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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. …

Wheat Streak Mosaic Virus Infects Systemically Despite Extensive Coat Protein Deletions: Identification Of Virion Assembly And Cell-To-Cell Movement Determinants, Satyanarayana Tatineni, Frank A. Kovacs, Roy C. French

Department of Plant Pathology: Faculty Publications

Viral coat proteins function in virion assembly and virus biology in a tightly coordinated manner with a role for virtually every amino acid. In this study, we demonstrated that the coat protein (CP) of Wheat streak mosaic virus (WSMV) (genus Tritimovirus; family Potyviridae) is unusually tolerant of extensive deletions with continued virion assembly and/or systemic infection. A series of deletion and point mutations were created in the CP cistron of wild-type and/or GFP-tagged WSMV and examined the effects of these mutations on cell-to-cell and systemic transport and virion assembly of WSMV. Mutants with overlapping deletions comprising N-terminal amino …

Calmodulin-Mediated Signal Transduction Pathways In Arabidopsis Are Fine-Tuned By Methylation, Joydeep Banerjee, Roberta Magnani, Meera Nair, Lynnette M. Dirk, Seth Debolt, Indu B. Maiti, Robert L. Houtz

Department of Plant Pathology: Faculty Publications

Calmodulin N-methyltransferase (CaM KMT) is an evolutionarily conserved enzyme in eukaryotes that transfers three methyl groups to a highly conserved lysyl residue at position 115 in calmodulin (CaM). We sought to elucidate whether the methylation status of CaM plays a role in CaM-mediated signaling pathways by gene expression analyses of CaM KMT and phenotypic characterization of Arabidopsis thaliana lines wherein CaM KMT was overexpressed (OX), partially silenced, or knocked out. CaM KMT was expressed in discreet spatial and tissue-specific patterns, most notably in root tips, floral buds, stamens, apical meristems, and germinating seeds. Analysis of transgenic plants with genetic dysfunction …

Quantitative Relationship Of Soil Texture With The Observed Population Density Reduction Of Heterodera Glycines After Annual Corn Rotation In Nebraska, Oscar Perez-Hernandez, Loren J. Giesler

Department of Plant Pathology: Faculty Publications

Soil texture has been commonly associated with the population density of Heterodera glycines (soybean cyst nematode: SCN), but such an association has been mainly described in terms of textural classes. In this study, multivariate analysis and a generalized linear modeling approach were used to elucidate the quantitative relationship of soil texture with the observed SCN population density reduction after annual corn rotation in Nebraska. Forty-five commercial production fields were sampled in 2009, 2010, and 2011 and SCN population density (eggs/100 cm3 of soil) for each field was determined before (Pi) and after (Pf) annual corn rotation from ten 3 3 …

Metagenomic Profiling Reveals Lignocellulose Degrading System In A Microbial Community Associated With A Wood-Feeding Beetle, Erin D. Scully, Scott M. Geib, Kelli Hoover, Ming Tien, Susannah G. Tringe, Kerrie W. Barry, Tijana Glavina Del Rio, Mansi Chovatia, Joshua R. Herr, John E. Carlson

Department of Plant Pathology: Faculty Publications

The Asian longhorned beetle (Anoplophora glabripennis) is an invasive, wood-boring pest that thrives in the heartwood of deciduous tree species. A large impediment faced by A. glabripennis as it feeds on woody tissue is lignin, a highly recalcitrant biopolymer that reduces access to sugars and other nutrients locked in cellulose and hemicellulose. We previously demonstrated that lignin, cellulose, and hemicellulose are actively deconstructed in the beetle gut and that the gut harbors an assemblage of microbes hypothesized to make significant contributions to these processes. While lignin degrading mechanisms have been well characterized in pure cultures of white rot basidiomycetes, little …

Identification Of Species Of Botryosphaeriaceae Causing Bot Gummosis In Citrus In California, A.O. Adesemoye, J.S. Mayorquin, D.H. Wang, M. Twizeyimana, S.C. Lynch, Akif Eskalen

