Plant Breeding and Genetics Commons^™

The Evolution Of Sexual Reproduction In Cuscuta (Convolvulaceae), Michael Wright

Theses and Dissertations (Comprehensive)

Cuscuta (Convolvulaceae), the dodders, is a genus of ca. 200 species of obligate stem parasites distributed across a great diversity of habitats worldwide. The existence of a handful of species that are dangerous crop weeds has led researchers to historically focus on their growth and control. Consequently, there is a dearth of information about their biodiversity, ecology, and in particular their reproductive biology. This thesis surveys aspects of sex allocation, floral evolution, floral rewards for pollinators, and mechanisms of reproductive assurance across the genus. I demonstrate that Cuscuta has evolved a broad spectrum of breeding systems, from obligate selfing to …

Molecular And Chemical Dissection Of Cellulose Biosynthesis In Plants, Darby M. Harris

Theses and Dissertations--Plant and Soil Sciences

Plant cell walls are complex structures that must not only constrain cellular turgor pressure but also allow for structural modification during the dynamic processes of cell division and anisotropic expansion. Cell walls are composed of highly glycosylated proteins and polysaccharides, including pectin, hemicellulose and cellulose. The primary cell wall polysaccharide is cellulose, a polymer composed of high molecular weight !- 1,4-glucan chains. Although cellulose is the most abundant biopolymer on Earth, there is still a lot to learn about its biosynthesis and regulation. This research began by applying a variety of analytical techniques in an attempt to understand differences in …

A Novel Gene Silencing Vector For Plant Genomics And Biotechnology, Dustin Hoover, Scott Nicholson, Vibha Srivastava

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

Gene silencing is a process of suppressing activity of specific genes by producing “interfering” RNA encoded by foreign genes. This process serves as the principle of genetic modification in plants and animals, which is an important tool in genomics and biotechnology, allowing scientists to manipulate organisms to better meet human demands. New approaches of gene silencing may enable improvements on current practices of genetic modification, and broaden the application and impact of gene silencing in biotechnology. Recently, a novel vector design consisting of the transcription of short gene fragments lacking transcription termination signals was demonstrated to be effective in partial …

Breeding Sorghum Cultivars For Processing, Gary Perterson

INTSORMIL Presentations

Discusses the diversity of traits in sorghum and details some aspects of breeding techniques.

Regalia-Induced Resistance In Powdery Mildew-Infected Grapevine Plants Correlates With The Induction Of Chalcone Synthase, Thomas Crottogini

Horticulture and Crop Science

No abstract provided.

Detection Of Soybean Seed Protein Qtls Using Selective Genotyping, Piyaporn Phansak

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

A quantitative trait locus (QTL) is a statically defined location of a gene governing that trait. QTL identification is the first step towards using marker-assisted selection (MAS) to introgress desirable QTL alleles into elite high-yield cultivars. Hundreds of high protein plant introductions (PIs) exist in the USDA germplasm collection and are a source of high protein alleles. Although 86 protein QTLs are currently listed in SoyBase, many are likely repeat discoveries of the same QTL(s), given the typical +/- 10 cM confidence intervals associated with QTL positions. Six germplasm accessions of maturity groups (MGs) II to IV that exhibited high …

Evaluation Of Novel Input Output Traits In Sorghum Through Biotechnology, Tejinder K. Mall

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important cereal crop world-wide as well as an important source of feed, fiber and biofuel. It is a C4 plant and is well adapted to environments subject to high temperature and water limitation. Despite these agronomic qualities, it suffers from limitations of sensitivity to low temperature and the grain has drawbacks in relation to functionality and digestibility. The objectives of this study are: 1. To promote seed germination at low temperature and to enhance the seedling cold tolerance. 2. To enhance the grain digestibility and functionality. In an attempt to …

Optimizing In Vitro Propagation Of Rosa Persica, Maryam Jafarkhani-Kermani, Pegah Khosravi, Somayeh Kavand

Publications and Research

Rosa persica with a distinctive red eye is a good candidate for addition to the breeding pool of roses. In order to optimize micropropagation of R. persica, three culture media (MS, QL and VS) were compared. The maximum growth rate was observed in the VS medium. Addition of FeEDTA (Fe: 65.4 mg/l), calcium gluconate (Cg: 2.7 g/l) and Gamborg vitamins (B5) instead of VS vitamins, alone or in combinationwith VS medium were compared. The maximum growth rate was obtained in the medium containing VS + Cg + B5 (VSCgB5). Various concentrations of BAP (0, 2, 4 and 8 μM ) …

Fusarium Head Blight: Winter Wheat Cultivar Responses And Characterization Of Pathogen Isolates, John Fredy Hernandez Nopsa

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Fusarium Head Blight (FHB) is a destructive disease of wheat (Triticum aestivum L). FHB reduces yield and grain quality and causes accumulation of the mycotoxin deoxynivalenol (DON) in grain. Cultivar resistance is one of the most effective management strategies for FHB. Experiments were conducted to 1) identify winter wheat cultivars with resistance to FHB and DON accumulation, 2) determine the effect of winter wheat cultivar on the relationship between FHB and DON concentration, and 3) identify the major species of Fusarium causing FHB in Nebraska and characterize its isolates. Differences (P ≤ 0.05) were detected among cultivars in …

