Plant Pathology Commons^™

Cross-Polarized Magic-Angle Spinning 13c Nuclear Magnetic Resonance Spectroscopic Characterization Of Soil Organic Matter Relative To Culturable Bacterial Species Composition And Sustained Biological Control Of Pythium Root Rot, Michael J. Boehm, Tianyun Wu, Alex G. Stone, Bart Kraakman, Donna A. Iannotti, G. Edwin Wilson, Laurence V. Madden, Harry A.J. Hoitink

Department of Plant Pathology: Faculty Publications

We report the use of a model system that examines the dynamics of biological energy availability in organic matter in a sphagnum peat potting mix critical to sustenance of microorganism-mediated biological control of pythium root rot, a soilborne plant disease caused by Pythium ultimum. The concentration of readily degradable carbohydrate in the peat, mostly present as cellulose, was characterized by cross-polarized magic-angle spinning 13C nuclear magnetic resonance spectroscopy. A decrease in the carbohydrate concentration in the mix was observed during the initial 10 weeks after potting as the rate of hydrolysis of fluorescein diacetate declined below a critical threshold level …

Promoters From Chlorellavirus Genes Providing Expression Of Genes In Prokaryotic And Eukaryotic Hosts, Amitava Mitra, James L. Van Etten

Department of Plant Pathology: Faculty Publications

The invention is directed to novel promoters or mutants thereof from Chlorella virus DNA methyltransferase genes. A Chlorella virus gene promoter is operably linked to a first and/or second DNA sequence encoding a gene that is different from the Chlorella virus gene to form an expression cassette. An expression cassette can be introduced into prokaryotic and/or eukaryotic cells and can provide for a high level of expression of the gene encoded by the first and/or second DNA sequence. The invention also provides a method for screening other Chlorella virus genes for promoters that can function to express a heterologous gene …

The Complete Nucleotide Sequence And Genome Organization Of The M Rna Segment Of Peanut Bud Necrosis Tospovirus And Comparison With Other Tospoviruses, Satyanarayana Tatineni, S. E. Mitchell, D. V. R. Reddy, S. Kresovich, R. Jarret, R. A. Naidu, S. Gowda, J. W. Demski

Department of Plant Pathology: Faculty Publications

The M RNA of peanut bud necrosis virus (PBNV; synonym groundnut bud necrosis virus) is 4801 nucleotides in length. It comprised two ORFs in an ambisense organization and terminal inverted repeats. The 3' large ORF (3363 nucleotides in the virus-complementary strand) encoded a protein with a predicted size of 127.2 kDa which was identified as the glycoprotein precursor (GP) of the G1 and G2 glycoproteins. A comparison of the deduced amino acid sequence of GP revealed 37 % identity and 58-59% similarity with that of tomato spotted wilt virus (TSWV, serogroup I) and impatiens necrotic spot virus (INSV, serogroup III), …

Peanut Bud Necrosis Virus: Purification Of Nucleocapsids And Sequence Homology Of Nucleocapsid Protein And Glycoprotein Precursor With Other Tospoviruses, Satyanarayana Tatineni, S. E. Mitchell, D. V. R. Reddy, S. Brown, S. Kresovich, R. Jarret, S. Gowda, R. A. Naidu, J. W. Demski

Department of Plant Pathology: Faculty Publications

A procedure for the purification of peanut bud necrosis virus (PBNV) nucleocapsids was developed. Virus particles were treated with nonionic detergent to disrupt the envelope membrane and free nucleocapsids were separated. into three lightscattering zones after sucrose gradient centrifogation. Nucleocapsids from the top zone contained S RNA and traces ofM RNA; whereas, nucleoplasids from the middle zone contained M RNA with detectable levels of S RNA and those from the bottom zone contained L RNA with traces of M and S RNAs. Clones from a cDNA library made from the purified PBNV Sand M RNAs were characterized and sequenced. Comparison …

Diagnosis And Resistance Breeding Of Peanut Bud Necrosis Virus, D. V. R. Reddy, Satyanarayana Tatineni, S. L. Dwivedi, A. S. Ratna, A. A. M. Buiel, G. V. Ranga Rao, S. N. Nigam, R. A. Naidu, H. T. Hsu, J. W. Demski

Department of Plant Pathology: Faculty Publications

The occu!fence of peanut bud necrosis (PBN) disease in India was first reported in 1968. The high incidence ofPBN disease during the 1960s coincided with largescale imports of the peanut cultivars Asiria Mwitundae and Spanish Improved, both of which are highly susceptible to PBN. Since then, a number of reports have been published in India describing bud necrosis under at least seven different names (Reddy 1988). Crop losses due to PBN have been estimated at USD89 million per year in India during 1976-1986. The disease is also currently recognized as economically important in Nepal (Sharma 1996), in Sri Lanka, and …

