bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature and Effects of Seed‐borneBotrytis cinereaorAlternaria linicolaon Emergence of Linseed (Linum usitatissimum) Seedlings
Authors: Harold J. F. S. , Fitt B. D. L. , Landau S.
Published: May 2008

Experiments were done at temperatures from 5 to 20 C to investigate the effects of infection of linseed seed (cv. Antares) byBotrytis cinereaorAlternaria linicolaon seedling emergence and to study transmission of the pathogens from seed to seedlings. In one experiment with freshly harvested seed, the maximum percentage emergence decreased linearly as the incidence ofB. cinereain seed increased from 0 to 83% at 18 C day/12 C night temperatures. In another experiment, the decrease in percentage emergence of seed associated with infection byB. cinerea.the transmission of the pathogen to seedlings to produce disease symptoms on their hypocotyls and the incidence of post‐emergence death all increased as temperature decreased from 20 to 5 C. However, the decrease in percentage emergence of seed associated with infection byA. linicolaand the transmission of the pathogen to seedlings to produce cotyledon lesions both increased as temperature increased from 5 to 20 C. There was little effect of either pathogen on the time from sowing to 36% of maximum emergence, which decreased with increasing temperature. In a subsequent experiment at 10 C comparing seed infected withB.cinereaorA. linicola.using the same seed sources as in the previous experiments, infection byA. linicoladecreased emergence more than infection byB. cinerea, even though the incidence ofA. linicolain the seed was smaller. Analyses of position and parallelism suggested that regressions of maximum percentage emergence (logitransformed) against temperature were fitted best by non‐parallel lines for seed infected byB. cinereaorA. linicola.
Influence of Pathogenic and Non‐pathogenic Bacteria on Soybean Suspension Cells
Authors: Müller J. , Vöulksch B. , Fritsche W.
Published: May 2008

Co‐cultivations of plant suspension cultures of soybean (Glycine max) with compatible phytopathogenic (Pseudomonas syringae pv. glycinea), incompatible phytopathogenic (Pseudomonas syringae pv. tomato), and different non‐pathogenic (Erwinia herbicola, Escherichia coli) bacteria were carried out. Growth and viability (triphenyltetrazolium chloride activity) of plant cells and bacteria as well as enzyme activities of peroxidase (PO), polyphenoloxidase (PPO), and phenylalanine ammonialyase (PAL) within the plant cells were investigated over an incubation period of 7 days. The compatible pathogen inhibited growth and viability of the plant cells after 1 day and led to the death of the majority of the plant cells by the seventh day. In contrast, the incompatible pathogen directly reduced growth and viability of the soybean cells and caused a strong induction of enzyme activities of PO and PAL to more than 4 times of the untreated control by the seventh day. The epiphytic bacterium Erwinia herbicola caused a slight inhibition of growth and viability of the plant cells after the second day of co‐cultivation. The PO activity increased in the same manner as in the incompatible interaction. The saprophytic Escherichia coli strain had a negligible influence on soybean suspension cells. All the bacteria tested except for Escherichia coli multiplied rapidly during co‐cultivation and reached populations of 108‐109 colonyfoming units/ml in the stationary phase. The results from this study demonstrate that the soybean suspension cells react differently to compatible, incompatible and saprophytic bacteria.
Pre‐harvest Fungal Colonization Affects Storage Life of Bing Cherry Fruit
Authors: Dugan F. M. , Roberts R. G.
Published: May 2008

Treatment of sweet cherry (Prunus avium cv. Bing) trees with either two mildewcide cover sprays or multiple (18) applications of topical and systemic fungicides produced cherry fruit that were either highly colonized or relatively uncolonized by fungi, respectively. Fruit from the multiple application treatment had a storage life of up to 8 weeks (7 weeks at 1‐4°C plus 1 week at simulated retail temperatures of 20–21°C), whereas the commerciallymanaged fruits (two mildewcides) were extensively colonized by fungi and extensively decayed when stored under the same conditions. Stringent post‐harvest disinfection did not significantly reduce postharvest decay, and only slightly reduced isolation frequency of fungi. The data obtained in this study suggest that the degree of preharvest fungal colonization is a primary determinant of the percentage of post‐harvest decay, and that pre‐harvest colonization can potentially be addressed by pre and post‐harvest management practices.
Changes in Pollen Viability and Concomitant Increase in the Incidence of Sorghum Ergot with Flowering Date and Implications in Selection for Escape Resistance
Authors: McLaren N. W.
Published: May 2008

Pollen viability and ergot severity were monitored in a line evaluation nursery at Potchefstroom and Bethlehem (South Africa). Percentage grain fill was also evaluated at the latter locality. Changes in pollen viability with flowering date were closely correlated with changes in ergot severity (r = 0.91 and r = 0.81 at Potchefstroom and Bethlehem, respectively). Pollen viability was significantly reduced by pre‐flowering daily minimum temperatures < 16°C at both localities during the period 23–27 days before flowering. The concomitant increase in ergot severity closely mirrored changes in pollen viability. Lines differed in their ability to tolerate low pre‐flowering minimum temperature. Lines with pollen viabilities > 60% despite pre‐flowering minimum temperature <14°C were observed. A number of lines with inherent low pollen viability, despite minimum temperatures >17°C were also found. Avoiding these in favour of vigourous pollen producers may contribute towards enhancing escape resistance in sorghum to ergot.
Rapid and Sensitive Detection of Xanthomonas fragariae by Simple Alkaline DNA Extraction and the Polymerase Chain Reaction
Authors: Zhang S. , Goodwin P. H.
Published: May 2008

