Plant Pathology Commons^™

Dynamics Of Small Rna Profiles Of Virus And Host Origin In Wheat Cultivars Synergistically Infected By Wheat Streak Mosaic Virus And Triticum Mosaic Virus: Virus Infection Caused A Drastic Shift In The Endogenous Small Rna Profile, Satyanarayana Tatineni, Jean-Jack M. Riethoven, Robert A. Graybosch, Roy French, Amitava Mitra

Department of Plant Pathology: Faculty Publications

Co-infection of wheat (Triticum aestivum L.) by Wheat streak mosaic virus (WSMV, a Tritimovirus) and Triticum mosaic virus (TriMV, a Poacevirus) of the family Potyviridae causes synergistic interaction. In this study, the effects of the synergistic interaction between WSMV and TriMV on endogenous and virus-derived small interfering RNAs (vsiRNAs) were examined in susceptible (‘Arapahoe’) and temperature-sensitive resistant (‘Mace’) wheat cultivars at 18 degrees C and 27 degrees C. Single and double infections in wheat caused a shift in the profile of endogenous small RNAs from 24 nt being the most predominant in healthy plants to 21 nt …

Quantification Of Yield Loss Caused By Triticum Mosaic Virus And Wheat Streak Mosaic Virus In Winter Wheat Under Field Conditions, E. Byamukama, S. N. Wegulo, S. Tatineni, G. L. Hein, R. A. Graybosch, P. Stephen Baenziger, R. French

Department of Plant Pathology: Faculty Publications

Triticum mosaic virus (TriMV) and Wheat streak mosaic virus (WSMV) infect winter wheat (Triticum aestivum) in the Great Plains region of the United States. The two viruses are transmitted by wheat curl mites (Aceria tosichella), which also transmit High Plains virus. In a field study conducted in 2011 and 2012, winter wheat cultivars Millennium (WSMV-susceptible) and Mace (WSMV-resistant) were mechanically inoculated with TriMV, WSMV, TriMV+WSMV, or sterile water at the two-leaf growth stage. Chlorophyll meter (soil plant analysis development [SPAD]) readings, area under the SPAD progress curve (AUSPC), grain yield (=yield), yield components (spikes/m², …

Studies On Sensitivity Reduction In Solo And Mixture Treatments And Fungicide-Induced Mutagenesis In Monilinia Fructicola, Guido Schnabel, F. Chen, Sydney E. Everhart, W. C. Bridges, X. Liu

Department of Plant Pathology: Faculty Publications

Three fungicide-sensitive Monilinia fructicola isolates were exposed in weekly transfers of mycelia to a dose gradient of a DMI and a QoI fungicide (azoxystrobin) in solo or mixture treatments and fungicide sensitivity as well as genetic changes were assessed. Isolates showed a faster reduction in sensitivity (higher resistance factors) to azoxystrobin than to SYP-Z048; this process was slower in the mixture treatment. The decrease of fungicide sensitivity was not a heritable trait. Genomic mutagenesis at 8 of 15 microsatellite loci was evidenced in one of three isolates tested after exposure to azoxystrobin. These non-coding regions of the genome either showed …

Methods For Using Cryptococcus Flavescens Strains For Biological Control Of Fusarium Head Blight, Brian B. Mcspadden Gardener, Pierce Anderson Paul, Michael J. Boehm, Xiaoqing Rong, David Schisler

Department of Plant Pathology: Faculty Publications

Disclosed are methods of identifying subspecies of Cryptococcus flavescens and methods of treating or suppressing Fusarium head blight with the different Cryptococcus flavescens species. In particular, two genotypes, Genotypes A and B, were identified using the disclosed real time PCR technique. The following Cryptococcus flavescens strains were identified as being either Genotype A or B and as being able to suppress Fusarium head blight: NRRLY-7373, YB-601, YB-602, Y-7377, Y-7372, Y-7375, Y-7374, Y-7376, YB-328, Y-7379, and YB-744.

