Department of Plant Pathology
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The Department of Plant Pathology at the University of Minnesota has a strong research and teaching emphasis in disease resistance, molecular genetics and genomics, control of diseases caused by biotic pathogens, wood deterioration, effect of air pollution on plants, biological control, ecology and evolution of plant-associated microbes, and in the physiology and molecular biology of plant-microbe interactions. The department also has a strong outreach emphasis through the extension service, plant disease clinic, and other avenues.
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Item Aegilops sharonensis: Origin, genetics, diversity, and potential for wheat improvement(Botany, 2009-08) Steffenson, Brian; Olivera, Pablo D.Aegilops sharonensis Eig (Sharon goatgrass; section Sitopsis) is an annual diploid grass species growing endemically in the coastal plains of Israel and southern Lebanon. It is a wild relative of wheat, with a genome closely related to the B genome of cultivated bread wheat. With the most limited distribution of any species in the genus Aegilops, Ae. sharonensis is rapidly losing its habitats, owing to the combined effects of modern agricultural intensification and expansion of urban and industrial areas. Aegilops sharonensis is known to be a rich source of genes providing resistance to important wheat diseases and abiotic stresses, but it has not been widely exploited. The presence of gametocidal genes that control preferential transmission of chromosome 4Ssh increases the difficulty of introgressing genes from Ae. sharonensis into wheat. However, successful introgression of the genes for resistance to leaf rust, stripe rust, and powdery mildew has been achieved. Studies on genetic and phenotypic diversity indicated that Ae. sharonensis is a highly diverse species, comparable with others that have a wider geographic distribution and more variable environments. Targeting the regions and sites with the highest diversity in Ae. sharonensis will facilitate the capture of the greatest variability and also the identification of novel and diverse genes for wheat improvement.Item Agronomic characteristics, malt quality, and disease resistance of barley germplasm lines with partial Fusarium head blight resistance(Crop Science, 2005-07) Steffenson, Brian; Urrea, Carlos A.; Horsley, Richard D.; Schwarz, Paul B.Fusarium head blight (FHB), incited by Fusarium graminearum Schwabe, has caused devastating losses in both yield and quality of barley (Hordeum vulgare L.) produced in the northern Great Plains from 1993 to 2003. Thirty-five barley germplasm lines with partial resistance to FHB have been identified in exotic and unadapted germplasm lines. Little is known about their agronomic characteristics, malt quality, and reaction to other diseases as compared to adapted cultivars. This information is needed so barley breeders can make informed decisions when planning crosses involving the resistant germplasm lines. The objective of this study was to compare the agronomic performance, malt quality, and disease reaction of barley germplasm lines with partial FHB resistance to cultivars grown in the northern Great Plains. Agronomic and malting data were collected on the 35 germplasm lines and five check cultivars grown in five environments in North Dakota from 1998 to 2000. Data for FHB severity and deoxynivalenol (DON, a mycotoxin produced by F. graminearum) accumulation were obtained for the same 40 entries grown in FHB-epidemic nurseries in North Dakota from 1997 to 1999. Seedling responses to foliar pathogens common in the northern Great Plains were determined in the greenhouse during fall 1997. None of the FHB-resistant barley germplasm lines had acceptable malt quality for all traits. Kernel plumpness, grain protein concentration, and malt extract were the traits impacted most severely. The FHB-resistant barley germplasm lines headed significantly later than the adapted barley cultivars. Most FHB-resistant germplasm lines were susceptible to the common foliar diseases of the northern Great Plains. At least four cycles of breeding will probably be necessary to develop FHB-resistant germplasm lines acceptable to producers and the malting and brewing industry.Item Alfalfa leaf protein concentrate: A sustainable protein source for aquaculture feeds(2019) Samac, Deborah A; Coburn, Jessica E M; Phelps, Nicholas; Wells, M ScottInterest in local, sustainable aquaculture is continuing to expand across the United States. To ensure profitability and high consumer acceptance, a plant-based