genetic control of waterlogging tolerance in wheat. The objective of this study was to determine the amount of genetic variation for vegetative stage waterlogging tolerance present within a wheat recombinant inbred line (RIL) population and to identify quantitative trait loci (QTL) associated with tolerance and productivity. Experiments were carried ...


Evaluating Economic Impacts Of Switchgrass Harvest Time, Nathanial Elsworth Cahill Dec 2013

Evaluating Economic Impacts Of Switchgrass Harvest Time, Nathanial Elsworth Cahill

Theses and Dissertations

This thesis deals with cost of production for cellulosic energy crops of switchgrass, miscanthus, and energy sorghum. The first chapter explains the rationale for development of decision support software called Energy Crop Analysis & Planning (ENCAP) and Switchgrass Harvest Date, Yield, Nutrient Removal Estimator (SHYNE). The second chapter examines harvest date implications on yield, nutrient removal, opportunity cost of modified sale dates, and post-harvest storage losses. This harvest date analysis leads to a profit maximizing harvest date from the perspective of the producer. While this harvest date may be optimal for the producer, biorefineries may be interested in sourcing switchgrass earlier ...


Selecting Drought Tolerant Soybean Genotypes Using Qtls Associated With Shoot Ureide And Nitrogen Concentrations, Alejandro Bolton Aug 2013

Selecting Drought Tolerant Soybean Genotypes Using Qtls Associated With Shoot Ureide And Nitrogen Concentrations, Alejandro Bolton

Theses and Dissertations

In soybean, nitrogen fixation is more sensitive to drought than other physiological processes like photosynthesis. The sensitivity of nitrogen fixation to drought has been associated with high shoot concentrations of ureide and nitrogen under well-watered conditions. Previous research by Hwang et al. (2013) detected quantitative trait loci (QTLs) in a KS4895 by Jackson population associated with shoot ureide and nitrogen concentrations. The present research evaluated the use of these QTLs in selecting genotypes with drought tolerant nitrogen fixation. Our objectives were to compare actual versus expected phenotype of recombinant inbreed lines (RILs) selected using molecular markers, and to evaluate the ...


Genome-Wide Association Mapping Identifies Qtls And Candidate Genes For Salt Tolerance In Soybean, Lei Huang Aug 2013

Genome-Wide Association Mapping Identifies Qtls And Candidate Genes For Salt Tolerance In Soybean, Lei Huang

Theses and Dissertations

Salinity is a common abiotic stress causing soybean yield loss worldwide. Use of tolerant cultivars is an effective and economic approach to coping with this stress. Toward this, research is needed to identify salt-tolerant germplasm and better understand the genetic and molecular basis of salt tolerance in soybean. The objectives of this study were to identify salt-tolerant genotypes, to search for SNPs and QTLs associated with salt tolerance, and to identify candidate salt tolerance genes. A total of 192 diverse soybean lines and cultivars were screened for salt tolerance in the greenhouse based on visual leaf scorch scores after 15 ...


Identification And Confirmation Of Quantitative Trait Loci For Seed Protein And Oil Content Of Soybean, Jiao Wang Aug 2013

Identification And Confirmation Of Quantitative Trait Loci For Seed Protein And Oil Content Of Soybean, Jiao Wang

Theses and Dissertations

Protein and oil are the major chemical constituents of soybean seed that affect the quality of soyfood, feed, and oil products. Therefore, soybean cultivars with high protein and/or high oil are desirable for the soyfood and feed markets. Use of molecular-marker-assisted selection will facilitate the breeding process of such cultivar development. The objectives of this research were to identify new quantitative trait loci (QTL) and confirm previously reported QTL associated with seed protein and oil content by using simple sequence repeat (SSR) markers and single nucleotide polymorphism (SNP) markers. Two recombinant inbred line (RIL) populations consisting of 242 individuals ...


