bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of a Virus Inhibitor, NS‐83, Derived from Plants, on Virus Infection and Multiplication in Tobacco
Authors: Li H. F. , White R. E. , Antoniw J. F.
Published: May 2008

Abstract The virus inhibitor NS. 83. when spraved onto tobacco seedlings. was ettective against mechanical inoculation of TMV when applied to the inoculated surface and when mixed with the virus before inoculation. When aphids were ased to transmit potato virus before spraving inosulated seedlings immediately after the intection feed decreased the number intecteé with the virus.

Like salicylic acid. when NS‐83 was injected into tobacco leaves lesion number, virus concen tration and lesion spread were decreased and pathogenesis related PR la protein associated with resisttance to plant pathogens was induced.

Zusammenfassung Die Einflüsse eines aus Pflanzen gewonnenen Virusinhibitors. NS‐83, auf Virusinfektion und ‐verinehrung in Tabakpflanzen

Nach einer Spritzhehandlung von Tabaksämängen war der Virusinhibitor NS‐83 wirksam gegen die schen mecbaniscb mit TMN inokulierte Oberfläche und auch. Wenn des Inhabitor mit dem Virus vor der laokulation gemischt wurde. Bei der Anwendung von Blattlausen. Um das Potato Virus Y zu übertragen, reduzierte eine Spritzbehandlung der Pllanzen mit NS‐83 unnittelbar nach der Futteruogsintektion die Anzabl von betallenen ptlanzen.

Älmlich wie Saheylsaure bewirkre NS‐83 nach dem Inizieren in Tabakblättern eine Reduzierung der Lästonenzahi der Viruskonzemration sowie der Lastionenausbreitung außerdem wurde eine Induktion des mit der Pathogenese gehoppelten Prla‐Proteines, das mit der Resistenz gegeniber Pflanzenpathogenen assozuert ist. hervorgeruten.
ELISA – Nachweis von Pflanzenviren mit Hilfe unterschiedlicher Reagenzstreifen
Authors: Reichenbächer D. , Reiss E. , Hans‐D. Hunger  , Richter J.
Published: May 2008

Abstract Detection of plant viruses by ELISA using different reagent strips

A simplified immunoassay for detection of plant viruses under field conditions was developed on the basis of the direct double antibody sandwich ELISA using dry reagent carriers immobilized on PVC‐supports which are arranged in a fan‐like manner. The fan consists of a first reagent carrier with antivirus IgG covalently bound to cyanuric chloride‐activated (CCA) paper while the second and third are filter papers impregnated with alkaline phosphatase labelled antivirus IgG and the fluorogenic subsrate, 4‐methylumbelliferylphosphate, respectively. Performing the test, the first carrier is contacted with a liquid sample containing the virus to be identified, the second and third carriers is contacted with a liquid sample containing the virus to be identified the second and third carriers are sequentially put one upon the other and the reactions carried out. The virus is detected by the reacted substrate fluorescing under a UV‐light. The applicability of the test is demonstrated with cucumber mosaic virus and potato virus X.
Ultrastructural Observations of Pterostilbene Fungitoxicity in Dormant Conidia of Botrytis cinerea Pers.
Authors: Pezet R. , Pont V.
Published: May 2008

Abstract Pterostilbene is a known phytoalexin produced by the Vitaceae. It was identified in the grape berries of Vitis vinifera (var. Gamay and Pinot). Its mode of action on conidia of Botrytis cinerea is a rapid destruction of ribosomes, endoplasmic reticulum, and of mitochondrial and nuclear membrane. Plasma membrane is completely disorganized in three hours. Respiration of the conidia is totally inhibited ten minutes after the addition of the phytoalexin. The physico‐chemical properties ofpterostilbene and the ultrastructural observations of its effects show that this compound could act on membrane proteins and interfere in mitochondrial respiration processes.
Modelling and Estimation of the Relative Potential for Infection of Winter Wheat by Inoculum of Gaeumannomyces graminis Derived from Propagules and Infected Roots
Authors: Gilligan C. A. , Brassett P. R.
Published: May 2008

Abstract A model was developed to estimate the mean number of infections of seminal roots of wheat exposed to two sources of inoculum of the take‐all fungus Gaeumannomyces graminis var. tritici, in an experimental system. The sources comprise discrete propagules of initial, soil inoculum and infected roots of volunteer plants that had been infected by the initial inoculum, prior to the growth of crop plants. The model was based on the probability of escape from infection by individual roots ofthe crop plants. Parameter estimation was by maximum likelihood. A model was first fitted to data for infection of roots from the soil inoculum. This yielded estimates for the efficiency of soil inoculum to cause infection in the absence of volunteer plants. The parameter for efficiency of infection by soil inoculum was resolved into components for inoculum density, survival of inoculum and the probability of success of individual propagules. The model was extended to include simultaneous exposure of crop roots to soil inoculum and to root inoculum on the volunteer plants. The presence of volunteer seedlings prior to sowing of crop plants resulted in an increase in the effectiveness of inoculum to cause disease. Sowing date and soil condition, as affected by addition of sand, were shown to have significant effects on the efficiency of both sources of inoculum.
Influence of Resveratrol on Germination of Conidia and Mycelial Growth of Botrytis cinerea and Phomopsis viticola
Authors: Hoos G. , Blaich R.
Published: May 2008