Smut Diseases Of Corn, Tamra Jackson-Ziems

Department of Plant Pathology: Faculty Publications

This NebGuide describes the two smut diseases of corn in Nebraska, common smut and head smut, including their symptoms, life cycle, and management.

Two smut diseases of corn occur in Nebraska (Figure 1). Despite their similar appearance, their disease cycles are very different, as are their yield loss potential and management strategies (Table 1).

Corn Disease Update, Tamra A. Jackson-Ziems, Thomas W. Dorn

Department of Plant Pathology: Faculty Publications

The growing conditions during 2013 contributed to several disease problems in corn. Cold and wet conditions early led to development of seedling diseases. The hail-damaged corn in many areas of the state during the season led to ear rot diseases that were exacerbated by cooler conditions and increased grain moisture. Diseases have been a problem throughout the season and could extend beyond harvest into storage of some corn.

Common Stalk Rot Diseases Of Corn, Tamra A. Jackson-Ziems, Jennifer M. Rees, Robert M. Harveson

Department of Plant Pathology: Faculty Publications

Extension Circular 1898 (EC1898)

Stalk rot diseases of corn are common, occurring in every field to some extent. Each year stalk rot diseases cause about 5 percent yield loss. Under some conditions, losses can exceed 10–20 percent, and in isolated areas losses have been as high as 100 percent. Stalk rot diseases reduce yield both directly and indirectly. Plants with prematurely rotted stalks produce lightweight, poorly filled ears because of the plant’s limited access to carbohydrates during grain fill. Infected stalks are converted from sturdy, solid rods to hollow tubes as the stalk pith pulls away from the outer rind, …

Disease Profiles: Nematodes Of Nebraska Field Crops, Tamra A. Jackson-Ziems, Loren J. Giesler, Robert M. Harveson, Kevin A. Korus, Stephen N. Wegulo

Department of Plant Pathology: Faculty Publications

Extension Circular 1908 (EC1908).

Many species of plant parasitic nematodes affect Nebraska field crops. Some of the more common and/or damaging nematodes are described here. The extent of crop injury depends on the species present, their abundance, and other crop stresses. Diagnosis of nematode injury is difficult because most plant parasitic nematodes can’t be seen with the naked eye and the type and severity of symptoms can vary widely. Most nematodes cause general symptoms that are not diagnostic and may mimic symptoms caused by other biotic or abiotic problems, such as herbicide damage, nutrient imbalances, water stress, and insect feeding. …

Plant Defense Suppression Is Mediated By A Fungal Sirtuin During Rice Infection By Magnaporthe Oryzae, Jessie Fernandez, Margarita Marroquin-Guzman, Renu Nandakumar, Sara Shijo, Kathryn M. Cornwell, Gang Li, Richard Wilson

Department of Plant Pathology: Faculty Publications

Crop destruction by the hemibiotrophic rice pathogen Magnaporthe oryzae requires plant defense suppression to facilitate extensive biotrophic growth in host cells before the onset of necrosis. How this is achieved at the genetic level is not well understood. Here, we report that a M. oryzae sirtuin, MoSir2, plays an essential role in rice defense suppression and colonization by controlling superoxide dismutase (SOD) gene expression. Loss of MoSir2 function in Δsir2 strains did not affect appressorial function, but biotrophic growth in rice cells was attenuated. Compared to wild type, Δsir2 strains failed to neutralize plant-derived reactive oxygen species (ROS) …

A Global Database Of Soil Nematode Abundance And Functional Group Composition, Johan Hoogen, Peter Mullen, 72 Other Scholars

Department of Plant Pathology: Faculty Publications

As the most abundant animals on earth, nematodes are a dominant component of the soil community. They play critical roles in regulating biogeochemical cycles and vegetation dynamics within and across landscapes and are an indicator of soil biological activity. Here, we present a comprehensive global dataset of soil nematode abundance and functional group composition. This dataset includes 6,825 georeferenced soil samples from all continents and biomes. For geospatial mapping purposes these samples are aggregated into 1,933 unique 1-km pixels, each of which is linked to 73 global environmental covariate data layers. Altogether, this dataset can help to gain insight into …

