Plant Pathology Commons^™

Comment On The Reinstatement Of Xanthomonas Citri (Ex Hasse 1915) Gabriel Et Al. 1989 And X. Phaseoli (Ex Smith 1897) Gabriel Et Al. 1989: Indication Of The Need For Minimal Standards For The Genus Xanthomonas, J. M. Young, J. F. Bradbury, L. Gardan, R. I. Gvozdyak, D. E. Stead, Y. Takikawa, A. K. Vidaver

Department of Plant Pathology: Faculty Publications

The proposals to reinstate Xanthomonas citri (ex Hasse 1915) Gabriel et al. 1989 and X. phaseoli (Smith 1897) Gabriel et al. 1989 are examined in terms of conventional criteria for describing new species. We suggest that the descriptions presented are insufficient in terms of modern practice for the purposes of formal classification in the genus Xanthomonas. To create guidelines for future reinstatements, the Judicial Commission of the International Committee on Systematic Bacteriology is requested to arrange for the preparation and promulgation of minimal standards for Xanthomonas. The pathovars proposed, X. campestris pv. aurantifolii Gabriel et al. 1989 …

Size Differences Among Root-Knot Nematodes On Resistant And Susceptible Alyceclover Genotypes, L. E. Powers, R. A. Dunn, R. Mcsorley

Department of Plant Pathology: Faculty Publications

The influence of plant resistance on the size of individual root-knot nematodes was determined in greenhouse experiments. Five genotypes of alyceclover were inoculated with second-stage juveniles of Meloidogyne incognita race 3 or M. arenaria race 1. Plants were harvested at selected intervals and stained for detection of the nematodes, which were dissected from the roots. Length, width, and sagittal-sectional area of each animal were measured using an image-analysis system, and areas of nematodes in all stages were compared at different times and across alyceclover lines. Nematodes feeding on roots of resistant lines were consistently smaller than those on susceptible plants, …

Sterol Composition Of The Corn Root Lesion Nematode, Pratylenchus Agilis, And Corn Root Cultures, David J. Chitwood, William R. Lusby

Harold W. Manter Laboratory of Parasitology: Faculty Publications

Sterols from mixed stages of the com root lesion nematode, Pratylenchus agilis, and uninfected corn root cultures were analyzed by gas chromatography-mass spectrometry. Twenty-eight sterols were identified in P. agilis, including nine not previously detected in nematodes. The major sterols were 24-ethylcholest-22-enol, 24-ethylcholesta-5,22-dienol, 24-methy1cholestanol, 24-ethylcholestanol, isofucostanol, and 24-ethylcholesterol. The principal corn root sterols were 24-ethylcholesta-5,22-dienol, 24-methylcholesterol, 24-ethylcholesterol, isofucosterol, and cycloartenol. Therefore, the major metabolic transformation of sterols by P. agilis was saturation of the sterol nucleus. In addition, very small amounts of 4α-methylsterols were biosynthesized by P. agilis. The 4-methylation pathway is unique to nematodes and was …

Origin And Evolution Of Defective Interfering Rnas Of Tomato Bushy Stunt Virus, David A. Knorr, Thomas Jack Morris

School of Biological Sciences: Faculty Publications

Viruses with defective genomes have been identified in association with virtually every major family of viruses and have been widely utilized as tools for investigating virus functions in animal cell culture systems (Perrault, 1981). It is generally thought that defective interfering viruses (DIs) arise through deletion, rearrangement, or recombination of a competent viral genome. DIs tack the ability for independent existence relying on their parental helper viruses to supply factors required for replication, maturation, and/or encapsidation (Huang and Baltimore, 1977). The interference attributed to DIs is thought to result from competition with the helper virus for factors required in trans …

Risk-Based Oversight Of Experiments In The Environment, Henry I. Miller, Robert H. Burris, Anne K. Vidaver, Nelson A. Wivel

Department of Plant Pathology: Faculty Publications

The new biology has come of age. Basic research in fields ranging from immunology to plant biology has been transformed so as to be almost unrecognizable to those whose biology education ended before 1970. The spillover into commercial development likewise has been remarkable. Hardly a week passes without news of some new advance in an area such as therapeutics, vaccines, or plants and animals for food, feed, or fiber. These uses of biotechnology in "contained" laboratories, pilot plants, greenhouses, and production facilities have engendered little controversy. The National Institutes of Health Guidelines for Research Involving Recombinant DNA have exempted from …