non-GMO source of protein is needed for replacing fishmeal in aquaculture diets. Most replacements in current use are derived from seeds, and often contain undesirable antinutritional components. Alfalfa (Medicago sativa) is a high biomass perennial legume that is grown across the U.S. for use in animal feeds. We evaluated the yield and composition of protein concentrates derived from fresh alfalfa foliage. Furthermore, a commercial alfalfa protein concentrate (APC) was used to replace fishmeal in diets for yellow perch (Perca flavescens) and rainbow trout (Oncorhynchus mykiss). Weight gains, growth rate, and feed conversion ratios were measured.Item Amplified fragment length polymorphism and virulence polymorphism in Puccinia hordei(Canadian Journal of Plant Pathology, 2007) Sun, Y; Neate, S.M.; Zhong, S; Steffenson, Brian; Friesen, T. L.Puccinia hordei is the causal agent of barley leaf rust. To study the genetic diversity in P. hordei, 45 isolates with diverse virulence patterns and geographical origins were analyzed using amplified fragment length polymorphism markers. Two pathotypes of Puccinia graminis f. sp. tritici and one isolate of P. graminis f. sp. secalis were included in the analysis for comparison. Six primer-pair combinations of amplified fragment length polymorphism were used and a total of 782 polymorphic markers were generated. Cluster analysis showed that P. graminis f. sp. tritici and P. graminis f. sp. secalis were distinctly different from P. hordei. The P. hordei isolates were clustered into five groups: group I contained a single, rare isolate that was virulent on all resistance genes except Rph13 and Rph15 ; group II contained a single isolate found to be virulent on the resistance gene Rph15 ; group III contained 2 isolates; group IV contained 24 isolates, 11 from the United States and 13 from diverse locations around the world; and group V contained 17 isolates, 7 from California, 7 from other states of United States, and 3 from central Europe. The study revealed that molecular diversity in P. hordei can be associated with virulence, but not well with geographic origin.Item Analysis of ergosterol in single kernel and ground grain by gas chromatography-mass spectrometry(Journal of Agricultural and Food Chemistry, 2006-05-11) Steffenson, Brian; Dong, Yanhong; Mirocha, Chester JA method for analyzing ergosterol in a single kernel and ground barley and wheat was developed using gas chromatography−mass spectrometry (GC-MS). Samples were saponified in methanolic KOH. Ergosterol was extracted by “one step” hexane extraction and subsequently silylated by N-trimethylsilylimidazole/trimethylchlorosilane (TMSI/TMCS) reagent at room temperature. The recoveries of ergosterol from ground barley were 96.6, 97.1, 97.1, 88.5, and 90.3% at the levels of 0.2, 1, 5, 10, and 20 μg/g (ppm), respectively. The recoveries from a single kernel were between 93.0 and 95.9%. The precision (coefficient of variance) of the method was in the range 0.8−12.3%. The method detection limit (MDL) and the method quantification limit (MQL) were 18.5 and 55.6 ng/g (ppb), respectively. The ergosterol analysis method developed can be used to handle 80 samples daily by one person, making it suitable for screening cereal cultivars for resistance to fungal infection. The ability for detecting low levels of ergosterol in a single kernel provides a tool to investigate early fungal invasion and to study mechanisms of resistance to fungal diseases.Item Antibacterial Activity of Plant Defensins Against Alfalfa Crown Rot Pathogens(2017) Sathoff, Andrew; Velivelli, Siva; Shah, Dilip; Samac, Deborah AAlfalfa (Medicago sativa) is the fourth most widely grown crop in the United States. Alfalfa crown rot is a disease complex that severely decreases alfalfa stand density and productivity in all alfalfa-producing areas. Currently, there are no viable methods of disease control. Plant defensins are small cationic antimicrobial peptides with a conserved signature of cysteines. The in vitro and in planta antifungal activity of plant defensins has been extensively studied. However, their antibacterial activity has been less well characterized. Defensins have a γ-core motif, a cluster of cationic and hydrophobic residues, which is essential for antimicrobial activity. The γ-core motifs of five synthetic defensins were tested for antibacterial activity against the bacterial pathogens in the alfalfa crown rot disease complex. Full length defensins, expressed using a Pichia pastoris expression system, were tested to compare antibacterial activity. A spread plate method was used to quantify antibacterial