Agronomy and Crop Sciences Commons^™

Ghd8 Controls Rice Photoperiod Sensitivity By Forming A Complex That Interacts With Ghd7, Peng Wang, Rong Gong, Ying Yang, Sibin Yu

Department of Agronomy and Horticulture: Faculty Publications

Background: Flowering time is one of the most important agronomic characteristics that ultimately determine yield potential and eco-geographical adaptation in crops. Ghd8 and Ghd7, two major flowering genes, have similar functions and large pleiotropic effects in controlling the heading date, plant height and grain yield of rice. However, these gene interactions at the genetic and molecular levels have not been determined to date.

Results: In this study, we investigated the genetic interaction between Ghd8 and Ghd7 by using a set of near-isogenic lines and a panel of natural germplasm accessions in rice. We found that Ghd8 affected multiple agronomic traits …

Application Of Autofluorescence For Confocal Microscopy To Aid In Archaeoparasitological Analyses, Johnica Jo Morrow, Christian Elowsky

Department of Agronomy and Horticulture: Faculty Publications

Confocal laser scanning microscopy (CLSM) was used to examine archaeoparasitological specimens from coprolites associated with La Cueva de los Muertos Chiquitos (CMC) located near present-day Durango, Mexico. The eggs for 4 different types of parasites recovered from CMC coprolites were imaged using CLSM to assist with identification efforts. While some of the parasite eggs recovered from CMC coprolites were readily identified using standard light microscopy (LM), CLSM provided useful data for more challenging identifications by highlighting subtle morphological features and enhancing visualization of parasite egg anatomy. While other advanced microscopy techniques, such as scanning electron microscopy (SEM), may also detect …

Challenges And Opportunities For Weed Control In Nebraska Popcorn, Ethann R. Barnes

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

Weed control in popcorn is challenging with limited herbicide options and popcorn’s perceived sensitivity to herbicides. Understanding the impact of weeds maximizes yield and profit. New herbicide-resistant crops increase chances of drift or misapplication into popcorn, which doesn’t have herbicide-resistant traits. Herbicides that are labeled in popcorn are often only conditionally labeled with reduce rates, warnings, or limited popcorn types. Dent-sterility in popcorn is contingent on the Ga1 gene (Ga1-s), but this system is at risk from Ga1-m field corn introduced from Mexico because it overcomes dent-sterility. This risk is under-assessed as Ga1-m carriers are undocumented and Mexican germplasm usage …

Canavalia And Dolichos Extracts For Sustainable Pest Biocontrol And Plant Nutrition Improvement In El Salvador, Carlos Martinez

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

Botanical repellents and pesticides are now being rediscovered as new tools for integrated pest management in order to reduce the use of toxic chemicals in crop production. Canavalia gladiata and Dolichos lablab are two Fabaceae very well adapted to farmlands of El Salvador, effective as living barriers and mostly as cover crops, however, they are not yet very well disseminated. This document describes the potential for using the liquid extracts and the dry flour of raw seeds of those plants for economic benefit and practical convenience for pest management in Salvadorian agriculture under field conditions. Seed extracts were useful when …

Variable Rate Irrigation Of Maize And Soybean In West-Central Nebraska Under Full And Deficit Irrigation, J Burdette Barker, Sandeep Bhatti, Derek M. Heeren, Christopher M.U. Neale, Daran Rudnick

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Variable rate irrigation (VRI) may improve center pivot irrigation management, including deficit irrigation. A remote-sensing-based evapotranspiration model was implemented with Landsat imagery to manage irrigations for a VRI equipped center pivot irrigated field located in West-Central Nebraska planted to maize in 2017 and soybean in 2018. In 2017, the study included VRI using the model, and uniform irrigation using neutron attenuation for full irrigation with no intended water stress (VRI-Full and Uniform-Full treatments, respectively). In 2018, two deficit irrigation treatments were added (VRI-Deficit and Uniform-Deficit, respectively) and the model was modified in an attempt to reduce water balance drift; model …

Measuring Impacts Of Uncertainty, Irreversibility, And Loss Aversion On The Adoption Of Crop Canopy Sensors Among Nebraska Corn Producers, Brooks Ronspies

Department of Agricultural Economics: Dissertations, Theses, and Student Research

