Plant Pathology Commons^™

Physiological And Morphological Correlation Of Rhizopus Stolonifer Spore Germination, James L. Van Etten, Lee Bulla Jr., Grant St. Julian

Department of Plant Pathology: Faculty Publications

Sporangiospores of Rhizopus stolonifer were examined at various stages of germination by scanning electron and phase-contrast microscopy. These observations were correlated with changes in spore dry weight, spore volume, respiration, and syntheses of ribonucleic acid, deoxyribonucleic acid, and protein during germination.

Corynebacterium Nebraskense, A New, Orange-Pigmented Phytopathogenic Species, Anne K. Vidaver, Manley Mandel

Department of Plant Pathology: Faculty Publications

A new species of Corynebacterium isolated from field corn is described. The isolates form a homogeneous group that is recognized as a new species, Corynebacterium nebraskense. The organism is characterized by orange-pig-mented colonies, inability to grow on 0.005% triphenyltetrazolium chloride agar, specific bacteriophage sensitivity, and a guanine plus cytosine content of 73.5 mol%. These and other characters differentiate this organism from other described phytopathogenic corynebacteria. The type strain of C. nebraskense is Fur-1 (= ATCC 27822 = NCPPB 2578).

Survival Mechanisms Of Phytopathogenic Bacteria, M. L. Schuster, D. P. Coyne

Department of Plant Pathology: Faculty Publications

Natural habitats usually do not provide bacteria the continuity of agricultural crops. With continuous culture. perpetuation of pathogen is no problem. Although agricul­ tural practices provide some discontinuity between crops. it is less than that in nature. Uniformity of crop germ plasm also favors inoculum buildup and perhaps perpetuation of the pathogens.

Results Of The Third International Winter Wheat Performance Nursery, J. E. Stroike, V. A. Johnson, J. W. Schmidt, P. J. Mattern, K. D. Wilhelmi

Nebraska Agricultural Experiment Station: Historical Research Bulletins

This is the third report of results from an International Winter Wheat Performance Nursery (IWWPN) organized in 1968 by the Nebraska Agricultural Experiment Station and the Agricultural Research Service, U.S. Department of Agriculture, under a contract with the Agency for International Development, U.S. Department of State. The nursery was designed to (1) test the adaptation of winter wheat varieties in a range of latitudes, daylengths, fertility conditions, water management, and disease complexes; (2) identify superior winter varieties to serve as recipient genotypes for high protein and high lysine genes, and (3) test the degree of expression and stability of the …

Rna Polymerase Activity Associated With Bacteriophage Φ6, James L. Van Etten, A. K. Vidaver, R. K. Koski, J. S. Semancik

Department of Plant Pathology: Faculty Publications

The Pseudomonas phaseolicola bacteriophage φ6 incorporated labeled UTP into an acid-insoluble precipitate. Incorporation was dependent on the presence of manganese acetate, ATP, GTP, CTP, and a short heat treatment of the phage; the reaction was stimulated by NH,Cl. The substitution of ¹⁴C-ATP, -CTP or -GTP for UTP, together with the appropriate unlabeled ribonucleoside triphosphates, disclosed that CMP was incorporated to the greatest extent followed by GMP, UMP, and AMP. Radioactive RNAs formed by the reaction were resistant to RNases A and T₁ in high salt but susceptible to these nucleases in low salt. The labeled RNA co-sedimented and …

Characteristics Of Deoxyribonucleic Acid Polymerase Isolated From Spores Of Rhizopus Stolonifer , Cheng-Shung Gong, Larry Dunkle, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Deoxyribonucleic acid (DNA)-dependent DNA polymerase was purified several hundredfold from germinated and ungerminated spores of the fungus Rhizopus stolonifer. The partially purified enzymes from both spore stages exhibited identical characteristics; incorporation of [³H] deoxythymidine monophosphate into DNA required Mg²⁺, DNA, a reducing agent, and the simultaneous presence of deoxyguanosine triphosphate, deoxycytidine triphosphate, and deoxyadenosine triphosphate. Heat-denatured and activated DNAs were better templates than were native DNAs. The buoyant density of the radioactive product of the reaction was similar to that of the template DNA. The enzyme is probably composed of a single polypeptide chain with …

