bluuebunny/crossref_metadata_2025 huggingface dataset:
PhytophthoraRoot Rot of Pepper Influence of Host Genotype and Pathogen Strain on the Inoculum Density‐Disease Severity Relationships
Authors: Palloix A. , Daubeze A. M. , Pochard E.
Published: May 2008

The relationship between inoculum density and mortality or infection was studied for various pepper varieties (Capsicum annuumL.) inoculated with zoospores of twoP. capsiciisolates. The inoculum concentrations required for 50% mortality (LD 50) varied greatly between pepper varieties andP. capsiciisolates: with one isolate, LD 50 was 40 zoospores/ml for a susceptible variety and reached 4,380 to 97,300 zoospores/ml for resistant varieties. For another isolate, LD 50 for the, same varieties ranged from 26 to 800 zoospores/ml. Comparisons between LD 50 and inoculum doses required for 50 % Infection (ID 50) also revealed differences between varieties but not between isolates. After multiple infection correction, regression slopes of infections/inoculum concentration were low for resistant varieties (0.28 to 0.50) but higher for susceptible varieties (0.72 to 0.94), indicating strong competition between spores for infection of resistant plants, but not for infection of susceptible plants. This analysis provided many criteria which can be used to differentiate susceptible from resistant varieties and to evaluate with precision the resistance level of the different resistance genitors used in our breeding program.
Physical Factors that Influence the Growth and Spread of Charcoal Rot Pathogen (Macrophomina phaseolina) Infecting Maize
Authors: Kaiser S. A. K. M. , Das S. N.
Published: May 2008

The rabi maize, that is being popularised in the eastern parts of the country may suffer from charcoal rot disease [Rhizoctonia bataticola Taub. Butl. (Macrophomina phaseolina (Tassi) Goid.)] if the pathogen gets timely entry into the host, as has been revealed in the present study. In vitro studies show that the spread of the pathogen within the maize stalk is influenced by high temperature, the optimum being 38°C. The role of RH on the incidence of this disease was, however, not well defined. These observations hold true as well for the data recorded in the field.
Isolation and Characterization in Gynura aurantiaca of a Possible Citrus Rhabdovirus
Authors: Rodriguez J. L. , Diaz‐Ruiz J. R. , Flores R.
Published: May 2008

Rhabdovirus particles were detected in greenhouse‐grown Gynura aurantiaca plants during a study of citrus diseases, and some of their biological and physicochemical properties were determined. The gynura plants displayed vein clearing of young leaves as the earliest symptom and later on, an anomalous growth of some leaves. This syndrome could be easily transmitted by graft, dodder and, with more difficulty, by sap inoculation. Electron microscopy showed bacilliform virions of about 260 × 70nm, in perinuclear spaces. Purified rhabdovirus particles inoculated to healthy plants were infectious, showing that this virus was the causal agent of the gynura syndrome. An estimate of the buoyant density in sucrose of the virus gave a value of 1.17g/,cm3. Analysis of virion proteins by SDS‐PAGE revealed four major bands of relative molecular mass 81.5, 56.6, 31.6 and 24.6 x 103, suggesting that these corresponds to the G, N, M1 and M2 proteins respectively, of the subgroup B of plant rhabdoviruses. From these data we conclude that the rhabdovirus here described should be placed in the potato yellow dwarf virus subgroup of plant rhabdoviruses. The fact that a Citrus could be the original source of the virus is discussed.
Oospore Formation in Phytophthora drechsleri f. sp. cajani
Authors: Singh U. P. , Chauhan V. B.
Published: May 2008

Phytophthora drechsleri f. sp. cajani (Pal et al.) Kannaiyan et al. causes stem and leaf blight in pigeon pea (Cajanus cajan [L.] Millsp.) in India. The asexual phase occurs in artificial culture as well as on the host tissue. Sparse oospore formation has been observed in old cultures. A technique has been evolved in which abundant mature oospores are formed on the leaflets of pigeon pea and also on glass slides using zoospores and mycelial discs on the former butonly mycelial discs on the glass slides. The largest number of oospores was formed after incubation for 36 h at 25°C.
Johnsongrass Chlorotic Stripe Mosaic and its Associated Viruslike Particles in Iran1
Authors: Izadpanah K.
Published: May 2008

A mosaic disease of Johnsongrass characterized by the presence of short and long chlorotic stripes in leaves and stunting of plants was found in two locations about 300 km apart in the Fars Province of Iran. The disease occurred in patches or along the irrigation ditches. The disease agent could not be transmitted mechanically or by certain insects and mites. About 0.5% of the seedlings, grown in soil from the root zone of diseased plants, developed the disease after 1–8 months. Electron microscopy, of leaf‐dip preparations showed presence of isometric viruslike particles (VLPs) of about 35 nm diameter in unusually high concentrations in diseased plants but not in healthy plants. VLPs from diseased leaves were purified by low‐pH clarification followed by differential and densitygradient centrifugation. Purified VLP preparations showed UV absorption spectrum typical of nucleoproteins. A260/A280 was 1.48. High titered antisera obtained by injecting rabbits with purified VLPs reacted with sap from diseased plants but not healthy plants. Purified VLP preparations and sap from diseased plants did not react with antisera to Bermuda grass etched line, Brachypodium sylvaticum, brome mosaic, maize chlorotic dwarf, maize rayado fino, maize white line mosaic and tobacco necrosis viruses.
Fatty Acid Profiles of Erwinia amylovora as Influenced by Growth Medium, Physiological Age and Experimental Conditions
Authors: Casano F. , Wells J. , van der Zwet T.
Published: May 2008