Abstract After inoculation of agar substrates containing resveratorl (an inducible stilbene characteristic for Vitaceae) with low concentrations (500/cm2) of Botrytis spores, developing germ tubes showed malformations and growth stopped. High, density inoculations (10,000/cm2) resulted in apparently normal growth, but stress conditions were indicated by the formation of a large number of sclerotia after 14 days. By contrast, growth of Botrytis and Phomopsis colonies starting from pieces of mycelium was slowed down by resveratrol concentrations 50 ppm and stopped by higher concentrations. More than 500 ppm (suspensions) induced rhythmical growth; at the front of the mycelium a clear zone appeared, which was free fromstilbene crystals but exhibited a brownish pigmentation. In liquid cultures pigmentation but no growth inhibition was observed. It is assumed that resveratrol is oxidized by fungal laccases whose isoenzyme bands can be stained with resveratrol after isoelectric focusing. The different effects of this substrate on fungal growth in liquid and on solid media is explained by the localized action of laccases on solid substances where the radius of diffusion is limited.
Systemic Fungal Growth of Fusarium culmorum in Stems of Winter Wheat
Authors: Snijders C. H. A.
Published: May 2008

Abstract Systemic fungal growth of Fusarium culmorum in winter wheat was investigated under conditions precluding secondary infections by water splash. Growth of F. culmorum in stem tissue was found in both wounded and soil inoculated plants with both methods resulting in a high level of infection. Crown rot can therefore lead to infection of the higher stem internodes under conditions not suitable for Fusarium dispersal. However, no evidence was found for systemic fungal growth leadingto infected heads. Existence of genetic variation for resistance to spread of F. culmorum in the host was found. This resistance was not correlated with resistance to Fusarium head blight.
Seed Transmission of Pea Seed‐borne Mosaic Virus in Peas: Early and Late Expression of the Virus in the Progeny
Authors: Khetarpal R. K. , Maury Y.
Published: May 2008

Abstract A seed lot of pea cv. Belinda was shown to transmit with high frequency a latent strain of Pea seed‐borne mosaic virus, weakly detectable in ELISA only 5 weeks after plant growth. This strain did not induce apparent symptoms on plants, was no more detectable in 9 week old plants and showed a reduced multiplication even on retro‐inoculating healthy pea plants; contrarily, the common strain could be easily detected in the seed and young seedlings on which it induced clearcut symptoms.
Comparison of Infection by W‐type and R‐type Isolates of the Eyespot Pathogen, Pseudocercosporella herpotrichoides, in Relation to Host Species and Cultivar, Temperature and Watering Regime in Controlled Environments
Authors: Bateman G. L. , Goulds A. , Ainsley A.
Published: May 2008

Abstract The incidence and severity of infection by W‐type and R‐type isolates of the eyespot pathogen, Pseudocercosporella herpotrichoides, were compared on artificially inoculated wheat (cvs Armada and Avalon) and barley (cv. Opera) grown in pots atdifferent temperatures (8–13°C and 16–21°C), and on wheat (cv. Avalon) with different watering regimes. On leaf sheaths of seedlings and on stems of older plants, infection was usually more prevalent after inoculation with the W‐type, although infection by the R‐type equalled that by the W‐type as the plants neared maturity. Infection by the W‐type, but not by the R‐type, was usually more prevalent on the more susceptible host species (wheat) or wheat cultivar (Armada). The warmer conditions duringseedling growth favoured seedling infection, but the cooler conditions during seedling infection favoured subsequent infection of the stems. Infection was greater with more frequent watering. Relative amounts of infection by the W‐type and R‐type were not influenced by temperature or watering regimes. It is suggested that epidemiological differences between the W‐type and R‐type, suspected from previous field observations, are more likely to result from inherent differences in virulence, from differences in the ways they interact with the host and with the microflora of the shoot base and from mutual interactions, rather than directly from interactions with the environment.
Untersuchungen über den Befall des Rübenzystennematoden (Heterodera schachtii Schmidt) durch pilzliche Eiparasiten in zwei Zuckerrüben‐Getreide‐Fruchtfolgen
Authors: Steudel W. , Müller J. , Schlang J.
Published: May 2008

Abstract Investigations on fungal egg parasites of the sugar beet nematode (Heterodera schachtii Schmidt) in two sugar beet‐cereal‐rotations

In two field trials with rotations of sugar beet‐cereals‐green manure the population dynamics of Heterodera schachtii was investigated as well as the frequency of its fungal egg parasites. During the rotation, highest rates of fungal parasitism (20–48%) were observed after years with sugar beet, independently of the nematode population density. In the interim parasitism decreased to about 10%. A highly significant correlation was found between nematode population density and the amount of parasitized eggs and larvae. The effect of resistant catch crops (oil radish‘Pegletta and white mustard‘Maxi’) on fungal egg parasites was not different from the effect of Phacelia or fallow. There are indications, however, that a high nematode multiplication on a susceptible catch crop promotes antagonistic fungi and, in consequence, a nematode population decrease may occur in the following sugar beet crop.
Isometric Virus‐like particles in Abies alba Mill. and Other Abies Species: Partial Purification and Improved Detection by Means of Immunoelectron Microscopy
Authors: Flachmann M. , Lesemann D.‐E. , Frenzel B. , Koenig R.
Published: May 2008

Abstract Two types of isometric virus‐like particles (VLPs) with diameters of c. 20 and 35 nm were detected in partially purified extracts from Abies alba Mill., A. homolepis Sieb. et Zucc., and five other Abies species. An immunoelectron microscopical test was developed by means of which the large VLPs could often be detected even in crude sap preparations. They were to be widespread in A. alba and A. homolepis in the Federal Republic of Germany and Southern France. Theirpresence in glasshouse‐grown seedlings of A. alba and A. homolepis shows that they are seed‐transmissible. The small particles were detected only in partically purified preparations. Neither type of VLP was found in coniferous genera otherthan Abies.
The Expression of Partial Resistance to Puccinia striiformis in Wheat. Effects on Colony Growth and Spore Production
Authors: Hyde P. M. , Elahinia S. A.
Published: May 2008

