Plant Biology Commons^™

The Tripartite Interaction Between Arbuscular Mycorrhizal Fungi, Rice, And Insects, Lina Bernaola Alvarado

LSU Doctoral Dissertations

Losses caused by pests remain an important limitation to achieving high rice yields in the United States. Arbuscular mycorrhizal fungi (AM fungi) are able to modify plant physiology by increasing plant growth or inducing defense responses against insect herbivores. However, studies of the role of AM fungi in agroecological factors, including natural occurrence, plant resistance, soil dependency, and plant tolerance, with specific regards to pests that feed on rice plants have not been conducted before. A three-year study revealed natural occurring colonization by AM fungi on rice roots sampled in four rice-producing areas in the southern United States. Overall, rice-AM …

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 …

A Stimulatory Role For Cytokinin In The Arbuscular Mycorrhizal Symbiosis Of Pea, Dane M. Goh, Marco Cosme, Anna B. Kislala, Samantha Mulholland, Zakaria M.F. Said, Lukáš Spíchal, R.J. Neil Emery, Stéphane Declerck, Frédérique C. Guinel

Biology Faculty Publications

The arbuscular mycorrhizal (AM) symbiosis between terrestrial plants and AM fungi is regulated by plant hormones. For most of these, a role has been clearly assigned in this mutualistic interaction; however, there are still contradictory reports for cytokinin (CK). Here, pea plants, the wild type (WT) cv. Sparkle and its mutant E151 (Pssym15), were inoculated with the AM fungus Rhizophagus irregularis. E151 has previously been characterized as possessing high CK levels in non-mycorrhizal (myc^-) roots and exhibiting high number of fungal structures in mycorrhizal (myc⁺) roots. Myc^- and myc⁺ plants were …

Mitotic Recombination And Rapid Genome Evolution In The Invasive Forest Pathogen Phytophthora Ramorum, Angela L. Dale, Nicolas Feau, Sydney E. Everhart, Braham Dhillon, Barbara Wong, Julie Sheppard, Guillaume J. Bilodeau, Avneet Brar, Javier F. Tabima, Danyu Shen, Clive M. Brasier, Brett M. Tyler, Niklaus J. Grünwald, Richard C. Hamelin

Department of Plant Pathology: Faculty Publications

Invasive alien species often have reduced genetic diversity and must adapt to new environments. Given the success of many invasions, this is sometimes called the genetic paradox of invasion. Phytophthora ramorum is invasive, limited to asexual reproduction within four lineages, and presumed clonal. It is responsible for sudden oak death in the United States, sudden larch death in Europe, and ramorum blight in North America and Europe. We sequenced the genomes of 107 isolates to determine how this pathogen can overcome the invasion paradox. Mitotic recombination (MR) associated with transposons and low gene density has generated runs of homozygosity (ROH) …

Using Drones For Precision Agriculture, Jiyul Chang, Madhav P. Nepal

iLEARN Teaching Resources

In this teaching module, students will learn what Precision Agriculture is and how to apply drone into Precision Agriculture practices. To use data (images) taken by drone, students will learn the basic theory of Remote Sensing. Using images, students learn how to make NDVI (Normalized Difference Vegetation Index) maps and how to apply drone (remote sensing technique) in agriculture.

Seasonal Origins Of Soil Water Used By Trees, Scott T. Allen, James W. Kirchner, Sabine Braun, Rolf T. W. Siegwolf, Gregory R. Goldsmith

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Rain recharges soil water storages and either percolates downward into aquifers and streams or is returned to the atmosphere through evapotranspiration. Although it is commonly assumed that summer rainfall recharges plant-available water during the growing season, the seasonal origins of water used by plants have not been systematically explored. We characterize the seasonal origins of waters in soils and trees by comparing their midsummer isotopic signatures (δ2H) to seasonal isotopic cycles in precipitation, using a new seasonal origin index. Across 182 Swiss forest sites, xylem water isotopic signatures show that summer rain was not the predominant water source …

Arabinose Substitution Effect On Xylan Rigidity And Self-Aggregation, Utsab Shrestha, Sydney Smith, Sai Venkatesh Pingali, Hui Yang, Mai Zahran, Llyod Breunig, Liza Wilson, Daniel Cosgrove, Hugh O'Neill, Loukas Petridis