Total cellular fatty acids for 20 strains of Erwinia amylovora grown on trypticase soy agar (TSA) for 3 days at 27°C, and for 3 strains grown on nutrient agar (NA), King's B (KB), glucoseyeast extract carbonate (GYCA) and TSA for 1, 3 and 6 days were analyzed by gas‐liquid chromatography. Forty one percent of total fatty acids were saturated even‐carbon straight chains, 6 % were saturated odd‐carbon chains, 34 % unsaturated acids, 6 % hydroxy‐substituted acids, 1 % branched chains, 7 % cyclic acids, and 4 % unidentified components. Composition was affected by growth medium, physiological age of cells, and chromatograph sensitivity. On TSA and NA saturated odd‐carbon and cyclic acids of the 3 strains (combining 1, 3 and 6‐day data) were higher than on KB and GYCA. Cyclic acids increased with physiological age on GYCA and KB medium. Even‐carbon straight chain and unsaturated fatty acids (major components) constituted a significantly lower percentage of total fatty acids in chromatograms of high sensitivity (30–50 components) than of low instrument sensitivity (15–20 components).
A Potential Defense Mechanism of Tomato Against the Late Blight Disease is Suppressed by Germinating Sporangia‐derived Substances from Phytophthora infestans
Authors: Storti E. , Pelucchini D. , Tegli S. , Scala A.
Published: May 2008

Hypersensitive browning, host cell death and phytoalexins (rishitin) synthesis in both callus cultures and cotyledons have been observed in a susceptible tomato cultivar following treatment with high molecular weight cell wall components from Phytophthora infestans race 1B. The growth of the pathogen was restricted on both elicited differentiated and undifferentiated tomato tissues. Subtance(s) released by germinating sporangia, but not by the mycelium, suppressed the hypersensitive reaction.
Production and Dispersal of Conidia of Peronospora pisi on Pea Leaves
Authors: Singh U. P. , Reddy D. H. K. B. , Gupta Sushma
Published: May 2008

The number of crops of conidiophores and conidia of Peronospora pisi produced on a single lesion on leaflets of pea (Pisum sativum L.) was determined both in vitro and in vivo by artificial inoculation. Only two crops were produced in vitro whereas five crops were discerned under in vivo conditions. There was a marked difference in the size of conidiophores and conidia formed under the above two conditions.

Temperature had a marked effect on the penetration of pea leaflets by conidial germ tubes of P. pisi. The pathogen penetrated the leaf tissues at 12‐14°C in 8.0‐8.5 h whereas more time (9.5‐16.5 h) was required for penetration at higher temperatures (15‐18°C).

Use of systemic fungicides has been suggested to control downy mildew of pea because of its capacity to produce more than one crop of propagules on the same lesion.

Maximum spore discharge in P. pisi was observed from 9.00 to 15.00 hours. However, presence of light, high temperature, lack of moisture on leaf surface and wind velocity affected spore discharge.
Scopolin, a Biochemical Marker for Resistance to Thielaviopsis basicola in Callus and Crown‐Gall Tissue Cultures of Tobacco
Authors: Gasser R. , Kern H. , Défago G.
Published: May 2008

Scopolin concentration increased in tissue cultures where Thielaviopsis basicola growth ceased (primary and established callus cultures of the resistant tobacco cultivar Ky 170) while it decreased in tissue cultures where fungal growth persisted (primary and established callus cultures of the susceptible tobacco cultivar Ky 151 and crown‐gall cultures of Ky 170 and Ky 151). The concentration of chlorogenic acid, scopoletin, and two other unknown soluble phenols varied after inoculation and no, correlation with tissue culture resistance could be established. Incorporation of Agrobacterium tumefaciens T‐DNA in the genome of both cultivars induced a drastic reduction of scopolin in inoculated tissue cultures. T‐DNA incorporation had less, influence on uninoculated tissues. Scopolin at concentrations found in tissue cultures was not toxic to the fungus.
Préparation des Antigenes des Mycoplasmes (MLO) Pathogènes de la Flavescence Dorée, à Partir de Tissus Végétaux
Authors: Caudwell A. , Kuszala Catherine , Fleury A.
Published: May 2008

Antigen preparation from plant tissues of pathogenic mycoplasms (MLO) causing flavescence doree disease

Extraction and purification of plant yellow's pathogen mycoplasms (MLO) from plant tissues is a difficult problem. It concerns indeed non cultivable, heterogeneous and fragile organisms which are localized in the fibrous and resistant phloem tissue. In a work directed by an infectivity test by leafhopper injection, our laboratory investigated the best host plant and the best extraction method for this type of pathogen.

Broad bean, Vicia faba gave better extracts than Vitis vinifera. Stems are better than petioles or lamina. The best results were obtained with the top region of the stem, at the level where symptoms are apparent on young plants.

The most efficient mincing method is achieved with razorblades moved alternatively by the rapid vertical movement of an electric knife.

The extraction medium already published (Caudwell and Kuszala 1986) has to be modified for plants by various additional components, histidine buffer, antioxidizers (glutathion 0.2 mg per ml) and polymers 0.5 to 1 p 100 PVP or Polyclar, 1–2 p 100 PEG). 1 g of plant infected tissue is minced in 4 ml of medium. The extracts are filtered through a 100 mesh nylon cloth. After this stage the purification method goes parallel to that used for leafhopper extracts (Caudwell and Kuszala 1986). It is possible to obtain 4 × 106 infectious units from 1 g of broad bean stem (for calculation, see C 1986). It is possible to obtain 4 × 106 infectious units from 1 g of broad bean stem (for calculation, see Caudwell 1977).