activity of defensins. Bacteria were grown out to an OD600 value of 0.1, and a 200 μL culture was incubated with shaking for 3 hours with concentrations of defensin peptide up to 30 μg/mL. The bacteria were serially diluted, and 100 μL was plated on to NBY plates. After 48 hours of incubation, the bacterial colonies were counted. The amount of defensin needed to inhibit growth of pathogen strains by 50% (IC50) was calculated. The core motif of MtDef4 was shown to be the most effective truncated peptide with IC50 values of 3.4 μM against Pseudomonas syringae pv. syringae and 4.52 μM against Xanthomonas alfalfae. Also, the corresponding full length MtDef4 peptide was found to be active against P. syringae pv. syringae and X. alfalfae with IC50 values of 0.43 μM and 0.68 μM, respectively. These experiments show the previously overlooked high biological activity of plant defensins against bacterial pathogens. Additionally, these results indicate that the γ-core-motif can be used to predict biological activity of the full-length defensin, and that transgenic expression of plant defensins in alfalfa has the potential to lead to improved crown rot resistance.Item Antimicrobial Activity of Brassica rapa Nectar Lipid Transfer Protein(2017) Sathoff, Andrew E; Samac, Deborah A; Holl, Catherine; Schmidt, Tony; Carter, ClayAntimicrobial peptides (AMPs) provide an ancient, innate immunity conserved in all multicellular organisms. In plants, there are several large families of AMPs defined by sequence similarity. The nonspecific lipid transfer protein (LTP) family is defined by a conserved signature of eight cysteines and has a compact structure with a lipid-binding hydrophobic cavity. The antimicrobial activity of LTPs varies greatly among plant species. An LTP from Brassica rapa (variety R-o-18) nectar was tested for antimicrobial activity. In a 96-well microplate, each well contained half strength potato dextrose broth, approximately 2000 spores, and concentrations of LTP peptide up to 300 μg/mL in a total volume of 100 μL. After 48 hours of incubation at 25 C in the dark, absorbance of the wells was measured at 595 nm on a microplate reader to quantify the inhibition of fungal growth. The amount of LTP needed to inhibit growth of pathogen strains by 50% (IC50) was calculated. This Brassica LTP was most effective against Trichoderma and Bipolaris oryzae with IC50 values of 0.78 μM and 1.71 μM, respectively. Additionally, both Colletotrichum trifolii and Alternaria solani had IC50 values of less than 4.0 μM. The activity of this Brassica LTP at such low biological values indicates that it is a potent defense protein. These results suggest that transgenic expression of antimicrobial LTPs has the potential to lead to improved broad-spectrum disease resistanceItem Aurora Sporealis 1924 - 2006 Personal Name and Subject Index(2008-10-28) Tertell, Susan M.; Van Why, Carol B.Comprehensive index of personal names and subjects found in the Aurora Sporealis magazines issued by the Plant Pathology Department from 1924-2006, accounting for spelling errors, name changes and nicknames.Item Aurora Sporealis 1973 Special Congress Edition(University of Minnesota: Department of Plant Pathology, 1973) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 1979(University of Minnesota: Department of Plant Pathology, 1979-05-17) University of Minnesota Department of Plant PathologyItem Aurora Sporealis 2003(University of Minnesota: Department of Plant Pathology, 2003) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2004(University of Minnesota: Department of Plant Pathology, 2004) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2005(University of Minnesota: Department of Plant Pathology, 2005) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2006(University of Minnesota: Department of Plant Pathology, 2006) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2007(University of Minnesota: Department of Plant Pathology, 2007) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2009(University of Minnesota: Department of Plant Pathology, 2009) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2011(University of Minnesota: Department of Plant Pathology, 2012-02-29) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2013(University of Minnesota: Department of Plant Pathology, 2014-02) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2014(University of Minnesota: Department of Plant Pathology, 2014-12) University of Minnesota: Department of Plant PathologyItem Aurora Sporealis 2015(University of Minnesota: Department of Plant Pathology, 2015-12) University of Minnesota Department of Plant Pathology