Identification Of Sources Of Rhizoctonia Root Rot Resistance In Common Bean And Mapping A New Source Of Bean Rust Resistance From The Tertiary Gene Pool Of Common Bean, Pamela A. Peña-Perdomo

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

An efficient screening method was developed and used to identify bean lines resistant to Rhizoctonia Root Rot caused by Rhizoctonia solani Kuhn. Two sets of 163 and 111 lines previously evaluated for drought tolerance at Mitchell, NE and Isabela, PR were evaluated for Rhizoctonia Root Rot resistance under greenhouse conditions. This root rot data was also correlated with yield under drought stress and non stress conditions. In the first set of lines the rhizoctonia mean score ranged from 1.7 to 3.9; and in the second set the rhizoctonia mean score was between 2.6 and 5.7. There was no significant correlation …

Plant Immunity Directly Or Indirectly Restricts The Injection Of Type Iii Effectors By The Pseudomonas Syringae Type Iii Secretion System, Emerson Crabill, Anna Joe, Anna Block, Jennifer M. Van Rooyen, James R. Alfano

Center for Plant Science Innovation: Faculty Publications

Plants perceive microorganisms by recognizing microbial molecules known as pathogen-associated molecular patterns (PAMPs) inducing PAMP-triggered immunity (PTI) or by recognizing pathogen effectors inducing effector-triggered immunity (ETI). The hypersensitive response (HR), a programmed cell death response associated with ETI, is known to be inhibited by PTI. Here, we show that PTI-induced HR inhibition is due to direct or indirect restriction of the type III protein secretion system’s (T3SS) ability to inject type III effectors (T3Es). We found that the Pseudomonas syringae T3SS was restricted in its ability to inject a T3E-adenylate cyclase (CyaA) injection reporter into PTI-induced tobacco (Nicotiana tabacum) cells. …

Reestablishing Diversity In Our Hardwood Forests: A Transplant Study Of Five Spring-Flowering Herbs, Danielle Racke

Masters Theses & Specialist Projects

Herbaceous communities are critical to the functioning of forest ecosystems. They recycle nutrients, help prevent erosion, provide critical microhabitats and maintain biodiversity. In the eastern United States, most hardwood forests are growing on land once entirely cleared or used for some form of agriculture. Although some of these forests are nearly 150 years old, they still have depauperate native herbaceous communities when compared to remaining old-growth forests. This long-term depletion may result from dispersal limitation or environmental limitation.

I tested the hypothesis that dispersal was the primary factor contributing to the absence of five spring-flowering herbaceous species in four secondary …

Xenia Effects On Quality Of Maize Female Inbred In Production Of Hybrid Seeds, Leandro Castañeda

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

In maize (Zea maize L.), cost of hybrid seed production is directly related to the yield and quality of seed obtained per hectare of female parent. It is also important to consider the effects that a male parent can exert on the development of hybrid seed in the female parent. This effect is known as xenia. The objectives of this study were to evaluate xenia effects on 1) yield as 80K units, 2) germination of the hybrid seed and 3) susceptibility of the hybrid seed to mechanical damage. One female inbred and four male inbred lines were selected from …

Genetic Mapping Of Quantitative Trait Loci Associated With Bioenergy Traits, And The Assessment Of Genetic Variability In Sweet Sorghum (Sorghum Bicolor (L.). Moench), Aatshwaelwe Lekgari Lekgari

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Sweet sorghum, a botanical variety of sorghum is a potential source of bioenergy because high sugar levels accumulate in its stalks. The objectives of this study were to explore the global diversity of sweet sorghum germplasm, and map the genomic regions that are associated with bioenergy traits. In assessing diversity, 142 sweet sorghum accessions were evaluated with three marker types (SSR, SRAP, and morphological markers) to determine the degree of relatedness among the accessions. The traits measured (anthesis date [AD], plant height [PH], biomass yield [BY], and moisture content [MC]) were all significantly different (P< 0.05) among accessions. Morphological marker clustered the accessions into five groups based on PH, MC and AD. The three traits accounted for 92.5% of the variation. There were four and five groups based on SRAP and SSR data respectively classifying accessions mainly on their origin or breeding history. The observed difference between SSR and SRAP based clusters could be attributed to the difference in marker type. SSRs amplify any region of the genome whereas SRAP amplify the open reading frames and promoter regions. Comparing the three marker-type clusters, the markers complimented each other in grouping accessions and would be valuable in assisting breeders to select appropriate lines for crossing. In evaluating QTLs that are associated with bioenergy traits, 165 recombinant inbred lines (RILs) were planted at four environments in Nebraska. A genetic linkage map constructed spanned a length of 1541.3 cM, and generated 18 linkage groups that aligned to the 10 sorghum chromosomes. Fourteen QTLs (6 for brix, 3 for BY, 2 each for AD and MC, and 1 for PH) were mapped. QTLs for the traits that were significantly correlated, colocalized in two clusters on linkage group Sbi01b. Both parents contributed beneficial alleles for most of traits measured, supporting the transgressive segregation in this population. Additional work is needed on exploiting the usefulness of chromosome 1 in breeding sorghum for bioenergy.