Pesticide Use On Crops In Nebraska - 1987, Maurice Baker, Nancy Peterson, Shripat T. Kamble

Nebraska Agricultural Experiment Station: Historical Research Bulletins

This is the third and most comprehensive study of pesticide use on crops in Nebraska. The first was completed in 1978 and the second one in 1982. The first study indicated that approximately 25 million pounds (11.34 million kg) of active ingredients were used on the major crops in Nebraska. This increased to approximately 30.2 million pounds (13.7 million kg) in 1982. The USDA requires accurate information to meet their responsibilities. Thus, this survey was undertaken to determine: 1) the use of pesticides on crops, pasture and rangeland and 2) to identify pest management practices.

Towards An Improved Taxonomy Of Xanthomonas, L. Vauterin, J. Swings, K. Kersters, M. Gillis, T. W. Mew, M. N. Schroth, N. J. Palleroni, D. C. Hildebrand, D. E. Stead, E. L. Civerolo, A. C. Hayward, H. Maraîte, R. E. Stall, A. K. Vidaver, J. F. Bradbury

Department of Plant Pathology: Faculty Publications

Improvement of the taxonomy of the genus Xanthomonas and especially of Xanthomonas campestris, which is subdivided into more than 125 pathovars, is discussed. Recent contributions to the taxonomy of Xanthomonas are reviewed, and on the basis of these data and unpublished data from several laboratories, the usefulness of different phenotypic, chemotaxonomic, and genotypic techniques is discussed. The heterogeneity of several X. campestris pathovars has been demonstrated by sodium dodecyl sulfate electrophoresis of whole-cell proteins and fatty acid fingerprinting. The host selectivity of the pathovars is not correlated with their relationships as revealed by DNA-DNA hybridization experiments. In order to …

Capping Of Tobacco Mosaic Virus Rna: Analysis Of Viral-Coded Guanylyltransferase-Like Activity, David Dunigan, Milton Zaitlin

Department of Plant Pathology: Faculty Publications

The 5’ end of tobacco mosaic virus (TMV) genomic RNA is capped with 7- methylguanosine. A virus-coded polypeptide with guanylyltransferase activity has been investigated. This enzyme is responsible for forming the 5’→5’ linkage of guanosine 5’-monophosphate to the 5’- diphosphate of an acceptor RNA, thereby forming the cap. A critical step in the mechanism for cap formation in the eukaryotic nucleus is for guanylyltransferase to bind covalently to guanosine 5’- monophosphate with the hydrolysis of pyrophosphate when guanosine 5’- triphosphate is the substrate. The TMV 126-kilodalton protein, which is most probably a component of the TMV replicase, was found to …

Proceedings Of The 17th Annual Meeting, Southern Soybean Disease Workers (March 20-22, 1990, Biloxi, Mississippi): Soybean Disease Control At A Crossroad, William S. Gazaway, Donald E. Hershman, J. Allen Wrather, Gary W. Lawrence, Glenn G. Hammes

Southern Soybean Disease Workers: Conference Proceedings

Contents

Southern Soybean Disease Workers Officers 1989-1990

Southern Soybean Disease Workers Program Committee 1989-1990

Southern Soybean Disease Workers Committee Chairmen 1989-1990

General session

Presidential address. B Gazaway

Keynote address. K Smith

Invited speakers

Future Impacts of Biotechnology on Soybean Production and Uses. X Delannay

Diseases of Soybean Associated with International Seed Trade. B Moore

Impact of Regulatory Change and GLP's on New Fungicide Discovery and Development. G Hammes

Graduate student papers

Double-Stranded RNA and Virus-Like Particles From the Soybean Stem canker Pathogen, Diaporthe phaseolorum var. caulivora. Y Lee, JP Snow, GT Berggren, and RA Valverde