Methods for DNA preparation from Xanthomonas fragariae in infected or artificially contaminated strawberry plants were compared in diagnostic assays using the polymerase chain reaction (PCR). The bacterium was detected using PCR with primers specific to a region of its hrp gene. Sensitivity of detection was 1.25 ×l 103 CFU ml‐1 using DNA from bacterial suspensions prepared by an alkali extraction method. This was 10‐fold more sensitive than DNA extraction by boiling, and was equal to that in which DNA was prepared by a more involved cetyltrimethylammonium bromide (CTAB) procedure. Sensitivity of detection from artificially contaminated strawberry tissues was 10‐fold less than that from cell suspensions. The results indicated that a rapid and simple method of alkali DNA sample preparation is applicable for the sensitive and reliable detection of X. fragariae and possibly other plant pathogenic bacteria.
Quantitative Assessment of Lesion Characteristics and Disease Severity Using Digital Image Processing
Authors: Tucker C. C. , Chakraborty S.
Published: May 2008

This work describes a dedicated software which detects and characterizes disease lesions on leaves to provide data on the number and type of lesions and the percentage of leaf area diseased (severity). The software, written in C2+, can be used with a standard computer in combination with a colour CCD camera and a frame grabber for image acquisition. The usefulness and adaptability of the software was evaluated using two foliar diseases, Alternaria blight of sunflower and oat leaf rust (Puccinia coronata f.sp. avenae), which differ in symptoms. Using image segmentation and classification techniques, the software discriminated disease symptoms from the healthy leaf area. The number and size of lesions and severity, obtained using the image processing software, were compared with those calculated using a software planimeter or visual assessment. Significant linear relationships between planimeter and the imaging software were obtained for lesion number and severity in oat leaf rust and for severity in sunflower blight. Artefacts, mistakenly classified as blight lesions by the imaging software resulted in an over‐estimation of the number of lesions. Future research is aimed at improving accuracy through better illumination during image capture. A dedicated, compact and portable hardware is currently being developed for field use as a self‐contained device for disease assessment.
The Natural Occurrence of Turnip Mosaic Potyvirus in Allium ampeloprasum
Authors: Gera A. , Lesemann D.‐E. , Cohen J. , Franck A. , Levy S. , Salomon R.
Published: May 2008

An isolate of turnip mosaic potyvirus (TuMV) was obtained from Allium ampeloprasum grown in commercial greenhouses in Israel. Symptoms on infected plants include systemic chlorosis and yellow stripes, accompanied by growth reduction. Leaves were distorted, often showing necrotic flecking. The virus was readily transmitted mechanically, and in a non‐persistent manner by aphids, among Allium, Chenopodium. Gomphrena and some Nicotiana spp. Purified preparations contained numerous filamentous particles similar to those observed in crude extracts of infected leaves. Particles from crude plant extracts had a normal length of 806 nm. Cells of infected plants contained cylindrical cytoplasmic inclusions with pinwheel, scrolls and laminated aggregates which indicated the presence of a potyvirus of Edwardson's subgroup III. and which resemble those of turnip mosaic virus (TuMV), The virus reacted strongly with antiserum to typical isolates of TuMV in immunoelectron microscopy and western blotting but not with antisera to several other potyviruses. Based on serological reactivity, electron microscopy, aphid transmission and cytopathology, the virus was identified as an isolate of TuMV.
Phytophthora Canker Resistance in Cacao: Role of Peroxidase, Polyphenoloxidase and Phenylalanine Ammonia‐lyase
Authors: Okey E. N. , Duncan E. J. , Sirju‐Charran G. , Sreenivasan T. N.
Published: May 2008

Peroxidase (PO) Polyphenoloxidase (PPO) and Phenylalanine ammonia‐lyase (PAL) activities in stem extracts of six cacao clones (IMC 67, ICS 1, TSH 1188, P 18, SCA 6 and TSH 1076) were measured spectrophotometrically in (i) healthy tissues; (ii) tissues wounded with a 3‐mm diameter cork borer and (iii) tissues inoculated with the canker pathogen Phytophthora palmivora. The results indicated significantly high (P < 0.05) activities of the three enzymes in extracts obtained from inoculated and wounded as opposed to those from healthy tissues. The activities of these enzymes were significantly higher in the extracts of IMC 67, low in TSH 1076, SCA 6 and P 18 and intermediate in TSH 1188 and ICS J. There was no significant difference in enzyme activities among the genotypes TSH 1076. SCA 6 and P 18 and also between ICS 1 and TSH 1188. Starch gel electrophoresis of PO indicated differences in banding pattern/band‐intensity amongst IMC 67, ICS 1 and SCA 6 and also between inoculated and uninoculated stems. These results are discussed in relation to lignin and phenol metabolism associated with plant resistance to pathogen attack.
Differential Responses of Guayule (Parthenium argentatum Gray) Genotypes to Culture Filtrate and Toxin from Macrophomina phaseolina (Tassi) Goidanich
Authors: Kuti J. O. , Schading R. L. , Latigo G. V. , Bradford J. M.
Published: May 2008

