bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Temperature on BYDV Concentration in Oat Plants and Virus Purification Efficiency, and Detection of a Putative Associated Satellite Virus
Authors: Forde S. M. D.
Published: May 2008

RPV and MAV‐like serotypes of barley yellow dwarf virus (BYDV), designated R‐568 and F, were found during sucrose density gradient centrifugation to suspend at 10 °C and 4 °C but to totally sediment at 15 °C and 12 °C, respectively. These properties were used to purify these serotypes, and antisera were then prepared.

Partially purified IgG from antiserum was used in immunosorbent electron microscopy (ISEM) and in enzyme‐labelled immunosorbent (ELISA) tests to detect BYDV RPV‐like serotypes. Using anti‐BYDV R‐568 polyclonal antiserum and the BYDV R‐568 serotype in ISEM tests, isometric virus particles of two sizes were trapped: the 28 nm particles of BYDV R‐568, and others 17 nm in diameter which may be those of a satellite virus.

The effects of temperatures on virus concentrations in oat plants infected with BYDV serotypes F and R‐568 were investigated. BYDV F and R‐568 concentrations in the roots and shoots were sensitive to changes in temperature between 10 °C and 25 °C. The concentrations of both viruses in the roots and shoots of infected plants could be manipulated by varying the temperature at which plants were grown. The ELISA absorbance values related to detection of F MAV‐like serotypes were higher in roots and shoots of oats grown at 10 °C than for oats grown at 25 °C. Conversely, cool temperatures reduced the absorbance values for R‐568 RPV‐like serotype in the roots, but less significantly in the shoots.
Hydrolytic Enzymes of Ungerminated and Germinated Conidia of Erysiphe graminis DC f. sp. hordei Marchal
Authors: Frič Fridrich , Wolf Gerhard
Published: May 2008

Activities of hydrolytic enzymes (esterase, lipase, phosphatase, protease, 1,3‐β‐glucanase, chitinase and amylase) were demonstrated in washings and extracts of ungerminated and germinated conidia of Erysiphe graminis f. sp. hordei, Marchal. No cellulase and only very little xylanase activity was detected. Considerable amounts, 65% of total conidia proteins can be extracted by shaking the conidia when the extraction medium contained non‐ionic detergent only. Different extraction procedures were used to determine enzyme distribution between exo‐ and endoconidial compartments and to evaluate the enzyme extraction efficiency from conidia.

The possible physiological roles of the hydrolytic enzymes in the ungerminated as well as in the germinated conidia were discussed.
Severe Outbreak of Pseudomonas syringae pv. avellanae on Hazelnut in Italy
Authors: Scortichini M. , Troplano F. G.
Published: May 2008

Pseudomonas syringae pv. avellanae, the causal agent of bacterial canker of hazelnut, has been isolated for the first time in Italy. Biochemical tests were consistant with the type‐strain of the microorganism and whole‐cell protein profiles of the studied isolates were similar to those of the type‐strain. When artifically inoculated, either in summer or in autumn, the isolates incited the same symptoms as those observed in the field.

The main symptoms are the failure of the buds to swell or their withering after breaking in spring; the chlorosis of the foliage and rapid withering of the leaves that remain attached on the twigs during summer; dark brown discolouration of the bark and cambium, necrosis in the primary roots and the final dieback of the plant. The pathogen killed more than 1,800 adult hazelnut plants in one orchard within a period of five years. The main differences of the symptomatology between bacterial canker and bacterial blight of hazelnut, caused by Xanthomonas campestris pv. corylina, and the “seccume” of the hazelnut are briefly discussed.
Laboratory Estimation of Field Resistance of Potato to Late Blight
Authors: Singh B. P. , Birhman R. K.
Published: May 2008

Based on quantitative measurement of components of field resistance of potatoes to late blight, a multiple linear regression equation is derived for laboratory estimation of Area Under Disease Progress Curve. The equation accounts for 82% of variation in Area Under Disease Progress Curve. Transformation of data or inclusion of more terms do not improve the equation significantly. The method is suggested as a replacement or supplement to field testing.
Scanning Electron Microscopy of Conidium Formation of Stemphylium vesicarium on Onion Leaves
Authors: Theresa A. S. Aveling , Rong I. H.
Published: May 2008

Onion leaves were inoculated with conidia of Stemphylium vesicarium and the development and morphology of conidiophores and conidia on the leaf surface were examined using scanning electron microscopy. Solitary, but usually fasciculate conidiophores emerged through the epidermis. Hyphae growing on or above the leaf surface also differentiated into conidiophores. Conidiophores were straight or flexuous, simple, smooth or verrucose and cylindrical but enlarged apically at the site of conidiumproduction. Smooth, round, bud‐like conidial initials were produced singly at the apex of the verrucose conidiophores. As conidia matured, they became oblong to ovoid and densely verrucose. Once the mature conidium seceded, a small pore was visible at the, apex of the conidiogenous cell. Conidiophores proliferated percurrently at the distal region, forming secondary conidiophores and conidia.
Induced Systemic Resistance Against Sphaerotheca fuliginea in Cucumber: Efficiency of Tobacco Necrosis Virus (TNV) and Copper Sulphate (CuSO4) in Eliciting Defence Reactions
Authors: Conti G. G. , Bassi M. , Maffi D. , Violini G. , Magnani L. , Gatti L.
Published: May 2008