Publications and Research

Substituted xylans play an important role in the structure and mechanics of the primary cell wall of plants. Arabinoxylans (AX) consist of a xylose backbone substituted with arabinose, while glucuronoarabinoxylans (GAX) also contain glucuronic acid substitutions and ferulic acid esters on some of the arabinoses. We provide a molecular-level description on the dependence of xylan conformational, selfaggregation properties and binding to cellulose on the degree of arabinose substitution. Molecular dynamics simulations reveal fully solubilized xylans with a low degree of arabinose substitution (lsAX) to be stiffer than their highly substituted (hsAX) counterparts. Small-angle neutron scattering experiments indicate that both wild-type …

Phylogenetic And Biogeographic Controls Of Plant Nighttime Stomatal Conductance, Kailiang Yu, Gregory R. Goldsmith, Yujie Wang, William R. L. Anderegg

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

The widely documented phenomenon of nighttime stomatal conductance (g_sn) could lead to substantial water loss with no carbon gain, and thus it remains unclear whether nighttime stomatal conductance confers a functional advantage. Given that studies of g_sn have focused on controlled environments or small numbers of species in natural environments, a broad phylogenetic and biogeographic context could provide insights into potential adaptive benefits of g_sn.

We measured g_sn on a diverse suite of species (n = 73) across various functional groups and climates‐of‐origin in a common garden to study the phylogenetic and biogeographic/climatic controls …

Extending The Osmometer Method For Assessing Drought Tolerance In Herbaceous Species, Robert J. Griffin-Nolan, Troy W. Ocheltree, Kevin E. Mueller, Dana M. Blumenthal, Julie A. Kray, Alan K. Knapp

Biological, Geological, and Environmental Faculty Publications

Community-scale surveys of plant drought tolerance are essential for understanding semi-arid ecosystems and community responses to climate change. Thus, there is a need for an accurate and rapid methodology for assessing drought tolerance strategies across plant functional types. The osmometer method for predicting leaf osmotic potential at full turgor ((o)), a key metric of leaf-level drought tolerance, has resulted in a 50-fold increase in the measurement speed of this trait; however, the applicability of this method has only been tested in woody species and crops. Here, we assess the osmometer method for use in herbaceous grassland species and test whether …

Transcriptomic Response Is More Sensitive To Water Deficit In Shoots Than Roots Of Vitis Riparia (Michx.), Vedbar Singh Khada, Kimberly Vaughn, Juan Xie, Padmapriya Swaminathan, Qin Ma, Grant Cramer, Anne Y. Fennell Dr

Agronomy, Horticulture and Plant Science Faculty Publications

Background: Drought is an important constraint on grapevine sustainability. Vitis riparia, widely used in rootstock and scion breeding, has been studied in isolated leaf drying response studies; however, it is essential to identify key root and shoot water deficit signaling traits in intact plants. This information will aid improved scion and rootstock selection and management practices in grapevine. RNAseq data were generated from V. riparia roots and shoots under water deficit and well-watered conditions to determine root signaling and shoot responses to water deficit.
Results: Shoot elongation, photosynthetic rate, and stomatal conductance were significantly reduced in water deficit (WD) treated …

Distribution And Population Structure Of The Invasive Nitellopsis Obtusa (Desv. In Loisel.) J. Groves And Native Species Of Characeae In The Northeast U.S.A., Robin Sleith

Dissertations, Theses, and Capstone Projects

Freshwater ecosystems are some of the most biologically diverse environments on Earth. Billions of humans rely on functioning freshwater ecosystems for drinking water and many other services. These ecosystems are increasingly threatened by human impacts including nutrient pollution, invasive species, and climate change. Here I contribute four research chapters that investigate freshwater diversity and ecosystem threats using the Characeae, a family of freshwater green macroalgae, as a study system. Characeae are a diverse and ancient group with more than 500 extant species and a fossil history spanning at least 250 million years. These algae are macrophytes in freshwater ecosystems, and …

Refernment: An R Package For Annotating Rna Editing In Plastid Genomes, Tanner A. Robison, Paul G. Wolf

Biology Faculty Publications

PREMISE OF THE STUDY: In the absence of cDNA, the annotation of RNA editing in plastomes must be done manually, representing a significant time cost to those studying the organellar genomes of ferns and hornworts.

