Plant Sciences Commons^™

Defining The Genetic Regulation Of Appressorium Formation In Cercospora Zeae-Maydis, Hazel Apiyo Buyu

Graduate Theses and Dissertations

Cercospora zeae-maydis is one of the primary pathogens associated with gray leaf spot, one of the most damaging foliar diseases of maize in the world. Gray leaf spot can be managed to some extent by cultural practices and fungicide applications. To infect maize, C. zeae-maydis grows towards stomata and forms infectious structures, termed appressoria, over stomatal pores. Prior research on the pathogen revealed that appressorium formation is crucial for foliar infection. Although several genes involved in pathogenesis have been identified in C. zeae-maydis, the molecular regulation of appressorium formation in this pathogen is poorly understood. Specifically, how the fungus senses …

Molecular Basis Of Pathogenesis And Host Determination In Cercospora Sojina: From Phenotypic To Genotypic Patterns, Wagner Calegari Fagundes

Graduate Theses and Dissertations

Frogeye leaf spot (FLS), caused by Cercospora sojina, is an important and recurrent disease of soybean in many production regions. Genetic resistance is potentially one of the most cost-effective and sustainable strategies to control FLS. However, C. sojina has already demonstrated the ability to overcome resistance conveyed by single R-genes (resistance genes) of soybeans, followed by the emergence of new physiological races. Although understanding population genomics and the virulence gene inventories in fungal plant pathogens is extremely important to improve disease control measures, studies regarding host specificity and pathogenesis in C. sojina are very limited. Therefore, the overarching goal of …

Understanding And Predicting Nematode Damage On Soybean Using Spatially Weighted Analysis, Barry Boney

Graduate Theses and Dissertations

Aerial imagery offers great potential as a predictive scouting method and could allow growers to better understand crop performance over time. Evidence suggests that the seed treatments fluopyram and abamectin result in decreased reproduction and root galling by Meloidogyne incognita, but yield protection in fields with higher or different nematode pressure is unclear. The objective of this work was to determine the efficacy of these seed treatments compared to 1,3-dichloropropene (1,3-D) applied site-specifically and then predict where these might best be applied to other fields. In a soybean field infested with M. incognita, apparent electrical conductivity was highly correlated with …

Water Conservation Practices For Irrigation Of Turfgrass Lawns, Daniel Sandor

Graduate Theses and Dissertations

Turfgrass lawns are widely used in residential and commercial landscapes, providing many environmental, aesthetic, and recreational benefits. However, concerns and scrutiny arise with perceived maintenance requirements, particularly with regards to irrigation. It is important to manage irrigation in order to maximize water conservation without significantly reducing lawn quality. A series of field and greenhouse studies were conducted to investigate how water usage might be reduced in irrigation practices with the following proposed objectives: 1) evaluate the use of rain and soil moisture sensors in a humid transition zone environment; 2) evaluate the effects of chronic drought stress between drought-resistant and …

Evaluation And Characterization Of Fitness Costs In Multiple Herbicide Resistant Echinochloa In Arkansas, Teal Marie Penka

Graduate Theses and Dissertations

Echinochloa spp. are major weed problems for rice (Oryza sativa L.) on a global scale. In the southern rice belt of the U.S.A., Echinochloa colona (L.) Link (junglerice) and E. crus-galli (L.) P. Beauv (barnyardgrass) are the most troublesome weeds. These species are morphologically diverse, and its high ploidy level augurs high genetic diversity, which favors high adaptability to stress, including herbicide selection pressure. The objectives of these studies were to 1) isolate resistant (R) and sensitive (S) biotypes from eight accessions of E. colona with different resistance profiles; 2) determine the resistance levels of selected R and S biotypes …

Influence Of Loss Of Function Of The Fatty Acid Desaturase 7 Gene On Photosynthetic Activity And Foliar Redox Status, Janithri Savindya Wickramanayake

Graduate Theses and Dissertations

Fatty Acid Desaturase7 (FAD7) is a chloroplast-localized enzyme that converts 16 and 18 carbon dienoic fatty acids to trienoic fatty acids. The suppressor of prosystemin-mediated response2 (spr2) mutant in tomato (Solanum lycopersicum) and the fad7-1 mutant in Arabidopsis (Arabidopsis thaliana) result in the loss of function of FAD7, which alter the fatty acid profiles of chloroplast membranes and enhance resistance against aphids. This research contributes toward the long-term goal of identifying factors that determine aphid resistance in FAD7 mutants. Previous data suggested constitutive differences between spr2 and WT including increased expression of genes associated with photosynthesis and differences in redox …