Abstract The resistance of wheat to Puccinia striiformis f. sp. tritici was investigated. The durable resistance of Hybride de Bersée and that resistance controlled by the factor YR14, in cvs Solitaire and Wembley were studied at the second and sixth leaf stages, using a point inoculation technique. Both resistance types had significant effects at both leaf stages but the most marked effects were evident on adult plants. At both leaf stages there was a high correlation between colony, length and urediniospore prodction.
Potato Protoplast‐derived Callus Tissue Challenged with Erwinia carotovora subsp. carotovora: Survival, Growth and Identification of Resistant Callus Lines*
Authors: Taylor RaymondJ. , Secor GaryA.
Published: May 2008

Abstract Potato (cv. Crystal) protoplast‐derived callus tissue was evaluated for survival and growth when exposed to Erwinia carotovora subsp. carotovora (strain Ecc71). Calli were either directly exposed to the pathogen by inoculation or to metabolites produced by the pathogen via a bilayer medium. Individual calli were inoculated with 0.5 μl of bacterial suspensions at 104, 105, 106, 107, 108 and 109 cfu/ml. The bilayer consistedof 10 ml of callus proliferation medium supplemented with pectin (2 g/l) and contained bacteria at 102, 103, 104, 105 and 106 cfu/ml. This medium was overlaid with 10 ml of bacteria free callus induction medium. Mean callus diameter of the inoculated treatments increased for 24 h, then declined. Over 90% of the inoculated calli were killed within 5 days but some survived as long as 14 days. Calli grown on the bilayer medium containing 106, 105 and 104 cfu/ml also decreased in size. Most were killed within 9 days but some survived 20 days. Calli exposed to 103 and 102 cfu/ml experienced limited growth with 20% and 7%, respectively, surviving after 27 days. Reactions to the pathogen varied considerably within the callus populations and individual calli with extended survival were identified in both experiments.
Effects of Nitrogen and Phosphorus on the Growth of Microorganisms Associated with Apple Replant Disease and on Apple Seedlings Grown in Soil Infested with these Microorganisms*
Authors: Utkhede R.S. , Smith E.M.
Published: May 2008

The growth of fungi causing apple replant disease (ARD) was inhibited by the addition of N and P to the growing medium. The population of bacteria antagonistic to ARD‐causing fungi was significantly increased in the growing medium supplemented with N 400 P 400 mg/l or greater. The application of nitrogen alone or in combination with phosphorus to soil infested with fungi or bacteria that cause apple replant disease significantly increased seedling height. The addition of P alone to these infested soils did not have any effect on seedling height. Significant increases in seedling height occurred with N applications when seedlings were grown in soil to which bacteria that are antagonistic to fungi causing ARD had been added. These results suggest that the application of N, with or without P, to apple replant soils may suppress the growth of ARD‐causing fungi or bacteria and promote the growth of antagonistic bacteria.
Virulence and Vegetative Compatibility of Dutch and Italian Isolates of Fusarium oxysporum f. sp. lilii
Authors: Löffler H.J. M. , Rumine P.
Published: May 2008

The virulence and vegetative compatibility of eight Dutch and four Italian isolates of Fusarium oxysporum obtained from lily were compared. The virulence was tested by determination of the specific interaction between the Fusarium isolates and eight lily cultivars. A specific interaction was not found, so the existence of races was not demonstrated. Six of the twelve isolates turned out to be non‐pathogenic for lily. The pathogenic isolates fell in four vegetative compatibility groups. No vegetative compatibility was found between isolates of F. oxysporum f. sp. lilii and those of f. sp. gladioli.
Resistance of Pepper Lines to the Movement of Cucumber Mosaic Virus
Authors: Nono‐Womdim R. , Marchoux G. , Pochard E. , Palloix A. , Gebre‐Selassie K.
Published: May 2008

The multiplication and the migration of cucumber mosaic virus (CMV) were studied in greenhouse conditions in one susceptible ‘Yolo wonder’ and two resistant ‘Milord’ and ‘Vania’ pepper varieties. DAS‐ELISA tests have revealed that the virus is replicated in inoculated leaves of the resistant varieties as high as in the susceptible variety. In the susceptible variety ‘Yolo wonder’, CMV migrated from the leaf lamina to the petiole two days after inoculation and it became systemic three days later regardless the season. In ‘Milord’ the virus migrated from the leaf lamina to the petiole five days after inoculation and it became systemic during the winter 16 days after inoculation. Whereas plants of the same genotype were not infected systemically during the summer. In ‘Vania’, during the two seasons, CMV spread from the blade to the petiole five days after inoculation, but the virus was not detected beyond the inoculated leaf. These results show that ‘Milord’ and ‘Vania’ are resistant to CMV migration. Therefore, the resistance to CMV migration is affected by plant genotype and temperature. The study of effect of pepper plant phenology on infection has revealed that resistance to CMV migration is also affected by the development stage of the plants.
Histopathology of Wheat Seedling Roots Infected with Pythium arrhenomanes
Authors: Mojdehi H. , Singleton L. L. , Richardson P. E.
Published: May 2008

