bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Energy in Pathogenic Variability of Pyricularia oryzae
Authors: Mohanty C. R. , Gangopadhyay S.
Published: May 2008

Pyricularia oryzae Cav. reacts differently to different varieties. IB race group attacked Zenith for three consecutive years for both rabi and kharif seasons under artificial inoculation condition. Three different isolates were obtained in IB race which differed in their pathogenicity giving a constant susceptible reaction to Zenith. The difference in energy potential of three isolates of P. oryzae was tested biochemically. Total sugar, protein and protein patterns were studied following modern methods. W isolate contained maximum amount of total sugar (18.3 μg/g), total protein (23.8 μg/g albumin equivalent) and seven distinct protein bands on polyacrylamide disc electrophoretic gel which was directly correlated with maximum infection value. So it was concluded that the aggressiveness of P. oryzae depends on its energy potentiality in terms of total protein and protein patterns.
Interactions of Cowpea Mosaic Virus with Cowpea Protoplasts1)
Authors: Smith A. G. , Durand D. P. , Hill J. H.
Published: May 2008

The capability of cowpea mosaic virus to attach to and infect protoplasts of immune, hypersensitive, and susceptible cowpea (Vigna unguiculata) lines was examined by inoculating protoplasts with either purified virus or radioiodinated purified virus 125I‐CPMV. Systems were used in which plants were immune and protoplasts susceptible, plants were immune and protoplasts resistant, and plants and protoplasts were susceptible to CPMV. No differences were observed in the attachment of 125I‐CPMV to resistant and susceptible protoplasts. Polycations, proteins, or virus particles were added to the inoculation medium to neutralize potential nonspecific interactions between cells and virus particles. The various additives induced quantitative differences in binding of virus particles to protoplasts.
Structural Aspects of the Parasitism of Sclerotia of Sclerotinia sclerotiorum (Lib.) de Bary by Coniothyrium minitans Campb.
Authors: Phillips A. J. L. , Price K.
Published: May 2008

Sclerotia of Sclerotinia sclerotiorum inoculated with pycnidiospores of Coniothyrium minitans were studied by means of light microscopy and transmission and scanning electron microscopy. The hyperparasite penetrated the walls of the rind cells by means of physical pressure and destroyed the cell contents. Penetration of medullary hyphae was by enzymic lysis and physical pressure; there was evidence to suggest that the hyperparasite may coil around the host cells before inserting infection hyphae.
Reactions of Soybean Leaves to Pseudomonas spp.
Authors: ÉRsek T. , Hevesi Mária
Published: May 2008

Comparative tests on the reactions of soybean cultivars to races of Pseudomonas glycinea were done. It was found that reaction denoted, on the basis of visible symptoms, intermediate between fully resistant and susceptible ones, was in accordance with, microscopic features observed as well as with phytoalexin content measured. The pattern of single cell death and the accumulated glyceollin level resembled rather the resistant than the susceptible plant response. Despite the delayed and weak resistant, hypersensitive‐like response of soybean leaves to infection, the bacteria multiplied in the intermediate combination similarly as in a compatible one. The strain of P. syringae isolated from, but non‐pathogenic to foxtail millet, initiated no hypersensitive reaction (HR), i. e. neither tissue necrosis nor glyceollin accumulation.

However, this strain, unlike saprophytes, multiplied like the HR‐inducing strain of P. syringae from apricot: after a short increase it ceased to multiply by 48 h.

These results suggested that some resistance mechanism unrelated to HR may account for resistance of soybean leaves to pseudomonads.
Characterisation of an Apparently Novel Soluble Protein Fraction found in Pathogen and Osmotically‐stressed Cucumber Cotyledons
Authors: Wagih E. E. , Raftopoulos A. E. , Archer S. A. , Coutts R. H. A.
Published: May 2008

Cotyledons of cucumber (Cucumis sativus L. cv. Ashley) were used to study the alterations that occur in the soluble protein fraction following either tobacco necrosis virus‐elicited necrosis or a period of mannitol‐induced osmotic‐stress. One apparently novel fraction (termed γ) was induced in the soluble protein fraction after necrosis or osmotic stress and was identified by disc‐PAGE and gel staining. Smaller amounts of the γ fraction were present in apparently healthy tissue adjacent to necrotic halves of cotyledons (AH tissue), but were absent from any other leaves on these plants. The γ fraction is probably representative of at least three different proteins, two of which are constituents of control tissue (a glycoprotein and possibly one or two RNAse isozymes) while the third is a protein of unknown nature, present as the bulk of the γ fraction and possibly synthesized de novo.

Following the radio‐active labelling of AH tissue it would appear that an increased protein synthesis, which is sensitive to the effects of translational inhibitors may result in the production of the γ fraction, but this is speculative. The major component of the γ fraction gave a single band on SDS PAGE, with an Mr of ca. 22,000 and focussed to a single band at pl 4,1 on IEF. While it is thought the bulk of the novel portion of the γ fraction is represented in these gel systems increased amounts of the constitutive glycoprotein component should be taken into consideration.

Soluble extracts of protoplasts isolated from AH tissue retained only constitutional RNAse isozyme(s), and were totally devoid of the rest of the γ fraction. This result suggests that the other component(s) of the γ fraction is (are) subcellularly located in the plasmodesmata, between the cell wall and plasma membrane or non‐covalently attached to either.
Supplementary Antimold Activity of Phosethyl AL, A New Brown Rot Fungicide for Citrus Fruits
Authors: Gutter Y.
Published: May 2008

Phosethyl Al (= Aliette) is a new and promising postharvest fungicide against brown rot of citrus fruits. Its effectiveness in controlling green mold (Penicillium digitaum), the major citrus fruit pathogen, was studied on artificially inoculated fruit and compared with that of sodium o‐phenylphenate (SOPP) and thiabendazole (TBZ).

