Agronomy and Crop Sciences Commons^™

Molecular Genetic Aspects Of Iron And Copper Cross-Talk In Arabidopsis Thaliana, Qingyuan Xiang

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

Iron (Fe) and copper (Cu) are essential micronutrients for plants and humans who consume plants. Their functions are tightly linked. For example, both of Fe and Cu work as cofactors in superoxide dismutase proteins to prevent reactive oxygen species damage. When Fe is removed from nutrient solution, plants uptake more Cu, but how plants sense and respond to Fe status is not fully understood. This thesis includes two projects that focus on Fe and Cu interaction, homeostasis and cross-talk in Arabidopsis thaliana.

Two Arabidopsis ecotypes, Kas-1 and Tsu-1, have difference in timing of Cu accumulation in rosettes under Fe …

Improving Establishment Of Seeded Buffalograss, Luqi Li

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

Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is a warm-season grass native to the North American Great Plains. Buffalograss is drought resistant, heat resistant and cold tolerant, and thus is well-adapted to many uses in areas that require low maintenance or erosion control. Since buffalograss is slow-growing, one challenge of establishing seeded buffalograss is to maximize seedling maturation and establishment before winter. We evaluated dormant seeding buffalograss in late fall and winter, when germination is not expected until soils warm in spring. We successfully dormant seeded ‘Sundancer’, ‘Bowie’ or ‘Cody’ buffalograss at 146 kg ha^-1 from late November though …

Effect Of Genotype, Environment, And Production Packages On Yield, Agronomic Characteristics, And End-Use Quality Of Winter Wheat, Madhav Bhatta

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

Grain yield and end-use quality are the most important characteristics for hard red winter wheat (Triticum aestivium L.). Improvement of grain quality characteristics of grain from a given growing season and location requires systematic understanding of the genotype chosen, the production environment, and also knowing the consequence of rate and time of individual production packages such as seed treatment, seed rate, nitrogen (N) fertilization, and foliar fungicide applications. The objectives of this study were to: identify the effects of seed rate, genotype, and N top-dressed on yield, agronomic characteristics, and end-use quality of winter wheat; and to determine …

Goss's Bacterial Wilt Development And Clavibacter Michiganensis Subsp. Nebraskensis Interactions With Spray Adjuvants, Sarah A. Schlund

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

Goss’s bacterial wilt and leaf blight of corn (Zea mays L.), causal agent Clavibacter michiganensis subsp. nebraskensis, was first confirmed in Dawson County, NE in 1969. Disease incidence decreased in the 1980’s due to various management strategies and disease developed sporadically until the early 2000’s when it re-emerged and was economically important. A Midwest, multistate survey conducted in 2011 suggested farming practices that may have contributed to the pathogen’s re-emergence. The use of agricultural pesticides was associated with Goss’s wilt. Since spray adjuvants are often used with pesticides, and physical characteristics of these adjuvants may enable infection of …

Assessing Multiple-Herbicide Resistance In A 2,4-D Resistant Waterhemp (Amaranthus Tuberculatus) Biotype From Nebraska – Student Research, Roberto Crespo

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

A waterhemp biotype was recently reported resistant to 2,4-D in Nebraska. In addition to the repeated use of 2,4-D, atrazine and imazathapyr were reported to be frequently used to control broadleaf weeds. Greenhouse experiments were conducted to confirm 2,4-D resistance and test for resistance to growth regulator herbicides and other herbicide modes-of-action (MoA). A single dose-response experiment showed reduced sensitivity in all three waterhemp biotypes to atrazine, imazethapyr and lactofen; therefore, they were generally considered resistant to those three herbicide MoA. None of the biotypes contained the Ser264 target-site mutation. Since the ametryn dose-response experiment resulted in all susceptible biotypes, …

Nitrogen And Water Effects On Canopy Sensor Measurements For Site-Specific Management Of Crops, Nicholas C. Ward