The possibility to extract MLO, either from infectious leafhoppers or from diseased plants enabled cross immunological assays involving antigens from one host and antibodies directed towards the other host antigens. The first step was the successful ISEM visualization of ttie MLOs (Caudwell et al. 1982), the second is the immunoenzymatic MLO‐detection (Boudon et al. 1986).
Antagonistic Activity of Neocosmospora vasinfecta var. africana (von Arx) Cannon & Hawksworth against Soil‐borne Fungi
Authors: Turhan Gülay , Grossmann F.
Published: May 2008

An isolate of Neocosmospora vasinfecta var. africana (F‐2) was assayed for its antagonistic activity against 15 soil‐borne fungi; 14 of them were important plant pathogens. The fungus exhibited a strong antibiotic effect against most of the fungi under test. While Pythium debaryanum, Macrophomina phaseolina, Phytophthora capsici, Sclerotinia sclerotiorum, Cochliobolus sativus and Alternaria alternata showed a very high degree of sensitivity as evidenced by the respectivezones of inhibition caused by the antagonist, Phoma betae, Rhizoctonia solani and Verticillium dahliae proved to be the most resistant. A mutual antibiosis existed between N. vasinfecta var. africana and five of the test fungi.

The culture filtrate of the antagonist, diluted ten times with PDA, suppressed the mycelial growth of P. debaryanum and P. capsici completely. Whereas in this test R. solani proved to be the least sensitive, the remaining test fungi showed some differences in their susceptibility, but in any case their growth was inhibited significantly as compared to the controls.
Effects of Salicylate on Systemic Invasion of Tobacco Plants by Various Viruses
Authors: Roggero P. , Pennazio S.
Published: May 2008

Salicylate watered onto soil in which White Burley tobacco plants were grown represents a reversible stress characterized by stomatal closure, slight slackening of plant growth and low chlorophyll loss. Salicylate affected viral pathogenesis in opposite ways. It had no effect against local and systemic infections by potato virus X (PVX), potato virus Y0 (PVY0) or tobacco mosaic virus (TMV), whereas it completely prevented systemic infection by alfalfa mosaic virus (AIMV) or tobacco, rattle virus (TRV) in a high proportion of treated plants. When infection moved from leaves inoculated with AIMV or TRV, the tendency to limit systemic spread was shown by the restriction of systemic infection to very limited areas erratically distributed in some uninoculated leaves.

The salicylate‐induced restriction of AIMV or TRV infectivity to inoculated leaves did not appear due to inhibition of virus multiplication because the inoculation of potentially resistant leaves of salicylate‐reated plants resulted in virus antigen accumulation comparable to that of untreated controls. Salicylate may therefore inhibit some long distance virus transport function.

Salicylate appears able to evoke true hypersensitivity only against systemic viruses able to induce local necrotic lesions, probably by activating some genetic information for resistance that is normally not expressed.
The Seed‐borne Inoculum of Peronospora manshurica, Causal Agent of Soybean Downy Mildew
Authors: Roongruangsree U‐Tai , Olson L. W. , Lange L.
Published: May 2008

The seed‐borne inoculum of P. manshurica is described using various microscopic techniques and staining reactions. The inoculum, in addition to the oospores, consists of a thin walled mycelium under the hourglass cell layer of the seed coat and a thick walled resting mycelium in the oospore crust on the seed surface. By a modified Feulgen staining technique it was possible to demonstrate that the thin walled and the thick walled resting mycelium as well as thin and thick walled oogonia contain nuclei which are Feulgen positive suggesting that portions of the mycelium of P. manshurica may survive even on the surface of dry, mature seeds.
The Differentiation of Infection Structures as a Result of Recognition Events between some Biotrophic Parasites and their Hosts
Authors: Mendgen K. , Schneider A. , Sterk M. , Fink W.
Published: May 2008

Most uredospores of rust fungi develop infection structures in a typical pattern so that they can infect the host plant. The function of these infection structures is divided into the following three phases:

In the recognition phase, the germ tube recognizes the cuticle and the stoma. This process may occur independently from the host plant since copies of the cuticle induce similar reactions of the fungus. During fungal growth on the epidermis, unspecific stress responses of the plant are triggered.

In the signal phase, the fungal substomatal vesicle and infection hypha(e) contact the host cells within the leaf parenchyma. A signal from the host induces further development of the fungus. Haustorium mother cell differentiation is effected and haustorium formation is initiated. At the same time, the fungus suppresses the synthesis of stress metabolites by the plant.

In the parasitic phase, the fungus penetrates the host cell and complex interactions between host and parasite begin. A highly specialized interface around the haustorium develops presumably in order to allow a more efficient nutrient transfer from host to parasite. Eventual defence reactions of the plant, generally on the race‐cultivar level, fail to be evoked or are suppressed in compatible combinations.
Expression of Resistance of Wheat to Fusarium graminearum and F. culmorum Under Various Experimental Conditions
Authors: Mesterházy Á.
Published: May 2008

The resistance ranking was very similar under different periods of incubation except the 17 and 24 h variants under plastic bags and with the presence or absence of Bayleton treatment. Very similar ranking was recorded also in the tests where four plot replicates were used, e.g. the reaction severity was so close in different plot replicates that one plot per genotype seemed to be enough for serial resistance tests. The significant plot × genotype interaction shows that relative resistance ranking may vary to some extent, but basic changes do not occur. Also similar cultivar reactions were observed at different levels of disease severity resulting from inoculation with isolates differing in pathogenicity. An average reaction to these levels is closer to the genetically determined resistance. Analysis of the behaviour of a cultivar at different disease severity levels helps to predict the field behaviour of a given genotype. The Bayleton treatment was ineffective against scab, although there was some interaction with cultivars.
Effect of Salicylic Acid and Phenylserine on the Hypersensitive Reaction of Tobacco to Tobacco Mosaic Virus
Authors: Wieringa‐Brants D. H. , Schets F. M.
Published: May 2008

Injection of leaves of tobacco (Nicotiana tahacum cv. ‘Xanthi’ nc) with salicylic acid (SA) or phenylsene (PS) had an effect on the local lesion development caused by tobacco mosaic virus (TMV), depending upon the concentration used and the time interval between injection and challenge inoculation. Maximum reduction in lesion size was obtained with 0.75 mM SA or with 8 mM PS. Concentrations higher than 1 mM SA or 25 mM PS damaged the leaf tissue, PS being far less toxic than SA. The leaves responded rapidly to injection with SA or PS. A time interval of only 1 h between injection and TMV inoculation reduced the lesion size significantly.