Plants of Cucumis sativus were eithe preinoculated with TNV or treated with drops of a 5% solution of CuSO4 on the cotyledons, and 5 days later challenge‐inoculated with Sphaerotheca fuliginea on the first true leaf. The induced systemic resistance was assessed by evaluating the percentage of conidial germination, the length of the hyphae derived from single conidia, the number of cells with lignified walls and that of cells containing haustoria. The number of necrotic cells was also recorded. Compared with controls, in TNV‐preinoculated plants conidial germination was lower, hyphal length shorter and the number of haustoria much reduced. The majority of haustoria was found in cells with lignified walls. Pretreatment with CuSO4, although inducing a slight increase of cell wall lignification, did not appreciably reduce the infection process. The number of necrotic cells was very low in all cases. These results suggest that, in this host/pathogen interaction, hypersensitive cell death has no part in the induced defence reaction, although a major role is played by the lignification process.
Peanut Chlorotic Ringspot Virus (PCRV), a Newly Discovered Virus Infecting Peanut (Arachis hypogaea L.)
Authors: Wagih E. E. , Melouk H. A. , Sherwood J. L.
Published: May 2008

A virus causing wide chlorotic ringspot (PCRV) associated with chlorotic line pattern and motthng on an Erictoides hybrid growing in USDA‐OSU greenhouses, Stillwater, Oklahoma, was discovered. The virus was isolated and characterized and found to differ in symptomology, host range and serological properties from all the previously described viruses infecting peanut, particularly those reported in the United States to be the most important ones, peanut mottle virus, peanut stripe virus, and tomato spotted wilt virus. The virus was transmitted by both mechanical inoctilation and grafting to fourteen peanut cultivars causing identical symptoms to those originally observed on the Erictoides hybrid. In addition to peanut, the virus systemically infected Pisum sativum L. ‘Little marvel’ causing mainly mosaic and Lupinus albus L. ‘Tiftwhite’ producing severe malformation and remarkable reduction in leaflet area. The virus did not infect many other plant species of which cowpea ‘California blackeye’ (Vigna unguiculata L.) and at least five cultivars of soybean (Glydne max L.) are known to be susceptible hosts to peanut mottle virus. Phaseolus vulgaris L. ‘Topcrop’ and Chenopodium amaranticohr Coste & Reyn were found to be two useful local lesion assay and diagnostic hosts for PCRV. The virus elicited necrotic local lesions on the first and chlorotic ringspots on the second. PCRV had a dilution end point between 10−5 and 10−6, thermal inactivation point between 55°C and 60°C, and longevity in vitro up to 6 days but not 7 days. Virus particles viewed hy electron microscopy and the negative stain uranyl aceute were flexuous filamentous particles ranging in length from 750–850 nm. In both indiren PAS‐ELISA and Ouchterlony double immunodiffusion test, PCRV was serologically related to a PMV isolate from Oklahoma (PMV‐OK.) but not to bean yellow mosaic virus, peanut stripe virus, potato virus Y, watermelon mosaic virus 1, watermelon mosaic virus 2, wheat streak mosaic virus, and zucchini yellow mosaic virus.
Involvement of Suppressor‐Glucans and Plant Epidermal Cells in Host‐Selective Pathogenesis of Phytophthora capsici
Authors: Sanchez L. M. , Doke N. , Ban Y. , Kawakita K.
Published: May 2008

Water‐soluble glucans (WSG) from a virulent isolate of Phytophthora capsici (PCAP‐3) which were released during germination of cystospore markedly suppressed the elicitor‐induced death of suspension‐cultured cells of susceptible sweet pepper and tomato but not that of resistant pepper and tobacco. PCAP‐3, its polygalacturonase (PGase)‐deficient mutant (PCAP3‐M16), and galacturonic acid non‐utilizable mutant carrying the PGase (PCAP‐1) activity could penetrate in epidermal cells of host leaves, but similarly caused a hypersensitive response (HR) on non‐injured leaves of resistant host (sweet pepper). In the case of inoculation on press‐injured leaves, however, both of the resistant and nonhost plant leaves became quite susceptible to PCAP‐3similar to susceptible hosts, but not to PCAP3‐M16 and PCAP‐1. The results suggested that host‐selectivity of P. capsici may be determined in the leaf epidermal cells where the suppressor glucans released during infection effectively suppressed the occurrence of hypersensitive reaction. Furthermore, during growth of the fungus in intercellular spaces of leaf tissues, PGase may contribute not only to the virulence experession but also the supply of initial nutrition for fungal growth in the intercellular space of host tissues.
A Comparison of Polypeptides from Teliospores of Tilletia controversa (Kuhn) and Tilletia tritici (Bjerk) Wint.
Authors: Banowetz G. M. , Doss R. P.
Published: May 2008

Teliospores from 12 races of Tilletia tritici (Bjerk.) Wint. and twelve isolates of Tilletia controversa (Kuhn) were sampled from field‐inoculated wheat (Triticum aestivum L.) differential cultivars. Proteins were extracted from the teliospores and analysed by one dimensional electrophoresis. An abundant 116 kD polypeptide detected in extracts from teliospores of all isolates of T. controversa was not detected in T. tritici teliospore extracts. Spores which were mechanically disrupted yielded greater quantities of the protein compared to intact teliospores, and this suggested the polypeptide was derived from within the teliospore. The presence of the polypeptide was correlated with dwarf bunt‐causing Tilletia‐ Isolates of dwarf bunt‐causing Tilletia that were intermediate between T. tritici and T. controversa in either morphology or germination characteristics contained the polypeptide while a common bunt‐causing race of T. tritici (T18) with intermediate characteristics lacked the protein. The 116 kD polypeptide present in all T. controversa isolates may provide a stable biochemical marker for identification of these teliospores in wheat shipments.
Development of Pseudocercosporella herpotrichoides (Fron) Deighton var. herpotrichoides and var. acuformis on Wheat Plants Measured by ELISA
Authors: Poupard P. , Grare S. , Cavelier N. , Lind V.
Published: May 2008

Using the ELISA method, the development of Pseudocercosporella herpotrtchoides var. herpotrichoides and var. acuformis in a susceptible cultivar of winter wheat was compared under controlled and held conditions. In the greenhouse, var. acufornis grew less vigorously, was slower in penetrating the coleoptile and the successive leaf sheaths and in colonizing the stem tissue than var. herpotrichoides. In the field, these differences were confirmed on the last leaf sheaths and the stem. At ripening stage, however, identical ELISA values were measured for both varieties. Moreover, a significant variation was observed between the individual isolates of each variety.