Bacteriophage Φ6: A Lipid-Containing Virus Of Pseudomonas Phaseolicola, Anne K. Vidaver, R. K. Koski, James L. Van Etten

Department of Plant Pathology: Faculty Publications

The purification and properties of a lipid-containing bacteriophage, φ 6, are described. The phage contains a lipid envelope which is probably essential for infection. Infectivity of φ 6 was lost in the presence of organic solvents, sodium deoxycholate, and phospholipase A. The fatty acid composition of the phage lipid was similar to that of the Pseudomonas phaseolicola host cells. The phage was composed of about 25% lipid, 13% RNA, and 62% protein. The buoyant density of φ6 was 1.27 g/ml in cesium chloride. The morphology of φ6 was unusual; it had a polyhedral head of about 60 nm surrounded by …

Protein Synthesis During Fungal Spore Germination: Differential Protein Synthesis During Germination Of Botryodiplodia Theobromae Spores, James L. Van Etten, Henry Roker, Eric Davies

Department of Plant Pathology: Faculty Publications

The preformed messenger ribonucleic acid in Botryodiplodia theobromae spores directs the synthesis of several relatively stable polypeptides.

Results Of The Second International Winter Wheat Performance Nursery, J. E. Stroike, V. A. Johnson, J. W. Schmidt, P. J. Mattern

Nebraska Agricultural Experiment Station: Historical Research Bulletins

The Second International Winter Wheat Performance Nursery was grown in 1970 at 38 sites in 23 countries. Four of the sites were in the southern hemisphere. Data were reported from 36 sites. The same 30 varieties evaluated in the First International Winter Wheat Performance Nursery were grown in this Second International Winter Wheat Performance Nursery. Twenty-eight varieties were winter wheats; two were spring wheats. Data on grain yield, test weight, maturity, plant height, lodging, shattering, winter survival, diseases, grain protein content and lysine content for 1970 are reported. Two-year mean data summaries also are reported.

Date Of Planting Studies Of Winter Wheat And Winter Barley In Relation To Root And Crown Rot Grain Yields And Quality, C. R. Fenster, M. G. Boosalis, J. L. Weihing

Nebraska Agricultural Experiment Station: Historical Research Bulletins

This study was undertaken to determine the nature of root and crown rot of wheat and to ascertain the proper time to plant winter wheat so as to conserve moisture, minimize root and crown rot and thereby maximize yield. Studies conducted for 15 years at several locations in western Nebraska reveal that planting date is a significant factor for higher yields, particularly in certain years.

Results Of The First International Winter Wheat Performance Nursery, J. E. Stroike, V. A. Johnson, J. W. Schmidt, P. J. Mattern

Nebraska Agricultural Experiment Station: Historical Research Bulletins

The International Winter Wheat Performance Nursery was organized by the Nebraska Agricultural Experiment Station and the Agricultural Research Service, U.S. Department of Agriculture, under a contract with the Agency for International Development, U.S. Department of State. There has been informal cooperation with the Food and Agriculture Organization, United Nations, and the International Maize and Wheat Improvement Center (CIMMYT), Mexico, D. F. Specific objectives of the nursery are to: (1) Test the adaptation of winter wheat varieties under a range of latitudes, daylengths, fertility conditions, water management and disease complexes (2) Identify superior winter varieties to serve as recipient genotypes for …

Preparation Of Biologically Active Ribosomal Subunits From Fungal Spores, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Ribosomal subunits were prepared from fungal spore ribosomes and reassociated to yield biologically active ribosomes.