Quantitative Trait Loci For Agronomic And End-Use Quality Performance And The Effect Of Soilborne Wheat Mosaic Virus In A Hard Winter Wheat Population In Nebraska, Nicholas A. Crowley

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

To better understand agronomic and end-use quality in wheat (Triticum aestivum L.) we developed a population containing 154 F6:8 recombinant inbred lines (RILs) from the cross TAM107-R7/Arlin. The parental lines and RILs were phenotyped at six environments in Nebraska and differed for resistance to Wheat soilborne mosaic virus (WSBMV), morphological, agronomic, and end-use quality traits. Additionally, a 2300 cM genome-wide linkage map was created for quantitative trait loci (QTL) analysis. Based on our results across multiple environments, the best RILs could be used for cultivar improvement. The population and marker data are publicly available for interested researchers for future research. …

Determining The Fate Of Hybridized Genomes In The Allopolyploid Brassica Napus, Tina Y. Wang

Master's Theses

Polyploidy is widely acknowledged as a widespread mechanism in the evolution and speciation of the majority of flowering plants. Allopolyploid forms through interspecific hybridization and whole genome duplication. While allopolyploids may display increased vigor relative to their progenitors, they can also face challenges to fertility following hybridization. Genetic changes in allopolyploids result from recombination between the hybridized subgenomes, which can influence phenotype and ultimately determine fitness of future generations. To study dynamic changes that follow allopolyploid formation, Brassica napus lineages were derived by hybridizing Brassica oleracea and Brassica rapa. Two lineages of B. napus were analyzed for genetic and phenotypic …

Origin Of The Polycomb Repressive Complex 2 And Gene Silencing By An E(Z) Homolog In The Unicellular Alga Chlamydomonas, Scott Shaver, J. Armando Casas-Mollano, Ronald L. Cerny, Heriberto D. Cerutti

Center for Plant Science Innovation: Faculty Publications

Polycomb group proteins play an essential role in the maintenance of cell identity and the regulation of development in both animals and plants. The Polycomb Repressive Complex 2 (PRC2) is involved in the establishment of transcriptionally silent chromatin states, in part through its ability to methylate lysine 27 of histone H3 by the Enhancer of zeste [E(z)] subunit. The absence of PRC2 in unicellular model fungi and its function in the repression of genes vital for the development of higher eukaryotes led to the proposal that this complex may have evolved together with the emergence of multicellularity. However, we report …

Grain Yield And Yield-Related Qtl Validation Using Reciprocal Recombinant Inbred Chromosome Lines In Wheat, Neway C. Mengistu

Department of Agronomy and Horticulture: Dissertations, Theses, and Student Research

Grain yield and yield-related traits are the most important economic factors for bread wheat (Triticum aestivum L.) improvement. Grain yield (GYLD) and yield-related quantitative trait loci (QTLs) were previously identified by using a population of recombinant inbred chromosome lines (RICLs) developed from cultivar ‘Cheyenne’ (CNN) and its substitution line CNN(WI3A), where the 3A chromosome of cultivar ‘Wichita’ (WI) was substituted for the CNN chromosome 3A. The objectives of this study were to identify and validate GYLD and yield-related QTLs previously identified in CNN(RICLs-3A) studies by using the mirror population WI(RICLs-3A), where chromosome 3A of CNN and WI were now …

The Green Revolution Of The 1960'S And Its Impact On Small Farmers In India, Kathryn Sebby

Department of Environmental Studies: Undergraduate Student Theses

The Green Revolution was initiated in the 1960’s to address the issue of malnutrition in the developing world. The technology of the Green Revolution involved bio-engineered seeds that worked in conjunction with chemical fertilizers and heavy irrigation to increase crop yields. The technology was readily adopted in many stated in India and for some was a great success. However, there were many farmers who could not afford the inputs necessary to participate in the Green Revolution and gaps between social classes widened as wealthy farmers got wealthier and poor farmers lagged behind. This paper discusses how small farmers were affected …

Combining Local- And Large-Scale Models To Predict The Distributions Of Invasive Plant Species, Chad C. Jones, Steven A. Acker, Charles B. Halpern

Botany Faculty Publications

Habitat-distribution models are increasingly used to predict the potential distributions of invasive species and to inform monitoring. However, these models assume that species are in equilibrium with the environment, which is clearly not true for most invasive species. Although this assumption is frequently acknowledged, solutions have not been adequately addressed. There are several potential methods for improving habitat-distribution models. Models that require only presence data may be more effective for invasive species, but this assumption has rarely been tested. In addition, combining modeling types to form ‘ensemble’ models may improve the accuracy of predictions. However, even with these improvements, models …