In vitro and in vivo experiments have shown that phosethyl Al is capable — although to a lesser extent than SOPP and TBZ — of inhibiting growth of P. digitatum and reducing the incidence of decay of citrus fruits, caused by a wild‐type, and apparently also by a benzimidazole‐resistant strain of this fungus.

The influence of times of treatment and modes of application (including temperature and duration of treatment, rinsing of the fruit) on the effectiveness of phosethyl Al, SOPP and TBZ in controlling green mold was studied and discussed. It is concluded that, under conditions of natural infection, phosethyl Al can be used for the postharvest control of Phytophthora‐caused brown rot without any apparent increase in the incidence of green mold in the treated fruits.
Pleospora drummondii spec. nov. und ihr Anamorph Stemphylium drummondii spec. nov.
Authors: Nirenberg H. I. , Plate H.‐P.
Published: May 2008

Pleospora drammondiispec. nov. and its anamorphStemphylium drammondiispec. nov.The causal organism of a leaf spot disease onPhlox drummondiiis described asPleospora drummondiispec. nov. and its anamorphStempbylium drummondiispec, nov. — in contrast to earlier reports from the USA, in which the fungus was identified asS. botryosum.
Scanning Electron Microscopy of Pseudomonas syringae pv, morsprunorum on Sweet Cherry Leaves
Authors: Roos Isabel M. M. , Hattingh M. J.
Published: May 2008

Scanning electron microscopy indicated that sub‐stomatal cavities on sweet cherry leaves are “protected sites” which shelter resident populations of Pseudomonas syringae pv. morsprunorum. Bacteria entered the stomata, multiplied in the cavities and emerged in a mass 6 days after inoculation. There were no visible symptoms, suggesting that the pathogen colonized the host in “sub‐clinical” numbers to generate populations which were then released onto the leaf surface under suitable conditions.
The Association of Brome Mosaic Virus and Wheat Rusts: I. Transmission of BMV by Uredospores of Wheat Stem and Leaf Rust
Authors: Erasmus D. S. , Von Wechmar M. B.
Published: May 2008

Both the stem and leaf rust fungi of wheat (Puccinia graminis f. sp. tritici, P. recondita f. sp. tritici) were investigated as potential vectors of brome mosaic virus (BMV), a pathogen of Gramineae. They were found to transmit BMV to healthy plants through uredospore transfer from hosts infected with both the viral and fungal pathogens. Virus was transmitted even to rust‐resistant and non‐susceptible hosts. Rust‐transmitted virus produced atypical symptoms on plants, could not be extracted by normal low pH methods, and multiplied only to low levels in leaf tissue. Extracted virus was shown to be similar to BMV‐type strain (ATC) by serology, density gradient centrifugation and immunospecific electron microscopy. The importance of the association of BMV with the rust fungus in natural infections is discussed.
The Genera and Species Spectrum of Cucumber Powdery Mildew in Czechoslovakia
Authors: Lebeda A.
Published: May 2008

In 1979 and 1980, the fungi causing cucumber powdery mildew were investigated in Czechoslovakia. In 37 localities in the major growing 102 samples of mildew were collected. Most of them came from cucumber leaves (especially from field cultures), few came from squash leaves. Studies of the imperfect stage served to identify, in the samples, two pathogen species, viz. Erysiphe cichoracearum and Sphaerotheca fuliginea have been found. E. cichoracearum predominated under field conditions; S. fuliginea was found in only two localities. In glasshouses S. fuliginea predominated.
Zur Rolle des Pektins bei der Ausprägung sorten‐ und jahresbedingter Unterschiede der Naßfäuleanfälligkeit von Kartoffelknollen
Authors: Weber J.
Published: May 2008

The influence of soil moisture and mean day temperature of July to September on pectin structure and soft rot resistance of potato tubers was investigated.

Tuber samples of middle early and middle late potato cultivars respectively were tested from 1976 to 1979.

Cultivar characteristics as well as growth conditions effect the pectin structure. The tuber tissue of soft rot resistant cultivars contains relative high amounts of esterified pectin. The pectin esterification was promoted by drought during vegetation periods (1976, 1978). A late rise of metabolic activity caused by rainfall at the end of the vegetation period (1978) increased the amount of soluble pectin in the cell wall. This lack of pectin stabilization facilitates tissue maceration by soft rot bacteria.

Increased pectin solubility was also caused by unfavorable storing conditions of potato tubers.

A low degree of esterification and high solubility of the cell wall pectin affect the relative resistance of potato tubers against soft rot caused by Erwinia carotovora var. atro‐septica (van Hall) Dye adversely.
Metabolites of Alternaria solani, Part IX: Phytotoxicity of Altersolanol A
Authors: Holenstein J. E. , Stoessl A.
Published: May 2008

The fungal tetrahydroanthraquinone altersolanol A has been found to exhibit nonspecific phytotoxicity to potato, tomato, pea and cress tissues, causing necrosis on leaves and inhibiting root growth.
Selection of Antagonistic Fluorescent Pseudomonas spp. and their Root Colonization and Persistence following Treatment of Seed Potatoes
Authors: Geels F. P. , Schippers B.
Published: May 2008