The potential for using cell‐free culture filtrate (CFCF) and toxin (phaseolinone) from Macrophomina phaseolina for rapid and effective screening procedures for charcoalrot resistance in guayule (Parthenium argentatum) germplasm was assessed. The CFCF and partially purified phaseolinone were incorporated into modified Murashige and Skoog solid medium aat the rates of 0‐100% (v/v) and 0‐1000 μg ml‐1 respectively. The medium pH was adjusted to 5.8 before solidifying with 0.8% agar. Fourweek‐old seedlings of 10 guayule genotypes were plantanted in the medium, incubated and rated for phytotoxic symptoms and tissue damage over a 15‐day period. In a green‐house study, seedling growth, phytotoxicity and damage severity were compared in 12‐week‐old guayule seedlings root‐inoculated with M. phaseolina microsclerotia. There were significant differences (P = 0.05) in genotypic responses to the fungus, the filtrate and the toxin inoculations. Time until phytotoxic symptoms developed was inversely related to the concentrations of CFCF and the toxin. Phytotoxic symptoms were produced 6 days after exposure to 50% CFCF and 48 h after exposure to 1000μg ml‐1 of partially purified phaseolinone. A comparison of photomicrographs of the control and toxintreated root tissues revealed no damage to the control roots and extensive damage to epidermal layers of the treated roots, which was evident 48 h after exposure to 100μg ml‐1 level of phaseolinone. Significant correlations were found between tolerance to the fungus and insensitivity to the culture filtrate (r = 0.89, P = 0.05) and the toxin (r = 0.95, P = 0.001) suggesting the possibility of screening for resistance to M. phaseolina using CFCF or phaseolinone. The genotypic reactions to the CFCF were also correlated with reactions to the toxin (r = 0.90, P = 0.05). Guayule breeding lines‘UC101 and‘P3‐1 exhibited the greatest tolerance to the pathogen and insensitivity to the CFCF or the toxin whereas‘Ca16′,‘Cal7′,‘N576′,‘N9‐5′, 11605’and‘N6‐5’were very susceptible to the pathogen and sensitive to the CFCF or the toxin.
Factors Affecting Germination and the Mode of Germination of Zygospores of Choanephora cucurbitarum
Authors: Yu M. Q. , Ko W. H.
Published: May 2008

Treatment of zygospores of Choanephora cucurbitarum with KMnO4, NaClO or H2O2 effectively activated the spores and induced their germination. The optimum concentration of KMnO4 for activation of zygospores was 0.25 to 0.5%. Zygospores were not able to germinate in darkness even after activation by KMnO4. When zygospores from 40 to 50‐day‐old cultures were treated with 0.5% KMnO4 solution for 60 min before incubation on water agar at 24% under light, about 50% germinated in 10 days. KMnO4 treatment killed more than 99% of residual mycelial fragments, sporangiospores and sporangiola in the zygospore suspension. During germination disappearance of oil droplets in zygospores occurred prior to the cracking on zygospore wall. Both sporangial germination and mycelial germination were found. Moreover, sporangiole germination was observed for the first time.
Pseudomonas syringae pv. syringae Causal Agent of Disease on Floral Buds of Actinidia deliciosa (A. Chev) Liang et Ferguson in Italy
Authors: Balestra G. M. , Varvaro L.
Published: May 2008

Pseudomonas syringae pv. syringae as causal agent of floral buds necrosis, has been isolated from kiwifruit plants cv. Hayward in Italy. The pathogen has been identified on the basis of morphological, biochemical and physiological features and also on the basis of pathogenicity. Symptoms, similar to those caused by Pseudomonas viridiflava—browning and darkening on floral buds, have been observed on kiwifruit plants in a wide area in the North of Latium region (central Italy), in Viterbo province.
Susceptibility and Resistance of Citrus Genotypes to Alternaria alternata pv. citri
Authors: Solel Z. , Kimchi M.
Published: May 2008

A survey of citrus cultivars in Israel in orchards where Alternaria brown spot was common on Minneola tangelos (mandarin × grapefruit), revealed the occurrence of the disease as typical foliar and fruit lesions on Dancy and Ellendale (mandarins), on Murcott tangor (mandarin × sweet orange), on Nova and Idith (mandarin hybrids), on Calamondin, and on Sunrise and Redblush (grapefruit). Isolates of Alternaria alternata from each of these hosts were proven to be pathogenic to Minneola tangelo.

The host range of A. alternata pv. citri from Israel was assayed by inoculating leaves of diverse citrus genotypes. Several mandarins and their hybrids (Dancy, Kara, King, Wilking, Satsuma, Minneola, Orlando, Mikhal, Idith, Nova, Page, Murcott), grapefruit (Marsh seedless), grapefruit × pummelo (Oroblanco), sweet orange (Shamouti, Valencia, Washington navel) Calamondin, and Volkamer citrus were susceptible. Several mandarins and their hybrids (Clementine, Avana, Yafit, Ortanique), Cleopatra, one sweet orange cultivar (Newhall), pummelo (Chandler), lemon (Eureka), Rough lemon, Rangpur lime, sweet lime, citron, limequat, sour orange, Troyer citrange and Alemow were resistant.
Flow Cytometric Analysis of Conidia of Fungi Isolated from Soybean Vascular Tissue
Authors: Gourmet C. , Gray L. E. , Rayburn A. L.
Published: May 2008

Flow cytometry was used to characterize isolates of Phialophora gregata using the fluorescence intensity of propidium iodide‐stained conidia. The isolates differed in their mean fluorescence intensity, ranging from 100.0 to 129.7 arbitrary units (AU). When the number of fluorescent events was plotted against intensity of fluorescence, a single peak was observed. Fluorescent patterns of Acremonium isolates from soybean vascular tissue were compared with those of P. gregata. Their mean fluorescence intensity ranged from 76.4 to 88.0 AU. With some of these isolates, multiple peak histograms were observed, corresponding to multiple spore sizes as well as single and double nucleated conidia. Using flow cytometry, we were able to distinguish P. gregata isolates from those of Acremonium, based on mean fluorescence intensity and/or the presence of multiple peaks. Flow cytometric analysis of propidium‐iodide stained conidia of Phialophora isolates should prove to be useful for determining the relative DNA content of different isolates collected from different geographic areas.
Variation Within and Between Phytophthora Species from Rubber and Citrus Trees in China, Determined by Polymerase Chain Reaction Using RAPDs
Authors: Zheng F. C. , Ward E.
Published: May 2008