Linkage Mapping For Soybean (Glycine Max) Flood Tolerance, Wade Stiles Hummer

Graduate Theses and Dissertations

Flood tolerance in soybean (Glycine max) is not a well-characterized trait, yet flooding damage is second only to drought stress in terms of yield reduction. The objectives of this study were to determine genetic variation for flooding tolerance in two populations of soybean recombinant inbred lines (RILs) and to identify and confirm flood tolerant QTL. Population A (WHA) consisted of 111 RILs derived from the cross 5002T by 91210-350 and Population B (WHB) consisted of 79 RILs from the cross RA-452 by Osage. Experiments were conducted at the Rice Research and Extension Center (RREC) near Stuttgart, AR in 2015 and …

Evaluation Of Rice Stink Bug, Oebalus Pugnax (F.), Damage And Monitoring Techniques In Rice, Oryza Sativa L., And Grain Sorghum, Sorghum Bicolor (L.), Aaron Joseph Cato

Graduate Theses and Dissertations

Rice stink bug, Oebalus pugnax (F.), is a serious pest of headed rice, Oryza sativa L. and an occasional pest of heading grain sorghum in the Mid-south. Work from this dissertation focuses on resolving gaps in and knowledge of rice stink bug sampling and management, and attempts to create a basis for rice stink bug damage assessment in future studies.

Field experiments were conducted from 2016-2018 to asses variation in sweep net sampling by observing producers, researchers, extension personnel, consultants and their workers. Large levels of variation were found in sweep lengths between observed sweepers and reliability of smaller sweep …

Physiological Characterization Of The Soynam Parental Lines Under Field Conditions, Akshita Mishra

Graduate Theses and Dissertations

The narrow genetic pool of soybean (Glycine max L. Merr.) in North America can limit its future yield gains. Among the worldwide germplasm collection of 45,000 unique landraces, only 80 contribute 99% to the collective parentage of North American soybean cultivars. Among these 80 landraces, just 17 contribute to 86% of the collective parentage of the modern cultivars. The Soybean Nested Association Mapping population (SoyNAM) was therefore developed with the objective of diversifying the soybean gene pool. Forty diverse soybean genotypes from maturity groups (MG) 1 through 5 were crossed with a common MG 3 parent to develop 40 recombinant …

Systems To Attract And Feed Pollinators In Warm-Season Lawns, Michelle Wisdom

Graduate Theses and Dissertations

Pollinating insects are responsible for the production of many agricultural crops and they require floral resources to fulfill their life-cycle. Ideally, pollinating insects will encounter a diversity of floral resources across their entire season of activity, and those floral resources can include both herbaceous and woody plant species. Managed turfgrass areas have been identified as potential locations for creating pollinator-friendly habitats. In the transition zone, where both warm- and cool-season turfgrass species are present, the persistence of herbaceous plants in warm-season turfgrasses such as bermudagrass (Cynodon spp.) and buffalograss (Buchloe dactyloides), may be affected not only by the competitive nature …

Effects Of Irrigation On Forage Growth Rates On Rotational Grazing Dairies, Zachary Davis

MSU Graduate Theses

The amount and timing of rainfall in Missouri can be very irregular. This causes issues for producers of agronomic products in the state who rely on forages for income. The most sensible approach to the problem is the use of irrigation. But there is little useful information to reference when implementing this management decision. By studying three different styles of irrigation (center pivot, spider, and k-line) on 4 species of forages native to Missouri (alfalfa, crabgrass, perennial ryegrass, and tall fescue/clover), this study provides valuable insight as to the cost and benefit of irrigation. The main goal is to produce …

Impacts Of Cover Crop Mixtures On Productivity Of Cropping Systems, Brionna Lee West

MSU Graduate Theses

A field study and a meta-analysis were conducted to compare the impact of cover crops on carbon and nitrogen dynamics and cash crop yield. The field study included six treatments: winter cereal rye, winter cereal rye-Austrian winter pea at two seeding rates, cereal rye-Austrian winter pea-radish at two seeding rates, and a no cover control. Meta-analysis data sets were compiled from studies published between 1994 and 2017. Treatments were grouped into the following classifications: monoculture, binary mix, polyculture, or control. In both the field study and meta-analysis, cover crops did not affect cash crop yield. However, plant biomass and plant …

Relative Contribution Of Physical Interference And Allelopathy To Weed Suppression By Winter Annual Cover Crop Mixtures, Alyssa D. Travlos