Understanding barriers to adoption of Precision Agricultural Technologies (PATs) is important to the growth of agricultural productivity, efficiency, and sustainability. This thesis proposes and evaluates a model for estimating the impact of uncertainty, irreversibility, and loss aversion on producers’ adoption of crop canopy sensors in order to explain adoption behavior that contradicts previous expectations about the conditions necessary for technology adoption. The model is evaluated using estimated statistical distributions of price and field characteristics designed to match observations of actual corn and nitrogen prices, and of conventional and crop canopy sensor based nitrogen application. Results from this model using expected …

New Approaches To Use Genomics, Field Traits, And High-Throughput Phenotyping For Gene Discovery In Maize (Zea Mays), Zhikai Liang

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

Maize is one of major crop species over the world. With lots of genetic resources and genomic tools, maize also serves as a model species to understand genetic diversity, facilitate the development of trait extraction algorithms and map candidate functional genes. Since the first version of widely used B73 reference genome was released, independent research groups in the maize community propagated seeds themselves for further research purposes. However, unexpected or occasional contamination may happen during this process. The first study in this thesis used public RNA-seq data of B73 from 27 research groups across three countries for calling single nucleotide …

Rust And Viral Mosaic Diseases In Biofuel Switchgrass, Anthony A. Muhle

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

Switchgrass (Panicum virgatum L.) is a perennial warm-season monocot that is indigenous to locations in North America east of the Rocky Mountains, and is considered a model grass for biofuel feedstock production. As switchgrass production increases, diseases pose a potential threat to biomass production and ethanol extraction. The two predominant switchgrass diseases in Nebraska are rust caused by Puccinia spp. and a viral mosaic disease caused by Panicum mosaic virus (PMV) and its associated Satellite panicum mosaic virus (SPMV). In this thesis, one study determined how SPMV affects PMV infection and systemic spread in two populations of switchgrass at different …

Hormonal Signaling Induced In Soybean By Lysobacter Enzymogenes Strain C3, Jessica C. Walnut

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

The biological control bacterium Lysobacter enzymogenes strain C3 has been shown to suppress fungal diseases by producing a suite of lytic enzymes and antimicrobial secondary metabolites. Previous studies have found that C3, when applied to grass and cereal plants, also is capable of inducing local and systemic resistance against fungal pathogens. It is unknown, however, whether the bacterium has the ability to induce resistance in dicots and what signaling pathways are involved. This study assessed the ability of C3 to trigger local and systemic induced resistance responses in soybean (Glycine max ‘Williams82’) by analyzing relative expression of salicylic acid …

Investigating Parental Effects On End-Use Quality In Hard Winter Wheat (Triticum Aestivum L.) Hybrids, Anthony Delaney

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

To optimize the performance and marketing of hybrid wheat, breeders need to understand the impact parents have on end-use quality. The goal of this study was to investigate the inheritance of end-use quality traits of hard winter wheat reciprocal hybrids produced by Easterly (2017). The 2016 analysis included 71 reciprocal hybrid combinations from 13 parents and the 2017 analysis included 79 reciprocal hybrid combinations from 14 parents. The reciprocals were composed of crosses between the top performing and bottom performing parents with respect to end-use quality as quantified by a Mixograph, a SDS sedimentation assay, and a SDS-SRC hybrid assay. …

An Integrated Genomics And Phenomics Approach To Study The Evolution Of C4 Photosynthesis, Daniel Santana De Carvalho

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

The C4 photosynthetic pathway was first described over 50 years ago. Today, it is known that C4 evolved independently > 60 in plant lineages, which involves understanding not only the genetic, but also the metabolic features and differences involved in this process. Also, several adaptations are involved in the evolution of this type of photosynthesis, for example: changes in leaf anatomy and the evolution of kranz anatomy, physiology and metabolic pathways. In order to further investigate this pathway, different technologies and methods have been developed to unravel genes involved in C4 photosynthesis. With the advances in molecular biology and bioinformatics tools …

Dual Biological Control: Characterization Of Fungi And Bacteria To Control Granary Weevil And Fungal Pathogens Of Stored Grain, Gülçin Ercan

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

Cereals are main food sources for humans and animals. However, during storage, cereal grains can be infested by insects and fungi. One of the most important insect storage pests is Sitophilus granarius (L., Coleoptera: Curculionidae). Adults and larvae can cause serious grain losses. In addition to insect pests, fungal pathogens may also invade the grain and cause economic loss, including contamination with mycotoxins, which threaten mammal health by causing serious disease. The most common mycotoxigenic grain fungi are species that belong to the genera Fusarium, Aspergillus and Penicillium. Currently, the most commonly used management strategies for insect and …