Variation among 39 isolates of Phytophthora of six morphological species (P. citrophthora. P. parasitka, P. capsici, P. palmivora and P. meadii. from rubber and citrus trees, and P. colocasiae from taro) was studied using random amplified polymorphic DNA (RAPD) analysis. Ten randomly‐chosen 10‐mer primers were used. Generally, the banding patterns were similar within species and different between species, but no one primer was able to distinguish all six species from one another. Cluster analysis on pooled data from all the primers gave six groups of isolates corresponding to the six morphological species. The group corresponding to P. citrophthora was divided further into subgroups that were related to host species and geographical location. This work confirmed the existing morphological classification of Phytophthora isolates from rubber and citrus trees in tropical China and showed the validity of using RAPDs to study the taxonomy of Phytophthora.
Characterization of DNA Sequences Cloned From Resting Spores of Plasmodiophora brassicae
Authors: Ito S. , Nakamura T. , Matsumoto T. , Maehara T. , Tanaka S. , Kameya‐Iwaki M. , Kishi F.
Published: May 2008

Forty‐four clones containing P. brassicae genomic DNA fragments were isolated from a partial genomic library (pUC118) of the fungus. Eleven DNA fragments were arbitrarily selected from them and partially sequenced. Southern blot analysis was performed using the 11 DNA fragments as probes to estimate the copy number of these DNA fragments in the P. brassicae genome and to see if they hybridized also to genomic DNA of host plant (Chinese cabbage). Five of those (Nos 24, 48, 54, 57, and 108) were of single‐copy and hybridized only to DNA bands of P. brassicae. Two fragments (Nos 4 and 15) were found to contain repetitive sequence of/“, brassicae. Three fragments (Nos 69,73, and 82) hybridized to DNA bands of both host and P. brassicae while the size and the number of the bands were different between host and P. brassicae. Data base searches revealed that one of the single‐copy fragments (No. 48) had high homology with yeast RNA polymerase II gene.
Effect of Leaf Age and Nodal Position on Receptivity of Rice Leaves to Infection by Pyricularia grisea
Authors: Yang Y. , Wilson L. T. , Makela M. E. , Marchetti M. A. , Krausz J. P.
Published: May 2008

The effect of leaf age and nodal position on leaf receptivity to rice blast, caused by Pyricularia grisea, was studied by inoculating potted Rosemont plants with blast pathogen race IC‐17, isolate 92T107. at different growth stages. Regressioti equations were used to describe the effect ofleaf age (degree days > 10 C) and nodal position on lesion density, the relative frequency of lesion appearance, and the lesion area distribtition. The number of sporulating lesions per cm2 of inoculated leaf area was highest for leaves inoculated early in their development and progressively lower for leaves inoculated later in their development. The average lesion density for less than 1‐day‐old leaves at nodal position 6 was about four times the density for 10‐day‐old leaves of the same nodal position. Lesion density was similar for leaves of less than 1‐day‐old from the 4th to the 7th nodal position, but dropped sharply from the 7th to the 11 th nodal position. The flag leaf was the least susceptible of all nodal positions. The average lesion density for young leaves of about 1‐day‐old at nodal position 6 was about 27 times the density for young flag leaves of the same age. The incubation period increased with leaf age. but was not obviously affected by leaf nodal position. Lesion area increased linearly with time, but was not affected by leaf age and nodal position. The results are of use for epidemiological investigations which rely on detailed quantitative leaf susceptibility data for accurate blast forecasts.
Variation of Rice Tungro Viruses: Further Evidence of Two Rice Tungro Bacilliform Virus Strains and Possibly Several Rice Tungro Spherical Virus Variants
Authors: Druka A. , Hull R.
Published: May 2008

Rice tungro disease is caused by two viruses: rice tungro spherical virus (RTSV) and rice tungro bacilhform virus (RTBV). Our results obtained using polymerase chain reaction (for RTBV) and western blot analysis (for RTSV) to study the epidemiology of tungro supported earlier studies that two RTBV strains. South East Asian and Indian, can be differentiated and also better defined the geographic distribution of these two strains.

Data on RTSV variation were not so conclusive and consistent as those on RTBV because of the high degree of microvariation of RNA genomes. Our approach for differentiation of RTSV led to three variants being identified, the geographic distribution of which does not correlate with that found for strains of RTBV.
Scanning Electron Microscopical Observation and X‐ray Microanalysis of Erysiphe pisi DC on Infected Leaves of Pea (Pisum sativum L)
Authors: Sugawajra K. , Singh U. P. , Kobavashi K. , Ogoshi A.
Published: May 2008

Observations on scanning electron microscope (SEM) and low vacuum scanning electron microscope (LVSEM) of Erysiphe pisi in infected leaves of pea (Pisum sativum). are reported together with data from X‐ray micro‐analysis. Morphology of ungerminated and germinated conidia was observed and LVSEM revealed halo formation around the penetration peg of the pathogen. X‐ray microanalysis of the composition of halo showed the accumulation of Si and P. Presence of S. Mg, Cl, K and Ca was also discerned. Deposition of Si in the halo and profuse growth of the pathogen indicate that Si deposition is not an essential signal for inducing resistance in the host. LVSEM appears to be a suitable and rapid method to study the morphology as well as halo formation in E. pisi. X‐ray microanalysis and LVSEM studies of E. pisi are reported for the first time.
A Microscopic Characterization of the Infection of Green and Red Pepper Fruits by an Isolate of Colletotrichum gloeosporioides
Authors: OH Boung‐JUN , KIM KI Deok , Kim Young Soon
Published: May 2008

