Agricultural Science Commons^™

Distribution Of Genomic Variation In The Usda Soybean Germplasm Collection And Relationship With Phenotypic Variation, Nonoy Batiller Bandillo

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

The USDA Soybean Germplasm Collection harbors a large stock of genetic diversity with potential to accelerate soybean cultivar development. The extent and nature of favorable alleles contained in the collection are not well known nor is the distribution of genetic variation and how it relates to phenotypic variation. The genotyping of the entire USDA Soybean Germplasm Collection marked the beginning of a systematic exploration of genetic diversity for genetic research and breeding. In this research, we conducted the first comprehensive analysis of population structure on the collection of ~14,400 soybean accessions [Glycine max (L.) Merr. and G. soja Siebold …

From Milpas To The Market: A Study On The Use Of Metal Silos For Safer And Better Storage Of Guatemalan Maize, José Rodrigo Mendoza

Department of Food Science and Technology: Dissertations, Theses, and Student Research

This project aimed to implement the use of metal silos to improve quality and safety of maize consumed by inhabitants of the highlands of Guatemala. This manuscript includes a literature review of the maize production chain in Guatemala, a survey about agricultural practices used in the region of study, as well as a characterization of the analyzed maize regarding its mycoflora, nutritional composition, and insect infestation. To better understand the current situation regarding agricultural practices and maize consumption, a survey was carried out. Sample consisted of 280 families representing 14 rural communities distributed in the townships of Todos Santos and …

Herbicide Resistantsorghum Mutants, Ismail M. Dweikat

Department of Agronomy and Horticulture: Faculty Publications

This disclosure provides for four different sorghum mutants that exhibit resistance to ALS-inhibiting herbicides. This dis closure also provides for methods of using such Sorghum mutants that exhibit resistance to ALS-inhibiting herbicides in breeding methods to make Sorghum hybrids, varieties, or lines. The Sorghum hybrids, varieties, and lines provided in this disclosure can be used in methods of controlling weeds.

Long-Term Sandhills Prairie Responses To Precipitation, Temperature, And Cattle Stocking Rate, John A. Guretzky, Cheryl Dunn, Heidi L. Hillhouse

Department of Agronomy and Horticulture: Faculty Publications

Understanding of Sandhills prairie, the most expansive sand dune region stabilized by perennial grasses in the Western Hemisphere, is limited by lack of long-term vegetation data. We used a 26-year dataset to evaluate Sandhills prairie responses to yearto- year variation in precipitation, temperature, and cattle stocking rate. Basal cover, a measurement that is constant seasonally and used to detect long-term changes in bunchgrass vegetation, was measured in 38–40 permanent plots positioned along four transects spanning 769 ha from 1979 to 2007. Across this period, total basal cover averaged 2.4 % and was dominated by warm-season grasses (81.1 %). Schizachyrium scoparium …

Using A Vnir Spectral Library To Model Soil Carbon And Total Nitrogen Content, Nuwan K. Wijewardane

Department of Agricultural and Biological Systems Engineering: Dissertations, Theses, and Student Research

n-situ soil sensor systems based on visible and near infrared spectroscopy is not yet been effectively used due to inadequate studies to utilize legacy spectral libraries under the field conditions. The performance of such systems is significantly affected by spectral discrepancies created by sample intactness and library differences. In this study, four objectives were devised to obtain directives to address these issues. The first objective was to calibrate and evaluate VNIR models statistically and computationally (i.e. computing resource requirement), using four modeling techniques namely: Partial least squares regression (PLS), Artificial neural networks (ANN), Random forests (RF) and Support vector regression …

A Brief History Of Corn: Looking Back To Move Forward, Jon Derek Pruitt

Doctor of Plant Health Program: Dissertations and Student Research

Maize was domesticated from teosinte in Mexico some 7,000 to 10,000 years ago and quickly spread through the Americas. It has become one of the most important crops at a local and global level. Two types, Northern Flint corn and Southern Dent corns provided the basis of the genetic background of modern maize hybrids. The development of hybrids, first double-cross and later single-cross hybrids, along with a transition to high input farming provided huge yield increases, which have continued to improve with improving technology.