Development of Soybean Varieties …

Degradation Of Wheat Streak Mosaic Virus Capsid Protein During Leaf Senescence, Myron K. Brakke, Rose N. Skopp, L. C. Lane

Department of Plant Pathology: Faculty Publications

Wheat streak mosaic virus capsid protein degraded in vivo by proteolysis as leaves senesced. The capsid protein of virus purified from young systemically infected leaves had an apparent size or 45 kDa in 12% sodium dodecyl sulfate-polyacrylamide gels with minor amounts of 43, 42, 33, and 3E kDa proteins. The proportion of smaller proteins increased with the age of the leaf. In some virus preparations only 3 1 kDa capsid protein was detected. In vitro proteolysis of virions with 45 kDa protein produced virions with 31 kDa protein. Virions with 31 kDa capsid protein sedimented slightly more slowly than those …

Identification Of Single Meloidogyne Juveniles By Polymerase Chain Reaction Amplification Of Mitochondrial Dna, T. S. Harris, L. J. Sandall, Thomas O. Powers

Department of Plant Pathology: Faculty Publications

Polymerase chain reaction (PCR) was used to amplify a specific 1.8-kb sequence of mitochondrial DNA from single juveniles and eggs from 17 populations of Meloidogyne incognita, M. hapla, M. javanica, and M. arenaria. Approximately 2 μg amplified product were produced per reaction. Restriction digestion of the amplified product with HinfI permitted discrimination of clonal lineages of the four species. Meloidogyne javanica, however, could not be separated from M. hapla by the enzymes used in these experiments. Various amplification conditions and nematode lysis procedures were examined in order to optimize the speed and quality of …

Distribution Of Soybean Cyst Nematode In Nebraska, Thomas O. Powers, L. J. Sandall, D. S Wysong

Department of Plant Pathology: Faculty Publications

A survey of 552 soybean fields in 20 counties in Nebraska in 1986-88 revealed 35 fields infested with the soybean cyst nematode (SCN), Heterodera glycines. Identification was confirmed with a greenhouse bioassay, using 'Lee 74' soybean, and by the application of a DNA hybridization probe derived from SCN mitochondrial DNA. Most of the SCN-infested fields were located on the Missouri River floodplain and in the southeastern corner of the state.

Chlorella Viruses Isolated In China, Yanping Zhang, Dwight Burbank, James L. Van Etten

Department of Plant Pathology: Faculty Publications

Plaque-forming viruses of the unicellular, eucaryotic, exsymbiotic, Chlorella-like green algae strain NC64A, which are common in the United States, were also present in fresh water collected in the People's Republic of China. Seven of the Chinese viruses were examined in detail and compared with the Chlorella viruses previously isolated in the United States. Like the American viruses, the Chinese viruses were large polyhedra and sensitive to chloroform. They contained numerous structural proteins and large double-stranded DNA genomes of at least 300 kilobase pairs. Each of the DNAs from the Chinese viruses contained 5-methyldeoxycytosine, which varied from 12.6 to 46.7% …

Perspectives On Process In Plant Virology, Myron K. Brakke

Department of Plant Pathology: Faculty Publications

The editors asked that I write a chapter on landmarks in plant virology, a topic that has been covered by several authors, for example by Henderson Smith (89), Bawden (9), Holmes (51), Markham (62), Harrison (44), Black (12), and Matthews (64). In 1 938, the first of these authors, Henderson Smith (89), divided his presidential address to the Society for Applied Biology between the control of plant-virus diseases and the nature of plant viruses. Progress since then has been much more rapid in the latter than in the former area. Henderson Smith could easily understand today's literature on losses, control, …

A Non-Capsid Protein Associated With Unencapsidated Virus Rna In Barley Infected With Barley Stripe Mosaic Virus, Myron K. Brakke, E. M. Ball, W. G. Langenberg

Department of Plant Pathology: Faculty Publications

Barley tissue with an acute systemic infection of barley stripe mosaic virus contained a large amount of unencapsidated virus RNA which was stable in extracts made in ribosome isolation buffer. The virus RNA in ribosome preparations sedimented in a broad band at 80S to 100S in sucrose gradients, which is less than the virion sedimentation rate of 180S to 200S. A protein of apparent M_r 60 000, which sedimented with the virus RNA, was present in ribosome extracts from infected plants but absent from those from uninfected plants. The protein is probably a virus protein because its apparent molecular …