Isolated tobacco cell walls incubated with SA yielded carbohydrate fractions capable of reducing lesion size significantly after injection. Cell walls incubated without SA or with PS did not yield active carbohydrate fractions.
Health Status (Virus) of Native North American Humulus lupulus in the Natural Habitat
Authors: Hampton R. O.
Published: May 2008

Ninety‐one native North American Humulus lupulus plants from natural habitats in seven western and mid‐western states of the U.S.A. were tested by ELISA serology for presence of two ilarviruses and three carlaviruses common to cultivated hops. All plants in natural habitats were free of detectable viruses. Propagations of 14 such plants from earlier collections had become infected, particularly with two carlaviruses (hop latent virus, American hop latent virus) after exposure for 22 years tobreeding nurseries. ELISA tests of some 284 hop plants primarily from breeding nurseries in Oregon indicated the following infection rates: Prunus necrotic ringspot virus, 85/284, 30%; apple mosaic virus, 88/234, 38%; hop mosaic virus, 59/158, 37 %; hoplatent virus, 104/158, 66 %; and American hop latent virus, 79/158, 50 %. Inoculum reservoirs of AHLV were sought among 53 principally perennial non‐Humulus plant species surrounding AHLV‐infected hop yards and nurseries. AHLV was neither indigenous to native North American H. lupulus nor detectable in these selected non‐Humulus plant species. Breeding nurseries and commercial hop yards, thus, were the only detectable inoculum reservoir for AHLV.
Penetration of the Periderm of Red Raspberry Canes by Leptosphaeria coniothyrium
Authors: Seemüller E. , Kartte Sylvia , Erdel M.
Published: May 2008

Umwounded raspberry canes were inoculated with Leptosphaeria coniothyrium. After penetration of the epidermis the fungus invaded the cortex readily. The accumulation of mycelium in this tissue lead to a partial digestion of the middle lamellae of the outermost cork layer within the polyderm. The fungus penetrated this single cell barrier through the openings between the separated cells and colonized the phelloid tissue between the first and second cork layer. After vigorous growth in this non‐suberized tissue the fungus penetrated the second cork barrier in the same way as the first layer. This mode of penetration was repeated until the fungus had spread beyond the periderm and into the vascular tissues. The invasion process occurred rather slowly and was enhanced by weakening of the canes by defoliation at the time of inoculation.
Latency of Infection in Unripe Avocados by Colletotrichum gloeosporioides is Not Due to Inadequate Enzyme Potential
Authors: Sivanathan S. , Adikaram N. K. B.
Published: May 2008

Colletotrichum gloeosporioides produced exo‐pectin lyase and protease in a) liquid cultures with incorporated washed cell wall material from unripe or ripe avocado and b) autoclaved immature fruit. The activity of exo‐pectin lyase and protease produced in liquid cultures incorporating washed cell walls from immature fruits was almost the same as when washed cell walls from ripe fruits were incorporated. Ripe fruit tissue rotted by the fungus contained exo‐pectin lyase, endo‐polygalacturonase (endo‐PG) and protease. The endo‐PG was found to be endogenous to avocado fruit, and had a pH optimum of 5.5. The pH optima of exo‐pectin lyase and protease were 8.5 and 7.5 respectively in all three enzyme preparations. All these enzyme preparations completely macerated avocado fruit tissue discs in vitro in less than 3 h of incubation but not potato tuber discs. Neither immature nor ripe fruit contained substances, proteinaceous or otherwise, which could inhibit the exo‐pectin lyase or protease activity of these preparations. The results indicated that C. gloeosporioides possesses sufficient enzyme potential to invade cell walls of unripe fruit and that the fruit tissue does not have a mechanism to inactivate such enzymes.
Bis‐thiourea Metal Complexes with Enhanced Antiphytoviral Activity
Authors: Davarski K. A. , Schuster G. , Vassilev G. N.
Published: May 2008

The activity of bis‐thiourea, diallyl‐bis‐thiourea and in part of diphenyl‐bis‐thiourea against potato virus X (PVX) can be augmented considerably by complexation of the mentioned compounds with Cu±±, Ni±±, and Co±±. Contrary to this, complexation with Fe±± and Cd±± does not augment or reduce the antiphytoviral activity. Most antiphytoviral active are the diallyl‐bis‐thiourea complexes with Cu±±, Ni±± and Co±±. The antiphytoviral activity of the Cu±± and Cd±± complexes with bisthiourea can be additionally augmented by combined treatment with small amounts of 2,4‐dioxohexahydro‐l,3,5‐triazine (DHT).
Tomato Yellow Leaf Curl Virus DNA Forms in the Viral Capside, in Infected Plants and in the Insect Vector
Authors: Czosnek H. , Ber R. , Navot N. , Antignus Y. , Cohen S. , Zamir D.
Published: May 2008