Effects Of Virus On Plant Fecundity And Population Dynamics, Holly R. Prendeville, Brigitte Tenhumberg, Diana Pilson

Brigitte Tenhumberg Papers

Microorganisms are ubiquitous and thought to regulate host populations. Although microorganisms can be pathogenic and affect components of fitness, few studies have examined their effects on wild plant populations. As individual traits might not contribute equally to changes in population growth rate, it is essential to examine the entire life cycle to determine how microorganisms affect host population dynamics. In this study, we used data from common garden experiments with plants from three Cucurbita pepo populations exposed to three virus treatments. These data were used to parameterize a deterministic matrix model, which allowed us to estimate the effect of virus …

Soil Microbial Community Distributions And Disease Suppressiveness In The Coastal Plain Of Georgia, Michael J. Sabula

College of Graduate Studies: Theses & Dissertations

This study compared the soil microbial communities of three vegetation types in the coastal plain of Georgia: 1. crop land actively in use for agricultural production, 2. transitional grassland in early stages of secondary succession, and 3. pristine unmanaged forest land. Microbial species diversity and quantities of microbial DNA were determined from each of these vegetation types at three separate locations near Statesboro, Georgia. Length heterogeneity PCR(LH-PCR) methods and subsequent analysis of fungal, bacterial, and metazoan communities by analysis of similarity (ANOSIM) revealed high within-group similarity by vegetation type, indicating land management intensity and vegetation cover is a strong determining …

The Effects Of Salinity On Pythium Disease Of Rice And Soybean, Terea Jeanette Stetina

Graduate Theses and Dissertations

Increasing salinity is an important factor limiting agricultural productivity worldwide. In addition to direct effects on growth and yield, diseases also may be affected. This study characterized the effects of soil salinity on seedling disease of soybean and rice caused by Pythium spp. Controlled environment experiments on soybean used two cultivars which differed in chloride tolerance and soil treated with a CaCl₂ solution to create a range of electrical conductivity (EC) levels. For soybean, soil was either not infested or infested with Pythium sylvaticum or P. aphanidermatum (pathogenic to soybean), or P. oligandrum (not pathogenic to soybean). Twenty-one days …

Effects Of Rain And Simulated Rain On Deoxynivalenol Levels In Grain And Chaff Of Winter Wheat With Fusarium Head Blight, Manoj Kumar Pun

Graduate Theses and Dissertations

Wheat grain affected by Fusarium head blight (FHB) contains the mycotoxin deoxynivalenol (DON) that is harmful to humans and animals. Reducing the amount of DON in grain is the goal of management practices for FHB so it is important to understand the factors affecting DON in grain. Some studies on the effects of late-season moisture found increases in DON while others found decreases due to leaching. The objectives of this study were to determine effects of late-season rain and misting on DON concentration in wheat spike tissues and to quantify the amount of DON leached from spikes. Field experiments were …

Phytophthora Foliage Blight Of Garden Phlox: Phytophthora Nicotianae On Phlox Paniculata, Daniel Drechsler

All Theses

Phytophthora foliage blight of garden phlox (Phlox paniculata ) - caused by Phytophthora nicotianae - is a devastating disease that has been seen consistently in nursery production facilities in South Carolina. However, this disease has not been characterized previously. This project was composed of three separate studies, each of which followed one of the three major components of the disease triangle (i.e., the synchronous occurrence of a susceptible host and a virulent pathogen within a conducive environment) to investigate the pathogenicity of P. nicotianae on P. paniculata . In one study, the efficacies of three inoculation methodologies to cause …

Impact Of Wheat Streak Mosaic Virus And Triticum Mosaic Virus On Transmission By Aceria Tosichella Keifer (Eriophyidae) And Virus Epidemiology In Wheat, Camila F. De Oliveira

Department of Entomology: Dissertations, Theses, and Student Research

The wheat curl mite (WCM), Aceria tosichella Keifer, transmits a complex of viruses, Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV) and Wheat mosaic virus (WMoV), to wheat, Triticum aestivum, in the Great Plains. Co-infection of wheat by these viruses is frequently observed, increasing disease severity and yield loss.