Systematic Infections For The Assay Of Plant Viruses, Myron K. Brakke

Department of Plant Pathology: Faculty Publications

The first infectivity assays of plant viruses relied on the percentage of inoculated plants becoming systemically infected. The use of systemic infections for assays became unfashionable, however, after the discovery of local lesions and the demonstration that their numbers depended on virus concentration. Continued emphasis on local lesions over the years led to the widely held belief that systemic infections could not be used for a reliable and accurate assay of plant viruses. There was never any good statistical evidence for this viewpoint. In fact, no thorough investigation has been published of the accuracy of "systemic assays" of plant viruses, …

Protein Synthesis During Fungal Spore Germination. Iv. Transfer Ribonucleic Acid From Germinated And Ungerminated Spores, James L. Van Etten, R. Kent Koski, Mahmoud El-Olemy

Department of Plant Pathology: Faculty Publications

Transfer ribonucleic acid (tRNA) fractions isolated from germinated and ungerminated spores of Botryodiplodia theobromae and Rhizopus stolonifer had acceptor activity for all 20 amino acids commonly found in protein, when tested with an enzyme fraction from germinated spores. Accordingly, it is unlikely that the absence of tRNA for a particular amino acid limits protein synthesis in fungal spores.

Characterization Of Xanthomonas Phaseoli Bacteriophages, Anne K. Vidaver, Max L. Schuster

Department of Plant Pathology: Faculty Publications

Ten bacteriophages for Xanthomonas phaseoli were characterized. On the basis of adsorption rates, latent period and burst size, plaque morphology, host range, efficiency of plating, ultrastructure, sensitivity to osmotic shock, streptomycin sensitivity, temperature effects on plating efficiency, and serology, the phages were separated into at least three groups. Some of the phages were infectious for Pseudomonas phaseolicola (four strains) and P. syringae (one strain) in a narrow temperature range. The taxonomic and ecological significance of this finding is discussed.

Protein Synthesis During Fungal Spore Germination Ii. Aminoacyl-Soluble Ribonucleic Acid Synthetase Activities During Germination Of Botryodiplodia Theobromae Spores, James L. Van Etten, Robert Brambl

Department of Plant Pathology: Faculty Publications

The specific activities of 13 aminoacyl-soluble ribonucleic acid (sRNA) synthetases were measured at various time intervals during the germination of Botryodiplodia theobromae conidiospores. The enzyme activities were low or absent in ungerminated spores, and they increased rapidly as germination proceeded. When extracts of the ungerminated spores were prepared with mortar and pestle, very little or no enzyme activity was detected. When the extracts were prepared with a mechanical homogenizer, however, they exhibited some enzyme activity, although less than did the extracts from germinated spores. Enzyme activities from germinated spores were approximately the same, regardless of the method of preparation. The …

Northern Corn Leaf Blight (Helminthosporium Turcicum Pass.) On Susceptible And Resistant Corn, Saffet Baydar

Open Access Master's Theses (through 2010)

The objectives of the research reported herein were to (1) become familiar with the technique of inoculating corn with Helminthosporium turcicum, (2) become familiar with a technique of evaluating the susceptibility of corn lines to H. turcicum, (3) become familiar with plant reaction and organism development in the various types of corn and (4) evaluate Turkish corn susceptibility in relation to various types of germ plasm in American corn lines in order to assist in combating the serious disease of Northern corn left blight in Turkey.

Comparative reactions of 10 Turkish, 5 multigenic resistant, 2 heterozygous monogenic …

Synthetic And Complex Media For The Rapid Detection Of Fluorescence Of Phytopathogenic Pseudomonads: Effect Of The Carbon Source, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