Colletotrichum gloeosporioides is a common pathogenic fungus in many plants. To investigate the specificity of the isolate C. gloeosporioides to green fruits, fungal behaviours and anthracnose development on green and red pepper fruits were compared using light and stereo microscopic techniques. When the isolate of C. gloeosporioides was inoculated on both green and red fruits, conidial germination, appressoria, and infection hyphae were observed on both fruits within 24 h after inoculation. The fungal invasion and colonization continued to the epidermal cells of green fruits, but not to those of red ones. Initial anthracnose symptoms were detected only on green fruits at 2 days after inoculation resulting in typical sunken necrosis within 5 days after inoculation. Thus the specificity of the isolate to green fruits may be due to successful invasion and colonization of the infection hyphae from appressoria into the epidermal cells through epicuticular layers of green pepper fnats, but not on red ones.
Development of Cloned DNA Probes for Phytoplasma Associated with Loofah Witches’ Broom
Authors: Kuan C. P. , Su H. J.
Published: May 2008

DNA was isolated from periwinkle (Catharanihus roseus) infected with a phytoplasma that originated in loofah witches’ broom affected by loofah. Cloned DNA inserts from six LfWB‐phytoplasma specific recombinant plasmids were not only labelled with digoxigenin, but also used as probes. Probes hybridized with DNA derived from LfWB‐phytoplasma affected periwinkle and loofah, but not with DNA from healthy plants or plants infected with phytoplasmas associated with elm yellows, red bird cactus, peanut witches’ broom, paulownia witches’ broom, Ipomoea obscura witches’ broom, aster yellows (two isolates), and sweet potato witches’ broom obtained with DNA from different phytoplasmas experimentally maintained in periwinkle. The probes could detect LfWB‐phytoplasma DNA with as little as 16 ng and 32 ng of DNA from periwinkle and loofah, respectively. The method proposed herein provides a means for specifically detecting and identifying of loofah witches’ broom phytoplasma, as well as confirming the notion that this phytoplasma represents a distinct strain cluster,
Resistance Against Pepper Severe Mosaic Potyvirus in Transgenic Tobacco Plants
Authors: Rabinowicz P. D. , Bravo‐Almonacid F. F. , Lampasona S. , Rodriguez F. , Gracia O. , Mentaberry A. N.
Published: May 2008

The coat protein gene of the pepper severe mosaic poty‐virus was introduced into tobacco plants. Several transgenic lines were assayed for virus resistance under greenhouse conditions. Line 232, showing higher levels of resistance than other transgenic plants, was studied in further detail. Upon challenge with PepSMV, R2 descendants from this line were monitored for virus accumulation for a period of 45 days. Virus titre was lower in plants of the line 232 than in control plants throughout the experiment. At 14 days post‐inoculation the transgenic plant line reached the maximum virus accumulation measured by ELISA. Those plants also showed a 1 week delay of virus accumulation by comparison with control plants. After reaching the peak at 14 days post‐inoculation the virus titre in line 232 decreased with respect to control plants, until the end of the experiment. These results are compatible with the presence of an RNA‐mediated resistance mechanism.
Calanthe Mild Mosaic Virus, a New Potyvirus Causing a Mild Mosaic Disease of Calanthe Orchid in Japan
Authors: Gara I. W. , Kondo H. , Maeda T. , Inouye N. , Tamada T.
Published: May 2008

Calanthe mild mosaic potyvirus (CalMMV), a previously undescribed virus found in several locations in Japan, causes mild leaf mosaic and flower colour breaking of Calanthe plants. CalMMV was mechanically transmitted only to Calanthe sp., Phalaenopsis sp. and Tetragonia expansa of 50 plant species tested and was transmitted by the aphid Myzus persicae in a nonpersistent manner. The virus has flexuotis particles about 764 nm long and induced the formation of intracellular cytoplasmic cylindrical inclusions. The virus particles contain a single poly‐peptide of 32.0 kDa and a single RNA of mol. weight 3.1 × 106. As determined by immuno‐electron microscopy, CalMMV is distantly related to the Japanese isolate of dendrobium mosaic potyvirus (DeMV‐J), but it showed no serological relationship to any of seven other potyviruses. The sequence of the 3′‐terminal 1306 nucleo‐tides of the viral genome was determined. The coat protein (CP) coding sequence is predicted to be 804 nucleotides in length, encoding a protein of 268 amino acids with a calculated mol. weight of 30 389. The 3′ noncoding region is 169 nucleotides long and is followed by a polyadenylate tract. The amino acid sequence of the CP of CalMMV was 73% homologous to that of DeMV‐J, but less than 66% to other potyviruses.
Ultrastructural Studies of the Intercellular Hypha aud Haustorium of Puccinia recondita f.sp. tritici
Authors: Hu G. G. , Rijkenberg F. H. J.
Published: May 2008

The ultrastructure of intercellular hyphae and D‐hati‐storia of P. recondita f.sp. tritici, and the host response to haustorial invasion, was investigated. The intercellular hyphae share common characteristics with those of other uredial stage rust fungi. Anastomosis was observed between intercellular hyphae. Two nucleoli were frequently observed in a single nucleus in the haustorium, indicating possible nuclear fusion between the two nuclei in D‐haustoria of this fungus. The close association of host organelles, such as the nucleus, Golgi bodies, endo‐plasmic reticulum, vesicles and mitochondria, with the developing haustorium, is described.
Effect of Combined Bacterial and Urea Treatment on Biodegradation of Wood by Basidiomycete Fungi
Authors: Ejechi B. O.
Published: May 2008