One hundred and twelve fluorescent Pseudomonas isolates from potato periderm were screened for antagonistic activity in vitro against 5 pathogenic and saprophytic fungi, 5 Gram‐positive bacteria including Streptomyces scabies and 4 Gram‐negative bacteria including Erwinia car. var. carotovora and Erwinia car. var. atroseptica. Fifty‐seven percent of the isolates showed wide spectrum inhibitory activity, mostly due to the production of fluorescent siderophores. Only 4 % of the isolates were very strong antagonists. By adding iron (Fe3+) to the test medium, the antagonistic activity drastically diminished but revealed some strong antagonists of which the antagonism was not affected. Apparently growth‐inhibiting substances other than siderophores were involved. Antibiotic‐resistant mutants of the antagonists were used to establish that the bacteria on the seed tubers migrated to the roots under different conditions. Drying of the treated potatoes gradually diminished the number of viable cells, but subsequent planting in moist soil led to substantial increases in the first three days. Initially high numbers of the antibiotic‐resistant antagonists on the roots tended to drop quickly in time, probably due to loss of resistance to the antibiotics in the selective medium.
Culturing Puccinia coronata on a Cell Monolayer of the Avena sativa Coleoptile
Authors: Mendgen K. , Dressler Elvira
Published: May 2008

A culture of Puccinia coronata on an epidermal cell monolayer dissected from the Avena sativa caleoptile is described. To induce fungal development, infection structure formation had to be induced with a heat treatment. The host cells were fed with 1 % sucrose (or glucose or manitol) to sustain fungal growth. Under these conditions, normal development of hyphae, haustoria with haustorial mother cells and uredospores occurred. Uredospores had normal infectivity.
Reactions in Maize Infected with Swedish Isolates of Barley Yellow Dwarf (BYDV)
Authors: Eweida M. , Tomenius Karin , Oxelfelt P.
Published: May 2008

Nine cultivars of maize (Zea mays L.) were tested for susceptibility to BYDV under three temperature ranges in the greenhouse. Three Swedish isolates of BYDV were used, two specifically transmitted by Rhopalosiphum padi (L.) (39/78) and by Sitobion avenae (Fabr.) (27/77), respectively, and the third by both species (70). The virus isolates were transmitted successfully from different grasses to maize and from infected maize to the susceptible oat cultivar “Sol II” by the respective aphid species. S. avenae showed very high ability to transmit the S. avenae specific isolate to and from maize plants.

The main symptoms that developed on maize were fine chlorotic irregular spots, reddish purple discoloration and malformed leaves.

The relationship between maize cultivar, temperature and percent of infection is discussed. Enzyme‐linked Immunosorbent Assay (ELISA) was used with success to detect the virus isolate 27/77 in susceptible and symptomless maize plants.

Electron microscopy of maize (cv. LG ll) infected with the 27/77 isolate of BYDV revealed virus‐like particles, about 22 nm in diameter, in the nuclei of companion cells, in the plasmodesmata connecting companion cells with mature sieve tubes, in the lumen of mature sieve tubes and in xylem tracheal elements.
Über die Pleomorphie von MLO in Catharanthus roseus (Vinca rosea)
Authors: Schmitt U. , Petzold H. , Marwitz R.
Published: May 2008

About the pleomorphism of MLO in Catharanthus roseus (Vinca rosea) MLO of the flower greening (virescence)‐type of Primula in the phloem of Catharanthus roseus (Vinca rosea) were fixed in two different ways. After prefixation with OsO4 they showed a diminished pleomorphic morphology, most MLO were spherical. With the fixation of KARNOVSKY (1965) and subsequent treatments with OsO4 and uranyl acetate, however, an extremely high pleomorphism was observed. Such pleomorphic MLO in single thin sections are probably the expression of a threedimensional network‐like connection. The concentration of MLO in the sieve elements seems to influence the pleomorphism only insignificantly.
Common Leafspot of Alfalfa: Ascospore Germination and Disease Development in Relation to Moisture and Temperature
Authors: Semeniuk G.
Published: May 2008

In a moist chamber Pseudopeziza medicaginis ascospores infected alfalfa (Medi sativa L.) moderately to abundantly within 6–10 h at 10–20 °C and within a longer time‐span outside this temperature range. Approximate limits of the range were 2.5 and 28 °C; no infection took place at 30 °C. At 14°C ascospores infected alfalfa abundantly at 98 %relative humidity (RH) and above, moderately at 97%, sparsely at 95 and 96%, but not at 94% and below. Ascospores were hydrophilic, germinating best at or near 100%, RH but did not germinate at or below 93 % RH. After infection was established, tiny leafspots became visible within 6–7 days at constant temperatures of 15–25°, 10 days of 10°C, 13 days of 5 °C, and 25 days of 2.5 °C. They failed to develop into normal size spots within 4 weeks at constant temperatures near 30 °C, or near 10 °C and lower. Temporary exposure of incipiently diseased plants 1–6 days to 30–38 °C adversely affected subsequent leafspot development at 20–24°C. Inhibition depended on temperature and on the extent of post‐infection disease development.
Clostero virus‐Like Particles of Two Types Associated with Diseased Grapevines
Authors: Milne R. G. , Conti M. , Lesemann D. E. , Stellmach G. , Tanne Edna , Cohen J.
Published: May 2008

Previous work led to the characterization of, and the production of an antiserum to a closterovirus referred to as grapevine stem pitting‐associated virus (GSP‐AV). Using this antiserum and immunoelectron microscopy, we now show that GSP‐AV is widespread in grapevines and that a second serologically distinct closterovirus‐like particle is also widely present. One or both of the closterovirus‐like particles were often but not always associated with leafroll symptoms. However, some plants indexed as suffering from stem pitting also contained one or both of the particles.