Increase in maize production also caused a rise in Western corn Rootworm (Diabrotica virgifera virgifera …

Managing Drought Stress In California Agricultural Systems, Gregory D. Brittain Jr.

Doctor of Plant Health Program: Dissertations and Student Research

California is currently facing a historic drought, and this has led many farmers in the state to severely cut back on irrigation. Optimal use of water for irrigation requires a comprehensive understanding of how plants respond physiologically to water stress (Chapter 1). By monitoring water requirements in crops and managing irrigation to meet those requirements, growers can significantly reduce water use (Chapter 2). This can be done through improving application efficiency of irrigation technology as well as increasing the water use efficiency of the crops themselves. Deficit irrigation practices can be used to manipulate the physiology of water use in …

A Vision For Extension: Case Studies On Managing Extreme Weather Challenges In Corn, Anthony J. Mcmechan

Doctor of Plant Health Program: Dissertations and Student Research

Global demand for corn is projected to rise in the coming decades to meet the food and fuel requirements of an increasing human population. Technological innovations have significantly improved corn yields over the past few decades; however, corn production is continually limited by unfavorable weather conditions. Extreme weather events put pressure on producers, adjustors, and consultants to make quick management decisions to maintain the highest return on their investment. Proper management decisions require an understanding of plant response and practical ways of applying this knowledge under real world conditions.

The following document was written after completing a six-month internship at …

Biology, Gene Flow, And Management Of Glyphosate-Resistant Common Waterhemp (Amaranthus Rudis Sauer) In Nebraska, Debalin Sarangi

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

Common waterhemp is the most troublesome weed in the midwestern United States. Growers from Nebraska reported failure to control common waterhemp following sequential applications of glyphosate in glyphosate-tolerant corn and soybean, which led to moderate to severe yield loss; justifying the need to confirm resistance and study the biology and management of common waterhemp. The objectives of this research were: 1) to confirm the presence of glyphosate-resistant (GR) common waterhemp biotypes in Nebraska and to evaluate their sensitivity to herbicides belonging to alternative sites-of-action; 2) to evaluate the response of common waterhemp to water stress; 3) to quantify pollen-mediated gene …

Information Thermodynamics Of Cytosine Dna Methylation, Robersy Sanchez Rodriguez, Sally Ann Mackenzie

Department of Agronomy and Horticulture: Faculty Publications

Cytosine DNA methylation (CDM) is a stable epigenetic modification to the genome and a widespread regulatory process in living organisms that involves multicomponent molecular machines. Genome-wide cytosine methylation patterning participates in the epigenetic reprogramming of a cell, suggesting that the biological information contained within methylation positions may be amenable to decoding. Adaptation to a new cellular or organismal environment also implies the potential for genome-wide redistribution of CDM changes that will ensure the stability of DNA molecules. This raises the question of whether or not we would be able to sort out the regulatory methylation signals from the CDM background …

Proceedings Of The 43rd Annual Meeting, Southern Soybean Disease Workers (March 9-10, 2016, Pensacola Beach, Florida), Trey Price, Tom Allen, Travis Faske, Eduardo Chagas Da Silva

Southern Soybean Disease Workers: Conference Proceedings

Contents

Schedule

Southern United States Soybean Disease Loss Estimates for 2015. TW Allen, CA Bradley, JP Damicone, NS Dufault, TR Faske, CA Hollier, T Isakeit, RC Kemerait, NM Kleczewski, SR Koenning, HL Mehl, JD Mueller, C Overstreet, PP Price, EJ Sikora, TN Spurlock, and H Young

Soilborne Disease Symposium (Tom Allen, moderator)

Integrated management of sudden death syndrome. D Mueller, L Leandro, Y Kandel, C Bradley, M Chilvers, A Tenuta, and K Wise

Field screening for stem canker: an outdated exercise or a necessary service for soybean growers? K Rowe and T Kirkpatrick

Nematode associated diseases in soybean. C Overstreet, …

Ws-2 Introgression In A Proportion Of Arabidopsis Thaliana Col-0 Stock Seed Produces Specific Phenotypes And Highlights The Importance Of Routine Genetic Verification, Mon-Ray Shao, Vikas Shedge, Hardik Kundariya, Fredric R. Lehle, Sally Ann Mackenzie