Department of Plant Pathology: Faculty Publications

Members of the Botryosphaeriaceae family are known to cause Bot gummosis on many woody plants worldwide. To identify pathogens associated with Bot gummosis on citrus in California, scion and rootstock samples were collected in 2010 and 2011 from five citrusgrowing counties in California. Symptoms observed on citrus included branch cankers, dieback, and gumming. Various fungal species were recovered from necrotic tissues of branch canker and rootstock samples. Species were identified morphologically and by phylogenetic comparison as ‘Eureka’ lemon, ‘Valencia’, ‘Washington Navel’, ‘Fukumoto’, grapefruit, ‘Satsuma’, and ‘Meyer’ lemon. Species were identified morphologically and by phylogenetic comparison of the complete sequence of …

Citrus Tristeza Virus-Host Interactions, W. O. Dawson, S. M. Garnsey, Satyanarayana Tatineni, S. Y. Folimonova, S. J. Harper, S. Gowda

Department of Plant Pathology: Faculty Publications

Citrus tristeza virus (CTV) is a phloem-limited virus whose natural host range is restricted to citrus and related species. Although the virus has killed millions of trees, almost destroying whole industries, and continually limits production in many citrus growing areas, most isolates are mild or symptomless in most of their host range. There is little understanding of how the virus causes severe disease in some citrus and none in others. Movement and distribution of CTV differs considerably from that of well-studied viruses of herbaceous plants where movement occurs largely through adjacent cells. In contrast, CTV systemically infects plants mainly by …

Uromyces Appendiculatus In Honduras: Pathogen Diversity And Host Resistance Screening, Maricelis Acevedo, James R. Steadman, Juan C. Rosas

Department of Plant Pathology: Faculty Publications

Bean rust, caused by the fungus Uromyces appendiculatus, is a major constraint for common bean production worldwide. Virulence of U. appendiculatus collected from wild and cultivated Phaseolus spp. was examined in 28 locations across Honduras. Host accessions representing wild and domesticated Phaseolus spp. collected at the same sampling locations were evaluated for resistance against U. appendiculatus. In total, 91 pathotypes were identified from 385 U. appendiculatus isolates according to their virulence on each of the 12 host differentials. No significant difference in pathogen total virulence, measured as the mean disease score, was found between locations. However, significant differences …

Neofusicoccum Luteum As A Pathogen On Tejocote (Crataegus Mexicana), Anthony O. Adesemoye, Joey S. Mayorquin, Akif Eskalen

Department of Plant Pathology: Faculty Publications

Tejocote (Crataegus mexicana), a small pome crab-apple-like fruit, is becoming economically important in California with increasing production, so consideration of diseases that hinder the yield is important. Diseased trees of tejocote were observed in four orchards of Riverside and San Diego Counties of California. Ten symptomatic/asymptomatic samples were studied from each of the orchards. Five most frequently isolated fungi were identified on the basis of morphological characters and sequence data of the internal transcribed spacer ITS1-5.8SITS2 and partial β-tubulin gene. Three isolates were identified as Neofusicoccum luteum and two as Phomopsis sp. Pathogenicity tests were conducted by inoculating …

Strong Genetic Differentiation Between North American And European Populations Of Phytophthora Alni Subsp. Uniformis, Jaime Aguayo, Gerard C. Adams, Fabien Halkett, Mursel Catal, Claude Husson, Zoltán Á. Nagy, Everett M. Hansen, Benoît Marçais, Pascal Frey

Department of Plant Pathology: Faculty Publications

Alder decline caused by Phytophthora alni has been one of the most important diseases of natural ecosystems in Europe during the last 20 years. The emergence of P. alni subsp. alni—the pathogen responsible for the epidemic—is linked to an interspecific hybridization event between two parental species: P. alni subsp. multiformis and P. alni subsp. uniformis. One of the parental species, P. alni subsp. uniformis, has been isolated in several European countries and, recently, in North America. The objective of this work was to assess the level of genetic diversity, the population genetic structure, and the putative reproduction …

Variants Of Triticum Mosaic Virus Isolated From Wheat In Colorado Show Divergent Biological Behavior, Dallas L. Seifers, Satyanarayana Tatineni, Roy French