METHODS AND RESULTS: We developed an R package to automatically annotate apparent nonsense mutations in plastid genomes. The software successfully annotates such sites and results in no false positives for data with no sequencing or assembly errors.

CONCLUSIONS: Compared to manual annotation, ReFernment offers greater speed and accuracy for annotating RNA editing sites. This software should be especially useful for researchers generating large numbers of …

An Albino Mutant In Brassica Rapa Maps To The Pdx2 Locus On Chromosome 10, Beatriz M. Garcia

STAR Program Research Presentations

We have identified an albino mutant in the plant Brassica rapa. This recessive mutation could provide insights into the photosynthetic pathways of all plants. Previously the mutation was mapped to chromosome 10 of Brassica rapa. To narrow down the chromosomal region containing the albino mutation, we grew a segregating population of plants. DNA was extracted from albino and wildtype (green) plants and genotyped using PCR markers on chromosome 10. The genotype detected using the INDEL2 marker perfectly predicted whether a plant was albino or WT. This indicates that the INDEL2 marker is tightly linked to the albino mutation. INDEL2 is …

Identification Of Climate And Genetic Factors That Control Fat Content And Fatty Acid Composition Of Theobroma Cacao L. Beans, Guiliana M. Mustiga, Joe Morrissey, Joseph Conrad Stack, Ashley Duval, Stefan Royaert, Johannes Jansen, Carolina Bizzotto, Cristiano Villela-Dias, Linkai Mei, Edgar B. Cahoon, Ed Seguine, Jean Philippe Marelli, Juan Carlos Motamayor

Center for Plant Science Innovation: Faculty Publications

The main ingredients of chocolate are usually cocoa powder, cocoa butter, and sugar. Both the powder and the butter are extracted from the beans of the cacao tree (Theobroma cacao L.). The cocoa butter represents the fat in the beans and possesses a unique fatty acid profile that results in chocolate’s characteristic texture and mouthfeel. Here, we used a linkage mapping population and phenotypic data of 3,292 samples from 420 progeny which led to the identification of 27 quantitative trait loci (QTLs) for fatty acid composition and six QTLs for fat content. Progeny showed extensive variation in fat levels …

Drought-Responsive Genes, Late Embryogenesis Abundant Group3 (Lea3) And Vicinal Oxygen Chelate, Function In Lipid Accumulation In Brassica Napus And Arabidopsis Mainly Via Enhancing Photosynthetic Efficiency And Reducing Ros, Yu Liang, Kai Kang, Lu Gan, Shaobo Ning, Jinye Xiong, Shuyao Song, Lingzhi Xi, Senying Lai, Yongtai Yin, Jianwei Gu, Jun Xiang, Shisheng Li, Baoshan Wang, Maoteng Li

Center for Plant Science Innovation: Faculty Publications

Drought is an abiotic stress that affects plant growth, and lipids are the main economic factor in the agricultural production of oil crops. However, the molecular mechanisms of drought response function in lipid metabolism remain little known. In this study, overexpression (OE) of different copies of the drought response genes LEA3 and VOC enhanced both drought tolerance and oil content in Brassica napus and Arabidopsis. Meanwhile, seed size, membrane stability and seed weight were also improved in OE lines. In contrast, oil content and drought tolerance were decreased in the AtLEA3 mutant (atlea3) and AtVOC-RNAi of Arabidopsis and in both …

Fad2 Gene Radiation And Positive Selection Contributed To Polyacetylene Metabolism Evolution In Campanulids1[Open], Tao Feng, Ya Yang, Lucas Busta, Edgar B. Cahoon, Hengchang Wang, Shiyou Lü

Center for Plant Science Innovation: Faculty Publications

Polyacetylenes (PAs) are bioactive, specialized plant defense compounds produced by some species in the eudicot clade campanulids. Early steps of PA biosynthesis are catalyzed by Fatty Acid Desaturase 2 (FAD2). Canonical FAD2s catalyze desaturation, but divergent forms can catalyze hydroxylation, conjugation, acetylenation, and epoxygenation. These alternate reactions give rise to valuable unusual fatty acids, including the precursors to PAs. The extreme functional diversity of FAD2 enzymes and the origin of PA biosynthesis are poorly understood from an evolutionary perspective. We focus here on the evolution of the FAD2 gene family. We uncovered a core eudicot-wide gene duplication event giving rise …