Two‐day‐old wheat seedlings were placed on the edge of a P. arrhenomanes culture for 3 h at 25°C, and transferred into test tubes (18 mm dia.) containing glass beads and 1 ml of sterile water. Roots were sampled every 6 or 12 h for 84 h, and observed with the scanning electron microscope, or serial sectioned for light microscopy. Roots were colonized extensively in the region of root hair formation near the tip within 30 h after inoculation. Extensive penetration occurred 0.1—2 mm behind the root tip, with hyphae breaching the endodermis and gaining entry into the stele. Behind this area, hyphae remained limited to the outer cortical cells, or did not penetrate at all. Hyphae grew intracellularly, and became irregularly inflated inside cells. In most cases, hyphae penetrated the roots directly through the epidermis with appressoria being formed, or through breaks on the surface. However, histological evidence suggested chemical action taking place both outside and inside the cells.
Soluble Proteins, Esterases and Superoxide Dismutase in Stem Tissue of Pepper Plants in Relation to Age‐related Resistance to Phytophthora capsici
Authors: Hwang ByungKook , Yoon Jae Young , Ibenthal W.‐D. , Heitefuss R.
Published: May 2008

Patterns of soluble proteins and isoenzymes of esterase and superoxide dismutase were investigated in healthy and infected stems of two pepper cultivars resistant and susceptible to Phytophthora capsici. By the use of two‐dimensional SDS‐polyacrylamide gel electrophoresis, it was possible to compare precisely the cultivars Hanbyul and Kingkun susceptible or resistant to P. capsici with respect to their protein patterns. The two‐dimensional electrophoresis identified three proteins (25—27 kD) from the healthy stem extracts of Kingkun, which were absent in Hanbyul. Some particular proteins appeared in pepper stems of both cultivars at later developmental stage of plants, suggesting their role in the expression of age‐related resistance. Some proteins which were not detectable in the healthy stem extracts also existed in large amounts in the diseased ones. By contrast, other proteins present in the healthy stems disappeared from the diseased stems. Some esterase isoenzymes appeared in the two cultivars only at late developmental stage. Other esterase isoenzymes were produced only in the diseased stems. There were no differences in the patterns of superoxide dismutases between the cultivars and also between developmental stages. Large activities of several superoxide dismutases were detected in the diseased stems.
Karl Otto Müller (1897—1978) und die Entdeckungsgeschichte der Phytoalexine
Authors: Höxtermann Ekkehard
Published: May 2008

Karl Otto Müller was an outstanding scientist in applied botany who substantially promoted modern plant breeding and phytopathology. In 1928 he started his experimental studies about phytophthora resistance of potatoes enlightening on an up to that time unknown defensive reaction of higher plants, which led to the postulation of phytoalexins 50 years ago.
Isolation of Solanapyrones A, B and C from Culture Filture and Spore Germination Fluids of Ascochyta rabiei and Aspects of Phytotoxin Action
Authors: Höhl B. , Weidemann C. , Höhl U. , Barz W.
Published: May 2008

Nine isolates of the fungus Ascochyta rabiei have been assayed for their ability to produce solanapyrone toxins. All isolates formed solanapyrone A, B and C which were secreted into the culture medium. Pronounced production of the toxins only occurred after onset of sporulation. The identification of the fungal products was achieved by cochromatography (TLC, HPLC), 1H‐NMR (solanapyrone A and B) and mass spectrometry (solanapyrone B). Work with A. rabiei isolate X showed that cultivation in chickpea seed extract medium in a surface culture provided best conditions for maximal toxin production. The accumulation of solanapyrones over the growth cycle was monitored. Germinating spores produced solanapyrones C and B whereas solanapyrone A was formed from the 6th day of the culture period on.

Application of a mixture of solanapyrones A, B and C to leaflets of intact plants from an A. rabiei resistant cultivar (ILC 3279) and a susceptible cultivar (ILC 1929) led to characteristic changes in leaf morphology which had earlier been obsevad in susceptible plants following infection with spores of A. rabiei. Attempts to demonstrate the occurrence of toxins in the infected leaf were unsuccessful. Application of solanapyrones to solanapyrones to chickpea cell suspension cultures (derived from both cultivars) led to pronounced losses in viability and to plasmolysis of cells.
Disease Development and Buildup of Resistance to Oxadixyl in Potato Crops Inoculated with Phytophthora infestans as Affected by Oxadixyl and Oxadixyl Mixtures: Experimental and Simulation Studies
Authors: Levy Y. , Cohen Y. , Benderly M.
Published: May 2008

Simulator predictions for the effect of oxadixyl and oxadixyl mixtures on the control of late blight in potato crops inoculated with Phytophthora infestans and the buildup of fungal resistance to oxadixyl were compared with data obtained in field experiments. The simulator, which considered fungus, fungicides and crop variables, predicted accurately the effect of fungicide sprays (oxadixyl, oxadixyl mixed with mancozeb, and oxadixyl mixed with mancozeb and cymoxanil) on blight development. The model predicted accurately both resistance buildup and infection in non‐treated crops and in crops treated with oxadixyl alone or in a mixture with mancozeb (SAN 518F), but overestimated the control efficacy of the three‐way mixture Pulsan.
Effect of Heat‐killed Bacteria on the Interaction of Pea with Pseudomonas syringae pv. pisi
Authors: Akpa A. D. , Archer S. A.
Published: May 2008

The effect of simultaneous treatment with heat‐killed and live bacteria on the responses of two pea cultivars, Early Onward and Hurst Green Shaft, to inoculation with two races, 1 and 2, of Pseudomonas syringae pv. pisi was investigated. Simultaneous application induced resistance in pea to the bacterial pathogen. The level of resistance response elicited in the host increased with increasing number of heat‐killed cells in the inoculum. Heat‐killed cells of neither race elicited the hypersensitive reaction. No symptoms were induced in plants of either cultivar from treatment of control plants with sterile distilled water or from treatment with heat‐killed bacterial cells only. Simultaneous treatment with heat‐killed and inoculation with live bacteria did not have any apparent effect on the trend of bacterial multiplication in vivo.
New Races of the Sunflower Downy Mildew Pathogen (Plasmopara halstedii) in Europe and North and South America
Authors: Gulya T. J. , Sackston W. E. , Viranyi F. , Masirevic S. , Rashid K. Y.
Published: May 2008