Molecular Diagnostics Of Three Diabrotica (Coleoptera: Chrysomelidae) Pest Species, Allen L. Szalanski, Thomas O. Powers

Department of Plant Pathology: Faculty Publications

A 257 bp region of the mitochondrial ND4 gene was analyzed for genetic variation in three species of corn rootworm, southern corn rootworm (Diabrotica undecim punctata howardi Barber, SCR), northern corn rootworm (D. barberi Smith and Lawrence, NCR), and western corn rootworm (D. virgifera virgifera LeConte, WCR). Nucleotide sequencing revealed 26 polymorphic sites. Genetic distances averaged 8% for all pair-wise comparisons among the three species. Restriction maps were constructed from sequence data and compared to potential species specific restriction sites. Polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) revealed three restriction enzymes (Alu I, Apo I …

Identification And Characterization Of Aspergillus Nidulans Mutants Defective In Cytokinesis, Steven D. Harris, Jennifer L. Morrell, John E. Hamer

Department of Plant Pathology: Faculty Publications

Filamentous fungi undergo cytokinesis by forming crosswalls termed septa. Here, we describe the genetic and physiological controls governing septation in Aspergillus nidulans. Germinating conidia do not form septa until the completion of their third nuclear division. The first septum is invariantly positioned at the basal end of the germ tube. Block-and-release experiments of nuclear division with benomyl or hydroxyurea, and analysis of various nuclear division mutants demonstrated that septum formation is dependent upon the third mitotic division. Block-and-releasee xperiments with cytochalasin A and the localization of actin in germlings by indirect immunofluorescence showed that actin participated in septum formation. In …

Effect Of Organic Matter Decomposition Level On Bacterial Species Diversity And Composition In Relationship To Pythium Damping-Off Severity, Michael J. Boehm, L.V. Mdden, H.A.J. Hoitink

Department of Plant Pathology: Faculty Publications

Rhizosphere bacteria were isolated from root tip segments of cucumber seedlings grown in a suppressive, slightly decomposed light-colored peat mix, a conducive, more decomposed dark-colored peat mix, and a suppressive dark peat mix amended with composted hardwood bark. The bacteria were identified by a gas chromatographic fatty acid methyl ester analysis. The total number of taxa recovered from a single root tip segment ranged from 9 to 18. No single taxon predominated on all root tip segments harvested from any of the mixes. The highest relative population density reached by a given taxon on any root tip segment was 45%. …

Three New Late-Midseason Subterranean Clovers Released For High Rainfall Pastures, Phil Nichols, Donald Nicholas

Journal of the Department of Agriculture, Western Australia, Series 4

Three new subterranean clovers - Denmark, Gou/bum and Leura - have been released in 1992 by the National Subterranean Clover Improvement Program. These subterranean clovers are black-seeded, have low oestrogen levels and improved disease resistance. Their release offers the potential for substantial improvements in pasture productivity in areas of southern Australia that have long growing seasons.

This article outlines some of the testing procedures and subsequent selection of these varieties and describes their characteristics and potential role in Western Australia.

Root Disease Of Cereals, G C. Macnish, Chang Sha Fang, Karen Mcroberts

Experimental Summaries - Plant Research

Effects of nitrogen source on take-all, 82N34, 77E4. Take-all, cultivar, fertilizer, fungicide interactions, 87MT47, 87MT48, 87MT49. Take –all decline, 86MT7. Rhizoctonia root rot. Rhizoctonia patch and soil compaction, 87E28. Rhizoctonia patch and short chemical fallow, 87E3, 87E38. Rhizoctonia strains and paddock history, 87E31. Rhizoctonia root rot - host effects on strains, 87BA4, 86E30. Fusarium crown rot. Fusarium crown rot and cultivars, 87ME2, 87ME4, 87ME3 ( abandoned ).