Effect Of Wheat Streak Mosaic Virus Infection On Total Dna And Chloroplast Ribosomal Rna In Wheat Leaves, Myron K. Brakke, J. L. White, R. G. Samson, J. Joshi

Department of Plant Pathology: Faculty Publications

The amount of chloroplast 23s rRNA relative to either DNA or to cytoplasmic 28s rRNA was reduced in young wheat leaves infected with wheat streak mosaic virus.
ChlorophyiJ was reduced in infected leaves. Fresh weight per leaf and DNA content per leaf were reduced in infected leaves, but DNA per g was increased.
Cytoplasmic ribosomal RN.A appeared to degrade more slowly during senescence in infected leaves than in uninfected. Virus was undetectable by density gradient centrifugation in systemicaliy infected leaves less than 6 cm long and reached its highest concentration when young leaves reached their maximum size. Mosaic developed in …

Chlorophyll, Chloroplast Ribosomal Rna, And Dna Are Reduced By Rarley Stripe Mosaic Virus Systemic Infection, Myron K. Brakke, J. L. White, R. G. Samson, Jay Joshi

Department of Plant Pathology: Faculty Publications

Barley stripe mosaic virus became systemic 3 days alter inoculation of barley plants in the two-leaf stage. The first leaf to show mosaic was leaf 3. which was 4.5 cm long at 3 days after inoculation when it was invaded by virus. Since all of Ieaf 3 showed mosaic, the events leading to mosaic occurred during cell expansion and after cell division. which is limited to the basal centimeter of young cereal leaves. Molecular changes associated with mosaic formation included a 509, reduction in chloroplast ribosomal RNA and chlorophyll, expressed as amount per unit DNA, in young leaves with an …

Comparisons Of Mitochondrial Dna From The Sibling Species Heterodera Glycines And H. Schachtii, A. D. Radice, Thomas O. Powers, Laurie J. Sandall, R. D. Riggs

Department of Plant Pathology: Faculty Publications

Restriction fragment patterns of mitochondrial DNA from sibling species of cyst nematodes Heterodera glycines and H. schachtii were examined. Fourteen restriction endonucleases recognizing four, five, and six base-pair sequences yielded a total of 90 scorable fragments of which 10% were shared by both species. Mitochondrial genome sizes for H. glycines and H. schachtii were estimated to be 22.5-23.5 kb and 23.0 kb, respectively. A single wild type mitochondrial genome was identified in all populations of H. glycines examined, although other mitochondrial genomes were present in some populations. The H. schachtii genome exhibited 57 scorable fragments, compared with 33 identified in …

Estimation Of Genetic Divergence In Meloidogyne Mitochondrial Dna, Thomas O. Powers, Laurie J. Sandall

Department of Plant Pathology: Faculty Publications

Restriction fragments from purified mitochondrial DNA can be readily detected following rapid end-labeling with [α-³²P] nucleoside triphosphates and separation by gel electropboresis. Mitochondrial DNA from 12 populations of Meloidogyne species was digested with 12 restriction enzymes producing more than 60 restriction fragments for each species. The mitochondrial genome of M. arenaria is the most genetically distinct of the four species compared. M. arenaria shows approximately 2.1-3.1% nucleotide sequence divergence from the mitochondrial genomes of M. javanica, M. incognita, and M. hapla. Among the latter three species, interspecific estimates of sequence divergence range from 0.7 to …

Effects Of Planting Date On Development Of Net Blotch Epidemics In Winter Barley In Pennsylvania, Leslie M. Delserone, H. Cole Jr.