Comparison of the effect of both varieties of P. herpotrichoides on 20 wheat cultivars characterized by different resistance levels showed significant interactions. The cultivars carrying the Pch‐1 gene always remained the less diseased genotypes. In general, var. acuformis developed less antigen in the cultivars than var. herpotrichoides. It is concluded, that in tests for resistance to P. herpotrichoides mixtures of many highly pathogenic isolates of both fungus varieties should be used. Less complex mixtures or single isolates may result in wrong estimates of resistance.
The Association of Discula destructiva (Red.) Hyphae With Cornus florida (L.) Trichomes
Authors: Brown D. A. , Windham M. T. , Graham E. T.
Published: May 2008

Detached, surface‐dismfested flowering dogwood (Cornus florida L.) leaves were inoculated with a Discula destructiva (Red.) spore suspension in an effort to identify inoculation and pre‐penetration phenomena in the dogwood anthracnose pathosystem. Scanning electron micrographs show an association of D. destructiva hyphae with trichomes on the flowering dogwood upper leaf surface. The basal area of these leaf hairs may provide an entry point for Discula spp. colonization of and penetration into the dogwood leaf; however, the possible significance of this area as a unique ecological niche on the dogwood phylloplane should not be ignored.
Cytochemical Detection of Cell Wall Bound Peroxidase in Rust Infected Broad Bean Leaves*
Authors: Medeghini Bonatti P. , Lorenzini G. , Baroni Fornasiero R. , Nali C. , Sgarbi E.
Published: May 2008

Cell wall bound peroxidase activity, cytochemically detected by 3,3‐diaminobenzidine (DAB), appears unevenly distributed in areolae of broad bean (cv. Aguadulce) leaves infected by the rust fungus Uromyces viciae‐fahae (Pers.) Schroet. DAB positivity is not significantly traceable at the periphery of the areola and close to the site of uredinium formation; heavy DAB deposits occur on walls of haustoria containing mesophyll cells. Induction of localized peroxidase activity appears strictly related to the haustorium mother cell differentiation, i.e. to the incipient parasitic phase; it does not, however, counteract the intracellular growth of the haustorium.
Identification of a Strain of Peanut Chlorotic Streak Virus Causing Chlorotic Vein Banding Disease of Groundnut in India
Authors: Satyanarayana T. , Sreenivasulu P. , Ratna A. S. , Reddy D. V. R. , Nayudu M. V.
Published: May 2008

A virus disease characterized by chlorotic vein banding, chlorotic line pattern along the margins or midrib of mature leaflets and chlorotic spots/rings was observed on commercial groundnut crops in Rayalaseema area of Andhra Pradesh with an incidence from 1% to nearly 60%. The virus was transmitted by mechanical inoculation in extracts prepared with 0.01 M potassium phosphate butter, pH 8.0 to 21 species from the Chenopodiaceae, Cruciferae, Leguminosae and Solanaceae, Chenopodium quinoa was found to be a good local lesion host. The virus was neither seed‐transmitted through 1591 groundnut seeds nor aphid‐transmitted by Aphis craccivora, Myzus persicae and Rhopalosiphum maidis either in non‐persistent or semi‐persistent manner. The virus remained infective in buffered tobacco leaf sap at a dilution of 10−5; in a 10−1 dilution of buffered sap the virus was infective for 2–3 days at 22–29°C or when heated to 65°C for 10 min but not to 70°C.

Clarification treatments with organic solvents with 10% chloroform was least damaging. The virus was purified from Nicotiana rustica leaves. Purified virus contained isometric particles of 51 nm in diameter with an electron dense core of 22 nm and two major polypeptides of 76 kDa and 36 kDa. A polyclonal antiserum to this virus was produced. In agar gel double diffusion, enzyme‐linked immunosorbent assay and in electro‐blot immunoassay rests the virus was related to peanut chlorotic streak virus and not to cauliflower mosaic, figwort mosaic and soybean chlorotic mottle viruses.
Systems of Designation of Pathotypes of Plant Pathogens
Authors: Limpert Eckhard , Clifeord Brian , Dreiseitl Antonin , Johnson Roy , Müller Kaspar , Roelfs Aean , Wellings Colin
Published: May 2008

To name pathotypes of plant pathogens, a variety of systems of designation has evolved, which was evaluated to find out the systems best suited. Virulence and avirulence/virulence formulae of pathotypes are by far advantageous over the use of consecutive numbers or letters given in chronological order of pathotype discovery. As soon as pathotype information surpasses a certain level of complexity, mathematical codes are most advantageous and, in particular, octal notation and coded triplets (tripletcode). To ease communication and comparisons of results, a more universal adoption of the most appropriate codes is recommended.
Occurrence of Agrobacterium tumefaciens Biovar 3 on Grapevine in Brazil
Authors: De Oliveira J. R. , Da Silva Romeiro R. , De Souza Leäo Lacerda B.
Published: May 2008