Two Distinct Nucleic Acid Binding Surfaces Of Cdc5 Regulate Development, Chao Wang, Mu Li, Guorui Li, Wensheng Zhao, Bin Yu, Junfeng Liu, Jun Yang, You-Liang Peng

Center for Plant Science Innovation: Faculty Publications

Cell division cycle 5 (Cdc5) is a highly conserved nucleic acid binding protein among eukaryotes and plays critical roles in development. Cdc5 can simultaneously bind to DNA and RNA by its N- terminal DNA-binding domain (DBD), but molecular mechanisms describing its nucleic acid recognition and the regulation of development through its nucleic acid binding remain unclear. Herein, we present a crystal structure of the N-terminal DBD of MoCdc5 (MoCdc5-DBD) from the rice blast fungus Magnaporthe oryzae. Residue K100 of MoCdc5 is on the periphery of a positively charged groove that is formed by K42, K45, R47, and N92 and is …

Comprehensive Analysis Of Aspergillus Nidulans Pka Phosphorylome Identifies A Novel Mode Of Crea Regulation, Liliane F. C. Ribeiro, Cynthia Chelius, Karthik R. Boppidi, Nisha S. Naik, Simin Hossain, Jessica J. J. Ramsey, Jyothi Kumar, Lucas F. Ribeiro, Marc Ostermeier, Bao Tran, Young Ah Goo, Leandro J. De Assis, Mevlut Ulas, Ozgur Bayram, Gustavo H. Goldman, Stephen Lincoln, Ranjan Srivastava, Steven D. Harris, Mark R. Marten

Center for Plant Science Innovation: Faculty Publications

In filamentous fungi, an important kinase responsible for adaptation to changes in available nutrients is cyclic AMP (cAMP)-dependent protein kinase (protein kinase A [PKA]). This kinase has been well characterized at a molecular level, but its systemic action and direct/indirect targets are generally not well understood in filamentous fungi. In this work, we used a pkaA deletion strain (ΔpkaA) to identify Aspergillus nidulans proteins for which phosphorylation is dependent (either directly or indirectly) on PKA. A combination of phosphoproteomic and transcriptomic analyses revealed both direct and indirect targets of PKA and provided a global perspective on its function. …

Closing Yield Gaps For Rice Self-Sufficiency In China, Nanyan Deng, Patricio Grassini, Haishun Yang, Jianliang Huang, Kenneth G. Cassman, Shaobing Peng

Department of Agronomy and Horticulture: Faculty Publications

China produces 28% of global rice supply and is currently self-sufficient despite a massive rural-to-urban demographic transition that drives intense competition for land and water resources. At issue is whether it will remain self-sufficient, which depends on the potential to raise yields on existing rice land. Here we report a detailed spatial analysis of rice production potential in China and evaluate scenarios to 2030. We find that China is likely to remain self-sufficient in rice assuming current yield and consumption trajectories and no reduction in production area. A focus on increasing yields of double-rice systems on general, and in three …

Manipulation Of Β-Carotene Levels In Tomato Fruits Results In Increased Aba Content And Extended Shelf-Life, Gianfranco Diretto, Sarah Frusciante, Claudia Fabbri, Nicolas Schauer, Lucas Busta, Zhonghua Wang, Antonio J. Matas, Alessia Fiore, Jocelyn K. C. Rose, Alisdair R. Fernie, Reinhard Jetter, Benedetta Mattei, Jim Giovannoni, Giovanni Giuliano

Center for Plant Science Innovation: Faculty Publications

Tomato fruit ripening is controlled by the hormone ethylene and by a group of transcription factors, acting upstream of ethylene. During ripening, the linear carotene lycopene accumulates at the expense of cyclic carotenoids. Fruit-specific overexpression of LYCOPENE β-CYCLASE (LCYb) resulted in increased β-carotene (provitamin A) content. Unexpectedly, LCYb-overexpressing fruits also exhibited a diverse array of ripening phenotypes, including delayed softening and extended shelf life. These phenotypes were accompanied, at the biochemical level, by an increase of abscisic acid (ABA) content, decreased ethylene production, increased density of cell wall material containing linear pectins with a low degree of …