MSU Graduate Theses

Cover cropping systems are widely used in crop production systems to prevent erosion, improve soil health, and suppress weeds. Common cover cropping systems include combinations of cereal rye (Secale cereale L.), Brassica species, legumes, and other winter annual species. Three cover crop mixtures (cereal rye alone, cereal rye plus winter pea, and cereal rye plus winter pea plus radish) were applied using three methods (fresh residue, dried leached residue, and leachate) to common waterhemp (Amaranthus tuberculatus var. rudis) and large crabgrass [Digitaria sanguinalis (L.) Scop.]. The experiment was conducted once in a greenhouse and once in a …

Mitigating The Risk For Glufosinate Resistance, Christopher John Meyer

Graduate Theses and Dissertations

While glufosinate-resistant weeds have not yet been identified in U.S. row crops, rapid evolution of glyphosate-resistance, and resulting cost to U.S. farmers, demonstrates the need to responsibly steward the limited number of herbicides available in agricultural systems. Field and laboratory experiments were conducted to: 1) Identify herbicide interactions that can occur in Enlist™ and Roundup Ready® Xtend® systems; 2) Identify herbicide interactions that occur when glufosinate is mixed with fomesafen, clethodim, and glyphosate; 3) Determine the optimum rate structure and application timings when multiple POST applications of glufosinate are applied to LibertyLink soybean; 4) Use 14C techniques to determine why …

Evaluation Of Soybean Maturity Group And Planting Date In A Soybean-Rice Rotation On Overall Crop Productivity, Carrie Ortel

Graduate Theses and Dissertations

Little is known about the effects of soybean (Glycine max L.) management techniques on soil-nitrogen (N) credit development and its impact on the subsequent rice (Oryza sativa L.) crop’s success. This study was conducted to determine how soybean maturity group (MG) and planting date effect overall soybean productivity and its influence on the following rice crop. Various soybean planting dates (optimum and late) and MGs (3.5, 4.7, 5.4, and 5.6) were grown and followed in rotation with a rice crop. Six rates of pre-flood fertilizer-N (0, 44, 89, 134, 179, 224 kg N ha-1) were applied to the rice crop. …

A Simple Metabolic Switch May Activate Apomixis In Arabidopsis Thaliana, David Alan Sherwood

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Apomixis, asexual or clonal seed production in plants, can decrease the cost of producing hybrid seed and enable currently open pollinated crops to be converted to more vigorous and higher yielding hybrids that can reproduce themselves through their own seed. Sexual reproduction may be triggered by a programmed stress signaling event that occurs in both the meiocyte, just prior to meiosis, and later in the egg just prior to embryo sac maturation. The prevention of stress signaling and the activation of a pro-growth signal prior to meiosis triggered apomeiosis, the first half of apomixis. The same approach was used prior …

Weed Control And Management For Vegetable Soybeans In Arkansas, Seth Bernard Abugho

Graduate Theses and Dissertations

Vegetable soybean [Glycine max (L.) Merr.], known as edamame, needs weed management tools. Releasing locally adapted edamame soybean varieties and registering herbicides are necessary for successful production and expanding the edamame industry. This research aimed to 1) identify herbicides labeled for grain soybean for potential use on edamame; 2) evaluate differential tolerance of edamame soybean varieties to selected grain soybean herbicides; and 3) identify a feasible edamame-based crop rotation system. For objective 1, 26 herbicide treatments were tested on AVS-4002 edamame including preplant (PPL), preemergence (PRE) and postemergence (POST) herbicides labeled for grain soybean. Preplant herbicides caused 9 to 28% …

Analysis Of The Soil Health Of Pastures Over-Seeded With Winter Annuals, Kathleen M. Bridges

LSU Doctoral Dissertations

Utilizing winter annuals in livestock pastures reduces feed costs of hay, and provides additional vegetative cover that is beneficial to the soil. However, how this practice affects the soil microbial communities has not been well studied. Two sites were included in this study. Both were commercial cattle grazing operations that over-seeded a mixture of grasses, legumes, and brassicas into pastures dominated by bahiagrass (Paspalum notatum). Soil health was assessed using a suite of physical, chemical, and biological properties. Soil physical assessments included bulk density and aggregate stability. Soil chemical assessments included macronutrients, pH, soil organic matter (SOM), total …

Genome Wide Association Studies For Identification Of Markers Linked To Sucrose Traits In Sugarcane, Nathanael Darrell Fickett