As “grapevine stem pitting‐associated virus” no longer seems appropriate as a name, we suggest changing it to grapevine virus A (GVA). We provisionally refer to the second closterovirus‐like virus as grapevine virus B (GVB).
Biological Control of Phytophthora Root Rot of Soybean by Hyphochytrium catenoides in Greenhouse Tests
Authors: Hsu S. C. , Lockwood J. L.
Published: May 2008

Mycelia of Hyphochytrium catenoides applied to soil artifically or naturally infested with Phytophthora megasperma var. sojae was effective in affording a high degree of protection of soybean plants against root rot in greenhouse tests. Seedling emergence, plant height and root diseases were restored to values near those of plants grown in soil without the pathogen, and root disease severity was greatly reduced, though never eliminated. Control was similar whether soil was treated with H. catenoides, then folded for 7 days before seeding, or if the flooding and prior incubation periods were eliminated. Abundant inoculum of H. catenoides was produced in a semi‐solid medium containing tryptone, glucose and yeast extract in which the colonies remained suspended. The inoculum, applied to vermiculite and stored in the laboratory, survived well: colony counts after 25 weeks were 63% of those present initially.
Effect of Bacterial Antagonist on Phytopthora cactorum and Apple Crown Rot
Authors: Utkhde R. S.
Published: May 2008

Bacterial antagonist B8 produced an inhibition zone with each of four Phytophthora cactorum isolates on corn meal agar (CMA) plates. Infections with three P. cactorum isolates were significantly reduced when the soil was simultaneously inoculated with B8. Growth of P. cactorum was completely inhibited on CMA amended with 40–100 per cent 10 fold concentrated B8 extract. Percent oospore germination of P. cactorum was significantly reduced when B8 was present in suspension for 9, 12 and 15 days from inoculation. Survival of oospores was significantly reduced at 60 and 90 mm depths in soil. Bacterial antagonist B8 significantly reduced the population of viable P. cactorum oospores in the top 30 mm of soil where oospores generally survive.
Occurrence of Falcarinol and Falcarindiol In Tomato Plants after Infection with Verticillium albo‐atrum and Characterization of Four Phytoalexins by Capillary Gas Chromatography‐Mass Spectrometry
Authors: Elgersma D. M. , Weijman A. C. M. , Roeymans H. J. , van Eijk G. W.
Published: May 2008

Falcarinol and falcarindiol were isolated from tomato vascular tissue infected with Verticillium albo‐atrum and identified. Separation and characterization of trimethylsilyl derivatives of four tomato phytoalexins could be obtained by capillary gas chromatographymass spectrometry.

We are most grateful to Dr. P. J. G. M. de Wit, Agricultural University, Wageningen, to Dr. D. T. Coxon, Food Research Institute, Norwich and to Dr. M. S. Kemp, Long Ashton Research Station, Bristol for making their analytical data available for us. Also thanks are due to Miss J. I. Liem, Mr. G. Verweij and C. Loriaux for their assistance.
Kugelige, umhüllte Mikrokonidien‐Aggregate als Überdauerungs‐ und Verbreitungseinheiten von Botrytis cinerea Pers.
Authors: Von Urbasch I.
Published: May 2008

Spherical, coated microconidia‐aggregates as survival and dispersal units of Botrytis cinerea Pers.

As a reaction to longer lasting unfavourable growth conditions Botrytis cinerea is able to form spherical microconidia‐aggregates enclosed in a protective coat. Genesis, structure and occurrence of these so far unknown microconidia‐aggregates are described and their function as survival and dispersal units of the fungus is discussed.
Natural Occurrence of a Strain of Cowpea Mild Mottle Virus on Groundnut (Arachis hypogaea) in India*)
Authors: Iizuka N. , Rajeshwari R. , Reddy D. V. R. , Goto T. , Muniyappa V. , Bharathan N. , Ghanekar A. M.
Published: May 2008

Vein‐clearing followed by downward rolling and necrosis of leaves and severe stunting of groundnut (Arachis hypogaea) plants were caused by cowpea mild mottle virus (CMMV). The virus was readily transmitted by mechanical sap inoculations to groundnut and to 10 plant species belonging to Leguminosae, Chenopodiaceae and Solanaceae. Chenopodium quinoa and Beta vulgaris were good diagnostic hosts. Diseased sap remained infective at 10–3 but not 10–4, when stored 8 to 9 days at 25 °C; for 10min at 75 °C but not 80°C. In limited tests, virus was not seed‐transmitted m groundnut or soybean. Virus was transmitted by Bemisia tabaci but not by Aphis craccivora or Myzus persicae. An antiserum for CMMV was produced and virus was serologically related to CMMV reported on cowpea and groundnut crinkle virus (GCV) from West Africa. Employing carbon diffraction grating replica as a standard the modal length of virus particles to be 610 nm. Infected cells contained large number of virus particles associated with endoplasmic reticulum.
Little Leaf: A Disease of Sweet Potato in Papua New Guinea Probably Caused by Mycoplasma‐Like Organisms
Authors: Pearson M. N. , Keane P. J. , Thiagalingham K.
Published: May 2008

A disease of sweet potato which causes dwarfing and shoot proliferation is reported from the Central Province of Papua New Guinea. The disease primarily effects yield by reducing tuber number and yield reductions of more than 50 % have been recorded. Mycoplasma like organisms have been detected in the phloem cells of diseased plants using electron microscopy and may be the cause of the disease. Early stage infections can be detected using fluorescent light microscopy and this may prove an appropriate method for rapid diagnosis of the disease. Treatment of diseased plants with tetracycline results in temporary symptom remission.
Transmission Studies with Cucumber Green Mottle Mosaic Virus
Authors: Rao A. L. N. , Varma A.
Published: May 2008