Department of Agronomy and Horticulture: Faculty Publications

Arabidopsis thaliana is an important model organism with a robust network of resources that has been of enormous value to the plant science research community. The use of isogenic material as a reference point or control is critical for many types of experiments in plant molecular biology and genetics. Recently, we noticed that some seed from a common source of the widely used Columbia-0 (Col-0) strain gave rise to plants showing features atypical for this strain. Whole-genome DNA-sequencing and allelespecific PCR assays confirmed that the abnormal individuals contain multiple introgressions from the ecotype Wassilewskija-2 (Ws-2), as described below. This …

Student-Conducted Farmer Video Interviews, Jenn K. Simons, Justin Van Wart, Charles Francis, Kristyn Harms

Department of Agronomy and Horticulture: Faculty Publications

High school agricultural education teachers have expressed concern about the lack of easily accessible educational materials dealing with contemporary topics in sustainable agriculture. There are numerous textbooks and monographs available for farmers and students at the college level, including the highly practical resources available from the Sustainable Agriculture Research and Education (SARE) book series on soil fertility (Magdoff and van Es, 2010), cover crops (Bowman et al., 2007) and building a farm business (DiGiacomo et al., 2003), among others. Although these are full of color photos and easily accessible graphs and tables, they are still in the print media category. …

Corn Era Hybrid Response To Nitrogen Fertilization, Krishna P. Woli, Matthew J. Boyer, Roger Wesley Elmore, John E. Sawyer, Lori J. Abendroth, Daniel W. Barker

Department of Agronomy and Horticulture: Faculty Publications

Corn (Zea mays L.) N use is of continued interest due to agronomic performance and environmental issues. This 2-yr study evaluated era hybrid response to fertilizer nitrogen (FN) rate in a factorial arrangement of one popular hybrid per five decades (1960–2000 eras) and five N rates (0–224 kg N ha^–1). An additional hybrid per era was grown at 168 kg N ha^–1. Hybrid productivity and nitrogen use efficiency (NUE) increased across the eras, but not between the 1980 and 1990 eras. Grain yield (GY) increased 65% and total plant biomass 43%, however, total plant nitrogen …

Growing Potato Profitably For Organic Dry Matter Production In Western Nebraska, Alexander Pavlista, Jessica J. Groskopf

Panhandle Research and Extension Center

Growing potato conventionally for dehydration is not economically feasible. The key cost would be seed under organic farming. The objective is to identify seed-piece sizes and spacings producing a profitable return for potato dehydration in western Nebraska. Atlantic potatoes were grown under dryland conditions using organic practices. Rain was 205, 270, and 360 mm in 2013, 2014, and 2015. Seed-pieces were hand-cut into five weights from 42.5 to 85.0 g and planted in five spacings from 15.2 to 45.7 cm. Seeding rates were 1.02 to 6.1 Mg/ha. Yield was highest at the spacing of 15.2 cm (16.1 Mg/ha) and decreased …

Mapping Qtls And Association Of Differentially Expressed Gene Transcripts For Multiple Agronomic Traits Under Different Nitrogen Levels In Sorghum, Malleswari Gelli, Sharon E. Mitchell, Kan Liu, Thomas E. Clemente, Donald P. Weeks, Chi Zhang, David R. Holding, Ismail M. Dweikat

Department of Agronomy and Horticulture: Faculty Publications

Background: Sorghum is an important C₄ crop which relies on applied Nitrogen fertilizers (N) for optimal yields, of which substantial amounts are lost into the atmosphere. Understanding the genetic variation of sorghum in response to limited nitrogen supply is important for elucidating the underlying genetic mechanisms of nitrogen utilization.