LSU Doctoral Dissertations

Sugarcane, being a complex aneu-polyploid, poses unique challenges to fine mapping of quantitative trait loci (QTL) controlling agronomic traits of interest. Genome-wide association studies (GWAS) could be a better alternative to identify molecular markers associated with specific traits due to high linkage disequilibrium in sugarcane. In the first study, marker-trait associations (MTAs) were evaluated for three sucrose traits, Brix, total recoverable sugar (TRS), and percent sucrose on 48 elite and historic Louisiana breeding clones using 1,062 alleles. These sucrose traits were highly correlated (P-value < 0.0001) at >0.96. TASSEL 5.1 and JMP Genomics 8.0 were compared with eight models run in each program. …

Soybean Response To Dicamba: Associated Injury Criteria And Development Of A Model To Predict Yield Loss, Matthew Ryan Foster

LSU Doctoral Dissertations

In research conducted using indeterminate soybean [Glycine max (L.) Merr.], fourteen injury criteria observed following dicamba at 0.6 to 280 g ae ha^-1 (1/1000 to ½ of 560 g ha^-1 use rate) were rated using a scale of 0= no injury, 1= slight, 2= slight to moderate, 3= moderate, 4= moderate to severe, and 5= severe. Greatest crop injury 15 d after treatment (DAT) was observed following dicamba applied at 0.6 to 4.4 g ha^-1 at V3/V4 for upper canopy pale leaf margins (3.8 to 4.2) and at R1/R2 for terminal leaf cupping (4.1 to 5.0) …

Effect Of Evapotranspiration Rate On Almond Yield In California, Dafne Isaac Serrano

Master's Theses

Since 2011, California has been under drought conditions. These conditions have not only affected water availability for farmers, but also production. California’s second most valuable crop, almonds, has been affected by drought conditions. This study used three models (Model 1-3) to describe almond yield variability from year to year and almond yield variability within a year in Kern County, CA. The study evaluated 185 almond farms that were classified in three locations (east side, west side and north west side). The years of the study were 2011 (wet year) and 2013-2015 (drought condition years). Model 1 determined a functional regression …

Identification Of Quantitative Trait Loci (Qtl) For Tolerance To Metribuzin In Soft Red Winter Wheat (Triticum Aestivum L.), Hugo Alfonso Anzueto Ponciano

LSU Master's Theses

Wheat is one of the world’s most important food crops and provides nearly 20% of the calories consumed. Wheat is the third most important crop after corn and rice on a global production scale. In Louisiana wheat harvest was about 6000 hectares in 2017. Wheat production is negatively affected by several biotic and abiotic factors including weather, diseases, and weeds. Metribuzin is a broad-spectrum herbicide commonly used in wheat because it is inexpensive and controls most of the common weeds in wheat fields. Metribuzin has benefits for the grower controlling weeds that might cause yield loss in varieties or lines …

Plant Stimuli-Responsive Biodegradable Polymers For The Use In Timed Release Fertilizer Coatings, Spencer Heuchan

Electronic Thesis and Dissertation Repository

The use of nitrogen-based fertilizers continues to accelerate with human population growth and increases in global food requirements. Enhanced efficiency fertilizers (EEFs) have been developed to improve the synchronization between nutrient supply and crop nutrient demand. However, many of the current controlled release fertilizers are coated with non-degradable polymers that contribute to accumulation of microplastics within ecosystems. This thesis describes research towards the development of a new class of fertilizer coatings using a self-immolative polymer known as poly (ethyl glyoxylate) (PEtG). PEtG itself does not have suitable properties to produce a viable coating but once blended with another degradable polyester …

The Effects Of Biochar And Nitrogen Stabilizers Application On Forage Crop Growth, Greenhouse Gas Emission And Soil Quality, Joseph Elias Rodrigues Mikhael

LSU Doctoral Dissertations

ABSTRACT

Forage systems are important for animal production. Nitrogen fertilization and herbicides use has led to a significant increase in forage production. Therefore, this study aimed to investigate the effects of biochar and N-(n-butyl) thiophosphoric triamide + dicyandiamide (NBPT+DCD) application on manure and urea fertilized soil by focusing on nitrogen fertilizer efficiency use, greenhouse gases emissions, microbial community, soil aggregate stability, and organic carbon functional groups. In addition, herbicides effect on greenhouse gases emission was assessed. Biochar and NBPT+DCD increased nitrogen use efficiency of both fertilizers managements and reduced the N₂O emissions following manure fertilization. However, NBPT+DCD was …

Band-Sowing With Hoeing For Weed Management In Organic Grains, Margaret R. Mccollough

Electronic Theses and Dissertations

Weeds remain the foremost production challenge for organic small grain growers in the Northeastern United States. Instead of sowing crops in narrow, single-line rows, band-sowing with inter-band hoeing is a cropping strategy that could provide superior weed control. In theory, band-sowing suppresses weeds in the intra-band zone by improving the spatial arrangement of the crop from that of typical rows to a more uniform pattern within the planted bands, maximizing interspecific and reducing intraspecific competition. Weeds in the inter-band zone are controlled by cultivating with aggressive sweeps; tine harrowing can target weeds in the intra- and inter-band zones.