Department of Plant Pathology: Faculty Publications

Triticum mosaic virus (TriMV) is a recently discovered virus infecting wheat. We compared Colorado isolates C10-492 and C11-775 with the 06-123 isolate. Comparisons were made using enzyme-linked immunosorbent assay (ELISA), infectivity assay, host range, dry weight (DW), inoculation of ‘Mace’ wheat with temperature-sensitive resistance to Wheat streak mosaic virus, and the deduced amino acid sequence of the coat proteins (CP) and P1 proteins. Both C10-492 and C11-775 infected ‘Gallatin’ barley and, when compared with 06-123, had significantly reduced ELISA values and virus titers in wheat. Both Colorado isolates caused symptomless infections in Mace, whereas 06- 123 caused mosaic symptoms. …

Modifying Lignin To Improve Bioenergy Feedstocks: Strengthening The Barrier Against Pathogens?, Scott E. Sattler, Deanna L. Funnell-Harris

Department of Plant Pathology: Faculty Publications

Lignin is a ubiquitous polymer present in cell walls of all vascular plants, where it rigidifies and strengthens the cell wall structure through covalent cross-linkages to cell wall polysaccharides. The presence of lignin makes the cell wall recalcitrant to conversion into fermentable sugars for bioenergy uses.Therefore, reducing lignin content and modifying its linkages have become major targets for bioenergy feedstock development through either biotechnology or traditional plant breeding. In addition, lignin synthesis has long been implicated as an important plant defense mechanism against pathogens, because lignin synthesis is often induced at the site of pathogen attack. This article explores the …

Isolation And Characterization Of The Grain Mold Fungi Cochliobolus And Alternaria Spp. From Sorghum Using Semiselective Media And Dna Sequence Analyses, Deanna L. Funnell-Harris, Louis K. Prom, Jeffrey F. Pedersen

Department of Plant Pathology: Faculty Publications

Mold diseases, caused by fungal complexes including Alternaria, Cochliobolus, and Fusarium species, limit sorghum grain production. Media were tested by plating Fusarium thapsinum, Alternaria sp., and Curvularia lunata, individually and competitively. Dichloran chloramphenicol rose bengal (DRBC) and modified V8 juice (ModV8) agars, found to be useful, were compared with commonly used agar media, dichloran chloramphenicol peptone (DCPA) and pentachloronitrobenzene (PCNB). Radial growth, starting with mycelia or single-conidia and hyphal tips, demonstrated an effect of media. For isolation of grain fungi, DRBC and ModV8 were similar or superior to DCPA and PCNB. When seedlings were inoculated with conidia of C. lunata, …

Efficacy Of Foliar Fungicides And Application Timing Of Stratego Yld On Field Corn In Nebraska, 2013, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. Corn hybrid NK ‘N68B’, rating of “fair” (7 out of 9) for gray leaf spot (GLS), not rated for common rust (CR), and “excellent” (2 out of 9) for southern rust (SR), was planted on 15 May in 30-in. rows at a target population of 31,763 plants/A. The trial area was disked with corn as the previous year’s crop. Nine treatments and a nontreated control were replicated six times in a randomized complete block design. Each plot was four …

Evaluation Of Foliar Fungicide And Application Timing On Field Corn Following Hail Event At Scal In Nebraska, 2013, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE to determine the potential effect of foliar fungicides and their application timing on lodging and yield after a late season hail event. Novartis corn hybrid N6800 GT with CruiserMaxx 250 seed treatment was planted on 24 May in 30 in. rows with a target population of 32,000 plants/A. Force 3G (4 oz/1,000 row ft) was applied in-furrow at planting. Lexar (3 qt/A) + Roundup UltraMax (32 fl oz/A) was applied on 5 Jun. The trial area had corn as …

Efficacy Evaluation Of Fortix And Headline Amp Application Timing In Field Corn In Nebraska, 2013, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. Corn hybrid NK ‘N68B’, rating of “fair” (7 out of 9) for gray leaf spot (GLS), not rated for common rust (CR), and “excellent” (2 out of 9) for southern rust (SR), was planted on 15 May in 30-in. rows at a target population of 31,763 plants/A. The trial area was disked with corn as the previous year’s crop. Nine treatments were replicated six times in a randomized complete block design. Each plot was four rows (10 ft) wide …

Evaluation Of Application Timing On Stratego Yld Efficacy Of Field Corn In Nebraska, 2012, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide timing trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 64-83, rating of “good” (6 out of 9) for gray leaf spot (GLS), “very good” (4 out of 9) for common rust (CR), and “good” (5 out of 9) for southern rust (SR), was planted on 26 Apr in 30-in. rows at a target population of 30,600 plants/A. The trial area was disked with corn as the previous year’s crop. Five foliar fungicide treatments and a non-treated control were replicated six times in a randomized complete …