Distribution And Control Of Glyphosate-Resistant Johnsongrass (Sorghum Halepense) In Arkansas Soybean, Dennis Brent Johnson Aug 2013

Distribution And Control Of Glyphosate-Resistant Johnsongrass (Sorghum Halepense) In Arkansas Soybean, Dennis Brent Johnson

Theses and Dissertations

Johnsongrass, once the most persistent and troublesome grass weed of row crops throughout the southern U.S., has previously been confirmed resistant to the acetolactate synthase (ALS) and acetyl-coenzyme A carboxylase-inhibiting herbicides in the Midsouth and has recently evolved resistance to glyphosate in Arkansas. The goal of this research was to establish the geographical distribution of herbicide-resistant johnsongrass in Arkansas and to develop herbicide programs for controlling glyphosate-resistant johnsongrass in Arkansas soybean. Johnsongrass accessions were collected from 14 counties in the Mississippi River Delta region of Arkansas and screened for resistance to four of the most commonly used postemergence herbicides ...


Genetic Diversity Of Seed Dormancy And Molecular Evolution Of Weedy Red Rice, Te Ming Tseng May 2013

Genetic Diversity Of Seed Dormancy And Molecular Evolution Of Weedy Red Rice, Te Ming Tseng

Theses and Dissertations

Rice is the grain with the third-highest global production. In the US, Arkansas is the largest rice producing state; however, an estimated 62% of the rice fields in the state are infested with red rice, and can cause up to 80% yield reduction in rice. Among its weedy traits, seed dormancy plays an important role in its persistence, and helps red rice escape weed management techniques thereby increasing the red rice soil seedbank. Red rice also has the potential to hybridize among themselves and with cultivated rice, thus resulting in diverse phenotypes and genotypes. In this study we measured variation ...


Local Food And Agriculture Awareness: The Literacy Of Local Produce And Agriculture In Northwest Arkansas, Kyle Colton Flynn May 2013

Local Food And Agriculture Awareness: The Literacy Of Local Produce And Agriculture In Northwest Arkansas, Kyle Colton Flynn

Theses and Dissertations

The Center for Disease Control and Prevention (CDC) suggests that adolescents and children, both male and female, are failing to meet the daily fruit and vegetable consumption requirements (Kim et al., 2011; Upton et al., 2012; Harris et al., 2012). Other studies have shown that with increased exposure and availability of produce, students (K-5) tend to consume more fruits and vegetables (Cullen et al., 2009; Evans et al., 2012). The purpose of this study is to identify whether Northwest Arkansas eleventh grade high school students possess experience and knowledge of local produce and agriculture. Out of 1054 students enrolled at ...


Dark Green Color Index As A Method Of Real-Time In-Season Corn Nitrogen Measurement And Fertilization, Upton Siddons May 2013

Dark Green Color Index As A Method Of Real-Time In-Season Corn Nitrogen Measurement And Fertilization, Upton Siddons

Theses and Dissertations

Corn (Zea mays L.) requires higher rates of nitrogen fertilizer than any other major U.S. crop partly because N fertilizers are subject to loss through various mechanisms. Because of this, corn may suffer from inadequate nitrogen fertilization or producers may over-apply nitrogen to compensate for early-season nitrogen losses. A timely, accurate, and precise method for measuring in-season corn N status is needed to allow producers to keep nitrogen use efficiency high within a growing season.

Using appropriate software, hue, saturation, and brightness values of digital images can be combined in a dark green color index (DGCI) which is closely ...


Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri) In Arkansas: Resistance Mechanisms And Management Strategies, Griff Michael Griffith May 2013

Glyphosate-Resistant Palmer Amaranth (Amaranthus Palmeri) In Arkansas: Resistance Mechanisms And Management Strategies, Griff Michael Griffith

Theses and Dissertations

Since 2000, there have been thirteen weed species confirmed resistant (R) to glyphosate in the United States, six of those resistant species are present in Arkansas. The goal of this research was to confirm and to determine the level of resistance in two R Palmer amaranth biotypes from Mississippi (MC-R) and Lincoln (LC-R) Counties, Arkansas, and one susceptible (S) biotype from Clarendon County, South Carolina, which had never been exposed to glyphosate. Shikimic acid concentration over time was significantly greater in the S biotype than both the MC-R and LC-R biotypes. The lethal dose required to kill 50% (LD50 ...