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 …

Effects Of Two Species Of Va Mycorrhizal Fungi On Drought Tolerance Of Winter Wheat, Michael F. Allen, Michael G. Boosalis

Department of Plant Pathology: Faculty Publications

Roots and soils from western Nebraska fields of native and planted grasslands, and winter wheat of varied fallow-wheat cultivation duration, were evaluated for vesicular-arbuscular (VA) mycorrhizal root infection and spore numbers and types. Increased cultivation decreased percentage mycorrhizal infection in wheat and reduced spore numbers of Glomus fasciculatus, the dominant VA mycorrhizal fungus in these soils. Spore numbers of other VA mycorrhizal fungi did not change significantly with cultivation although mean numbers of G. mosseae increased with continued wheat production. Water relations and growth were determined for greenhouse-grown non-mycorrhizal, G. fasciculatus-infected, and G. mosseae-infected wheat in wet …

Influence Of Vesicular-Arbuscular Mycorrhizae On Water Movement Through Bouteloua Gracilis (H.B.K.) Lag Ex Steud, Michael F. Allen

Department of Plant Pathology: Faculty Publications

Root growth characteristics and water transport were compared between non-mycorrhizal Bouteloua gracilis and vesicular-arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus. Mycorrhizal plants did not have significantly different leaf area or root length from non-mycorrhizal plants, hut did have significantly fewer and shorter root hairs. Mycorrhizal plants had 50% lower leaf resistance with no change in leaf or root water potentials; thus transpiration was increased 100% with a 50% reduction in whole-plant, soil-to-root and root-to-leaf resistance. Assuming that the difference in water uptake was due to transport via the mycorrhizal hyphae, estimated fungus-to-root transport was 2◦8 x 10^{-5 …}

The Plant Pathogenic Corynebacteria, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

The plant pathogenic corynebacteria are a fascinating group of bacteria that produce effects as diverse as any in the microbial world, ranging from wilts to abnormal growths. Several new pathogens have been discovered since this group was reviewed by Jensen (75), Starr (157), and Lelliott (96). Most subsequent reviews have dealt with taxonomy. The areas covered in this review necessarily reflect my biases and limitations. However, this review attempts to be comprehensive in some areas, and it calls attention to other areas that would benefit from more detailed investigation.

Influence Of Phosphate Source On Vesicular-Arbuscular Mycorrhizae Of Bouteloua Gracilis, Michael F. Allen, James C. Sexton, Thomas S. Moore Jr., Martha Christensen

Department of Plant Pathology: Faculty Publications

Non-mycorrhizal and vesicular-arbuscular mycorrhizal Bouteloua gracilis infected with Glomus fasciculatus were grown in defined media containing different phosphate sources and compared with respect to phosphate content and form, biomass, chlorophyll concentration, and root phosphatase activity. The phosphate sources were sodium monobasic phosphate, a mixture of sodium monobasic phosphate and calcium phytate, and calcium phytate. Inositol and inositol plus calcium were added to the sodium phosphate medium as additional treatments. Mycorrhizal infection was highest in roots of plants grown in the presence of phytate (75%). Lower root infection levels were noted in plants from the sodium phosphate (19%) and mixed phosphate …

Effects Of Reduced Tillage And Multiple Cropping On Plant Diseases, Donald R. Sumner, Ben Doupnik Jr., M. G. Boosalis

Department of Plant Pathology: Faculty Publications

In the past, tillage research on plant diseases was concerned primarily with practices that buried plant residues in single-crop production systems. The burial of plant debris to destroy pathogens is an ancient agricultural prac­ tice (34). Each crop was tested as a single entity, and most crop rotations were based on one crop per year. Interest in notill and conservation tillage systems and mUltiple cropping has increased in the past two decades be­ cause of the scarcity and increased cost of fossil fuels, periodic world food shortages, and the concern over soil erosion (73,110). These concerns are of such paramount …

Comparative Water Relations And Photosynthesis Of Mycorrhizal And Non-Mycorrhizal Bouteloua Gracilis H.B.K. Lag Ex Steud., Michael F. Allen, William K. Smith, Thomas S. Moore Jr., Martha Christensen

Department of Plant Pathology: Faculty Publications

The rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus fasciculatus, to determine the influence of vesicular-arhuscular mycorrhizae on water status, stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and phosphorus content. Mycorrhizal infection increased transpiration rates by over 100% with 50 to 70% lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different between mycorrhizal and non-mycorrhizal plants indicating that whole-plant resistance to water transport was reduced by more than 50%. Photosynthetic rates under saturating light conditions increased 68% with infection as a consequence of a 33% reduction in stomatal …

Prospects For Control Of Phytopathogenic Bacteria By Bacteriophages And Bacteriocins, Anne K. Vidaver

Department of Plant Pathology: Faculty Publications

The last review on bacteriophages and bacteriocins of phytopathogenic bacteria was that of Okabe & Goto (98). All but one (21) of the subsequent reviews (II, 12, 60, 94, 104) have dealt primarily with viruses and bacteriocins of bacteria other than phytopathogens. The most recent microbiological compendia that in­ clude bacteriophages and bacteriocins are of limited value for phytobacteriolo­ gists because the authors generally overlook or ignore such agents (29, 47, 77, 119). However, Adam's classic .book (4), the review by Bradley (II), and the bibliography of Raettig (102) are still of value to phytobacteriologists as are reviews dealing principally …

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.