Assessing Variation In Us Soybean Seed Composition (Protein And Oil), Yared Assefa, Larry C. Purcell, Montse Salmeron, Seth Naeve, Shaun N. Casteel, Peter Kovacs, Sotirios Archontoulis, Mark Licht, Fred Below, Herman Kandel, Laura E. Lindsey, John Gaska, Shawn Conley, Charles Shapiro, John M. Orlowski, Bobby R. Golden, Gurpreet Kaur, Maninderpal Singh, Kurt Thelen, Randall Laurenz, Dan Davidson, Igancio A. Ciampitti

Department of Agronomy and Horticulture: Faculty Publications

Soybean [Glycine max (L.) Merr.] seed composition and yield are a function of genetics (G), environment (E), and management (M) practices, but contribution of each factor to seed composition and yield are not well understood. The goal of this synthesis-analysis was to identify the main effects of G, E, and M factors on seed composition (protein and oil concentration) and yield. The entire dataset (13,574 data points) consisted of 21 studies conducted across the United States (US) between 2002 and 2017 with varying treatments and all reporting seed yield and composition. Environment (E), defined as site-year, was the dominant …

Assessing The Value Of Grazed Corn Residue For Crop And Cattle Producers, Daren Redfearn, Jay Parsons, Mary Drewnoski, Marty Schmer, Rob Mitchell, James Macdonald, Jaymelynn Farney, Alexander Smart

Department of Agronomy and Horticulture: Faculty Publications

Integrated crop–livestock systems have included grazing perennial grasses during the spring and summer and corn (Zea mays L.) residues during the winter. Our objectives were to identify opportunities for expanded corn residue use through grazing and provide an economic assessment for value-added grazing. We estimated the economic value to the crop sector through grazing leased corn residue at over $95 million for Nebraska, South Dakota, Kansas, and North Dakota under current management. Additionally, gross economic value to the livestock sector in these states was estimated at greater than $191 million. Advantages for increased grazing use of corn residue include …

Climate-Smart Practices For Improvement Of Crop Yields In Mid-Hills Of Nepal, Roshan Subedi, Laxmi Dutt Bhatta, Erica Udas, Nand Kishor Agrawal, Keshab Datta Joshi, Dinesh Panday

Department of Agronomy and Horticulture: Faculty Publications

Farming in Nepal mostly represents the hill farming system with the dominance of small-holder farmers. In recent days, farmers in the country are impacted by climate change. Events of surface runoff, landslides, and soil erosions, along with changes in rainfall pattern and intensity have elevated a decline in crop productivity and soil fertility. Considering the situation, a pilot project on Resilient Mountain Village was implemented in Kavrepalanchowk district of Nepal from 2014–2016 with a participatory approach to demonstrate climate-smart practices. These practices include the application of locally prepared bio-fertilizer (named as “jholmal”), green manuring in rice (Oryza sativa L.) …

Drought Stress Tolerance In Wheat And Barley: Advances In Physiology, Breeding And Genetics Research, Ahmed Sallam, Ahmad M. Alqudah, Mona F. A. Dawood, P. Stephen Baenziger, Andreas Borner

Department of Agronomy and Horticulture: Faculty Publications

Climate change is a major threat to most of the agricultural crops grown in tropical and sub-tropical areas globally. Drought stress is one of the consequences of climate change that has a negative impact on crop growth and yield. In the past, many simulation models were proposed to predict climate change and drought occurrences, and it is extremely important to improve essential crops to meet the challenges of drought stress which limits crop productivity and production. Wheat and barley are among the most common and widely used crops due to their economic and social values. Many parts of the world …

Generating High Density, Low Cost Genotype Data In Soybean [Glycine Max (L.) Merr.], Mary M. Happ, Haichuan Wang, George L. Graef, David L. Hyten

Department of Agronomy and Horticulture: Faculty Publications

Obtaining genome-wide genotype information for millions of SNPs in soybean [Glycine max (L.) Merr.] often involves completely resequencing a line at 5X or greater coverage. Currently, hundreds of soybean lines have been resequenced at high depth levels with their data deposited in the NCBI Short Read Archive. This publicly available dataset may be leveraged as an imputation reference panel in combination with skim (low coverage) sequencing of new soybean genotypes to economically obtain high-density SNP information. Ninety-nine soybean lines resequenced at an average of 17.1X were used to generate a reference panel, with over 10 million SNPs called using …