Fluorescence is of diagnostic value for differentiating among species of aerobic pseudomonads (R. Y. Stanier, N. J. Palleroni, and M. Doudoroff, J. Gen. Microbiol. 43:159, 1966). The standard medium for detecting fluorescence is Medium B (E. 0. King, M. K. Ward, and D. E. Raney, J. Lab. Clin. Med. 44:301, 1954), which supports fluorescent pigment production of most pseudomonads tested (0. Jessen, Pseudomonas aeruginosa and other green fluorescent pseudomonads, A taxonomic study, Munksgaard, Copenhagen, 1965; R. Y. Stanier et al., J. Gen. Microbiol. 43:159, 1966). Minerals (J. V. King, J. J. R. Campbell, and B. A. Eagles, Can. J. …

Changes In Fungi With Age I. Chemical Composition Of Rhizoctonia Solani And Sclerotium Bataticola , David Gottlieb, James L. Van Etten

Department of Plant Pathology: Faculty Publications

The chemical composition of the mycelium of Rhizoctonia solani and Sclerotium bataticola was determined in cells of various ages. The percentage, per unit of dry weight, of soluble amino nitrogen, deoxyribonucleic acid (DNA), ribonucleic acid (RNA), ergosterol, and protein decreased with age in both fungi. Total lipids and fatty acids increased with age in S. bataticola but remained constant in R. solani. Total carbohydrate increased with age in R. solani and decreased in S. bataticola. Fewer changes with age were observed when the results were calculated in ratio to DNA. There was no change in the ratios of protein, …

Changes In Fungi With Age Ii. Respiration And Respiratory Enzymes Of Rhizoctonia Solani And Sclerotium Bataticola, James L. Van Etten, H. Peter Molitoris, David Gottlieb

Department of Plant Pathology: Faculty Publications

The rate of respiration of Rhizoctonia solani and Sclerotium bataticola decreased with age. This decrease in respiratory rate might be produced by a decrease in the specific activity of one or more enzymes involved in carbohydrate metabolism. Specific activities in cell-free extracts were measured for most of the enzymes in the hexose monophosphate shunt, Embden-Meyerhof-Parnas pathway, tricarboxylic acid cycle, and terminal electron-transport system. In addition, glucose oxidase, isocitritase, and malic enzyme were measured. In R. solani, increases in activity with age occurred for hexokinase, α-glycerolphosphate dehydrogenase, malic dehydrogenase, and cytochrome oxidase. Decreases occurred for phosphohexokinase, aconitase, nicotinamide adenine dinucleotide-specific …

Biochemical Changes During The Growth Of Fungi: Ii. Ergosterol And Fatty Acids In Penicillium Atrovenetum, David Gottlieb, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Changes in the lipid constituents of Penicillium atrovenetum were studied during the growth and development of this fungus. The stages in development, as measured by the dry weight, were divided into four phases: lag, log, stationary, and death. The total fatty acids on a dry-weight basis increased from a minimum in the spores to a maximum near the end of the log phase of growth. The major fatty acids were palmitic, stearic, oleic, and linoleic. Myristic, pentadecanoic, palmitoleic, heptadecanoic, linolenic, arachidic, and heptadecenoic acids, together with two unidentified components, were also present in the fatty acid fraction. Compared to ungerminated …

Density-Gradient Centrifugation: Non-Ideal Sedimentation And The Interaction Of Major And Minor Components, Myron K. Brakke, J. M. Daly

Department of Plant Pathology: Faculty Publications

A small amount of southern bean mosaic virus was contained in a narrow zone after density-gradient centrifugation, but in a much wider zone after centrifugation with a large amount of a second virus. Zone-spreading of a major component by non-ideal sedimentation in density-gradient centrifugation can cause zone spreading of a minor component that the major component overlaps.