Microbial Response To Biodegradable Mulch: Can Degradation Rate Be Accelerated By Management?, M. Benjamin Samuelson

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

Single-use, petroleum-based polyethylene mulch is ubiquitous in certified organic mulched vegetable systems, representing a broken nutrient cycle and a waste concern. Current organic-allowable biodegradable mulches cannot match the performance of polyethylene, in part because of the requirements that they contain 100% bio-based feedstock, and biodegrade within two years after soil incorporation. It is valuable to understand whether management can influence postharvest degradation rate of mulch films. Two biodegradable mulches: a potentially organic nonwoven polylactic acid and wood particle prototype (PLA), and a widely-adopted non-organic starch/copolymer blend, Bio360® (BLK), were used in field trials in two distinct ecoregions of Nebraska, at …

How Do Ecological Resilience Metrics Relate To Community Stability And Collapse?, Caleb P. Roberts, Dirac L. Twidwell Jr, David G. Angeler, Craig R. Allen

Department of Agronomy and Horticulture: Faculty Publications

The concept of ecological resilience (the amount of disturbance a system can absorb before collapsing and reorganizing) holds potential for predicting community change and collapse—increasingly common issues in the Anthropocene. Yet neither the predictions nor metrics of resilience have received rigorous testing. The crossscale resilience model, a leading operationalization of resilience, proposes resilience can be quantified by the combination of diversity and redundancy of functions performed by species operating at different scales. Here, we use 48 years of sub-continental avian community data aggregated at multiple spatial scales to calculate resilience metrics derived from the cross-scale resilience model (i.e., cross-scale diversity, …

Identification Of Loci Controlling Adaptation In Chinese Soya Bean Landraces Via A Combination Of Conventional And Bioclimatic Gwas, Ying-Hui Li, Delin Li, Yong-Qing Jiao, James C. Schnable, Yan-Fei Li, Hui-Hui Li, Huai-Zhu Chen, Hui-Long Hong, Ting Zhang, Bin Liu, Zhang-Xiong Lui, Qing-Bo You, Yu Tian, Yong Guo, Rong-Xia Guan, Li-Juan Zhang, Ru-Zhen Chang, Zhiwu Zhang, Jochen Reif, Xin-An Zhou, Patrick S. Schnable, Li-Juan Qiu

Department of Agronomy and Horticulture: Faculty Publications

Landraces often contain genetic diversity that has been lost in modern cultivars, including alleles that confer enhanced local adaptation. To comprehensively identify loci associated with adaptive traits in soya bean landraces, for example flowering time, a population of 1938 diverse landraces and 97 accessions of the wild progenitor of cultivated soya bean, Glycine soja was genotyped using tGBS. Based on 99 085 high-quality SNPs, landraces were classified into three subpopulations which exhibit geographical genetic differentiation. Clustering was inferred from STRUCTURE, principal component analyses and neighbour-joining tree analyses. Using phenotypic data collected at two locations separated by 10 degrees of latitude, …

Herbicide Drift Influence On Amaranthus Spp. Herbicide Resistance Evolution, Bruno Canella Vieira

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

The adverse consequences of herbicide drift towards sensitive crops have been extensively reported in the literature. However, no information is available on the consequences of herbicide drift onto weed species inhabiting boundaries of agricultural fields. Exposure to herbicide drift could be detrimental to long-term weed management as several weed species have evolved herbicide resistance after recurrent selection with low herbicide rates. Despite the herbicide drift exposure and its potential implications on resistance evolution and weed management, resistance prone weed species such as Palmer amaranth (Amaranthus palmeri) and waterhemp (Amaranthus tuberculatus) are often neglected and not properly …

Biomethane Production From Distillery Wastewater, Zachary Christman

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

Distillery wastewater treatment is a great ecological problem, for example, India produces 2.7 billion liters of alcohol that results in 40 billion liters of wastewater. However, this material can be seen as a resource since 11 million cubic meters of biogas at 60% methane could be produced in addition to cleaning the water. The distillery has two options of what to do with the biogas. The first is to use the biogas to fuel the distillery making the production plant more energy efficient and removing some of the need to buy natural gas. The other is to upgrade the biogas …

Introduction To Sorghum Paper Production, Zachary Christman

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

Sorghum is a tall grass used for many commercial products such as fodder and syrup. The 10 to 15 feet stalk of the plant has lower lignin than wood and provides a fiber length of 2.31 mm in the outer covering and 1.38 mm for the leaf. Sorghum fiber makes a high quality, strong paper suitable for printing, packaging and paperboard.