Tomato yellow leaf curl virus (TYLCV) DNA was used as a probe to identify and analyze virus‐related DNAs in the viral capside, in infected tomato plants and in the virus vector, the whitefly. In addition to the single‐stranded viral genomic DNA, double‐stranded virus‐related DNA molecules were detected in infected plants. Not all of the virus‐related DNA forms are present simultaneously in the infected plant. The double‐stranded molecules, which are probably the replicative form of the viral genome, have been purified from an infected tomato plant. In the viruliferous whitefly, only the single‐stranded unit‐size viral genome was detected.
Alteration of Bark Proteins Associated with Citrus Tristeza Virus (CTV) Infection on Susceptible Citrus Species and Scion‐Rootstock Combinations
Authors: Moreno P. , Guerri J. , Ortiz J.
Published: May 2008

The effect of citrus tristeza virus (CTV) on bark protems of susceptible citrus species and scion‐rootstock combinations was studied by polyaerylamide gel electrophoresis (PAGE). Protein pattern of sour orange bark from CTV‐infected trees on this rootstock showed reduced intensity in a protein band, about 20,000 daltons molecular weight, as compared with similar CTV‐free trees. This protein modification appears specifically associated with decline induced by tristeza since it was observed on trees of different ages and scion‐rootstock combinations, grown in various locations and infected with several CTV isolates, but not on trees exhibiting decline from other causes. The observed protein alteration was localized in the ribosomic fraction.

No protein alteration, associated with CTV infection could be found on lemon bark, although this citrus species also behaves as a CTV‐susceptible rootstock.

Electrophoretic profiles obtained from CTV infected Mexican lime and Etrog citron seedlings also showed reduced intensity in a protein band with the same electrophoretic mobility as the tnodified band of sour orange.
A Tobamovirus Causing Heavy Losses in Protected Pepper Crops in Spain
Authors: Alonso E. , García Luque I. , Avila‐Rincón M. J. , Wicke B. , Serra M. T. , Díaz‐Ruiz J. R.
Published: May 2008

During a four‐year (1982–1985) survey of plant viruses infecting pepper cultivars grown under plastic in the Southeastern region of Spain, a tobamovirus was found to be the major disease agent of this crop. The virus produces slight or no symptoms on the leaves, but causes chlorotic mottling, malformation and reduction in size with occasional necrosis on the fruits and was able to infect all commercial pepper cultivars tested, including those resistant to other tobamoviruses, causing a catastrophic disease. The biological and serological characterization of the virus showed that it is very similar to pepper mild mottle virus (PMMV) (Wetteret al. 1984) and therefore we have termed it as Spanish strain of PMMV (PMMV‐S). The need of grouping all the so‐called “pepper strains” of tobacco mosaic virus (TMV) as a new distinct member of the tobamovirus group with the name of PMMV is emphasized.
Defense Reactions in Host and Nonhost Plants Against the Soybean Rust Fungus (Phakopsora pachyrhizi Syd.)
Authors: Hoppe H. H. , Koch E.
Published: May 2008

Growth and development of two races of the soybean rust fungus (Phakopsora pachyrhizi Syd.) were compared on host and nonhost plants. Both groups had several lines of defense, each of which could stop a part of attacking uredospores. Germ tubes and appressoria were produced equally well on hosts and nonhosts. A reduced formation of penetration hyphae contributed to the resistance of nonhosts and resistant host genotypes. In the epidermal cells of wheat and barley leaves, lower frequencies of penetration hyphae coincided with the production of papillae‐like structures which were not penetrated. The last line of defense of all nonhosts was localized in the epidermal cell where the growth of the penetration hyphae was arrested definitively. The colony development in these species was suppressed completely. In highly resistant host genotypes the last defense reaction occurred later as a hypersensitive cell collapse which interrupted the growth of the rust colony.
Identification of Alfalfa Mosaic Virus in Greek Alfalfa Crops
Authors: Avgelis A. , Katis N.
Published: May 2008

Alfalfa mosaic virus (AMV) was found to be the prevalent virus disease in alfalfa crops in Central and Northern Greece. The virus was identified on the basis of the host symptomatology, aphid and seed transmission, particle morphology and serological tests. AMV was largely detected in commercial seeds of local grown alfalfa cvs by ELISA. Infected seed lots appear to be the main source responsible for the widespread distribution of the virus in Greek alfalfa fields.
Mixed Infection of Asclepias curassavica L. in Ecuador: Rhabdovirus‐like Particles and Phytomonas sp.
Authors: Dollet M. , Gargani D.
Published: May 2008

In Ecuador, some Aselepias curassavica L. plants express leaf yellowing and premature death. Examination of symptomatic leaves by electron microscopy revealed a mixed infection of Phytomonas and Rhabdovirus‐type particles. The origin of the pathological symptoms is discussed.
Effect of Nitrogen Fertilization and Growth Suppression on Pitch Canker Development on Loblolly Pine Seedlings
Authors: Solel Z. , Bruck R. I.
Published: May 2008

One‐yr‐old loblolly pine seedlings of two half‐sib families, grown in sand, were fertilized three times per week with nutrient solution containing 20 μg/ml (low) or 80 μg/ml (high) nitrogen. Nitrogen concentration in the nutrient solution was either constant throughout the experiment, or interehanged after the inoculation of stems or shoots with Fusarium subglutinans, 55 days after initiation of fertilization. Growth was suppressed by a weekly excision of shoots branching from the stem apex. Either high nitrogen nutrition or shoot excision generally enhanced canker elongation on stem inoculated plants; the combination of both was extremely conducive for disease development. With intact plants of family 8–68, interchange of pre‐inoculation low nitrogen nutrition with high nitrogen after inoculation enhanced canker elongation and rate of wilt. Nitrogen content varied in wood, bark and needles, as well as with time intervals, but was consistently in accordance with nitrogen level in the nutrient solution. In shoot excised plants, nitrogen content was higher than in the respective treatment without shoot excision. The higher nitrogen nutrient accelerated disease development on inoculated shoots, compared to low nitrogen, on both pine families. With respective treatments, stem cankers were larger and rates of shoots exhibiting lesions or wilt were higher on plants of family 8–68 than on 8–61. It is postulated that the disease enhancing effect associated with higher nitrogen content in stem tissues results from an increased nitrogen availability to the pathogen.
Rapid Immunofluorescent Detection of the Grapevine Flavescence Doree Mycoplasmalike Organism in the Salivary Glands of the Leafhopper Euscelidius variegates Kbm
Authors: Lherminier J. , Terwisscha van Scheltinga T. , Boudon‐Padieu E. , Caudwell A.
Published: May 2008