Current genetic work classifies WCM populations into two genotypes, Type 1 and Type 2. It has been shown that different mite genotypes are able to transmit viruses at varying rates. WCM-virus relations are very specific and can impact vector biology. In this study, the primary objective was to determine …

Managing Fusarium Wilt In Watermelon Production, Zachary Snipes

All Theses

Fusarium wilt of watermelon, caused by Fusarium oxysporum f. sp. niveum , was first described in 1894 in South Carolina and Georgia and has become a limiting factor in watermelon production worldwide. In recent years, restriction on use of the soil fumigant methyl bromide and the recent development of more virulent races of Fusarium oxysporum f. sp. niveum has created a critical need for alternative management techniques. In 2011-2013 field experiments were designed to evaluate the efficacy of incorporating a cover crop of hairy vetch into the soil to manage Fusarium wilt. Colony-forming units (CFU) of Fusarium oxysporum were sampled …

Molecular And Biochemical Mechanisms Of Pathogenesis In The Maize Foliar Pathogen Cercospora Zeae-Maydis, Winfred-Peck Dorleku

Graduate Theses and Dissertations

GLS is a serious foliar disease of maize, a major staple crop grown commercially in the USA for both human and animal feed production, and increasingly, for ethanol production. The disease is caused by two Cercospora species, C. zeae-maydis and C. zeina, both of which infect maize in the USA and in other parts of the world, with yield losses potentially greater than 50%, depending on local conditions. In culture, C. zeae-maydis produces a phytotoxic, host non-specific perylenequinone, cercosporin, and abscisic acid (ABA), for which there is no known pathological or physiological function in the fungus. Experimental evidence indicates …

Arabidopsis 56–Amino Acid Serine Palmitoyltransferase- Interacting Proteins Stimulate Sphingolipid Synthesis, Are Essential, And Affect Mycotoxin Sensitivity, Athen N. Kimberlin, Saurav Majumder, Gongshe Han, Ming Chen, Rebecca E. Cahoon, Julie M. Stone, Teresa M. Dunn, Edgar B. Cahoon

Center for Plant Science Innovation: Faculty Publications

Maintenance of sphingolipid homeostasis is critical for cell growth and programmed cell death (PCD). Serine palmitoyltransferase (SPT), composed of LCB1 and LCB2 subunits, catalyzes the primary regulatory point for sphingolipid synthesis. Small subunits of SPT (ssSPT) that strongly stimulate SPT activity have been identified in mammals, but the role of ssSPT in eukaryotic cells is unclear. Candidate Arabidopsis thaliana ssSPTs, ssSPTa and ssSPTb, were identified and characterized. Expression of these 56–amino acid polypeptides in a Saccharomyces cerevisiae SPT null mutant stimulated SPT activity from the Arabidopsis LCB1/LCB2 heterodimer by >100-fold through physical interaction with LCB1/LCB2. ssSPTa transcripts were …

Response Of Near-Isogenic Sorghum Lines, Differing At The P Locus For Plant Colour, To Grain Mould And Head Smut Fungi, Deanna L. Funnell-Harris, L. K. Prom, Scott E. Sattler, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Leaves and stalks of many sorghum genotypes accumulate dark red or purple pigments upon wounding while some plants, called ‘tan,’ do not. Grains with unpigmented ‘white’ pericarps grown on tan plants are more desirable for food. The hypothesis tested was that pigments in plants protected grain against the panicle diseases grain mould and head smut. Near-isogenic tan or purple plant color genotypes with white grain were planted at Lincoln and Ithaca, NE and Corpus Christi, TX. The field grown grain was plated onto semi-selective media to detect the presence of grain colonisation by mould genera Alternaria, Fusarium and Curvularia. …