A laboratory investigation of the effect of two ureolytic bacteria (Proteus sp. and Bacillus sp.) on growth of wood‐rot fungi (Gloeophyllum sepiarium, Gloeophyllum sp., Pleurotus sp. and Trametes sp.) in media and wood containing urea, was carried out. Biomass of the wood‐rot ftingi was markedly reduced in potato dextrose/peptone/ urea (PDPU) broth to which ureolytic bacteria was introduced after 4 days growth of the fungi. Interaction studies on non‐urea containing agar plates did not indicate any antagonism between bacteria and wood‐rot fungi while sterile filtrates from 24 h PDPU cultures of ureolytic bacteria indicated that presence of ammonia prevented or markedly reduced growth of the fungi. Bacterial ureolytic activity produced volatiles which reduced wood‐rot fungal growth. Biodegradation was markedly reduced in wood treated with urea and ureolytic bacteria before exposure to wood‐rot fungi. Similar treatment of wood previously inoculated with the fungi significantly retarded on‐going decay. Wood‐rot fungi isolated from treated wood showed reduced growth. Inhibition of wood‐rot fungal activity is attributed to production of ammonia by the bacteria and the stress imposed by the resultant hostile alkaline pH.
Histopathology of Infection of Minneola Tangelo by Alternaria alternata pv. dtri and the Effect of Host and Environmental Factors on Lesion Development
Authors: Solel Z. , Kimchi M.
Published: May 2008

After inoculation of Minneola leaves with conidia of Alternaria alternata pv. citri, germ lubes randomly grew over the leaf surfaces. Twenty‐four h after inoculation, appressoria appeared over the epidermal cells; they formed infection hyphae that penetrated into the leaf, and developed intercellular branching hyphae which resulted in minute necrotic lesions. During the following 2–3 days, the lesions grew into large necrotic spots, subsequently accompanied by a dark discoloration of the veins extending from the lesions. Susceptibility of the leaves was negatively correlated with their age: mature leaves (approximately 2 months old) were very resistant to infection. Lesions developed faster when leaves were inoculated on the abaxial rather than the adaxial surface. There was no difference in disease severity on detached or intact leaves, or between leaves incubated in darkness or under natural light. Fruit were highly susceptible throughout the whole season.
RAPD‐based Molecular Probes for the Blackleg Fungus Leptosphaeria maculans (Phoma lingam): Evidence for Pathogenicity Group‐specific Sequences in tbe Fungal Genomes
Authors: Voigt K. , Schleier S. , Wostemeyer J.
Published: May 2008

Polymerase chain reaction (PCR) primers, specific for the aggressive pathogenicity group of the rape seed pathogen Leptosphaeria maculans, were obtained according to the following experimental outline: DNA bands that differentiate between aggressive (A) and nonaggressive (NA) isolates were generated by the random amplified polymorphic DNA approach (RAPD). Differential RAPD bands were checked for pathogenicity group‐specificity and sequenced by a combination of chemical and dideoxynucleotide chain termination methods. Based on the DNA sequence longer and highly specific primer pairs for conventional PCR under stringent conditions were designed, which were tested on 97 isolates of L. maculans belonging to different pathogenicity groups. The primer pair specific for the aggressive pathogenicity group unequivocally identifies A‐isolates. The primer pair designed for the N A‐isolates. cross‐reacts with A‐isolates showing positive signals in 28 out of 63 cases. The combined application of A‐ and NA‐specific primers identifies all isolates unambiguously. The method does not require pure fungal cultures. L. macuians can be detected directly in infected plant material within a single working day. The experimental outhne presented in this communication is proposed as a general method for obtaining taxon‐specific PCR primer pairs.
Variation in Pathogenicity Among Isolates of Phytophthora dandestina
Authors: Purwantara A. , Fletr S. P. , Keane P. J.
Published: May 2008

Studies on 25 isolates of Phytophthora dandestina collected from four states in southern Australia identified the presence of diversity in pathogenicity but not in morphology among isolates. Race 0 was found in all states except New South Wales, race 1 was found in all states, and races 2 and 3 were found only in Victoria and New South Wales, respectively. Race 4 was identified in Victoria and Western Australia. There was no apparent change in pathogenicity of the fungus following 10 (every 20 days) or 20 (every 10 days) cycles of subculturing. There was also no shift towards higher aggressiveness or virulence during 10 cycles of the fungus through susceptible or resistant cuitivars.
Cytochemistry of the Interaction between Wheat (Triticum aestivum) and Puccinia recondita f.sp. tritici Localization of Cellulose, Chitin, Glucose/Mannose, Galactose and Fucose
Authors: Hu G. G. , Rukenberg F. H. J.
Published: May 2008