Potassium For Pastures, Walter Jacob Cox

Journal of the Department of Agriculture, Western Australia, Series 4

IVIany pastures in the south-west of Western Australia are deficient in potassium or need regular dressings for maximum growth. This article indicates areas and situations in which potassium might be needed, shows how deficiency is diagnosed and gives recommended rates of application.

Paspalum Vaginatum : For Salty Seepages And Lawns, C V. Malcolm, I. A. F. Laing

Journal of the Department of Agriculture, Western Australia, Series 4

PASPALUM VAGINATUM, aptly termed "sea shore paspalum" has an amazing ability to thrive in wet salty situations. It is also a good lawn grass.

Seed of the grass is not available but it may easily be established by planting pieces.

This article reviews where and how the grass may be used.

Dehulling And Scarifying Serradella Seed, J R. Weeldenburg, R. W. Smith

Journal of the Department of Agriculture, Western Australia, Series 4

YELLOW FLOWERED SERRADELLA is growing in popularity as a pasture legume on coastal sandy soils in Western Australia, and its use may increase further when new selections become available.

However, its rate of entry into commerce has been limited by the poor germination of the seed available.

Legumes Or Artificial Nitrogen?, N J. Halse

Journal of the Department of Agriculture, Western Australia, Series 4

Choosing between legumes and artificial nitrogen is not the problem which many farmers are making it.

This article deals with the choice in the mixed cereal and sheep farms of the Western Australian wheatbelt.

Cyanogenetic Plants Of Western Australia, T E H Aplin

Journal of the Department of Agriculture, Western Australia, Series 4

THIS article deals with the more important cyanogenetic plants found in Western Australia.

It also deals with plants which have not been proved as cyanogenetic but which do produce toxic effects similar to those produced by cyanogenetic plants.

Symptoms, post mortem appearances and the treatment for affected stock are also dealt with.

Loquat Diseases : Black Spot And Fleck, R F. Doepel

Journal of the Department of Agriculture, Western Australia, Series 4

Black spot is common on loquats and renders affected fruit unmarketable.

Another disfiguring fungal disease, fleck, has also become established in this State.

The newer fungicide dodine is recommended for controlling both these diseases.

Inoculation And Lime Pelleting Of Leguminous Seeds, O M. Goss, W. A. Shipton

Journal of the Department of Agriculture, Western Australia, Series 4

MOST of the extensive areas of new land being brought into cultivation in Western Australia are very sparsely populated with the rhizobial root nodule bacteria which are essential for successful legume pasture establishment.

These bacteria, therefore, must be introduced into the soil where, under favourable conditions, they will develop nodules on the roots (Fig. 1).

Puccinellia : Outstanding Saltland Grass, C V. Malcolm, S. T. Smith

Journal of the Department of Agriculture, Western Australia, Series 4

"Puccinellia" is a tussocky perennial grass with an outstanding ability to survive salty and waterlogged conditions.

Considerable areas of saltland in Western Australia are suited to its growth.

Seed is now available commercially and in this article the conditions to which the grass is suited are described and establishment and management methods are suggested.

Slime Moulds [Replaced By Farmnote 114/77], Department Of Agriculture, Western Australia

Journal of the Department of Agriculture, Western Australia, Series 4

DURING autumn and spring, yellow or grey masses of slimy or powdery material suddenly appear on the blades of lawn grass and other low-growing plants and render them unsightly.

The organisms responsible are known as slime moulds.

Establishing Wheatbelt Pastures? Don't Use A Cover Crop, J A C Smith, D. B. Argyle

Journal of the Department of Agriculture, Western Australia, Series 4

One of the factors which influence the establishment of improved pasture in the West Australian wheatbelt is whether the pasture legume is sown with a cover crop or not.

Mediocre establishment can follow when a cover crop is used and it is recommended that, for rapid establishment, any pasture legume should be sown without a cover crop.

Rust Of Snapdragons, O M. Goss

Journal of the Department of Agriculture, Western Australia, Series 4

RUST is possibly the most destructive disease attacking antirrhinums or snapdragons.

In Western Australia, the disease first appeared in 1955 and since that time has become very prevalent and widespread, frequently with devastating effects.