University of Nebraska-Lincoln Libraries: Faculty Publications

The influence of planting date on fall and spring net blotch epidemics (caused by Pyrenophora teres) was evaluated with the winter barley cultivar Pennrad. Experiments were conducted in Centre County, Pennsylvania, in 1982 and 1983 and in Lancaster County, Pennsylvania, in 1983. The three planting dates evaluated corresponded to the recommended date as well as dates I wk earlier and later than recommended for each specific location. Planting date had a significant influence on fall net blotch epidemics, with the greatest and least disease severities observed in the earliest and latest plantings, respectively. When spring environmental conditions were warm …

Concentration Of Maize Chlorotic Mottle Virus Increased In Mixed Infections With Maize Dwarf Mosaic Virus, Strain B, Karen-Beth Goldberg, Myron K. Brakke

Department of Plant Pathology: Faculty Publications

The concentration of maize chlorotic mottle virus (MCMV) was up to 5.4 times higher in plants infected with both MCMV and maize dwarf mosaic virus. strain R (MDMV-BE. rhan in plants infected with MCMY only. The concentration of MDMV-B was the same in doubly and singly infected plants. Plants infected with both viruses had a reduced level of chlorophyIl and a lower than normal ratio of chloroplast to cytoplasmic rRNA. Purified MCMV had an extinction coefficient of 6.7 cm² mg^-1 at 260 nm, an absorption maximum at 258 nm, minimum at 240 nm, and 25% RNA.

Wheat Streak Mosaic Virus Cylindrical Inclusion Body Protein, M. K. Brakke, E. M. Ball, Y. H. Hsu, W. G. Langenberg

Department of Plant Pathology: Faculty Publications

A protein of apparent molecular weight 66000 was purified from wheat plants infected with wheat streak mosaic virus. Antiserum to this protein, labelled with gold, specifically stained cylindrical inclusions in ultrathin sections of virus-infected cells. Antiserum to the M_r 66000 protein did not react with capsid protein in Western blots, nor did antiserum to capsid protein react with the M_r 66000 protein. Both antiserum reacted with homologous antigens. The concentration of the M_r 66000 protein in extracts from infected leaves was about 100 µg per g of leaves, which is higher than the usual concentration of virions.

Virus Disease Of Small Fruits, R. H. Converse

School of Biological Sciences: Faculty Publications

This illustrated handbook was compiled by international authorities on virus and viruslike diseases of small fruits. Crops covered are in the plant genera Fragaria (strawberry), Vaccinium (blueberry and cranberry), Ribes (currant and gooseberry), and Rubus (blackberry and raspberry). The history, geographic distribution, importance, symptoms, transmission, cause, detection, and control of virus and viruslike diseases attacking these crops are discussed.

Differential Effects Of Lithium Chloride On In Vitro Growth Of Clavibacter Michiganense Subsp. Nebraskense Depending Upon Inoculum Source, Mary L. Smidt, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

The bacterium Clavibacter michiganense subsp. nebraskense (Corynebacterium michiganense subsp. nebraskense) was grown in broth cultures and inoculated into corn plants. The plating efficiency of cells from broth cultures was essentially the same on nutrient broth-yeast extract and the semiselective medium for this bacterium, CNS. However, when cells were isolated from Goss bacterial wilt- and blight-infected corn, very few were recovered on CNS compared with the amount recovered on nutrient broth-yeast extract agar. When lithium chloride was omitted from the CNS, recoveries from infected corn were nearly the same as on nutrient broth-yeast extract agar. No other ingredient of CNS …

Differential Effects Of Lithium Chloride On In Vitro Growth Of Clavibacter Michiganense Subsp. Nebraskense Depending Upon Inoculum Source, Mary L. Smidt, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

The bacterium Clavibacter michiganense subsp. nebraskense (Corynebacterium michiganense subsp. nebraskense) was grown in broth cultures and inoculated into corn plants. The plating efficiency of cells from broth cultures was essentially the same on nutrient broth-yeast extract and the semiselective medium for this bacterium, CNS. However, when cells were isolated from Goss bacterial wilt- and blight-infected corn, very few were recovered on CNS compared with the amount recovered on nutrient broth-yeast extract agar. When lithium chloride was omitted from the CNS, recoveries from infected corn were nearly the same as on nutrient broth-yeast extract agar. No other ingredient of …

Restriction Endonuclease Activity Induced By Pbcv-1 Virus Infection Of A Chlorella-Like Green Alga, Yuannan Xia, Dwight Burbank, Lothar Uher