Results: A bi-parental mapping population consisting of 131 recombinant inbred lines (RILs) was used to map quantitative trait loci (QTLs) influencing different agronomic traits evaluated under normal N (100 kg.ha⁻¹ fertilizer) and low N (0 kg.ha⁻¹ fertilizer) conditions. A linkage map spanning 1614 cM was developed …

Proteomic Profiling Of Maize Opaque Endosperm Mutants Reveals Selective Accumulation Of Lysine-Enriched Proteins, Kyla J. Morton, Shangang Jia, Chi Zhang, David R. Holding

Department of Agronomy and Horticulture: Faculty Publications

Reduced prolamin (zein) accumulation and defective endoplasmic reticulum (ER) body formation occurs in maize opaque endosperm mutants opaque2 (o2), floury2 (fl2), defective endosperm*B30 (DeB30), and Mucronate (Mc), whereas other opaque mutants such as opaque1 (o1) and floury1 (fl1) are normal in these regards. This suggests that other factors contribute to kernel texture. A liquid chromatography approach coupled with tandem mass spectrometry (LC-MS/MS) proteomics was used to compare non-zein proteins of nearly isogenic opaque endosperm mutants. In total, 2762 proteins were identified that were enriched for biological processes such …

Simulating Long-Term Impacts Of Cover Crops And Climate Change On Crop Production And Environmental Outcomes In The Midwestern United States, Andrea D. Basche, Sotririos V. Archontoulis, Thomas C. Kaspar, Dan B. Jaynes, Timothy B. Parkin, Fernando E. Miguez

Department of Agronomy and Horticulture: Faculty Publications

It is critical to evaluate conservation practices that protect soil and water resources from climate change in the Midwestern United States, a region that produces one-quarter of the world’s soybeans and one-third of the world’s maize. An over-winter cover crop in a maize–soybean rotation offers multiple potential benefits that can reduce the impacts of higher temperatures and more variable rainfall; some of the anticipated changes for the Midwest. In this experiment we used the Agricultural Production Systems sIMulator (APSIM) to understand how winter rye cover crops impact crop production and environmental outcomes, given future climate change. We first tested APSIM …

Decipher The Molecular Response Of Plant Single Cell Types To Environmental Stresses, Mehrnoush Nourbakhsh-Rey, Marc Libault

Department of Agronomy and Horticulture: Faculty Publications

The analysis of the molecular response of entire plants or organs to environmental stresses suffers from the cellular complexity of the samples used. Specifically, this cellular complexity masks cell-specific responses to environmental stresses and logically leads to the dilution of the molecular changes occurring in each cell type composing the tissue/organ/plant in response to the stress.Therefore, to generate a more accurate picture of these responses, scientists are focusing on plant single cell type approaches. Several cell types are now considered as models such as the pollen, the trichomes, the cotton fiber, various root cell types including the root hair cell, …

Organic Struggle: The Movement For Sustainable Agriculture In The United States [Book Review], Charles A. Francis

Department of Agronomy and Horticulture: Faculty Publications

Organic Struggle chronicles the challenges encountered by innovators in a growing segment of the U.S. food production and marketing system. Practiced for millennia by farmers before the introduction of chemical fertilizers and pesticides, and first developed more formally in Europe, organic farming practices began to gain prominence in the United States only in the 1950s. Far more than a system for producing food, this strategy has become a focus for those supporting healthy and pesticide-free products, for some who embrace the organic system as a food movement, and by many who disagree with the current domination of the country’s food …

Draft Genome Sequence Of Erwinia Tracheiphila, An Economically Important Bacterial Pathogen Of Cucurbits, Lori R. Shapiro, Erin D. Scully, Dana Roberts, Timothy J. Straub, Scott M. Geib, Jihye Park, Andrew G. Stephenson, Erika Salaau Rojas, Quin Liu, Gwyn Beattie, Mark Gleason, Consuelo M. De Moraes, Mark C. Mescher, Shelby G. Fleischer, Roberto Kolter, Naomi Pierce, Olga Zhaxybayeva

Department of Agronomy and Horticulture: Faculty Publications

Erwinia tracheiphila is one of the most economically important pathogens of cucumbers, melons, squashes, pumpkins, and gourds in the northeastern and midwestern United States, yet its molecular pathology remains uninvestigated. Here, we report the first draft genome sequence of an E. tracheiphila strain isolated from an infected wild gourd (Cucurbita pepo subsp. texana) plant. The genome assembly consists of 7 contigs and includes a putative plasmid and at least 20 phage and prophage elements.