Occurrence of crown gall on grape was observed in a vineyard in Minas Gerais State, Brazil. Isolations of the pathogen yielded a bacterium which incited galls on grapevine, tomato and bryophillum. The bacterium was confirmed as Agrobacterium tumefaciens and its characterization showed it to be biovar 3. This is the first report on the occurrence of the biovar 3 of A. tumefaciens on grapevine in Brazil.
Characterization of Rhizoctonia solani associated with Sore Shin and Leaf Spot Symptoms on Tobacco in Zimbabwe
Authors: Mpofu S. I. , Julian A. M.
Published: May 2008

The relationship between Rhizoctonia solani isolates derived from leaf spot and sore shin symptoms on tobacco was characterized by determining nuclear number, hyphal diameter, anastomosis grouping (AG) and pathogenicity. The leaf spot isolates had significantly more nuclei per cell, and wider hyphae than the sore shin isolates. Anastomosis pairings with known tester strains confirmed the leaf spot isolates to be AG 3, and the sore shin isolates to be AG 4. Pathogenicity testing indicated that the leaf spot isolates were pathogenic to all parts of the plant, whereas the sore shin isolates tended to form lesions on stems only.
Serological Relationship and Chemical Composition of Exopolysaccharides (EPS) from Different Pathotypes of Xanthomonas campestris pv. Citri and Xanthomonas campestris pv. Manihotis
Authors: Bach E. E. , Guzzo S. D.
Published: May 2008

The exopolysaccharides (EPS) of five isolates of two pathotypes (A and C) of Xanthomonas campestris pv. citri and two isolates of X. campestris pv. manihotis have been isolated and partially characterized with regard to their sugar composition through gas chromatography. Results showed that except for one isolate of the pathotype C of X. campestris pv. citri which lacks galactose in its EPS, all the others are qualitatively identical in their sugar composition. However, quantitative differences were observed within and among the different isolates. Serological reactions among the different isolates showed that pathotype A of X. campestris pv. citri reacts only with the isolates of X. campestris pv. manihotis, while these also react with one of the isolates of pathotype C of X. campestris pv. citri. However, the isolate of pathotype C is cross‐reactive with the other isolate of the same pathotype which does not react with X. campestris pv. manihotis. This suggests a new pathogenic variant of pathotype C in Brazil, serologically distinct of the other isolates at least regarding the serological relationship with X. campestris pv. manihotis. Data did not permit any conclusion concerning the relationship between the sugars of each EPS and the serological recognition among the isolates.
Inhibition of Potato Spindle Tuber Viroid (PSTVd) Infectivity with Antisense RNA Transcripts
Authors: Matoušek J. , Trněná L. , Rakouský S. , Riesner D.
Published: May 2008

Antisense RNA was mixed with natural potato spindle tuber viroid (PSTVd) at 200‐fold molar excess and hybridized in vitro before inoculation of tomato plants. Inhibition of viroid infectivity was then characterized by percent infected plants of inoculated plants (percent of infectivity) and amount of PSTVd in infected leaves. For short RNA complementary to nucleotides 42–78, the inhibitory effect was much lower than for the corresponding antisense DNA oligonucleotides under the same experimental conditions. An almost complete block of PSTVd infection was observed, however, using complete minus monomers of PSTVd, suggesting that double stranded PSTVd RNA is not infectious. For antisense RNA complementary to nucleotides 338–359/1–87, 264–359/1–94, and 88–337, percent of infectivity was 67%, 8% and 17% and levels of PSTVd relative to control (100%) were 48%, 20% and 35%, respectively. Double stranded complexes formed between PSTVd and antisense RNAs were detectable using antibody specific fordouble stranded RNA and the sizes of the double‐stranded stretches were estimated using a nuclease S1‐protection assay. It was found that double‐stranded RNA was formed during co‐transcription of antisense RNA and PSTVd monomers of plus polarity at 37°C, and, to a lesser extent, during hybridization of antisense RNA and PSTVd monomers at lower temperature (after initially heating the samples to 40°C). In addition, antisense RNA inhibited infectivity of dimeric PSTVd transcripts of plus polarity with high efficiency if added during transcription. Co‐transcription of PSTVd dimers with antisense RNAs yielded RNA species showing virtually no infectivity. Nuclease S1‐protection assays revealed double‐stranded RNAs having lengths predominantly in the range, of the corresponding antisense RNAs.
Effect of Rust Infection on Cell Walls of Barley and Wheat; Immunocytochemistry Using Anti‐Barley Thionin as a Probe
Authors: Ebrahim‐Nesbat F. , Rohringer R. , Heitefuss R.
Published: May 2008

Polyclonal antiserum prepared against barley cell wall thionin was used to localize and quantitate immunoreactive material on the cellular level in healthy and rust‐infected leaves of barley and wheat. Three types of sites were used for the immunocytochemical analysis: as control sites, mesophyll cell walls were selected in uninoculated leaves, and in leaves that were inoculated with rust but where the sites were not in contact with the pathogen: these were compared with mesophyll cell walls that were in contact with intercellular rust hyphae in inoculated leaves.

Similar amounts of cell wall thionin were detected in all 3 barley cultivars before inoculation. At sites where intercellular hyphae of Puccinia hordei had made contact with mesophyll cell walls, less thionin was found in the compatible host cv. Larker, but in incompatible hosts (cvs. Gold and Bolivia) the thionin concentration did not differ from that of the controls.