Collections of the causal agent of sunflower downy mildew (Plasmopara balstedii) (PH) from several European and North and South American countries were used to inoculate a series of sunflower inbred lines to differentiate races. Race 3 was identified from Argentina; race 4 from France, Hungary, and Bulgaria; race 6 from Canada and France; and race 7 from Argentina. This is the first report of race 3 in South America and of race 4 in Europe, and is the first identification of races 6 and 7. Reactions of USDA lines RHA‐274, RHA‐325, and DM‐2 differentiate races 2, 6, and 7, with RHA‐274 resistant to all three. Thirty‐three commercial hybrids from 11 countries were tested; 70 % were resistant to race 2, only 27 % had resistance to race 6, and none were resistant to race 4. Surveys to determine the relative proportions of the various races within each country are needed to assess their potential impact. The USDA lines HA‐335, HA‐336, HA‐337, HA‐338, HA‐339, RHA‐340, HA‐R4, and HA‐R5 are resistant to all seven mildew races and could be utilized for the production of PH resistant hybrids. For the short term, it appears that seed treatment with metalaxyl may be the most effective control.
Potato Virus X—a New Report from Turnip (Brassica rapa L.) in India
Authors: Samad Abdul , Naqvi Q. A. , Garg I. D. , Twhouvenel J.‐C.
Published: May 2008

A virus isolated from turnip in Aligarh, India, which caused mild mosaic, mottling and curling of leaves followed by overall stunting of plants, was characterized as potato virus X (PVX) on the basis of its host range, biological and physical properties, particle morphology, ultrastructural studies, and serological relationship.
Control of Rhizoctonia solani and Cotton Seedling Disease by Laetisaria arvalis and a Mycophagous Insect Proisotoma minuta (Collembola)
Authors: Lartey RobertT. , Curl E. A. , Peterson CurtM. , Williams J. C.
Published: May 2008

Laetisaria arvalis and a mycophagous, rhizosphere‐inhabiting collembolan, Proisotoma minuta, were evaluated in sterilized and nonsterilized soil for suppression of Rhizoctonia solani in a greenhouse environment. R. solani was applied to soil at rates between 10 and 150 mg of colonizedoat inoculum/kg soil. L. arvalis was applied directly to soil at 100 mg/kg or as a seed dressing, either alone or in combination with a population of P. minuta at 1000/kg soil. L. arvalis significantly reduced incidence and severity of cotton seedling disease caused by R. solani; the seed treatment provided better suppression than when L. arvalis was applied to soil. Combination of the fungal agent with P. minuta enhanced suppression of R. solani more than with either agent used alone. Control benefit was linearly increased when increased numbers of insects were applied with L. arvalis.
Consecutive and Simultaneous Competition ELISA of Monoclonal Antibodies: Characterization of Epitope Relationships or Immunoglobulin Idiotypes
Authors: Kubanek C. A. , Hill J. H. , Van Deusen R. A. , Durand D. P.
Published: May 2008

A panel of monoclonal antibodies prepared against cowpea severe mosaic virus was divided into two groups based upon presence or absence of competition with a biotinylated antibody in competition ELISA. Antibodies that did compete could be further characterized by comparison of competition curves obtained from assays performed in simultaneous and consecutive manners. These two types of competition assays provide an easy method to define intially relationships among epitopes on antigens and to characterize specific immunoreactivity of different antibodies to the antigen.
Biological Control Activity of Three Trichoderma Isolates Against Fusarium Wilts of Cotton and Muskmelon and Lack of Correlation with their Lytic Enzymes
Authors: Ordentlich A. , Migheli Q. , Chet I.
Published: May 2008

The enzymatic activity and the biocontrol ability of two new isolates of Trichoderma spp. (T‐68 and Gh‐2) were compared in laboratory and glasshouse experiments with a previously studied T. harzianum strain (T‐35). In dual culture tests with Fusarium oxysporum f. sp. melonis and F. oxysporum f. sp. vasinfectum, isolates T‐68 and Gh‐2 overgrew the colonies of Fusarium, whereas T‐35 failed to parasitize both wilt pathogens. Under glasshouse conditions, the three isolates of Trichoderma were effective in controlling Fusarium wilt of cotton but only T‐35 was effective against F. oxysporum f. sp. melonis on muskmelon. When the three Trichoderma isolates were grown on liquid media containing laminarin, colloidal chitin or F. oxysporum f. sp. melonis cell walls as sole carbon sources, maximum β‐1,3‐glucanase and chitinase specific activity in the culture filtrates of all fungi was reached after 72h of incubation. When culture filtrates of the three Trichoderma isolates were incubated with freeze‐dried mycelium of F. oxysporum f. sp. melonis or F. oxysporum f. sp. vasinfectum, different concentrations of glucose and N‐acetyl‐D‐glucosamine were released. Overall no correlation was found between enzymatic activity and the biocontrol capability against Fusarium wilt on muskmelon and cotton.
A Simulation Model for Assessing Soybean Rust Epidemics
Authors: Yang X. B. , Dowler W. M. , Tschanz A. T.
Published: May 2008