Addressing The Challenges Facing Wheat Production: Nebraska And International Breeding Efforts, Sarah Blecha

Doctor of Plant Health Program: Dissertations and Student Research

Bread wheat, Triticum aestivum L., provides 20 percent of the global daily calorie intake. It is the third most important food crop, after rice and corn. Biotic challenges significantly reduce wheat yield; chemical control can be a solution but can be cost prohibitive for subsistence farmers. For many farmers, genetic resistance to biotic stresses can be the most cost effective solution.

The International Center for Agricultural Research in the Dry Areas (ICARDA) and the Nebraska Small Grains Breeding Program have been addressing these wheat production challenges. ICARDA is part of an international research consortium to increase wheat yield and tolerance …

Science Communication In Agriculture: The Role Of The Trusted Adviser, Lee Galen Briese

Doctor of Plant Health Program: Dissertations and Student Research

Agronomy is not simply the selling of agricultural products to farmers, nor is it the process of solving singular production problems. Agronomy is defined as the integrated, holistic perspective of agriculture (ASA, 2019) and “agronomists are specialists in crop and soil sciences, as well as ecology” (ASA, 2019). While scientific investigation and discovery are essential to understanding systems function, the tangible benefits from our knowledge stems from the application to solve problems. Clear communication is vital to successfully help stakeholders understand the importance of the science and help scientists understand the challenges stakeholders face. However, to successfully put science into …

Integrated Management Of Phytophthora Stem And Root Rot Of Soybean And The Effect Of Soil-Applied Herbicides On Seedling Disease Incidence, Vinicius Castelli Garnica

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

Soybean seedling diseases and Phytophthora stem and root rot (PSRR; caused by Phytophthora sojae) are two of the most economically important diseases in North Central U.S. Remarkable differences in disease incidence occur each year, which demonstrate that abiotic and biotic factors must interact for disease onset and development. During 2017 and 2018, field studies were conducted to (i) address the efficacy of seed treatment and genetic resistance for PSRR management on soybean population, canopy coverage (CC), and yield, and (ii) investigate potential interactions between pre-emergence (PRE) herbicides and the incidence of seedling diseases in alluvial soils in Nebraska.

Despite …

Dna Barcoding Of Pratylenchus From Agroecosystems In The Northern Great Plains Of North America, Mehmet Ozbayrak

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

Pratylenchus species are among the most common plant parasitic nematodes in the Great Plains Region. The objectives of this study were to barcode Pratylenchus specimens for species identification in the Great Plains region using mitochondrial CO1 DNA barcode. In order to (1) determine species boundaries, (2) assess the host associations of barcoded Pratylenchus, (3) to determine the distribution patterns across the Great Plains Region and, (4) to evaluate the species status of P. scribneri and P. hexincisus by a multivariate morphological analysis of haplotype groups identified by DNA barcoding. Soil samples, primarily associated with eight major crops, were collected …

Use Of Annual Forage Mixtures In Crop/Livestock Production Systems In Nebraska, Nathan Paul Pflueger

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

Success of integrating annual forages into crop and livestock systems throughout Nebraska may be variable depending on field location, field/forage crop management, and precipitation. There are many different warm- and cool-season annual forage species available for integrating crop and livestock systems at different times of the year. Mixtures of cereal species, such as oats (Avena sativa)) and spring peas (Pisum sativum)), are often used to optimize forage quantity and forage quality. Our two-year, three location study across Nebraska’s precipitation gradient suggested that forage quantity and quality may vary by location due to different precipitation amounts received …

Effect Of Soil-Applied Protoporphyrinogen Oxidase Inhibitor Herbicides On Soybean Seedling Disease, Nicholas J. Arneson

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

Seedling disease is one the most economically important diseases of soybean in the United States. It is commonly caused by Fusarium spp., Rhizoctonia solani, Pythium spp., and Phytophthora sojae, alone, or together as a disease complex. Fungicide seed treatments continue to provide the most consistent management of seedling diseases. Soil-applied protoporphyrinogen oxidase (PPO) inhibitor herbicides are used preemergence in soybean production to manage several broadleaf weeds. Applications of PPO-inhibitors can result in phytotoxic injury to soybean when environmental conditions are not favorable for soybean growth. These environmental conditions can favor seedling disease development as well. In this thesis, two …