Assessing Precipitation, Evapotranspiration, And Ndvi As Controls Of U.S. Great Plains Plant Production, Maosi Chen, William J. Parton, Melannie D. Hartman, Stephen J. Del Grosso, William K. Smith, Alan K. Knapp, Susan Lutz, Justin D. Derner, Compton J. Tucker, Dennis S. Ojma, Jerry D. Volesky, Mitchell B. Stephenson, Walter H. Schacht, Wei Gao

Department of Agronomy and Horticulture: Faculty Publications

Productivity throughout the North American Great Plains grasslands is generally considered to be water limited, with the strength of this limitation increasing as precipitation decreases. We hypothesize that cumulative actual evapotranspiration water loss (AET) from April to July is the precipitation-related variable most correlated to aboveground net primary production (ANPP) in the U.S. Great Plains (GP). We tested this by evaluating the relationship of ANPP to AET, precipitation, and plant transpiration (Tr). We used multi-year ANPP data from five sites ranging from semiarid grasslands in Colorado and Wyoming to mesic grasslands in Nebraska and Kansas, mean annual NRCS ANPP, and …

Can Ratoon Cropping Improve Resource Use Efficiencies And Profitability Of Rice In Central China?, Shen Yuan, Kenneth G. Cassman, Jianliang Huang, Shaobing Peng, Patricio Grassini

Department of Agronomy and Horticulture: Faculty Publications

Identifying cropping systems with small global warming potential (GWP) per unit of productivity is important to ensure food security while minimizing environmental footprint. During recent decades, double-season rice (DR) systems in central China have progressively shifted into single-crop, middle-season rice (MR) due to high costs and labor requirements of double-season rice. Ratoon rice (RR) has been proposed as an alternative system that reconciliates both high annual productivity and relatively low costs and labor requirements. Here we used onfarm data collected from 240 farmer fields planted with rice in 2016 to evaluate annual energy balance, environmental impact, and net profit of …

Development And Characterization Of Wheat-Thinopyrum Junceiforme Chromosome Addition Lines, Dilkaran Singh

Electronic Theses and Dissertations

Production of wheat is challenged by dynamic biotic and abiotic stresses. Genetic improvement via alien gene transfer is an effective approach to tackle such challenges. Alien gene transfer played an important role in the history of wheat crop improvement. Sea wheatgrass (SWG; Thinopyrum junceiforme, 2n = 28, genomes J1J1J2J2) is a wild relative of wheat. In our previous work, we have developed a complete amphiploid between cultivated emmer and SWG and shown that SWG is resistant to wheat streak mosaic virus, Fusarium head blight and wheat stem sawflies (due to the solid stem) and tolerant to waterlogging, salinity, heat, and …

Isolation And Identification Of Potential Bioinoculants Based On Phosphate Solubilizing And Plant Growth Promoting Benefits, Rachel Raths

Electronic Theses and Dissertations

Conservative models have shown that as populations rise, food production needs to double by 2050. Population increase and the green revolution have caused fertilizer inputs to increase since the 1960’s, increasing environmental issues and production costs. These intensive practices have led to degraded arable land and there has been an increase in urbanization meaning we need to make best use of the farming land that is available and ensure it is sustainable for future food production. Due to this, there has been a higher demand for research on more environmentally and economically friendly approaches to food production. Plant growth promoting …

Disease Resistance In Wheat And Its Relatives, Ethan James Andersen

Electronic Theses and Dissertations

Plants have evolved a complex defense system against pests and pathogens utilizing many types of receptors, signaling factors, and defense compounds to detect pathogen presence and respond effectively. Since many pathogens have evolved immunesuppressing effectors used to reduce plant resistance, plants have evolved a family of receptors that detect pathogenic effectors as a result of an evolutionary arms race. These receptors contain Nucleotide-Binding Site and Leucine-Rich Repeat domains and are called NBS-LRR or NLR proteins. Many grasses possess huge genomes with hundreds of NLR-encoding genes, often found in clusters at the extra-pericentromeric regions of chromosomes, where unequal crossing over causes …