A soybean rust (causal agent Phakopsora pachyrhizt) simulation model was developed for assessing disease epidemics as a part of pest risk analysis. Equations describing environmental effects on disease components were developed by re‐analyzing previous data with a view toward a systems approach. The infection rate was predicted well using dew period and temperature after inoculation as independent variables (R2=0.88, P < 0.0001). The exponential models which used physiological day as an independent variable explained 98% of the variations of latent period and senescence of disease lesions. The simulation model was validated with data from 72 sequential planting experiments during 1980 and 1981 in Taiwan. Time of onset for these epidemics varied from 25—60 days and 50—80 days after planting soybean cultivars TK 5 and G 8587, respectively. The epidemic periods were 75—95 for TK 5 and 100—120 days for G 8587. Variation of epidemics was accurately predicted by the simulator. Predicted disease curves fit well the observed disease curves for the recognized cropping seasons, spring‐ and autumn‐seeded crops. For G 8587, which is very sensitive to photoperiod, the data from spring and autumn gave a better fit compared with data from pre‐summer planting. The model underestimated disease epidemics during the winter, probably because the plant growth model failed to reflect the photoperiod rection of soybean. The simulation model was validated with data from other experiments conducted in three cropping seasons in 1979 and 1980. Determination coefficients of the regression between observed and predicted disease severity were significant.
The Effects of Temperature on the Susceptibility of Potato Plants to Infection and Accumulation of Potato Leafroll Virus
Authors: Syller J.
Published: May 2008

Temperature both before and after aphid inoculation with potato leafroll virus (PLRV) greatly influenced the susceptibility of potato plants to infection and virus accumulation, as evaluated with ELISA using cultivars with different ratings for the resistance to PLRV. Pre‐incubation at 15 compared to 27 °C increased the susceptibility of plants to infection and a subsequent PLRV accumulation. The virus was detected by ELISA in a greater proportion of plants and reached a higher concentration, when the plants were kept at 27 than at 15 °C after inoculation. The mean ELISA values obtained with PLRV‐infected plants in the 15/27 combination of the pre‐/post‐inoculation temperatures over the period 1—6 wks after inoculation were significantly higher than those in the 27/27, 15/15 and 27/15 treatments, and the values obtained in the 27/27 treatment were significantly higher than those in the 15/15 and 27/15 ones. A hypersensitive‐like intolerance reaction to PLRV occurred in the resistant cv. Irga only in the plants kept at 27 °C after inoculation.
The Effect of Bacillus subtilis on in vitro Growth and Pathogenicity of Agrobacterium tumefaciens
Authors: Hassanein F. M. , El‐Goorani M. A.
Published: May 2008

Five isolates of Bacillus subtilis isolated from the soil, were found to be antagonistic to 6 isolates of Agrobacterium tumefaciens in vitro.

Inoculation of B. subtilis in wounded castor bean plants 30 min before or simultaneous inoculation with A. tumefaciens resulted in excellent control of the crown gall symptoms on the host within 50 days of inoculation.

Application of B. subtilis 30 min after inoculation with A. tumefaciens did not result in appreciable disease reduction.

Treatment of the tested plants by B. subtilis did not induce any phytotoxic injury or growth retarding side effects.

It appears that B. subtilis could potentially be incorporated for crown gall control. However, further tests are needed to test this biological control agent with other plant species especially fruits, nuts and vine nursery stock.
Localization of Closteroviruses on Grapevine Thin Sections and Their Identification by Immunogold Labelling
Authors: Faoro F. , Tornaghi R. , Belli G.
Published: May 2008

Different fixation and embedding procedures have been tested in order to facilitate closterovirus identification on thin sections of leafroll‐affected grapevine plants. Standard fixation with glutaraldehyde followed by osmium tetroxide proved to be the most reliable for cytopathological studies while simultaneous fixation with glutaraldehyde, picric acid and osmium tetroxide facilitated the discrimination between aggregates of P‐proteins and virus particles in routine e. m. work. However the identification of every single virion among P‐protein filaments was only possible by means of post‐embedding immunogold labelling carried out on non‐osmicated tissues embedded in London Resin White. This technique has also been applied to both section sides thus allowing the identification of different closteroviruses contemporaneously present in the same phloem tissue. Numerous ultrastructural observations of different grapevine cultivars infected with either GVA, or GLRaV‐I or GLRaV‐III evidentiated the presence of some recurrent and peculiar cytopathic effects that can be used as diagnostic parameters for at least two of the above viruses.
Pseudomonas syringae pv. syringae as One of the Factors Affecting the Ice Nucleation of Grapevine Buds in Controlled Conditions
Authors: Luisetti J. , Gaignard J. L. , Devaux M.
Published: May 2008

Ice nucleation in grapevine buds (cv. Pinot noir) was studied in freezing chamber in container grown plants. The ice nucleation of individual 278 buds at different stages of their development (between stage B and stage E according to Baggiolini scale) was measured by differential thermal analysis. Treatments were applied to plants to modify the Pseudomonas syringae pv. syringae content of buds and alter their water potential.

Based on the results it was pointed out that (i) the ice nucleation temperatures of buds were generally normally distributed, (ii) the probability of bud nucleation at a given temperature was, to a certain extent, dependent on the amount of Pseudomonas present, (iii) the modification of water potential following an artificial rain led to a signification increase of the probability of bud nucleation and (iv) the nucleation probability did not increase significantly with the bud development between stage B and stage E.
Systemic Acquired Resistance to Virus Infections and Ethylene Biosynthesis in Asparagus Bean
Authors: Pennazio S. , Roggero P.
Published: May 2008

Systemic acquired resistance (SAR) was induced in asparagus bean following inoculation with tobacco necrosis virus (TNV) or tobacco rattle virus (TRV), viruses that produce a hypersensitive reaction in this plant. SAR was expressed against challenge by TNV as reduction in lesion size, but not as inhibition of viral antigen accumulation.