A study of the cytochemistry of the interaction between wheat and Puccinia recondita f, sp. tritici, using various enzyme‐ and lectin‐conjugated colloidal gold probes provided additional information on the nature and composition of the walls of fungal hyphae, the haustorial mother cell, the haustorial neck, the haustorial body, and the extrahaustorial matrix. Using a cellulase‐conjugated gold probe, cellulose (the major component of the host cell wall) was not detected in the extrahaustorial matrix or in the host tubules associated with the invading haustorium. Wheat germ agglutinin (WGA)‐gold conjugates, which detect chitin oligomers (N‐acetylglucosamine residues), bound to two inner wall layers of the intercellular hypha, four inner wall layers of the haustorial mother cell (HMC), and the wall layers of older haustorial bodies, WGA did not bind to the haustorial neck, the walls of the young haustorial body or the extrahaustorial matrix. Concanavalin A‐ (ConA‐) and Lentil agglutinin (LTA)‐gold complexes, which specifically recognize man‐nose/glucose residues, bound to the wall layers of intercellular hyphae, HMCs, haustorial necks and young haustorial bodies. Colloidal gold conjugates with peanut agglutinin (PNA) which detect galactose residues, soybean agglutinin (SBA) which are specific to both galactose and N‐acetylgalactosamine residues, and Helix pomatia agglutinin (HPA) which recognizes N‐acetylgalactosamine residues, respectively, bound to these residues in the sections, PNA and SBA labelled the cell walls of intercellular hyphae, HMCs, haustorial necks, young haustorial bodies and the extrahaustorial matrix, PNA and SBA also bound to the host cell wall and to the host extracellular matrix, HPA bound weakly to the walls of haustorial bodies and the extrahaustorial matrix, Ulex europeaus agglutinin (UEA 1)‐gold complex, specific to α‐fucose residues, bound to the wall layers of intercellular hyphae and HMCs, and bound weakly to the extrahaustorial matrix. The composition of wall layers of the haustorial body of P. recondita f, sp, tritici appears to change as the haustorium matures.
Detection of Viable Cells of Ralstonia solanacearum in Soil Using a Semiselective Medium and a PCR Technique
Authors: Ito S. , Ushuima Y. , Fujii T. , Tanaka S. , Kameya‐Iwaki M. , Yoshiwara S. , Kishi F.
Published: May 2008

A semiselective medium (PCCG) and a polymerase chain reaction (PCR) technique were combined to detect viable cells of Ralstonia (Pseudomonas) solanacearum E. F. Smith (synonym Burkholderia solanacearum) in soil. DNA was extracted from 92 strains of soil bacteria including R. solanacearum that grew on PCCG and then used as template for PCR with a pair of primers designed to amplify a single fragment (281 bp) of R. solanacearum DNA. The 281‐bp fragment was amplified only from DNA of R. solanacearum (12 strains). For DNA from soil bacteria other than R. solanacearum, the PCR amplification generated no products for 66 strains, a single DNA band with different sizes from 281 bp for 2 strains, and several DNA bands for 12 strains. Southern analysis showed that any of those products other than the 281‐bp fragment had no homology with the 281 ‐bp fragment of R. solanacearum, indicating the specificity of the primers to generate the 281‐bp fragment from R. solanacearum. A simple method consisting of a plating step using PCCG and succeeding PCR for amplifying the 281‐bp fragment from colonies on PCCG was described.
Genetic Instability of Rishitin Metabolism and Tolerance and Virulence on Potato Tubers of a Strain of Gibberella pulicaris
Authors: Weltring K.‐M. , Loser K. , Weimer J.
Published: May 2008

Two strains of the potato pathogen Gibberella pulicaris were analysed for the ability to metabolize the phytoalexin rishitin and for virulence on potato tubers. While strain R‐6380 was always virulent and able to metabolize the phytoalexin, strain R‐7843 showed significant variation in both traits. Analysis of eight sectors of a radially grown culture of this strain revealed that six had a virulent, rishitin‐metabolizing phenotype, one had an avirulent, rishitin‐nonmetabolizing phenotype, and one had an intermediate phenotype for both traits. Similar results were found for single spores isolated from one of two spore suspensions from different agar cultures. In all cases high virulence was associated with fast metabolism of rishitin; weakly virulent strains only slowly degraded the phytoalexin. Restriction‐fragment‐length‐polymorphism (RFLP) analysis of sectors with contrasting phenotypes and measurement of the nuclear DNA content from these sectors indicate that the sectors were identical to the original strain (R‐7843) with respect to these traits. It is therefore concluded that the variations observed in virulence and in the ability to metabolize rishitin are the result of spontaneous genetic changes in strain R‐7843, The concurrent changes in tolerance, metabolism and virulence are further indicators of a relationship among these traits and lend support to the hypothesis that phytoalexin metabolism is important in pathogenicity.
Induced Resistance to Apple Scab: Microscopic Studies on the Infection Cycle of Venturia inaequalis (Cke.) Wint.
Authors: Ortega F. , Steiner U. , Dehne H.‐W.
Published: May 2008

Application of Methyl 2,6‐Dichlorisonicotinate (DCINA) induced resistance in apple against Venturia inaequalis. The effects of induced resistance on the infection cycle of the fungus were investigated by fluorescence microscopy. Induced resistance interfered with all stages of infection except conidial germination and appressorium formation. The establishment of primary stromata after penetration of the cuticle was affected by induced resistance as indicated by a delay in the visualisation of these structures. Only 10% of the primary stromata further expanded and differentiated runner hyphae in induced resistant plants. Contrarily in unprotected plants, runner hyphae were formed at 100% of the successful penetration sites. Characteristically, circular fluorescing structures appeared associated with stunted penetration sites. The epidermal cells underneath these infection sites showed no hypersensitive response. On induced resistant plants the number and length of runner hyphae was reduced. In most cases neither colonisation nor sporulation occurred due to the inhibition of secondary stroma formation. Possible mechanisms of induced resistance in apple plants are discussed.
Taxonomy and Pathogenicity of Phoma exigua var. populi var. nov. Causing Necrotic Bark Lesions on Poplars
Authors: Gruyter J. de , Scheer P.
Published: May 2008