Two cultivars of wheat were studied with respect to immunoreactive material in their mesophyll cell walls, the universal rust suscept cv. Little Club and the highly rust‐resistant cv. Khapli. Before inoculation, leaves of cv. Khapli contained about twice the amount of immunoreactive material in mesophyll cell walls than those of cv. Little Club. This relation was unchanged in walls that had made contact with P. graminis tritici, but in non‐contacted walls of infected cv. Little Club leavest, he concentration of this material had risen to levels typical for those of cv. Khapli. Tests for immunoreactive material with pre‐embedding cytochemistry yielded negative results, indicating that it is not exposed on the surface of mesophyll walls in barley and wheat.
Inhibition of Imidazolegly cerolphosphate Dehydratase of Phytophthora Parasitica by Aminotriazole in situ and after Cloning and Expression of the Respective Gene (HIS3) in Escherichia coli
Authors: Karlovsky P.
Published: May 2008

The HIS3 gene of Phytophthora parasitica was isolated from a plasmid library by complementing E. coli his B463 to histidine prototrophy. The gene, encoding imidazolegly cerolphosphate dehydratase, was expressed in E. coli independently of the promoter of the cloning vector. The growth of Phytophthora parasitica was far more sensitive to 3–amino–1,2,4–triazole (amitrole) than that of the E. coli w.t. The inhibition was fully counteracted by histidine. E., coli with a defective imidazoleglycerolphosphate dehydratase complemented by the Phytophthora gene exhibited the same high sensitivity against amitrole as Phytophthora itself. The expression of genes in E. coli is suggested for, screening potential inhibitors of enzymes in pathogenic organisms.
Reactivity of Two Monoclonal Antibodies to the Cylindrical Inclusion Protein of Potato Virus Y
Authors: Boudazin G. , Vergnet C. , Gélie B. , Meyer M. , Grosclaude J. , Maury Y.
Published: May 2008

Monoclonal antibodies (mAbs) were produced to the cylindrical inclusion (CI) protein of a necrotic strain of potato virus Y (PVY‐N) and their reactivity tested with nine PVY isolates and 12 other potyviruses. mAb 95 showed a reactivity range larger than PVY, unlike mAb 88 which only recognised the PVY isolates. Moreover, immunogold labelling of the Cls of PVY‐N, either in situ or in cell extracts, was only obtained with mAb 88, thus showing that the corresponding virus‐specific epitope is located at the surface of the Cl polymer.
Invasiveness of Avirulent Strains of Pseudomonas solanacearum in Tomato Cultivars, Resistant or Susceptible to Bacterial Wilt
Authors: Grimault V. , Prior P.
Published: May 2008

Tomato plant colonization by avirulent strains of Pseudomonas solanacearum was studied. The strain 8217R a spontaneous rough mutant was able to penetrate into roots by nature opennings and colonize plants at high levels. The strain 8173, a hrp‐ engineered fluidal mutant, colonized the plants to a lesser extent than 8217R. There was no difference in colonization observed at taproots and hypocotyls between resistant and susceptible cultivars with the avirulent strains 8217R and 8173, contrary to the plant‐virulent strain interaction. Results indicated that the bacterial spread was limited in the two cultivars regardless of their resistance or susceptibility and suggested the existence of a host defence mechanism, limiting the bacterial spread.
Development and Evaluation of a Laboratory‐Based Technique for Screening Somaclonal Regenerants of Watercress (Rorippanasturtium‐aquatium) for Resistance to Crook Root Disease (Spongospora subterranea f. sp. nasturtii)
Authors: Arnold D. L. , Flegmann A. W. , Clarkson J. M.
Published: May 2008

A laboratory based method has been developed for infecting watercress with the crook root fungus (Spongospora subterranea f.sp. nasturtii). This utilised plastic trays of nutrient solution on which watercress shoots, supported by floats, were grown for a pre‐inoculation period of 14 days before an inoculum consisting of 1 g of crook roots was added. Seven watercress someclones derived from plantlets regenerated from callus of a parental commercial control line (clone A) were tested onthree separate occasions. No variation within the parental control plants was seen but significant variation both between and within the individual somaclones over successive tests was observed. Two somaclones showed increased resistance to crook root disease compared with parental control plants.
Expression of Resistance to CMV Migration in Pepper Seedlings
Authors: Dogimont C. , Daubeze A. M. , Palloix A.
Published: May 2008

Previous studies have shown that the partially resistant genotypes of pepper (Capsicum annuumL.), ‘Milord’ and ‘Vania’ are able to localize CMV infection in some shoots of the plants when inoculated at an adult stage. We have observed that the virus migration is restricted to the inoculated cotyledons when young seedlings of these genotypes are inoculated with the Fulton CMV/N strain. In the same conditions, susceptible genotypes become systematically infected. We have shown that the levelof resistance expression depends on the plant development stage, the environmental conditions and the inoculum concentration. The most favourable conditions to discriminate resistance to CMV migration at an early stage of plant development have been defined.
Differential Sensitivity of Wheat Embryos against Extracts Containing Toxins of Septoria nodorum: First Steps towards in vitro Selection
Authors: Keller B. , Winzeler H. , Winzeler M. , Fried P. M.
Published: May 2008

As a first step towards the development of an in vitro‐selection system for septoria nodorum blotch resistance, wheat embryo culture on media containing extracts from Septoria nodorum was established. Extracts prepared from inoculated wheat grains had a toxic activity. Control extracts from uninoculated grains showed at least a 10‐fold lower toxic activity. Two wheat breeding lines susceptible to Septoria nodorum showed reduced growth in the presence of the fungal extract whencompared to a breeding line known to have good resistance in the field. A test with seven additional wheat lines showed a good agreement between field resistance of the ear and embryo resistance. Mellein is one of the toxins produced by Septoria nodorum and was used in pure form for in vitro‐selection. It showed toxic effects at 50 μg/ml, a concentration which is about 200‐fold higher than the mellein concentration in the diluted extract with embryotoxic activity. This indicates the importance of additional toxic compounds in the crude extract. Mellein acted non‐selectively on embryos of the different cultivars.
Effect of Host‐race Combination on Resistance of Sunflower, Helianthus annuus L., to Downy Mildew Plasmopara balstedii
Authors: Mouzeyar S. , de Labrouhe D. Tourvieille , Vear F.
Published: May 2008