Biochemical Changes During The Growth Of Fungi: I. Nitrogen Compounds And Carbohydrate Changes In Penicillium Atrovenetum, David Gottlieb, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Changes in the biochemical constituents of cells were studied during the growth and development of Penicillium atrovenetum. Growth of the fungus, as measured by the dry weight, could be divided into four phases: lag, log, stationary, and death. The percentages of total nitrogen, cold trichloroacetic acid-soluble nitrogen, ribonucleic acid (RNA), and protein increased to a maximum during the lag phase, and subsequently decreased as the fungus aged. The percentage of deoxyribonucleic acid (DNA) was always slightly higher in the spores than in the mycelium. The DNA in the mycelium decreased in the lag phase, and then increased slightly to …

Hyperparasitism, Michael G. Boosalis

Department of Plant Pathology: Faculty Publications

Much of the research on hyperparasitism has been of a descriptive nature, based primarily on studies with dual cultures in synthetic media. The main contributions from these investigations concern the host range of the parasite, the mode of penetration and infection, and the morphological changes of the host and the parasite resulting from parasitism.

More recent studies on hyperparasitism emphasize the effect of environmental factors, especially nutrition, on the susceptibility of the host. Research on the physiology of hyperparasitism has been limited. Nevertheless, this important aspect of the problem should continue to receive increased attention as hyperparasitism is extremely amenable …

Mycorrhizae Of Ponderosa Pine In Nebraska Grassland Soils, R. W. Goss

Nebraska Agricultural Experiment Station: Historical Research Bulletins

While the genus Pinus has been the subject of extensive mycorrhizal studies there are only a few scattered references to western yellow pine, P. ponderosa, and no detailed descriptive literature on the mycorrhizae of this species. P. ponderosa is indigenous to Nebraska and the one species most extensively grown in local nurseries for windbreaks and farm plantings. Similarly, there is little information on mycorrhizae in the Great Plains between the forested regions of the Mississippi River states and the Rocky Mountains. Because this predominantly grassland area is sparse in natural tree growth the individual tree as an ornamental or …

Ec59-1822 Plant Diseases: Peony Blight, John L. Weihing

University of Nebraska-Lincoln Extension: Historical Materials

EC 59-1822 is about plant diseases and especially peony blight (also called Botrytis blight) and how to control it.

False Smut Of Buffalograss, John L. Weihing

Nebraska Agricultural Experiment Station: Historical Research Bulletins

False smut of buffalograss, Buchloe dactyloides (Nutt.) Engelm., caused by Cercospora seminalis Ell. & Ev. is a disease that destroys the unfertilized ovary. The disease was first reported by J. B. Ellis and B. M. Everhart in 1888. They gave only a brief description of the disease and named the causal fungus Cercospora seminalis. There are no etiological studies of false smut recorded in the literature. The origin of the term "false smut" is unknown to the author, but it so descriptively fits the general appearances of the disease that one readily understands its usage. The following studies were …

Streak Mosaic Of Wheat In Nebraska And Its Control, R. Staples, W. B. Allington

Nebraska Agricultural Experiment Station: Historical Research Bulletins

This bulletin reports the results of studies on the epidemiology of wheat streak mosaic under Nebraska conditions. Particular attention is given to the occurrence and certain characteristics of the mite vector of the virus, the relation of weather and other factors to some of its activities, a correlation of certain mite situations with epidemics of the disease, and recommendations for disease control.

Nebraska Plant Disease 4-H Club Manual : Extension Circular 19-01-2, John L. Weihing

Nebraska 4-H Clubs: Historical Materials and Publications

This 4-H extension circular, EC 19-01-2, EC 19012, is used for the Nebraska Plant Disease Club manual. Members of the 4-H plant disease club will learn to recognize the usual signs or symptoms of several types of disease, to collect, preserve and classify disease samples and specimens, to exhibit these specimens at public events such as fairs and to demonstrate methods for control of plant disease.

Secretion Of Amylase By Rumex Virus Tumors In Vitro, L. G. Nickell, M. K. Brakke

Department of Plant Pathology: Faculty Publications

The secretion of extracellular enzymes by intact cells of higher plants apparently is a rare occurrence. One example of it is the secretion of an extra, cellular amylase by the tissue of a virus-induced tumor from the root of Rumex wetosa L. An amylase is secreted in sufficient quantities by this tissue to enable it to grow as well in vitro on a starch-containing medium as on one containing sucrose.