Department of Plant Pathology: Faculty Publications

An enzyme was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1 which exhibits type I1 restriction endonuclease activity. The enzyme recognized the sequence GATC and cleaved DNA 5' to the G. Methylation of deoxyadenosine in the GATC sequence inhibited enzyme activity. In vitro the enzyme cleaved host Chlorella nuclear DNA but not viral DNA because host DNA contains GATC and PBCV-1 DNA contains GmATC sequences. PBCV-1 DNA is probably methylated in vivo by the PBCV-1-induced methyltransferase described elsewhere (Y. Xia and J. L. Van Etten, Mol. Cell. Biol. 6:144-1445). Restriction endonuclease activity was first detected …

Dna Methyltransferase Induced By Pbcv-1 Virus Infection Of A Chlorella-Like Green Alga, Yuannan Xia, James L. Van Etten

Department of Plant Pathology: Faculty Publications

A DNA methyltransferase was isolated from a eucaryotic, Chlorella-like green alga infected with the virus PBCV-1. The enzyme recognized the sequence GATC and methylated deoxyadenosine solely in GATC sequences. Host DNA, which contains GATC sequences, but not PBCV-1 DNA, which contains GmATC sequences, was a good substrate for the enzyme in vitro. The DNA methyltransferase activity was first detected about 1 h after viral infection; PBCV-1 DNA synthesis and host DNA degradation also began at about this time. The appearance of the DNA methyltransferase activity required de novo protein synthesis, and the enzyme was probably virus encoded. Methylation of …

Restriction Endonuclease Activity Induced By Pbcv-1 Virus Infection Of A Chlorella-Like Green Alga, Yuannan Xia, Dwight Burbank, Lothar Uher, Dietrmar Rabussay, James L. Van Etten

Department of Plant Pathology: Faculty Publications

An enzyme was isolated from a eucaryotic, Chlorella-lie green alga infected with the virus PBCV-1 which exhibits type II restriction endonuclease activity. The enzyme recognized the sequence GATC and cleaved DNA 5' to the G. Methylation of deoxyadenosine in the GATC sequence inhibited enzyme activity. In vitro the enzyme cleaved host Chlorella nuclear DNA but not viral DNA because host DNA contains GATC and PBCV-1 DNA contains G^mATC sequences. PBCV-1 DNA is probably methylated in vivo by the PBCV-1-induced methyltransferase described elsewhere (Y. Xia and J. L. Van Etten, Mol. Cell. Biol. 6:1440-1445). Restriction endonuclease activity was …

Species-Specific Restriction Site Polymorphism In Root-Knot Nematode Mitochondrial Dna, Thomas O. Powers, E. G. Platzer, Bradley C. Hyman

Department of Plant Pathology: Faculty Publications

Research was initiated to physically characterize the mitochondrial genomes of several Meloidogyne spp. and host-races, to address questions regarding their systematics and dispersal, and to assess the possibility of developing molecular diagnostics for these nematodes. Techniques were developed for purification and rapid detection of mitochondrial DNA from root-knot nematodes. Mitochondrial DNAs among Meloidogyne spp. were demonstrated to exhibit extensive divergence. The potential for using the rapidly diverging mitochondrial genomes as a diagnostic assay for M. incognita, M. hapla, M. arenaria, and M. javanica is discussed.

Transposon Mutagenesis And Excision Of R' Plasmids By Conjugative, Chimeric Plasmid Puw942 In Extra-Slow-Growing Rhizobium Japonicum Strains, Alahari Arunakumari, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

Transposons Tn501 (specifying mercury resistance) and Tn7 (specifying resistance to trimethoprim and streptomycin) were introduced into extra-slow-growing Rhizobium japonicum by conjugal transfer of the 82 kilobase chimeric plasmid pUW942. Mercury-resistant transconjugants were obtained at a frequency of 10^-7 to 10^-9. The transfer frequency of streptomycin resistance was lower than that of mercury resistance, and Tn7 was relatively unstable. pUW942 was not maintained as an autonomously replicating plasmid in R. japonicum strains. However, some of the Hg^r transconjugants from the RJ19FY, RJ17W, and RJ12S strains acquired antibiotic markers of the vector plasmid pUW942. Southern hybridization of plasmid …