Study of resistance of sunflower, Helianthus annuus L., to downy mildew, Plasmopara halstedii, shows that both susceptible and resistant seedlings are always infected by the fungus, then hypersensitive‐like reactions occur in the parenchyma and necroses form around the parasite. Comparison of 21 incompatible combinations (resistance) shows that the extent of the fungus growth differs according to the host‐race combination. With type I resistance, the fungus is limited to the roots andthe lower part of the hypocotyl. With the type II resistance, the fungus grows throughout the whole length of the hypocotyl and may sporulate on the cotyledons.
Genetic Variability in Pectic Enzymes of Rhizoctonia solani Isolates Causing Bare‐patch Disease of Cereals
Authors: Yang H. A. , Zhou J. , Sivasithamparam K. , Tommerup I. C. , Barton J. E. , O'Brien P. A.
Published: May 2008

Field isolates of Rhizoctonia solani obtained from three discrete bare patches in a wheat field in Western Australia were characterized by pectic zymogram grouping. The genetic background of pectic enzymes was analysed by comparing the zymograms of asexual homokaryons and sexual progenies derived from field isolates. The 170 field isolates obtained from the field site produced indistinguishable pectic zymograms. However, variations among field isolates of the same zymogram group were detected, on the basis of zymograms of their resultant protoplast‐regenerated cultures. Asexual sibling homokaryons derived from each of the field isolates were heterogeneous for their pectic enzymes. Homokaryons with a common heterokary on incompatibility factor, obtained from a field isolates were homogeneous for pectic enzymes. Basidiospore progenies of a field isolate segregated widely in pectic zymograms. It appeared that the expression of pectic enzymes by field isolates involved multiple genetic factors. The variation of zymograms among homokaryotic strains suggests that each field isolate of R. solani contains two types of nuclei, although cells of vegetative hyphae are multinucleate.
Scanning Electron Microscopy of Apothecia of Sclerotinia trifoliorum Erikss. and Related Species
Authors: Arseniuk E. , Macewicz J.
Published: May 2008

The technique of scanning electron microscopy (SEM) was used to study the microanatomy of apothecia of Sclerotinia trifoliorum Erikss., S. sclerotiorum (Lib.) de Bary, and S. minor Jag., In the sterile tissue zones of apothecia, the only interspecific difference detected was that one in the structure of the apothecial margin of small‐ and large‐sclerotium Sclerotinia spp., The ectal excipulum, at the apothecial margin in S. minor appeared to be comprised of textura globulosa with globose cells. Whereas, in S. trifoliorum and S. sclerotiorum it appeared to be comprised of textura porrecta with prosenchymatous cells.

The other interspecific difference reported in this paper is a dimorphism in spore size (ratio 4:4) in asci of S. trifoliorum. Otherwise, the microanatomy of ascocarps of S. trifoliorum and S. sclerotiorum was identical to that one of S. minor. Differences in the density of hyphae in the medullary excipulum in the apothecial disks of the three species studied were not detected. The presence of a membranous film over the hymenium of the ascocarp of S. trifoliorum or, any other species, as well as the bundlelike structure of the apothecial stipes in the studied species, as described in earlier reports, was also not found.
Isolation and Partial Characterization of Peanut Top Paralysis Virus (PTPV), a Destructive Virus Causing a New Disease in Peanut (Arachis hypogaea L.)
Authors: Wagih E. E. , Melouk H. A. , Sherwood J. L.
Published: May 2008

A destructive virus, causing top paralysis to peanut, was discovered in the wild germplasm collection growing in the USDA‐ARS greenhouses, Stillwater, Oklahoma, USA. The symptoms observed on the wild plant were restricted to a few leaves as green batches in a light green to yellow background with some leaflets having lost most of the basal part of the laminae leaving the top portion rolling upwards forming a cone. The virus was mechanically transmitted to cultivated peanut (Arachis hypogaeaL,.) where it caused more severe and destructive symptoms including stunting, severe malformation of leaves and partial or complete disappearance of leaflet laminae. This virus differed in symptomology, host range, and/or serological reactivity from allpeanut viruses reported in the literature, particularly those causing leaf malformation and stunting. The virus induced necrotic local lesions on Phaseolus vulgaris L. cv. “Topcrop” and chlorotic local lesions with necrotic centres bordered withvery bright intense red color on Chenopodium amaranticolor. In both passive indirect enzyme‐linked immunosorbent assay (PAS‐ELISA) and Ouchterlony double immunodiffusion test, the virus did not react with antisera against brome mosaic, bean yellow mosaic, peanut stripe, potato Y, tobacco mosaic, watermelon mosaic 1, watermelon mosaic 2, wheat soilborne mosaic, wheat streak mosaic, and zucchini yellow mosaic viruses.