Efficacy Evaluation Of Foliar Fungicide Products On Diseases Of Field Corn In Nebraska, 2012, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 64-83, rating of “good” (6 out of 9) for gray leaf spot (GLS), “very good” (4 out of 9) for common rust (CR), and “good” (5 out of 9) for southern rust (SR), was planted on 26 Apr in 30-in. rows at a target population of 30,600 plants/A. The trial area was disked with soybean as the previous year’s crop. Five foliar fungicide treatments and a nontreated control were replicated six times in a randomized complete …

Efficacy Evaluation Of Foliar Fungicide Application Timing In Field Corn In Nebraska, 2012, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 64-83, rating of “good” (6 out of 9) for gray leaf spot (GLS), “very good” (4 out of 9) for common rust (CR), and “good” (5 out of 9) for southern rust (SR), was planted on 26 Apr in 30-in. rows at a target population of 30,600 plants/A. The trial area was disked with corn as the previous year’s crop. Six foliar fungicide treatments and a non-treated control were replicated six times in a randomized complete …

Major Fusarium Diseases On Corn, Wheat, And Soybeans In Nebraska, Bo Liu, Loren J. Giesler, Tamra A. Jackson-Ziems, Stephen N. Wegulo, Robert M. Harveson

Department of Plant Pathology: Faculty Publications

Fusarium species have been associated with many important diseases of corn, wheat, and soybean, causing significant yield loss in Nebraska; some produce mycotoxins that are harmful to both human and animal consumers. These pathogens are very common in agricultural field soil across the Midwest and cause numerous types of diseases.

What’S New In Plant Pathology, Loren Giesler, Tamra A. Jackson-Ziems, Casey Schleicher, Kevin Korus

Department of Plant Pathology: Faculty Publications

Extension Plant Pathology Team Update

Plant and Pest Diagnostic Clinic Update

Disease Management Products

Table 1. Foliar Fungicide Label Updates

Table 2. New Products

Impacts Of Drought On Disease Development And Management, Stephen Wegulo, Loren Giesler, Robert Harveson, Tamra A. Jackson-Ziems, Bo Liu, Kevin Korus

Department of Plant Pathology: Faculty Publications

Drought conditions such as those that occurred in Nebraska in 2012 can impact the development of plant diseases. In general drought slows down or prevents the development of plant diseases caused by pathogens that thrive under moist conditions. However, some diseases are favored by drought. This is because when plants are stressed due to lack of moisture or excessive heat, they become more susceptible to these diseases. This article presents examples of diseases of agronomic crops favored by drought and how to manage them. Data are provided on the effect of dry or wet conditions on the profitability of applying …

Occurrence And Distribution Of Triticum Mosaic Virus In The Central Great Plains, E. Byamukama, D. L. Seifers, G. L. Hein, E. De Wolf, N. A. Tisserat, M. A. C. Langham, L. E. Osborne, A. Timmerman, S. N. Wegulo

Department of Plant Pathology: Faculty Publications

Wheat curl mite (WCM)-transmitted viruses—namely, Wheat streak mosaic virus (WSMV), Triticum mosaic virus (TriMV), and the High Plains virus (HPV)—are three of the wheat-infecting viruses in the central Great Plains of the United States. TriMV is newly discovered and its prevalence and incidence are largely unknown. Field surveys were carried out in Colorado, Kansas, Nebraska, and South Dakota in spring and fall 2010 and 2011 to determine TriMV prevalence and incidence and the frequency of TriMV co-infection with WSMV or HPV in winter wheat. WSMV was the most prevalent and was detected in 83% of 185 season–counties (= s-counties), 73% …

Product Comparison Of Foliar Fungicide Efficacy On Diseases Of Field Corn In Nebraska, 2013, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide efficacy trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. Corn hybrid NK ‘N68B’, rating of “fair” (7 out of 9) for gray leaf spot (GLS), not rated for common rust (CR), and “excellent” (2 out of 9) for southern rust (SR), was planted on 15 May in 30-in. rows at a target population of 31,763 plants/A. The trial area was disked with corn as the previous year’s crop. Eight treatments and a non-treated control were replicated six times in a randomized complete block design. Each plot was four rows …