Muts Homolog1 Silencing Mediates Orf220 Substoichiometric Shifting And Causes Male Sterility In Brassica Juncea, Na Zhao, Xinyue Xu, Yashitola Wamboldt, Sally Ann Mackenzie, Xiaodong Yang, Zhongyuan Hu, Jinghua Yang, Mingfang Zhang

Department of Agronomy and Horticulture: Faculty Publications

Cytoplasmic male sterility (CMS) has consistently been associated with the expression of mitochondrial open reading frames (ORFs) that arise from genomic rearrangements. Spontaneous fertility reversion in CMS has been observed in several cases, but a clear understanding of fertility reversion controlled by nuclear genetic influences has been lacking. Here, we identified spontaneous fertile revertant lines for Brassica juncea CMS cytoplasm in which the mitochondrial genome has undergone substoichiometric shifting (SSS) to suppress ORF220 copy number. We placed ORF220, with or without a mitochondrial targeting presequence, under the control of the CaMV35S and AP3 promoters in Arabidopsis to confirm that ORF220 …

Prospects Of Genomic Prediction In The Usda Soybean Germplasm Collection: Historical Data Creates Robust Models For Enhancing Selection Of Accessions, Diego Jarquin, James Specht, Aaron Lorenz

Department of Agronomy and Horticulture: Faculty Publications

The identification and mobilization of useful genetic variation from germplasm banks for use in breeding programs is critical for future genetic gain and protection against crop pests. Plummeting costs of next-generation sequencing and genotyping is revolutionizing the way in which researchers and breeders interface with plant germplasm collections. An example of this is the high density genotyping of the entire USDA Soybean Germplasm Collection. We assessed the usefulness of 50K SNP data collected on 18,480 domesticated soybean (G. max) accessions and vast historical phenotypic data for developing genomic prediction models for protein, oil, and yield. Resulting genomic prediction models explained …

Corn (Zea Mays L.) Seeding Rate Optimization In Iowa, Usa, Mark A. Licht, Andrew W. Lenssen, Roger W. Elmore

Department of Agronomy and Horticulture: Faculty Publications

Collecting soil, topography, and yield information has become more feasible and reliable with advancements in precision technologies. Combined with the accessibility of precision technologies and services to farmers, there has been increased interest and ability to make site-specific crop management decisions. The objective of this research was to develop procedures to optimize corn seeding rates and maximize yield using soil and topographic parameters. Experimental treatments included five seeding rates (61 750; 74 100; 86 450; 98 800; and 111 150 seeds ha^-1) in a randomized complete block design in three central Iowa fields from 2012 to 2014 (nine …

Construction Of High Resolution Genetic Linkage Maps To Improve The Soybean Genome Sequence Assembly Glyma1.01, Qijian Song, Jerry Jenkins, Gaofeng Jia, David L. Hyten, Vince Pantalone, Scott A. Jackson, Jeremy Schmutz, Perry B. Cregan

Department of Agronomy and Horticulture: Faculty Publications

Background: A landmark in soybean research, Glyma1.01, the first whole genome sequence of variety Williams 82 (Glycine max L. Merr.) was completed in 2010 and is widely used. However, because the assembly was primarily built based on the linkage maps constructed with a limited number of markers and recombinant inbred lines (RILs), the assembled sequence, especially in some genomic regions with sparse numbers of anchoring markers, needs to be improved. Molecular markers are being used by researchers in the soybean community, however, with the updating of the Glyma1.01 build based on the high-resolution linkage maps resulting from this research, …

Genome-Wide Discriminatory Information Patterns Of Cytosine Dna Methylation, Robersy Sanchez, Sally A. Mackenzie

Department of Agronomy and Horticulture: Faculty Publications

Cytosine DNA methylation (CDM) is a highly abundant, heritable but reversible chemical modification to the genome. Herein, a machine learning approach was applied to analyze the accumulation of epigenetic marks in methylomes of 152 ecotypes and 85 silencing mutants of Arabidopsis thaliana. In an information-thermodynamics framework, two measurements were used: (1) the amount of information gained/lost with the CDM changes I_R and (2) the uncertainty of not observing a SNP LC_R. We hypothesize that epigenetic marks are chromosomal footprints accounting for different ontogenetic and phylogenetic histories of individual populations. A machine learning approach is proposed to …