However, in reciprocal cross reactions the virus seemed to share a common antigenic determinant with a peanut mottle virus isolate from Oklahoma (PMV‐OK). The virus had flexuous filamentous particles with a length of 750–850 nm, falling within the range reported for the potyvirus group. The virus was successfully purified and the molecular weight of its protein subunit was found to be 30000 d. A polyclonal antiserum was raised in rabbits against the virus and used for reciprocal serological tests.
Broad Spectrum Detection of Cucumber Mosaic Virus (CMV) Using The Polymerase Chain Reaction
Authors: De Blas C. , Borja* M. J. , Saiz M. , Romero J.
Published: May 2008

Primers complementary to conserved sequences of cucumber mosaic virus (CMV) RNA 3 were designed and reverse transcription‐polymerase chain reaction was directly performed in crude sap extracts of CMV‐infected plants. All isolates assayed belonging to subgroups I or II from different Spanish geographical locations and infecting tobacco, tomato and cucumber plants were detected. No amplification was observed in healthy or tomato aspermy virus (TAV)‐infected plants, nor in CMV‐infected pepper plants.A, dilution as low as 10‐7 in tobacco crude sap extracts or 100 fg of purified virus (c. 50 000 virus particles) could be detected, results showing that this procedure is 102 times more sensitive than enzyme‐linked immunosorbent assay (ELISA).
Grafting Tomato Cultivars Resistant or Susceptible to Bacterial Wilt: Analysis of Resistance Mechanisms
Authors: Grimault V. , Prior P.
Published: May 2008

Grafting experiments were carried out in order to understand tomato resistance mechanisms to Pseudomonas solanacearum. Resistant scions grafted on susceptible root‐stocks wilted, indicating that vascular tissues of resistant cultivars were not tolerant to higher bacterial populations than susceptible ones. Colonization frequencies and bacterial densities observed in plant grafted on resistant or susceptiblle root‐stocks showed that resistance was correlated to the limitation of bacterial spread in the lower part of the stem.
Induction of Growth Increase and Systemic Resistance to Exserohilum turcicum in Maize by Foliar Spray of Phosphates
Authors: Reuveni R. , Reuveni M. , Agapov V.
Published: May 2008

A single foliar spray of 0.1 M solution of phosphate salts on the upper side of maize (cv. ‘jubilee') leaves 1, 2 and 3 at the 5–6 fully–expanded leaf‐stage, 2‐4 h before inoculation induced systemic resistance to northern leaf blight caused by Exserohilum turcicum. Nine days after challenge, protection was demonstrated by 91% reduction in the size and 69% in the number of E. turcicum lesions developing on leaves 4, 5, 6 and 7. Appropriate mixing of phosphate solution with KOH revealed that the level of protection was not necessarily dependent on the pH of the solution. The size and number of lesions decreased to 62% and 56%, respectively, 12 days after challenge. There was no damage or chlorotic stipling on the induced leaves (1, 2, and 3) as a result of the phosphate spray. There were no significant differences in the reduction in the number or size of the lesions obtained when the foliar spray was applied 2‐4 h or 1, 3, 6, 8, or 10 days before inoculation. One foliar spray ofK2HPO4 on leaves 1, 2 and 3 in these intervals before inoculation, remarkably stimulated growth of inoculated plants, which was expressed by several parameters. The possible dual use of phosphate salts as foliar fertilizers and as resistance‐inducing agents is discussed
Licht‐ und elektronenmikroskopische Untersuchungen zur Wirkung eines Kulturfiltrates von Erwinia herbicola B 247 und von Herbicolin A auf Fusarium culmorum
Authors: Kempf H.‐J. , Ebrahim‐Nesbat F. , Wolf G.
Published: May 2008

Light and electron microscopical studies on the effect of a culture filtrate of Erwina herbicola B 247 and herbicolin A on Fusarium culmorum

The effect of a culture filtrate of Erwinia herbicola B 247 and the antibiotic herbicolin A, respectively, on the hyphae of Fusarium culmorum was studied in vitro using light and electron microscopy. The light microscopy revealed a swelling and disruption of the hyphae tips with a release of cytoplasm. Ultrastructural investigations demonstrated the appearance of electron‐dense material of a round or tubular structure in the cell wall. On its inner side, an accumulation of electron‐dense material formed a spongy structure associated with the altered plasma membrane. Finally, a complete dissolution of the cell wall was observed.
Characterization of an Isolate of Zucchini Yellow Mosaic Virus form Cucumber in Singapore
Authors: Wong S. M. , Chng C. G. , Chng C. Y. , Chong P. L.
Published: May 2008

Zucchini yellow mosaic virus (ZYMV) was first found in cucumber in Singapore in 1989. This virus was propagated in Cucurbita pepo cv. First Taste and mechanically transmitted to 12 species of six families. It induced milder symptoms than the Connecticut and Florida strains of ZYMV in infected leaves of C. pepo cv. Zucchini Elite. ZYMV‐S is neither seed nor aphid transmissible. Immunoelectron microscopy revealed that ZYMV‐S is distantly related to WMV‐2, Moroccan WMV, and TelMV, but not, related to PRSV or ZYFV. Cytoplasmic pinwheels and scrolls were observed in ultrathin sections of infected leaf cells by light, confocal laser scanning, and transmission electron microscopy. The molecular weights of the viral coat protein and cytoplasmic inclusion protein, RNA and dsRNA were estimated to be 3.2 × 10−1, 6.1 × 104, 3.23 × 106 and 6.53 × 106 daltons, respectively.
Detection of Double‐Stranded RNA (DSRNA) in Crude Extracts of Virus‐Infected Plants by Indirect ELISA
Authors: Aramburu J. , Moreno P.
Published: May 2008