Cucumber green mottle mosaic virus may spread in bottlegourd under field conditions through soil contaminated with infected plant debris followed by contact. No seed transmission was noticed in bottlegourd (Lagenaria siceraria) or vegetable marrow (Cucurbita pepo) although pollen grains and cotyledons from infected bottlegourd flowers or seeds, respectively, contained negliginle amounts of virus. Cucumber leaf beerles (Raphidopalpa fevicollis) are probable vectors since their regurgitated fluid and excretes contained infective virus particles. No vector fungi were found in the soil around infected bottlegourd plants.
Developmental Morphology of Hop Stunt Viroid‐infected Hop Plants and Analysis of Their Cone Yield1)
Authors: Momma T. , Takahashi T.
Published: May 2008

Infection of hop plants with hop stunt viroid (HSV) results in the retardation of the growth rate except for the rate of leaf emergence and the disappearance of the fold‐like structure over the epidermal cell. Mature cones from HSV‐infected hop plants remained small‐sized and the content of α‐acid was half to one third of that of HSV–free hop cones. In HSV‐infected hop cones, the lupulin glands are distributed most abundantly on the bracteoles and the perianths and their numbers are reduced by at least 60% of that in the HSV‐free control. Scanning electron micrographs confirm that most of the lupulin glands on bracteoles from HSV‐infected hop cones shrivel severely, but not those from HSV‐free hop cones. They also reveal that the lupulin glands on the perianths from both, HSV‐free and HSV–infected hop cones become withered. Moreover, spherical granules (1.2 to 1.9μm in diameter) were not observed on the surface of the lupulin glands from HSV‐infected hop cones.
Combined Gene Effects on Resistance against Erysiphe graminis DC. f. sp. hordei Marchal Analysed by Means of Double Mutants1)
Authors: Heun M. , Röbbelen G.
Published: May 2008

The effect of genes for resistance against powdery mildew of barley was determined microscopically in stained leaf segments 44 h after inoculation and compared with the visual was established between the number of haustoria and the visual disease symptoms. Deviations were expressed after C17 Am inoculation of the mutant B682, which exhibited low infection grade although high numbers of haustoria were formed; thus the induced resistance gene of B682 is expressed only in later stages of the infection process. On the other hand, after inoculation of SR1 with the ml‐o virulent isolate HL3 high infection grade was measured following low haustoria numbers; obivously, this isolate is able to grow more intensively after first haustoria have been formed.Consequently, the close relation between haustoria numbers and infection grade is reestablished in the double mutants under HL3 infection. The implications of this finding for resistance breeding are discussed.
Resistance of Three Bean Cultivars to Uromyces phaseoli Expressed Through Sporulation of the Fungus
Authors: Aust H. J. , Bergamin Filho A. , Menten J. O. M.
Published: May 2008

Sporulation of the rust fungus Uromyees phaseoli was checked on three different Brasilian bean cultivars on the upper and lower leaf surface of primary leaves in a growth chamber at 21°C. Although the sporulating area of the pustules was greater on the upper leaf surface, the pustules on the lower leaf surface produced nearly two times more spores on all three cultivars.

The total number of spores produced per pustule was 41,600/81,000 spores (upper/ lower leaf surface) for the susceptible cultivar Rosinha G‐2/C‐21 and for the cultivars which possess horizontal resistance: Carioca/C‐224 29,600/49,500 spores (upper/lower leaf surface), Roxo/C‐743 32,964/50,700 spores (upper/lower leaf surface). The two cultivars with horizontal resistance produced nearly a third less spores than the susceptible cultivar.
Untersuchungen zur Bildung extrazellulärer Hemicellulasen durch Pseudocercosporella herpotrichoides in vitro
Authors: Redlhammer S. , Menke G. , Grossmann F.
Published: May 2008

Investigations on the production of extracellular hemicellulases by Pseudocercosporella herpotrichoides in vitro

For all 15 isolates of Pseudocercosporella herpotrichoides investigated, xylanase as well as arabanase activity could be demonstrated. After cultivation of 3 weeks, the activity of the enzymes reached a peak. The activity of xylanase was considerably increased by addition of xylan in comparison to Maltzin as the sole source of carbohydrate. Also the arabanase activity could be increased significantly by addition of araban or xylan as compared to the Maltzin variant.

The optimum temperature with regard to activity and stability of xylanase ranged at 50°C. The pH‐optimum for xylanase activity was found to be at pH 5.0, and the enzyme was stable in ° range between pH4.0 and 8.0 (9.0). In case of arabanase, the temperature optimum varied between 40 and 50°C; up to this temperature, the enzyme was also stable. At pH 5.0, the arabanase activity reached its optimum; stability was observed in ‐ pH range between 4.0 and 9.0.

In extracts prepared from autoclaved wheat coleoptiles which were inoculated with Pseudocercosporella herpotrichoides, the presence of the enzymes xylanase, arabanase, cellulase and polymethylgalacturonase could be demonstrated. The enzyme activities of the inoculated samples were considerably higher than those of non‐inoculated controls. The differences, in most cases, were statistically significant.

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Changes in Phenolic Acids in Groundnut Leaves Infected with Rust
Authors: Reddy M. N.
Published: May 2008

Quantitative changes of individual phenolic acids in rust‐infected groundnut leaves were studied at various stages of disease development. There was no qualitative change in the phenolic acids. However, the concentration of the phenolic compounds increased due to infection more particularly of chlorogenic and trans and cis caffeic acids.
MBC‐resistente Freilandpopulationen von Pseudocercosporella herpotrichoides in langjährigem Überwachungsversuch
Authors: Fehrmann H.
Published: May 2008

MBC resistant field populations of Pseudocercosporella herpotrichoides in a long‐term monitoring experiment