Expression Of Apoplast-Targeted Plant Defensin Mtdef4.2 Confers Resistance To Leaf Rust Pathogen Puccinia Triticina But Does Not Affect Mycorrhizal Symbiosis In Transgenic Wheat, Jagdeep Kaur, John Fellers, Alok Adholeya, Siva L.S. Velivelli, Kaoutar El-Mounadi, Natalya Nersesian, Thomas Clemente, Dilip Shah

Department of Agronomy and Horticulture: Faculty Publications

Rust fungi of the order Pucciniales are destructive pathogens of wheat worldwide. Leaf rust caused by the obligate, biotrophic basidiomycete fungus Puccinia triticina (Pt) is an economically important disease capable of causing up to 50 % yield losses. Historically, resistant wheat cultivars have been used to control leaf rust, but genetic resistance is ephemeral and breaks down with the emergence of new virulent Pt races. There is a need to develop alternative measures for control of leaf rust in wheat. Development of transgenic wheat expressing an antifungal defensin offers a promising approach to complement the endogenous resistance genes …

Molecular Characterization Of Resistance To Soybean Rust (Phakopsora Pachyrhizi Syd. & Syd.) In Soybean Cultivar Dt 2000 (Pi 635999), Tri D. Vuong, David R. Walker, Binh T. Nguyen, Tuyet T. Nguyen, Hoan X. Dinh, David L. Hyten, Perry B. Cregan, David A. Sleper, Jeong D. Lee, James G. Shannon, Henry T. Nguyen

Department of Agronomy and Horticulture: Faculty Publications

Resistance to soybean rust (SBR), caused by Phakopsora pachyrhizi Syd. & Syd., has been identified in many soybean germplasm accessions and is conferred by either dominant or recessive genes that have been mapped to six independent loci (Rpp1 -Rpp6), but No U. S. cultivars are resistant to SBR. The cultivar DT 2000 (PI 635999) has resistance to P. pachyrhizi isolates and field populations from the United States as well as Vietnam. A F_6:7 recombinant inbred line (RIL) population derived from Williams 82 × DT 2000 was used to identify genomic regions associated with resistance to SBR in …

Grain Sorghum Leaf Reflectance And Nitrogen Status, Akwasi A. Abunyewa, Richard B. Ferguson, Charles S. Wortmann, Stephen C. Mason

Department of Agronomy and Horticulture: Faculty Publications

Nitrogen deficiency is a common but readily managed constraint to grain yield. A quick and nondestructive detection of crop N status using remote sensing could be a means to increased N use efficiency. Research was conducted in a greenhouse in 2006 at the University of Nebraska-Lincoln to establish the relationship of spectral reflectance with N status in leaves of grain sorghum, to develop indices for interpretation of the results and to predict chlorophyll content. Nitrogen stress decreased chlorophyll meter reading and leaf N content, but increased leaf and canopy reflectance. The SPAD values were significantly increased by both water and …

Genome-Wide Association Mapping Of Qualitatively Inherited Traits In A Germplasm Collection, Nonoy B. Bandillo, Aaron J. Lorenz, George L. Graef, Diego Jarquin, David L. Hyten, Randall L. Nelson, James E. Specht

Department of Agronomy and Horticulture: Faculty Publications

Genome-wide association (GWA) has been used as a tool for dissecting the genetic architecture of quantitatively inherited traits. We demonstrate here that GWA can also be highly useful for detecting many major genes governing categorically defined phenotype variants that exist for qualitatively inherited traits in a germplasm collection. Genome-wide association mapping was applied to categorical phenotypic data available for 10 descriptive traits in a collection of ~13,000 soybean [Glycine max (L.) Merr.] accessions that had been genotyped with a 50,000 single nucleotide polymorphism (SNP) chip. A GWA on a panel of accessions of this magnitude can offer substantial statistical …