Systemic stimulation of ethylene‐forming enzyme (EFA) activity, in the absence of any ethylene increase or 1‐aminocyclopropane‐1‐carboxylic acid (ACC) accumulation, was associated with SAR. Formation of local necrotic lesions was necessary for both induction of SAR and stimulation of EFA, because early removal of inducer leaves prevented both events. SAR was expressed at rather constant level between 7 and 12 days after inducing infection. EFA stimulation declined with time and was no longer detected 7 days after inducing infection.

SAR was not expressed against cucumber mosaic virus, that infect asparagus bean systemically. Prior inoculation with TNV or TRV was ineffective to reduce CMV antigen content or to minimize the pathogenic effect of this virus in systemically infected leaves.
Isozyme Variability in Isolates of Some Facultative Phytopathogenic Fungi
Authors: Newton A.C.
Published: May 2008

Gel electrophoresis was used to examine the variation in isozymes within and between the facultative pathogen species Septoria nodorum, Ustilago maydis and Rhynchosporium secalis. Variation was found in all three species, U. maydis being the most variable. The variation between isolates of R. secalis was sometimes unstable, reflecting variability in other characters. The determinants of isozyme variability, particularly in relationship to the general biology of different fungi, are discussed.
Immunocytochemical Evidence for the Presence of Barley Thionins in Rachis and Stalk of Wheat: Decrease of Antibody Binding at Fusarium culmorum Penetration Sites
Authors: Ebrahim‐Nesbat F. , Apel K. , Heitefuss R.
Published: May 2008

In thin sections of wheat rachis and stem, embedded in Spurr's resin, prefixed with glutaraldehyde and postfixed with osmium, large amounts of barley thionins were localized in cell walls with anti‐thionin‐protein A/gold. Reduced binding to thionin was detected in cell walls penetrated by Fusarium culmorum, suggesting that cell wall thionins were degraded by the fungus.
Barley Yellow Striate Mosaic Virus as the Cause of a Major Disease of Wheat and Millet in Iran
Authors: Izadpanah K. , Ebrahim‐Nesbat F. , Afsharifar A. R.
Published: May 2008

Barley yellow striate mosaic virus (BYSMV) was identified in Iran by electron microscopy and serology. The virus was widespread in the Fars province causing mosaic, stunting and head sterility in wheat and mosaic symptoms in Setaria spp. In 1989, about 1/3 of wheat plants in the Bajgah Experiment Station, 15 km north of Shiraz, were infected. The yield in individual plants was drastically affected. Rhabdovirus particles were consistently observed in leaf‐dip preparations and thin sections from the infected plants. The virus was transmitted by Laodelphax stritellus to wheat. It reacted with BYSMV antisera from Italy and Morocco but not with antisera to several other rhabdoviruses of gramineous plants.
The Association of Peroxidase Activity and Resistance of Maize to Exserohilum turcicum
Authors: Shimoni M. , Bar‐Zur A. , Reuveni R.
Published: May 2008

Peroxidase activity in leaves of maize (Zea mays L.) differing in susceptibility to Exserohilum turcicum has been investigated in relation to their resistance to Northern Leaf Blight (NLB) caused by the fungal pathogen E. turcicum. In non‐inoculated plants, high peroxidase activity was detected in leaves of the resistant isolines B37HtN and B73HtN as compared with the susceptible isolines B37 and B73 and the sweet corn variety Jubilee. After inoculation with E. turcicum, peroxidase activity increased in both susceptible and resistant isolines B73 and B73HtN. However, marked enhancement of peroxidase activity was detected 6 days after inoculation and became remarkable in isoline B73HtN, although symptomes started to show up in both susceptible and resistant plants only 10 days after inoculation.

Using polyacrylamide gel electrophoresis separations, different banding pattern of isoperoxidases was found in the susceptible plants as compared with the resistant ones. In non‐inoculated plants, three differential bands which appeared in the resistant isoline B37HtN, were absent in the susceptible Jubilee plants, and were as traces in the isoline B37. These bands first appeared in Jubilee and as clear bands in B37, only after inoculation with E. turcicum. The association of these isoperoxidases and resistance of maize to E. turcicum is discussed.
Gehalt an Beet Necrotic Yellow Vein Virus (BNYVV) in der Hauptwurzel von Zuckerrübenpflanzen verschiedener Sorten und deren Leistung unter Rizomaniabefall im Feld
Authors: Bürcky K. , Büttner G.
Published: May 2008

BNYVV concentration in the tap roots of sugar beet varieties grown in rhizomania‐infested fields

During plant development, the BNYVV concentration in several commercially available rhizomania‐tolerant sugar beet varieties and one susceptible variety was examined as an index of the intensity of infection. The root weight, sugar content and sugar yield of the same varieties in fields naturally infested with rhizomania were also measured.

Significant negative correlations were found between the average virus concentration in the tap root and yield parameters in infested fields. These were largely independent of the growth stage of beet plants used for virological investigations. However, the negative correlations between virus concentration and yield were not significant if rhizomania‐tolerant varieties only were compared.