In, long‐term field experiment, since 1975/1976 winter whaet was grown continuously for eight years. One half of the 1‐ha field was sprayed once a year with carhendazim against eyespot (Pseudocercosporella, herpotrichoides); another application of MBC/TBZ was, after heading. From 1978/1979 seed was treated with MBC also. The other half of the field remained untreated all the time. During the first five years, in the sprayed plot the relative proportion of MBC‐resistant conidia increased steadily, but on a very low level only. During the next three years, however, there was a sharp increase in the level of MBC‐resistance in the sprayed plot. — In the unsprayed plot, at the end of the eight year period the level of MBC‐resistance in the field population of the fungus still was low.
Seed Transmission of Maize Dwarf Mosaic Virus in Sweet Corn
Authors: Mikel M. A. , D'Arcy Cleora J. , Ford R. E.
Published: May 2008

Sweet corn seed from several maize dwarf mosaic virus (MDMV)‐infected hybrids grown in the field were tested for transmission of MDMV through the seed. Seeds collected in 1979, 1980, 1981, and 1982, were germinated in the greenhouse the following winters. Only one seedling of 22,189 was MDMV‐infected During the last three years, seed were dissected at different maturities and the seed parts tested for the presence of MDMV by both infectivity and enzyme‐linked immunosorbent assay (ELISA). At 21 days after pollination, MDMV always was detected in the pericarp, but rarely in the endosperm or embryo. No MDMV was detected in the embryo of mature kernels, but virus occasionally was detected in the endosperm and pericarp. MDMV was regularly detected in unfertilized kernels and whole silks, but not in pollen by infectivity, ELISA or serological specific electron microscopy. MDMV was detected in glumes and whole anthers.
The Antigens of Wheat Rosette Stunt and Northern Cereal Mosaic Viruses are Related
Authors: Lundsgaard T. , Tien P. , Toriyama S.
Published: May 2008

Leaf tissue from plants infected with northern cereal mosaic virus (NCMV) and wheat rosette stunt virus (WRSV) was extracted with a buffer containing a non‐ionic detergent. The extracts were tested by double immunodiffusion test for comparing the G protein antigens and by immunosorbent electron microscopy with decoration for comparing the nucleocapsid antigens. The heterologous reactions could not be distinguished from the homologous, thus indicating close relationship or identity of the two viruses.
Comparisons between Phytoalexin Concentrations and the Extent of Rotting of Potato Tubers Inoculated with Erwinia carotovora sub sp. atroseptica, E. carotovora sub sp. carotovora or E. chrysanthemi
Authors: Lyon G. D.
Published: May 2008

Isolates of Erwinia carotovora sub sp. atroseptica, E. carotovora sub sp. carotovora and E. chrysanthemi were compared for their ability to rot potato tubers and to elicit the accumulation of phytoalexins. With three incubation temperatures (15, 22 and 30°C) tubers were more susceptible at higher temperatures and mean rot weights were inversely correlated with mean rishitin concentrations. However, within treatment variation between tubers in the extent of rotting was not correlated with rishitin concentration suggesting that other factor(s) also affect resistance. Phytoalexins, including 15‐dihydrolubimin, 3‐hydroxylubimin, phytuberin and solavetivone, were measured by high pressure liquid chromatography using a silica column.
Die Reaktion anfälliger und resistenter Gerstensorten auf pilzliche Krankheitserreger
Authors: Priehradný S.
Published: May 2008

Response to fungus pathogen in susceptible and resistant barley cultivars IV. Water‐ and dry matter content

The changes in dry matter‐ and water content dynamics in the root and shoots of barley infected with the fungus Erysiphe graminis f. sp. hordei Marchal were studied in variously receptive cultivars. Cultivation of plants in solid (perlite) or liquid medium was compared.

The response of susceptible barley to mildew infection is characterized at First by an increase in water content and slightly in dry matter of shoots accompanied with an unsignificant decrease in root growth. However, as the fructification progressed, barley growth is reduced in all investigated parameters. The infected resistant barley indicates unsignificantly increased values in water content of shoots, only.

In the susceptible host the growth of roots in relation to shoots is markedly reduced after infection.

The percentage of water content of shoots is slightly increased in both cultivars during the first phases of infection. Then, in susceptible barley it declines, compared with the control, from the stage of full developed fructification. In the resistant barley it doesn't change more expressively. In roots of infected plants the increased hydratation is found during the whole observation period (in the resistant barley only with plants growing in liquid medium).
An in situ Freeze‐Fracture Study of Spiroplasma citri and the Corn Stunt Spiroplasma
Authors: Schmitt U. , Petzold H. , Marwitz R.
Published: May 2008

Spiroplasma citri and the corn stunt spiroplasma in sieve cells of Catharanthus roseus were investigated using freeze‐fracture electron microscopy. Only the particle studded fracture faces of the plasmalemma could be exposed and not the surfaces of both the extraplasmatic and the plasmatic leaflet. The extraplasmatic fracture face (EF) shows a lower particle density than the plasmatic fracture face (PF). On the PF particle free areas could be observed, which are helically arranged in helical filaments. We suppose that the cytoplasmic fibrils, probably involved in motility processes and in maintaining the helical shape, underly the particle free area only.
Multiplication of Pseudomonas syringae pv. phaseolicola “in planta”
Authors: Rudolph K.
Published: May 2008

Multiplication ofPseudomonas phaseolicolawas determined in 17 different bean cultivars (Phaseolus vulgaris) and 9 other plant species, and the effect of different inoculation methods and conditions was also studied.

In susceptible leaves, a generation time of 2.1 h was determined in the early phase (2 days after inoculation). Different multiplication rates in susceptible and resistant leaves were clearly observed 4 days after inoculation. At this time the first small water‐soaked spots were visible in the susceptible cultivars. Bacteria multiplied up to the 7th day after inoculation with a maximum of 109cells per cm2leaf (equal to ca. 4 × 1010bacterial cells/cm3). At the same time, the water‐soaked spots had reached their maximum size in most cases. Thus, bacterial multiplication and development of water‐soaked spots paralleled each other.