Polyclonal rabbit antibodies, prepared against partially purified mycoplasmalike‐organisms (MLO) from Grapevine Flavescence Dorée‐infected plant extracts, were used to detect MLO in situ in excised salivary glands of the experimental vector Euscelidius variegates Kbm by an indirect immunofluorescent staining technique. Glands were examined from the fourth to the tenth week after the start of MLO acquisition. MLO detection was compared using this method, the transmission test and the ELISA technique applied to insects corpses after removal of salivary glands.
A Preparation Method of Aspergillus spp. for Scanning Electron Microscopy
Authors: Weidenbornur M. , Uzih A. , Hamacher J. , Hindori H. , Weltzitzien H. C.
Published: May 2008

For scaning electron microscopy (SEM) of Aspergillus flavus Link und A. petraku Vörös. Simultaneous fixation and drying in osmium tetroxide (O5O4 vapours was superior to the conventional preparation methods. Which involve critical point drying. Mycelium exposed to vapours from a solution of 2% O5O4 for 24 h at ca. 20°C retained its turger and natural structures. Best results were achived when young mycelium was used. whereas old mycelium always collapased, irrespective of the fixation method used.

Use of this method for fixation of Aspergillus spp. is therefore preferable to convennonal methods which are laborious. time‐consuming and often interfere with the natural habit of structures. It may also prove usefull with other fungal structures.
Serological Comparison of Antigens Related to Local Virus and Bacterial Infections and Aspecific Stresses in Tobacco Leaves
Authors: El‐Kady S. , Gáborjányi R. , Király Z.
Published: May 2008

Two “new” precipitin bands (antigens) detected by the immunodiffusion test were demon strated in leaf extracts of tobacco inoculated with tobacco mosaic virus (TMV), Pseudomonas tabaci or treated with mercuric chloride, sodium azide or sodium hypochlorite. One of the precipitin bands was stronger, than the other, These antigens were also detected in the upper, non‐infected leaves of tobacco plants when the lower leaves were locally stressed (necrotized) either by TMV or by chemical injury. The “new” antigens formed in the upper leaves were detected even if the TMV‐inoculated lower leaves were removed one day after inoculation. The “new” antigens were identical both in the lower and upper leaves and their induction was independent from the stress whether pathogenic or chemical.

A coincidence exists between the appearance of “new” antigens and acquired resistance, but this does not mean necessarily a cause‐and‐effect relationship between the two phenomena. Our experiments indicate that the induction of the synthesis of “new” stress proteins in tobacco is aspecific and the proteins formed are related to the aspecific stress itself rather than to pathogenesis.
Effect of Flavin Inhibitors on Photoactivation of Oospores of Phytophthora cactorum
Authors: Banihashemi Z. , Mitchell J. E.
Published: May 2008

When dark‐grown mature oospores of Phytophthora cactorum were activated to germinate by exposure to 5 uW cm‐2nm‐1 of fluorescent light at 20–22°C in the presence of certain flavin inhibitors such as KI, salicylhydroxamic acid and phenylaceric acid at 40. 1. and 0.1 mM respectively, photoactivation and hence subsequent germination of oospores were inhibited without appreciable irreversible effect on oospore viability. Likewise, when applied during the light period, NaN3 and KCN at 1 mM reduced photoactivation but had a minimal effect on dark reactions. Diphenylamine, an inhibitor of certain carotenoids, had no effect on photoactivation of oospores. The data suggest that the photoreceptor pigment for activation of oospore germination is a flavin.
Suppression of Damping off on Pepper Caused by Pythium ultimum Trow and Rhizoctonia solani Kühn by Some New Antagonists in Comparison with Trichoderma harzianum Rifai
Authors: Turhan Gürhan , Turhan Kutsi
Published: May 2008

Pot experiments were designed to evaluate the efficacy of Streptomyces nobilis, S. ochraceiscleroticus, Neocosmospora vasmfecta var. Africana and Acrophialophora levis isolates in reducing the damping‐off on pepper in comparison with a strong mycoparasitic isolate of Trichoderma harzianum.

Two pathogenic and five potential antagonistic isolates were grown seperately m flasks containing a mixture of sand‐perlite‐corn meal and potato‐sucrose broth for 4 weeks. Soil infestation was achieved by mixing these stock cultures separately into the pot soils. Disease incidence was expressed as the percentages of dead seedlings in each pot and the protective values of the antagonists were calculated according to Abbott formula.

Results indicated that all of the five test isolates have provided the seedhngs with protection of statistical value against Pythium uhimum and Rhizocionia solani reducing disease incidence between 28.14 to 79.14 % and 22.76 to 66.83 %, respectively. However, T. harzianum isolate proved to be the least effective antagonist against both pathogens.
In vitro Culture of Grapevine Infected by Closterovirus Type III*
Authors: Barba M. , Cupidi A. , Faggioli F.
Published: May 2008

Herbaceous cuttings collected in autumn from a closterovirus type III infected grapevine plant (cv. Merlot) were micropropagated in vitro.