Establishment Of Perennial Legumes With An Annual Warm-Season Grass As A Companion Crop, Martina N. La Vallie

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

The yields of perennial forage legumes are often hindered during the establishment year due to slow germination rates and weed competition. This study was conducted to determine if sorghum-sudangrass (Sorghum bicolor x S. bicolor var. sudanese) is a compatible annual companion crop for increased forage production, weed suppression, and legume establishment. In 2016, sorghum-sudangrass was paired with alfalfa (Medicago sativa L. ‘Ranger’), birdsfoot trefoil (Lotus corniculatus L.), Illinois bundleflower [Desmanthus illinoensis (Michx.) MacMill. ex B.L. Rob. & Fernald], purple prairie clover (Dalea purpurea Vent.), red clover (Trifolium pratense L.), and roundhead lespedeza (Lespedeza capitata Michx.). We studied effects of a …

Modeling And Economic Analysis Of A Crop–Livestock Production System Incorporating Cereal Rye As A Forage, Eric R. Coufal

Department of Agricultural Economics: Dissertations, Theses, and Student Research

This thesis consists of two chapters using agent-based modeling for a crop-livestock production system incorporating human labor. The first chapter examines the principles used to develop a fundamental simulation pertaining to grazing cereal rye (Secale cereal L.) with calves. Within the software guidelines, the base model has the ability to capture diverse system interactions between livestock/plants and land management with human labor efficiency. AnyLogic incorporates agent-based modeling while combining with discrete event modeling and system dynamics. The purpose of the model was to find the economic returns of grazing cover crops relative to the area of Mead, Nebraska. In …

Genome-Wide Association Studies In Maize And Sorghum, Preston Hurst

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

Genome-wide association studies are used to identify genetic variants associated with a particular phenotype. GWAS has been used in a variety of taxa, from humans, to fish to plants . The present analysis is focused on two species important to the human species: maize and sorghum. A GWAS in maize was carried out on the modification of the Ga1-s allele. The Ga1 locus has long been studied as being involved in a unilateral crossing barrier . However, it has long been suspected that the locus is modified by background genetic factors . GWAS was used to observe candidates for this …

Nutrient Management Suggestions For Corn, Charles A. Shapiro, Richard Ferguson, Charles S. Wortmann, Bijesh Maharjan, Brian T. Krienke

Department of Agronomy and Horticulture: Faculty Publications

Fertilizer nutrient requirements for corn are based on expected yield and soil nutrient availability. The preplant nitrogen (N) recommendation equation, with adjustment for fertilizer cost and time of application, is retained from the previous edition of this publication. Suggestions for in-season nitrogen decisions are briefly outlined. The major change is providing a phosphorus (P) recommendation based on yield history with an implied intent to build and maintain soil test P above the critical level, which has not changed.

Development Of A Nitrogen Recommendation Tool For Corn Considering Static And Dynamic Variables, Laila A. Puntel, Agustin Pagani, Sotirios V. Archontoulis

Department of Agronomy and Horticulture: Faculty Publications

Many soil and weather variables can affect the economical optimum nitrogen (N) rate (EONR) for maize. We classified 54 potential factors as dynamic (change rapidly over time, e.g. soil water) and static (change slowly over time, e.g. soil organic matter) and explored their relative importance on EONR and yield prediction by analyzing a dataset with 51 N trials from Central-West region of Argentina. Across trials, the average EONR was 113 ± 83 kg N ha⁻¹ and the average optimum yield was 12.3 ± 2.2 Mg ha⁻¹, which is roughly 50% higher than the current N rates used …

Improving The Distribution And Use Of Biogas By Conversion To Methanol, Zachary Christman

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

In this technology review, the process of turning an average biogas into methanol will be presented. The purpose is to find a better method of transporting the energy contained within biogas so that it may be used in industry as a value added product. The first step is removal of hydrogen sulfide, a corrosive chemical that can breakdown mechanical parts. The second step is carbon capture and conversion of the biogas into hydrogen. The final step is the hydrogenation of carbon dioxide into methanol using a copper catalyst and an alcohol co-catalyst.