In resistant leaves, no water‐soaked spots appeared, and the final bacterial concentration was 1/1000–1/100 of that in susceptible leaves. Gomparison of races 1 and 2 in several bean cultivars indicated the non‐existence of a gene‐for‐gene relationship with this disease. Old leaves were less susceptible to infection. Some bacterial multiplication was also observed in non‐host plants. There was a general correlation between bacterial multiplication in the non‐host plants and their botanical relation toPhaseolus vulgaris.
Bacterial Canker of Sweet Cherry (Prunus avium) in Poland
Authors: ŁYskanowska M. K.
Published: May 2008

In Polish climatic conditions cherry cankers resulting from infection byPseudomonas morsprunorumcontinue development in summer, but the rate may be slower than in the period from April to June.

However, from the well established, active canker developing under the dwarf shoot of the susceptible variety‘Hedelfińska’in July noP. morsprunorumwere isolated. On the other hand, numerous strains of the genusErwiniawere found there which caused a hyper sensitivity reaction (HR) on tobacco leaves. From the cracks on the current‐year cherry shoots, due to fresh infection and from symptomless leavesP. morsprunorumstrains were isolated, always accompanied by those of theErwiniagenus in the approximate proportion 1: 1 or 1:2.

The strains ofErwiniagenus seemed similar to the DC and YC strains isolated by BILLING and BAKER from pear and apple trees infected by fireblight and also to the strains in group III of the bacteria isolated by CROSSE from cherry leaves.

In two tests (immediately after isolation and after 4 months of storage) the strains of theErwiniagenus and 3 nonidentified isolates induced HR. At a third test, after 10 months of preservation these strains were HR‐negative in contrast to theP. morsprunorumisolates.

The fact that strains of theErwiniagenus inducing HR were isolated in large numbers from active cherry canker where pathogenic bacteria were not detected, may indicate that they play some role in the development of cherry tree canker.
Bacterial Rot of Dieffenbachia maculata (Lodd.) G. Don. Caused by Erwinia chrysanthemi
Authors: Leyns F. , Verdonck L. , de Cleene M. , Swings J. , de Ley J.
Published: May 2008

Five bacterial isolates were obtained in a nursery near Gent (Belgium) from diseased Dieffenbachia maculata (Lodd.) G., Don. cv. Compacta, cv. Camillo and cv. Veerle plants. They were identified by API 20E, API 50 CHE and API ZYM systems as Erwinia chrysanthemi. These strains and seven collection strains were pathogenic to all three D. maculata cultivars tested: cv. Camillo, cv. Compacta and cv. Tropic Snow. Inoculation in the stem or petiole was the only effective method for obtaining systemic infection. The petiole appeared to be the part of the plant in which disease developed most readily. Wounding was required for the induction of the disease. Temperatures between 25° and 30° C, a relative air humidity of 75 % or more and low light intensity (0.5 ft‐c) favoured the disease, whereas high inoculum sizes (106 or more cells) accelerated and increased it. Histological studies showed tissue degradation in infected areas. Petioles were most severely affected. Transport of bacteria seemed to occur after vessel infection in stem or petiole tissues.
Lutte Contre les Microorganismes Pathogènes des Végétaux: les Inducturs de Resistance
Authors: Ahl Patricia
Published: May 2008

Disease control by inducers of resistance

Induces of resistance open a new way in the search for control. It may be assumed that inducers of resistance will be used more and more in the coming years.
A Strain of Guinea Grass Mosaic Virus from Pearl Millet in the Ivory Coast
Authors: Kukla B. , Thouvenel J.‐C. , Fauquet C.
Published: May 2008

A virus disease of pearl millet (Pennisetum americanum) in the Ivory Coast has symptoms consisting of a light‐green mosaic of variable severity, followed. by dwarfing. The causal virus is mechanically transmissible and aphid‐borne, but not seed‐borne. It was purified, has flexuous filamentous particles about 820 nm long, and is a member of the potyvirus group. Its host range, and biological, physico‐chemical and serological properties indicate that it is a strain of guinea grass mosaic virus.
Endogene Hyphen bei Botrytis cinerea Pers.
Authors: Urbasch Irene
Published: May 2008

Endohyphae in Botrytis cinerea Pers.

Genesis, following differentiation and significance for pathogenesis

The formation of endohyphae (secondary hyphae) in different cell types of Botrytis cinerea Pers. (6 isolates) is described. The following differentiation possibilities of these endohyphae within and—after egress—outside their cells of origin are presented. The influence of external factors (substrate, temperature, humidity, O2‐concentration) on these processes is considered. The significance of the endohyphae for pathogenesis is mainly due to their direct infectivity as well as the ability to develop normal mycelium.
Spezifität beim „Attachment” von Agrobacterium an Wundrandzellen von Kalanchoe?
Authors: Bauer G. , Beiderbeck R.
Published: May 2008

Tumorinduktion durch A. tumefaciens an Blärtern von Kalanchoe wird stark gehemmt durch Zellwandpräparationen aus jungen und reifen Geweben von monocotylen und dicotylen Pflanzen. und aus Tumorzcllen und auch durch Filterpapier‐Homogenate und lebende und tote Pseudomonas‐Zellen. Die Hemmung wird nachweisbar, wenn die Zellwandpräa‐rationen oder die Pseudomonas‐Zellen zugleich mit A. tumefaciens oder vor dem A. tumefaciens in pflanzliche Wunden inokuliert werden. Postinokulation bceintflußt die Tumorbildung nicht.