Product Comparison Of Foliar Fungicide Efficacy On Diseases Of Field Corn In Nebraska, 2012, C. M. Schleicher, T. A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

A foliar fungicide comparison trial was conducted at the University of Nebraska-Lincoln South Central Agricultural Laboratory near Clay Center, NE. DeKalb corn hybrid DKC 64-83, rating of “good” (6 out of 9) for gray leaf spot (GLS), “very good” (4 out of 9) for common rust (CR), and “good” (5 out of 9) for southern rust (SR), was planted on 26 Apr in 30-in. rows at a target population of 30,600 plants/A. The trial area was disked with corn as the previous year’s crop. Eleven treatments and a non-treated control were replicated six times in a randomized complete block design. …

Grain Storage Management To Minimize Mold And Mycotoxins, Thomas W. Dorn, Tamra A. Jackson-Ziems

Department of Plant Pathology: Faculty Publications

As most dryland corn producers are aware, the dry and hot growing season in 2012 resulted in reduced corn yields with moderately lower test weights. Along with the reduced test weights are concerns about potential mycotoxin contamination in the drought-stressed grain.

The only way to know for sure if there are mycotoxins in your grain and which specific mycotoxins are present is to collect representative grain samples and have them tested by a certified laboratory.

Many species of fungi can cause ear rot diseases and molding of grain. Most of these fungi become associated with the grain in the field …

Spatio-Temporal Patterns Of Pre-Harvest Brown Rot Epidemics Within Individual Peach Tree Canopies, Sydney E. Everhart, A. Askew, L. Seymour, H. Scherm

Department of Plant Pathology: Faculty Publications

Tree canopies are architecturally complex and pose several challenges for measuring and character-izing spatial patterns of disease. Recently developed methods for fine-scale canopy mapping and three-dimensional spatial pattern analysis were applied in a 3-year study to characterize spatio-temporal development of pre-harvest brown rot of peach, caused by Monilinia fructicola, in 13 trees of different maturity classes. We observed a negative correlation between an index of disease aggregation and disease incidence in the same tree (r = −0.653, P < 0.0001), showing that trees with higher brown rot incidence had lower aggregation of affected fruit in their canopies. Significant (P ≤ 0.05) within-canopy aggregation among symptomatic fruit was most pronounced for early-maturing cultivars and/or early in the epidemic. This is consistent with the notion of a greater importance of localized, within-tree sources of inoculum at the beginning of the epidemic. Four of five trees having >10 blossom blight symptoms per tree showed a significant positive spatial association of pre-harvest fruit rot to blossom blight within the …

Foliar Treatment Timing Trials For Management Of Goss’S Bacterial Wilt And Blight Of Field Corn In Nebraska, 2012, H. H. Oser, T. A. Jackson-Ziems, J. L. Brungardt

Department of Plant Pathology: Faculty Publications

One experimental hybrid, DKC 37-38, with a Goss’s wilt rating of 7 out of 9 (“poor”), was planted at the University of Nebraska Agricultural Research and Development Center (ARDC) near Mead, NE on 2 Jun. Corn was planted at 32,000 seeds per acre in a field that received minimum tillage. The previous year’s crop was corn. Each plot was 30 ft long and contained two rows spaced 30-in. apart. Alleys were cut between plots reducing plot length to 28 ft. All plots were irrigated with an overhead sprinkler center pivot irrigation system. . . . There were no significant differences …

Corn Disease Update, Tamra A. Jackson-Ziems, Craig B. Langemeier, Greg R. Kruger

Department of Plant Pathology: Faculty Publications

Goss's Bacterial Wilt and Blight ... Symptoms ... 2011 Survey results ... New alternate hosts identified ... Goss's Wilt Management Strategies ... More Resources ... Literature Cited

Aspergillus Ear Rot and Aflatoxin Contaminated Grain ... Table 1. FDA Action Levels for Aflatoxin in Feed and Food ... Testing for Aflatoxin ... High risk factors for aflatoxin contamination in corn ... Scouting for Aspergillus Ear Rot ... Harvest and Storage ... More Resources

Stalk Rot Diseases ... Scouting for Stalk Rot Diseases ... Management ... More Resources