Results showed thai cultured plants did not present any leaf symptoms even if they grow slower than healthy control plants by a ratio of about 1/2.

The virus concentration, as estimated by electron microscopy, was found constant when observed fortnightly over a period of 75 days. The number of particles was about 30 times higher than in viral preparations obtained from infected material collected in the field.
Effects of Bean Leaf Age on Pathogenicity by Botrytis fabae
Authors: Heilbronn Jacqueline , Harrison J. G.
Published: May 2008

Leaves from field bean plants grown out of doors were inoculated with conidia of B. fabae immediately after detaching from stems. The oldest leaves developed more lesions than youngest ones, although they were not chlorotic. On intact plants at high humidities, established lesions on young leaves increased in size at only half the rate of those on old. but still green leaves. Seven days after inoculation a higher proportion of lesions on old leaves bore conidia than those on young leaves, but leaf age had no significant effect on numbers of conidia per mm2 of lesion area.

Young leaflets from bean plants grown in a controlled environment or in the field challenged with β. cinerea accumulated more phytoalexins than did old ones.
Studies of Didytmella bryoniae (Auersw.) Rehm: Development in the Host
Authors: de Neergaard Eigil
Published: May 2008

Growing hyphae of Didymella bryoniae (Auersw.) Rehm are found in the stem tissue of cucumber, and the fungus can colonize nearly all types of tissue. The presence of the pathogen in the lignified elements suggests a spread of the disease up and down from the site of primary infection, even when the stem is strongly decomposed. The fungus dtsplays hyphal dimorphism in the infected tissue and a remarkable feature is stromatic‐like structures in the host tissue close to fruiting bodies. Staining reveals no histological host reaction to fungal penetration of cell walls. The pathogen is characterized by the early development of its sexual stage.
Storage of Wheat FoliagePrior to Enzyme‐Linked Immunosorbent Assay for Detection of Wheat Soil‐Borne Mosaic Virus
Authors: Armitage C. R. , Hunger R. M. , Sherwood J. L. , Weeks D. L.
Published: May 2008

Plant samples, collected at various times during a growing season, are frequently stored prior to evaluating resistance to wheat soil‐borne mosaic virus (WSBMV) by enzyme‐linked immunosorbent assay (ELISA). Leaves of winter wheat cvs Sage and Vona, showing symptoms of WSBMV infection, were cut in half along the midrib. Each half was either: 1) refrigerated at 4 °C, 2) frozen at −20 °C, 3) frozen at –70 °C, or 4) desiccated with CaCl2. Relative virus antigen titres were evaluated for individual leaf halves by ELISA. ELISA absorbance means from desiccated leaf halves were consistently higher than absorbance means from corresponding leaf halves that had been frozen. This distinction suggests that virus antigen decreases during freezing but is retained during chemical desiccation. All 4 methods of storage were found to be suitable for short‐term storage prior to qualitative evaluations by ELISA, but chemical desiccation was the superior method for long‐term storage and for storage of foliar samples prior to quantitative evaluations by ELISA.
Monoclonal Antibodies for Detection and Serotyping of Cucumber Mosaic Virus
Authors: Haase Anita , Richter J. , Rabenstein F.
Published: May 2008

Two monoclonal antibodies (MAbs) to cucumber mosaic virus (CMV) were selected from a panel of MAbs for use in the direct DAS (double antibody sandwich)‐ELISA. Two different test procedures were developed: an ELISA with polyclonal and monoclonal antibodies (mixed ELISA) for the routine detection of CMV and a MAb‐ELISA with two MAbs directed against different epitopes for the specific detection of the N serotype which is prevalent in GDR. The conventional two‐step incubation of plates precoated with IgG was compared with simultaneous incubation of test sample and labelled antibody (one‐step incubation). The mixed ELISA proved to be more sensitive than the direct DAS‐ELISA with polyclonal antisera in detecting CMV in crude sap of infected plants. On the other hand, the MAb‐ELISA could be used for serotyping of CMV isolates which is important in epidemiological investigations and in resistance breeding. Both the two‐step and the one‐step procedures gave similar results with some advantages of the latter procedure. One‐step incubation is not only time‐saving but seems to be also more sensitive with regard to the detection limit. However, care must be taken to circumvent the hook‐effect occurring at high virus concentrations.
Nonspecific Phytotoxic Effects of Sirodesmins on Host and Nonhost Plants of Leptosphaeria maculans
Authors: Badawy H. M. A. , Hoppe H. H.
Published: May 2008

Sirodesmin PL, deacetylsirodesmin PL and sirodesmin C were isolated from cultures of an aggressive strain of Leptosphaeria maculans, purified by thin layer and column chromatography, and tested on leaves and roots of 14 host and non‐host plants of the pathogen. The sirodesmins showed no host‐specificity. However, various plant species developed symptoms of different severities. In both bioassay systems deacetylsirodesmin PL had a lower phytotoxicity than sirodesmin PL and sirodes‐min C. Our results show that sirodesmins belong to the non‐host‐specific phytotoxins.
Elimination of Apple Mosaic Virus and Raspberry Bushy Dwarf Virus from Infected Red Raspberry (Rubus idaeus L.) by Tissue Culture
Authors: Theiler‐Hedtrich R. , Baumann Gisela
Published: May 2008

Experiments with ApMV infected ‘Malling Landmark’ and RBDV infected ‘Schamp;önemannamp;’ and ‘Trentamp;’ plants were carried out to evaluate

a) the dependence of virus eradication on explant size and mass propagation.

b) the reliability of results of ELISA tests on in vitro plantlets.