Diese Ergebnisse bestätigen zwar das „Attachment” als einen wichtigen Schitt bei der Tumorinduktion, stellen aber die Spezifität des Vorgangs in Frage.
Botrytis cinerea: Activité Antifongique dans les Jeunes Grappes de Vitis vinifera, Varieté Gamay
Authors: Pezet R. , Pont V.
Published: May 2008

Botrytis cinerea: fungicidal activity in young grape berries of Vitis vinifera (Gamay)

Extracts of young grape berries of Vitis vinifera (Gamay) inhibit the germination of conidia of Botrytis cinerea. This inhibitory activity is present in extracts obtained from clusters at bloom stage and is maintained until a developmental stage close to the maturity. These extracts ruptured the cellular membranes.
The Effects of Co‐Infection by Sunn‐Hemp Mosaic Virus (SHMV) and Fusarium oxysporum on the Growth of French Bean
Authors: Gbaja I. S. , Chant S. R.
Published: May 2008

In the seedlings of three cultivars of French bean (Phaseolus vulgaris), ‘Prince,’‘Masterpiece’ and ‘Pinto’, co‐infection by Sunn‐hemp mosaic virus (SHMV) with either of the vascular wilt pathogens, Fusarium oxysporum f. sp. phaseoh (Fop) or f. sp. tracbeiphilum (Fot) caused greater losses in total fresh weight and in leaf area compared with uninfected plants or plants infected singly with any one of these pathogens. Co‐infection of a fourth cultivar (‘Canadian Wonder’) had no greater effects on growth reduction than single infection. The concentration of SHMV in the leaves of ‘Prince’ and to a greater extent in the leaves of ‘Masterpiece’ increased more after double infection than with infection by the virus alone. The nature and possible mechanisms of the pathogenic effects in French bean are discussed.
Phytopathogenic Fusarium oxysporum Schlecht, as a Necrotrophic Mycoparasite
Authors: Vajna L.
Published: May 2008

Fusarium oxysporum f. sp. dianthi, f. sp. lycopersici, f. sp. cepae, f. sp. niveum and one unidentified F. oxysporum isolate proved to be active necrotrophic mycoparasites. In dual cultures hyphae of Trichoderma hamatum, T. longibrachiatum, T. pseudokoningii, T. harzianum, Botrytis cinerea and Rhizoctonia solani were parasitized and destroyed by F. oxysporum. One isolate of Phytophthora sp. was not affected. Mutual parasitism between F. oxysporum and T. pseudokoningii and T. longibrachiatum has been observed, too. Details of parasitic hyphal interactions: hyphal coiling, penetration sites, resistance sheat formation, hyphal invasion and internal growing are described. The mycoparasitic feature as well as antimicrobial metabolic production of F. oxysporum is probably a common phenomenon to ensure this important plant pathogenic species to compete successfully against other soil‐borne fungal pathogens and saprophytes.
Leakage from Seedling Roots, Inoculated with Phytophthora cinnamomi
Authors: Cahill D. , Weste Gretna , Grant B.
Published: May 2008

A sequential study of electrolyte leakage from roots inoculated with Phytophthora cinnamomi demonstrated changes in leakage in response to infection. These changes may be characterised in terms of susceptibility and resistance. Field resistant species showed two types of response (i) rapid leakage 2—4 h after inoculation, such as in Eucalyptus calophylla, E. maculata and Gahnia radula, (ii) no significant increase in leakage with infection, for example in cereals and in juncus bufonius. Susceptible species, such as Xanthorrhoea australis, E. sieberi and E. marginata showed slow but continually increasing leakage after inoculation, and usually lost significantly more electrolyte than field resistant species.

Both electrolyte leakage and susceptibility of two Eucalyptus species varied with root temperature. Roots of both the susceptible and field resistant Eucalyptus species grown at 14°C showed similar leakage patterns to those grown at 24°C although no lesions formed at 14°C. Both amount of leakage and lesion length increased at 28°C. E. marginata (susceptible) lost significantly greater quantities of electrolyte than E. calophylla at each temperature tested. Leakage from artificially wounded roots did not vary with either temperature or with host susceptibility.

No significant changes in conductivity were recorded with saprophytic colonization of roots, or with incubation in either low molecular weight culture filtrate or β‐glucan solutions. Vacuum infiltration with the culture filtrate or the β‐glucan slightly increased initial electrolyte loss in comparison with that of the controls.

The increased leakage from infected roots may be toxin mediated or due to enzymie degradation of host plasma membranes, and occurred within the region of the limited lesion in the case of field resistant species, compared with the larger zone of extending necrosis characteristic of susceptible species.
Screening for Spontaneous Virulent Mutants of Erysiphe graminis D.C. f.sp. hordei on Barley lines with Resistance Genes Ml‐a1, Ml‐a6, Ml‐a12 and Ml‐g
Authors: Torp J. , Jensen H. P.
Published: May 2008

Abstact

Seedlings of 4 barley lines with powdery mildew resistance genes Ml‐a1, Ml‐a6 Ml‐a12 and Ml‐g were inoculated with powdery mildew culture CR3 which is avirulent to the 4 host lines. The inoculation density was 1.2 infectious conidia per mm2, and in total 50 million conidia were screened for the occurrence of virulent mutans. During 30 cycles of screening, 43 putative virulent mutants were selected, multiplied and tested. They could be grouped in 5 different genotypes according to virulence spectrum. Based on the virulence spectre, mating type, biochemical tests and analyses of test crosses, 3 of the types were rejected as being of mutational origin, and the verification of the remaining 2 were not consistent with the expectations deduced from a gene‐for‐gene interaction. Provided that none of the genotypes found were of mutational origin, the spontaneous mutation frequency from avirulence to virulence in barley powdery mildew is therefore below 2 × 10–8.

A reconstructation experiment showed that the density of avirulent inoculum did not reduce the survival rate of rate virulent genotypes