A Phoma disease causing necrotic lesions on poplars has been observed in The Netherlands in the period of 1993–96. The disease symptoms as well as the morphology of this Phoma correspond with previous records from Germany and Italy. The disease has been ascribed to Phoma urens Ell. & Ev. but the American holotype of P. urens contained a Sclerophoma species. In vivo and in vitro the European fungus most resembles the plurivorous Phoma exigua Desm., therefore it is classified as a variety of the latter. The differentiating characteristics are presented. In pathogenicity tests on Populus (x) euramericana“Robusta”, Phoma exigua var. populi proved to be an opportunistic pathogen, causing distinct necrotic lesions after inoculation on injured cuttings. In a pathogenicity test on nine clones of four poplar species using two isolates of P. exigua var. populi differences of susceptibility were observed. Among five clones of P. (x) euramericana tested, disease development was most severe on the clones ‘Robusta”, ‘Florence Biondi’ and ‘Agathe F’. The clones ‘Ellert’ and especially “Spijk” proved to be less susceptible. The two P. exigua var. populi isolates showed differences in pathogenicity when tested on two Populus nigra clones. Inoculation with the most pathogenic isolate showed a moderate to high susceptibility of the P. nigra clones ‘Ankum’ and ‘Vereecken’, respectively. Populus (x) inter‐americana‘Donk’ and Populus trichocarpa‘Blom’ proved to be moderately susceptible to both P. exigua var. populi isolates.
Severity of Alternaria Leaf Spot and Seed Infection by Alternaria sesami (Kawamura) Mohanty and Behera, as Affected by Plant Age of Sesame (Sesamum indicum L.)
Authors: Ojiambo P. S. , Ayiecho P. O. , Nyabundi J. O.
Published: May 2008

Alternaria leaf spot incited by Alternaria sesami, was monitored to determine the effect of plant age on disease severity and seed infection by A. sesami in plots containing sesame accession SPS SIK 110 plants of five different ages. The increase in percentage leaf area blighted and percentage defoliation fit the Gompertz model more closely than the logistic model. Rates of increase in blighted leaf area and defoliation, and areas under disease curves (AUDPC) varied among the five different plant ages. Plant ages with larger AUDPCs generally had faster rates of disease progress. Plants inoculated at 8 and 12 weeks of age were most susceptible to the disease and those inoculated at 4 weeks exhibited the least susceptibility. Seed infection was determined by the oat‐meal agar plate method and the infection was highest in plants infected at 8 and 10 weeks of age and least in plants infected at 4, 6 and 12 weeks of age.
Real‐time Quantitative PCR: DNA Determination in Isolated Spores of the Mycorrhizal Fungus Glomus mosseae and Monitoring of Phytophthora infestans and Phytophthora citricola in their Respective Host Plants
Authors: Böhm J. , Hahn A. , Schubert R. , Bahnweg G. , Adler N. , Nechwatal J. , Oehlmann R. , Obszwald W.
Published: May 2008

Specific primers and dual‐labelled fluorogenic probes were designed for polymerase chain reaction (PCR)‐based detection of both, mycorrhizal and pathogen DNA. Based on the on‐line connection with an automated ABI Prism 7700 sequence detector, amplicon quantification was directly performed during the PCR. The starting copy numbers of target sequences present in each reaction were calculated by comparing the Ct‐values of unknown samples to the Ct‐values of standards with known amounts of DNA. The Ct‐value depends on the input of starting copies and is defined as that cycle number at which a statistically significant increase in the reporter fluorescence can first be detected. DNA was extracted from 11 as well as 100 spores of the mycorrhizal fungus Glomus mosseae and quantified by using the fluorescent PCR technology. Furthermore, DNA of Phytophthora infestans, causal agent of late blight of potatoes, was quantified after extraction from artificially infected potato tubers and naturally infected field plants. Phytophthora citricola DNA, causing root‐rot diseases, was quantified after isolation from artificially inoculated seedling roots of beech and oak. The results demonstrate that novel real‐time PCR techniques are a powerful universal tool in modern phytopathological research.
Symptomless Resistant Response Instead of the Hypersensitive Reaction in Tobacco Leaves after Infiltration of Heterologous Pathovars of Pseudomonas syringae
Authors: Klement Z. , Bozsó Z. , Ott P. G. , Kecskés M. L. , Rudolph K.
Published: May 2008

Following the infiltration of heterologous pathovars of Pseudomonas syringae two localized responses develop in a parallel manner in tobacco leaves: an early form of induced resistance (EIR) and the hypersensitive reaction (HR). The EIR inhibits the metabolic activity of infiltrated bacteria and the leaf tissue remains symptomless whereas HR also inhibits bacteria, but the leaf tissue shows confluent necrosis or necrosis of individual plant cells, depending on the inoculum concentration. After infiltration of a heterologous strain the rapid development of HR usually masks the effects of EIR which is developing at the same time. The aim of this study was to characterize the conditions in which EIR occurs in the absence of HR following the infiltration of heterologous pathovars of Pseudomonas syringae pathovars. A study was made of numerous experimental interactions of heterologous bacteria/tobacco leaves in which the HR induction time of the bacteria and/or the EIR response of the plant were modified. When (a) the HR induction time was extended by chloramphenicol treatment of bacterial cells or by using transposon mutants (Tn5), or (b) the time needed for the development of EIR was shortened (at 30°C or in young leaves) the heterologous strains were unable to induce visible HR. But when the EIR was suppressed in tobacco leaves by pretreatment with cycloheximide or thermal shock (50°C for 13 s) the HR appeared. Comparison of results of numerous experiments revealed that solely EIR was present if its development time was shorter than the induction period of HR. This interpretation was confirmed by the infiltration of partially purified harpinPss into tobacco leaves, where it caused plant cell death in the presence of EIR.