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

Water and nitrogen (N) are undoubtedly the two largest agricultural inputs globally. Coupled with advances in site-specific management technology their integration into production agriculture will allow for the most efficient use these crop input resources. Active canopy sensors offer the ability to measure biophysical plant traits rapidly and make assessments about plant status. Specifically, optical sensor measurements of light reflectance assess plant N status allowing for in-season and on-the-go N recommendations and applications; while infrared thermometers (IRT) measurement of canopy temperature can be used a tool for irrigation management. To evaluate how these technologies work among different plant stress environments …

Biochemical And Proteomic Profiling Of Maize Endosperm Texture And Protein Quality, Kyla J. Morton

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

The research described herein, focuses on the biochemical and proteomic analysis of the maize endosperm and what influences kernel texture. Quality Protein Maize (QPM) is a hard endosperm version of the high-lysine opaque2 (o2) mutant but the genes involved in modifying the soft o2 endosperm are unknown. Pyrophosphate (PPi)-dependent fructose 6-phosphate 1-phosphotransferase (PFP) catalyzes the ATP-independent conversion of fructose 6-phosphate to fructose 1, 6-bisphosphate in glycolysis. We found a large increase in transcript and protein levels of the alpha regulatory subunit of PFP (PFPα) in QPM endosperm. In vitro enzyme assays show a significant increase in forward PFP …

Genetic Engineering Online Lessons Improve Teaching And Increase Knowledge And Accepting Attitudes Among Students, Grace Troupe

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

Genetic engineering has been used in the production of food in the U.S. for nearly three decades, however, science literacy in genetic engineering among consumers is still low. To address this problem, an online resource called The Journey of a Gene (passel.unl.edu/ge) was created to help incorporate genetic engineering education in high school and college curriculums. Here we report two studies conducted to evaluate the effectiveness of The Journey of a Gene in 1) improving student knowledge and attitudes about genetic engineering and 2) helping teachers increase their knowledge as well as quantity and quality of genetic engineering instruction. In …

Impact Of Arbuscular Mycorrhizal Fungi On The Physiology Of Maize Genotypes Under Variable Nitrogen And Phosphorus Levels, Roberto Crespo

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

It is important to increase our understanding of AM fungal and maize genotype interactions, the impact of N and P fertilization and water condition on the symbiosis, and on the physiology and nutritional status of maize plants. In two greenhouse experiments AM inoculated plants exhibited root colonization values around 70% which was confirmed by the presence of the AM lipid biomarker (C16:1cis11). Nitrogen fertilization increased AM root colonization, but only compared to unfertilized plants. Root colonization and biomarker concentration in root and soil were similar among inoculated maize genotypes across conventional and drought tolerant hybrids. Mycorrhizal inoculation had a positive …

Biology And Control Of Glyphosate-Resistant Giant Ragweed., Simranpreet Kaur

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

Giant ragweed is a troublesome, early emerging, summer annual weed found throughout the eastern and midwestern corn and soybean growing regions of the United States. Since the emergence of giant ragweed varies at different locations, our first objective was to determine the emergence pattern of giant ragweed in Nebraska and how spring tillage influences emergence. Results of a two-year study suggested that giant ragweed emerged from late March until mid-June, with the majority of emergence ceasing by early May. Spring tillage could be used as an alternative method for managing glyphosate resistant giant ragweed.

Water stress can affect the growth …

Maize Yield And Components As Influenced By Environment And Agronomic Management, Jeremy J. Milander

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

Yield component analysis research on dent maize and waxy maize (Zea mays L.) as related to crop management is limited in Europe and the United States. Two research studies were conducted in 2012 and 2013 at Mead and North Platte, NE and Zagreb, Croatia with the objective to determine the influence of environment, water regime, hybrid, and plant population on maize yield and yield components. Grain yield, ears m^-2, kernels ear^-1, kernels row^-1, rows ear^-1, ear length and circumference, and kernel weight were measured. Environment and water regime altered maize yield …