With ApMV a correlation between virus elimination and explant size was observed, whereas with RBDV even plantlets from the smallest established explants were still infected. With ApMV, in vitro multiplication for three subsequent subcultures did not lead to further virus elimination, with RBDV this was observed in two cases.

ELISA test results for both viruses, ApMV and RBDV, were identical when small in vitro plantlets, long‐term stored plants, or potted plants from the same origin were tested, indicating that virus tests are possible with very young plant material and can be used to select virus‐free plants in vitro. Tissue culture permits long‐term storage of plant viruses. It is also suitable tor plant virus propagation and could be a useful aid in plant virus purification.

For commercial multiplication only virus‐indexed plant material should be used for establishment and further propagation in vitro.
Partial Characterization of Artichoke Virus M
Authors: Di Franco A. , Gallitelli D. , Vovlas C. , Martelli G. P.
Published: May 2008

A virus with filamentous particles 697 nm in length was isolated from artichoke plants in Southern Italy and identified as a new possible member of Carlavirus group, for which the name artichoke virus M (AVM) is suggested.

AVM could not be transmitted by sap inoculation to herbaceous hosts and was always present in artichoke in mixed infections with other viruses. Virus particles had a buoyant density in CsCl of 1.31 g × cm−3 and contained a single species of nucleic acid with an apparent size of 7.5 Kb and a single coat protein species with a mol. wt of 31,000. The virus was distantly related serologically to carnation latent and poplar mosaic carlaviruses but not to other members of the group including the recently described artichoke latent S carlavirus. Cytological alterations consisted of complex cytoplasmic inclusions composed of deranged organelles, lipid droplets and accumulations of membranes.
The Extracellular Acidic and Basic Pathogenesis‐Related Proteins of Soybean Induced by Viral Infection
Authors: Roggero P. , Pennazio S.
Published: May 2008

Seventeen major host‐encoded pathogenesis related (PR)‐proteins have been found in intercellular fluids of necrotic virus‐infected soybean leaves. None of them was present in fluids of healthy controls. By native and SDS‐denaturing polyacrylamide gel electrophoresis, ten major acidic PR‐proteins have been identified and classified on the basis of their molecular weight in three groups: group 1 included four proteins of 16–17 Kd; group 2, three proteins of 26 Kd; group 3, three proteins of 32 Kd. Seven PR‐proteins were basic, and were classified in three groups: group 1 included three proteins of 16 Kd; group 2, one protein of 23 Kd; group 3, three proteins of 32 Kd.

As found for tobacco and potato, soybean PR‐protein patterns show high number of acidic and basic proteins.
Untersuchungen zum Wirkungsspektrum und zur Wirkungsweise zweier quarternärer Ammoniumverbindungen gegenüber phytopathogenen Viren
Authors: Bockholt S. , Hellwald K. H. , Buchenauer H.
Published: May 2008

Investigation of the influence of two quarternary ammonium compounds on some viruses and their mode of action

The inhibitory effect of benzyl‐dimethyl‐hexadecylammoniumchloride (BDHA) and N‐benzyl‐N‐dodecyl‐N‐bis (2‐liydroxyethyl)‐ammoniumchloride (BDBA) to various phytopathogenic viruses was studied. These substances were selected from 10 other quarternary ammonium compounds tested. They showed an inhibitory activity against BMV‐, CMV‐, CMoV‐, PVX‐, TMV‐ and TNV‐infections.

Studies on the mode of action of BDBA and BDHA in the virus‐host‐system TMV/Nicotiana tabacum var. Xanthi nc. revealed that the compounds exhibited besides a pre‐infectional also a post‐infectional inhibitory activity. Further, it has been shown that they display a direct inhibitory effect on TMV. The longlasting pre‐infectional effect of the compounds resulted not only in a reduction of formation of local lesions, but also in a smaller size and a lower antigene content of the lesions. An antiviral activity was also detected in non‐treated younger leaves of treated plants 10–14 days after treatment. This phenomenon was linked with the appearance of some new proteins in the intercellular fluids.
Erwinia amylovora Infection of Hawthorn Blossom
Authors: Wilson M. , Sigee D. C. , Epton H. A. S.
Published: May 2008

Stamens of freshly opened flowers of hawthorn were inoculated with E;. amylovora and the development of blossom infection was monitored by viable bacterial counts and light and electron microscopy. Some bacterial multiplication occurred on the anther surface, over the dehiscence zone and over the junctions ot the anther‐wall cells. bacteria invaded the anther loculc, via the ruptured dehiscence zone, and possibly also vid the stomata surrounding the filament insertion. bacteria within the locule multiplied rapidk with estimated doubling‐times which were longer than those derived from in vitro data. Pollen grains Irom infected anthers were found to be heavily eontaminated with bacteria.

The invasion of anther tissue, with the production of contaminated pollen, may be important epidemiologieally both as a phase of rapid bacterial multiplication and in the insect‐mediated spread of this disease.
Distribution of Streptomycin Resistant Strains of Erwinia amylovora in Egypt during 1988
Authors: El‐Goorani M. A. , El‐Kasheir H. M. A. , Shoeib Alia A. , Hassanein Ferial M.
Published: May 2008

A survey of the occurrence of strains of Erwinia amylovora resistant to streptomycin in certain Egyptian pear orchards was earned out during April and May 1988. Twenty‐two isolates out of 604 isolates collected from 11 orchards showed resistance to streptomycin. All the streptomycin resistant (Strr) strains isolated in the present work were resistant to high levels of streptomycin with minimal inhibitory concentrations ranging from 1000 to 3000 μg/ml. The occurrence of Strr strains in Egypt is still limited and the population of resistant strains was at relatively low level. However, such occurrence of E. amylovora with resistance to streptomycin is a potentially serious situation.