The possibility that virus concentration might be used as a criterion for selection in addition to yield performance is discussed. This may lead to selection that is targeted more directly at rhizomania resistance and thereby accelerate breeding work.
Variation in Pathogenicity and Virulence of Strains of Xanthomonas campestris pv. glycines, the Incitant of Bacterial Pustule of Soybean
Authors: Hokawat S. , Rudolph K.
Published: May 2008

Standardized methods were developed to determine the pathogenicity and the degree of virulence of Xanthomonas campestris pv. glycines (Xcg) as well as the reaction of soybean plants in the greenhouse. A glass atomizer is described which allowed uniform inoculation without damaging the leaves. Optimum bacterial concentration was determined as 6 × 106 CFU/ml for the pathogenicity test and 1.3 × 105 CFU/ml for the virulence test. A total of 64 isolates were tested. Forty‐five strains were designated as pathogenic, six of which were considered highly virulent. It was shown, for the first time, that large differences in the virulence of Xcg strains exist.

All the highly virulent strains of Xcg were fresh isolates from diseased soybean leaves collected in Thailand. On the other hand, all the “old” cultures from bacterial collections possessed a low or very low virulence. Decrease of virulence of the pathogen did not occur very fast, however, that is: not within 2 years when stored on YDC‐agar slants. Therefore, the bacteria may be kept on slants at 15 °C for short time storage, but the strains should be preserved permanently as lyophilized cultures.
Differential Reactions Between the Genus Brassica and Aggressive Single Spore Isolates of Leptosphaeria maculans
Authors: Badawy H. M. A. , Hoppe H.‐H. , Koch E.
Published: May 2008

Based on sirodesmin production and pathogenicity tests with Brassica cotyledons, strains of Leptosphaeria maculans were classified as aggressive (pathotype group A), or non‐aggressive (pathotype group NA). NA strains caused no differential reactions. However, the pathotype group A could be divided into 5 sub‐groups. AO isolates caused non‐sporulating lesions with dark margins while Al isolates sporulated on cotyledons of most Brassica hosts tested. Only the cv. Erfurter Zwerg (B. oleracea var. botrytis) reacted resistant against AO and Al strains. A2 isolates caused resistance reactions on cotyledons of the cvs. Quinta (B. napus var. oleifera) and Runde (B. rapa var. rapa). A3 and A4 isolates were not detectable in our material. Isolates of these pathotype groups, supplied by Dr. P. H. Williams, Madison, USA, caused differential reactions on the oilseed rape cvs. Glacier, Quinta and Jet Neuf. In glasshouse and field experiments strains of pathotype groups Al, A2 and NA were tested on true leaves and hypocotyls of different oilseed rape cultivars. The low aggressiveness of NA isolates was evident under all experimental conditions. A2 strains caused resistance reactions not only on cotyledons but also on true leaves and hypocotyls of Quinta. Moreover, compared with Al, pathotype group A2 was more aggressive on hypocotyls of Jet Neuf. The resistance of this cultivar against Al isolates was clearly visible on hypocotyls and true leaves but not on cotyledons.
Susceptibility of Grafted Malus Taxa and Hybrids to Apple Proliferation Disease
Authors: Kartte Sylvia , Seemüller E.
Published: May 2008

Seedlings of a great number of Malus species, subspecies, cultivars and hybrids were graft‐inoculated with the apple proliferation MLO. The scion cultivars were M. pumila cv.‘Cox's Orange Pippin’and‘Golden Delicious’. The grafted trees responded very differently to infection. According to recovery rate, witches’broom formation, mortality, and development of the MLO population, the tested material could be divided into 5 groups. Group I corresponds to the domestic apple M. pumila and is characterized by a low recovery rate, a low mortality, a high frequency of witches’broom formation, and a high MLO titer. Group II differs from group I mainly by a higher mortality. In group III, mortality is like in group II but recovery is higher while witches’broom formation and MLO titer are significantly lower. Group IV is characterized by a mortality of more than 50 %. Both witches’broom formation and the numbers of MLOs in the phloem are usually low. In group V, most of the trees recovered or showed never symptoms while mortality was low. After inoculation the MLO population was low or appeared degenerate. During recovery the number of MLO‐positive samples decrease so that by the end of the observation period the organisms could not longer be detected in most cases. Group V consists of apomictic rootstock selections deriving from crosses of M. sieboldii and M. sargentii with M. pumila. Due to the combination of low mortality with the apparent elimination of the MLOs within a few years this group fulfills the requirement of resistant rootstocks suitable for controlling apple proliferation.
Histopathology of Apple Proliferation in Malus Taxa and Hybrids of Different Susceptibility
Authors: Kartte Sylvia , Seemüller E.
Published: May 2008

Malus taxa and hybrids (“taxa”) grafted with M. pumila cv.‘Golden Delicious’differ significantly in their susceptibility to apple proliferation which is caused by a mycoplasma‐like organism (MLO). These differences are correlated with the severity of anatomical aberrations and the numbers of MLOs in the phloem. The roots of declining trees of highly susceptible taxa with a mortality of more than 50 % are characterized by extensive phloem necrosis and the depletion of starch. MLOs are either not detectable or are present in low numbers, or the population appears degenerate when viewed by fluorescence microscopy. In comparable trees of a hybrid of M. sieboldii×M. pumila which shows a high recovery rate, both phloem necrosis and starch depletion are less pronounced, and the MLO numbers are low or the organisms are not detectable. Decline‐tolerant taxa such as M. silvestris or M. pumila×M. baccata are little affected. Their phloem conditions and starch content do not differ significantly from that of healthy trees. However, the MLO titer is high. The histopathology of the scion cultivar of all groups examined is rather similar to that of the roots of the decline‐tolerant taxa. Only in a late stage of decline, phloem necrosis increases while starch content and MLO numbers decrease in the scions grafted onto highly susceptible stockls.