Chapter one …

Evaluation Of Acetochlor And Other Very-Long-Chain Fatty Acid-Inhibiting Herbicides In Arkansas Rice, Michael E. Fogleman

Graduate Theses and Dissertations

The prevalence of herbicide resistance and lack of effective management options for controlling problematic weeds such as barnyardgrass and weedy rice in Arkansas rice production has led to exploration of alternative herbicide sites of action (SOA). Very-long-chain fatty acid (VLCFA)-inhibiting herbicides are not currently labeled for use in U.S. rice production but have been used with success in other row crops and in rice production in Asia. Based on preliminary research, rice tolerance and weed control were evaluated following various application timings and rates of acetochlor and pethoxamid, in addition to several other VLCFA-inhibiting herbicides. Rice tolerance to acetochlor was …

Dissection Of Soil Waterlogging Tolerance In Soft Red Winter Wheat Using Genomic Approaches, Marlovi Andrea Acuna-Galindo

Graduate Theses and Dissertations

Genomic methods including genome wide association analysis (GWAS), genomic selection (GS) and RNA-seq allow for faster selection of superior breeding lines and for identification and resolution of candidate genes. A panel of 240 soft red winter wheat (Triticum aestivum L.) cultivars and breeding lines were subjected to soil waterlogging stress over two seasons at Stuttgart, AR and St. Joseph, LA, US. Total concentrations of P, K, Ca, Mg, Mn, Fe, Al, B, Cu, Na, S and Zn were determined in wheat shoots post-waterlogging using inductively coupled plasma spectroscopy. Yield components kernel number per spike (KNPS), kernel weight per spike (KWS) …

Association Mapping And Genomic Selection For Yield And Agronomic Traits In Soft Winter Wheat, Dennis Bulusan Lozada

Graduate Theses and Dissertations

Tools such as genome-wide association study (GWAS) and genomic selection (GS) have expedited the development of crops with improved genetic potential. While GWAS aims to identify significant markers associated with a trait of interest, the goal of GS is to utilize all marker effects to predict the performance of new breeding lines prior to testing. A GWAS for grain yield (GY), yield components, and agronomic traits was conducted using a diverse panel of 239 soft winter wheat (SWW) lines evaluated in eight site-years in Arkansas and Oklahoma. Broad sense heritability of GY (H2=0.48) was moderate compared to other traits including …

Methane Emissions From Rice Production On A Silt-Loam Soil In Arkansas, Joshua Jeffry Humphreys

Graduate Theses and Dissertations

Methane (CH4) emissions from rice (Oryza sativa L.) production are a source of concern in the environmental and agricultural communities. New and/or revised agronomic methodologies will be needed to identify production practice combinations that reduce CH4 emissions without decreasing yields. The objective of this multi-year study was to evaluate the effects of water management (i.e., full-season flood and mid-season drain) (2015), cultivar (i.e., pure-line cultivar ‘LaKast’ and the RiceTec hybrid “XP753”) (2015), soil organic matter (SOM) concentration (2016), and tillage [conventional tillage (CT) and no-tillage (NT)] and urea-based fertilizers [N-(n-butyl) thiophosphoric triamide (NBPT)-coated urea and non-coated urea] (2017) on CH4 …

Effect Of Allelic Variation In Rht Loci On Plant Height And Grain Yield Of Soft Red Winter Wheat (Triticum Aestivum L.), Habib Hayat

Graduate Theses and Dissertations

Plant height in wheat (Triticum aestivum L.) is controlled in large part by two major Rht genes, Rht-B1 and Rht-D1, which pleiotropically impact lodging and grain yield. Prior to the Green Revolution, wheat varieties contained only ‘wild-type’ Rht alleles (Rht-B1a and Rht-D1a) and were tall and prone to lodging. Introgression of a semi-dominant mutation at either of these two loci (Rht-B1b or Rht-D1b) results in a semi-dwarf phenotype and reduced plant height. When combined (Rht-B1b and Rht-D1b) an extremely short double-dwarf phenotype is observed. The objective of this study was to determine the impact of allelic variation in Rht-B1 and …