An antiserum against polyinosinic‐polycytidylic acid (In‐Cn) was used to detect double‐stranded RNA (dsRNA) by indirect ELISA (ELISA‐I). DsRNA from cucumber mosaic virus (CMV) and plum pox virus (PPV)‐infected plants was detected using different types of extracts. The pH of the extraction buffer was very important in dsRNA detection, the highest optical density values being obtained at pH 6 or in aqueous extracts. Extracts heated at 80°C for 2 min showed increased optical density values compared with unheated extracts. DsRNA from Nicotiana benthamiana plants infected with each of six PPV isolates was readily detected by ELISA‐I 50 days after inoculation. ELISA values then obtained with the In‐Cn antiserum were generally higher than those obtained by double antibody sandwich ELISA using an antiserum to virus coat protein. Purified dsRNA from the same infected plants showed no visible band, but it produced a fluorescent background when analysed by polyacrylamide gel electrophoresis.
Quick Decline of Macadamia Trees: Association with Phytophthora capsici
Authors: Ko W. H. , Kunimoto R. K.
Published: May 2008

Some macadamia trees in commercial orchards in Hawaii showing quick decline syndrome had bleeding from the trunk. Phytophthora capsici was isolated from c. 67% of such sites, and was shown to kill branches of artificially‐inoculated healthy macadamia trees. The pathogen was detected in both diseased and apparently healthy bark and isolated from wood 80 mm away from the bark. Results suggest that trunk infection by P. capsici may lead to girdling and rapid decline, and attract insects which then cause some bleeding by making wounds at the sites of recent infection.
Cross‐Reactive Antigens Between Pea and Some Fungal Plant Pathogens
Authors: Scala F. , Cristinzio G. , Coppola L. , Del Sorbo G.
Published: May 2008

Antiserum to pea was used to analyse cross‐reactive antigens (CRA) between pea and some fungal plant pathogens with different levels of specificity towards this host by using both double diffusion and immunoblotting techniques. Non pathogens of pea were also included in the study. Nectria haematococca MPVI, the three formae speciales dianthi, lycopersici and pisi of Fusarium oxysporum and Ascochyta pisi produced strong reactions with both techniques. In N. haematococca MPI, F. solani f. sp. phaseoli, V. dahliae and Phoma medicaginis var. pinodella instead, reactions were not detected by double diffusion but only the more sensitive immunoblotting technique. No CRA were observedin, the non‐specific pathogens Rhizoctonia solani, Sclerotium rolfsii and Sclerotinia sclerotiorum, as well as in the non‐pathogen Phytophthora capsici. The immunoblotting patterns of the most reactive fungi showed common bands with molecular weights of 84, 75 and 62 kDa. Some bands were present only in the specific pathogens N. haematococca MPVI and F. oxysporum f.sp. pisi. The possible involvement in host‐parasite interactions of cross‐reactive antigens which are, present in the analyzed fungi is discussed.
Cytopathology of Anthers and Pollen From Lettuce Plants Infected by Lettuce Mosaic Virus
Authors: Hunter D. G. , Bowyer J. W.
Published: May 2008

Thin sections of mature anthers and pollen grains from three lettuce (Lactuca sativa) plants infected with lettuce mosaic potyvirus (LMV) were studied by immunogold labelling. Labelled LMV particles were present externally on the exine of pollen grains from all plants, but were observed internally in the pollen grains from only one plant. Within mature pollen grains the virus particles were associated with the cytoplasmic bundle inclusions typical of infection by potyviruses. The tapetal plasmodium and the epidermal and endothecial layers of mature anthers from all infected plants also contained labelled virus particles, together with pinwheel and bundle inclusions.
Partial Characterization of a Gene for a 31 kD Protein of Pseudomonas syringae pv. syringae Apparently Involved in Pathogenicity
Authors: Niepold F. , Nickel Antje , Landsmann J.
Published: May 2008

P. syringae pv. syringae strain R32 causes the bacterial brown spot disease on bush beans. A 31 kD protein was detected which is involved in the pathogenic response. Monospecific antibodies directed against this 31 kD‐protein were used to screen a protein expression gene bank made from the wild type strain R32. A 0.8 kb DNA insert of a clone which gave a positive reaction with the monospecific antibodies was used in hybrizations to clone a larger chromosomal fragment. A km‐cassette (kmresistance) was integrated into this chromosomal DNA‐fragment preventing the expression of the 31 kD‐protein. This construct was integrated into the chromosomal of the wild type strain R32 viahomologous recombination resulting in the 31 kD‐protein deficient mutant LMI. Biotests with the host plant (bean) and with tobacco leaves showed no symptoms or hypersensitive reaction (HR) when the mutant LMI was inoculated. However, atypical chlorotic and necrotic lesions compared to the wild type strain R32 were found on tobacco leaves when the mutant LMI was incubated for more than 2 weeks. Complementation of the LMI mutant with a plasmid harbouring the corresponding wild type R32 DNA fragment resulted in an isolate (LMIC) which showed a partial restoration of the HR on tobacco but no brown spot disease symptoms on bush beans. The 31 kD‐protein could be detected serologically in LMIC.
Comparison of Three Methods for Assessing Plum Pox Virus Variability: Further Evidence for the Existence of Two Major Groups of Isolates
Authors: Bousalem M. , Candresse Th. , Quiot‐Douine L. , Quiot J. B.
Published: May 2008

Twenty‐eight plum pox virus isolates from several European and Mediterranean countries were compared by electrophoretic mobility of their coat protein subunit measured by Electroblot Immuno‐Assay (EBIA), antigenic properties of the N‐ and C‐terminal parts of the coat protein and restriction fragment length polymorphism (RFLP) and analysis of polymerase chain reaction (PCR) amplification of the C‐terminal part of the coat protein gene. Similar results were obtained by each of the three methods. These confirm the existence of the two major subgroups of PPV, and which we now propose to designate PPV‐D and PPV‐M, respectively.