bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytopathology and Ultrastructure of Some African Isolates of Maize Streak and Sugarcane Streak Viruses
Authors: Ammar E. D.
Published: May 2008

Samples of maize leaves naturally infected with maize streak virus (MSV) from Malawi and South Africa, as well as sugarcane leaves naturally infected with sugarcane streak virus (SSV) from Egypt, were examined by light (LM) and transmission electron, microscopy (TEM). Intranuclear inclusions, detectable by both methods, were found mainly in mesophyll and bundle sheath cells, and less frequently in vascular parenchyma and immature phloem cells. At higher TEM magnifications, these inclusions consisted, of crystalline or noncrystalline aggregates of isometric geminivirus–like particles (VLP) that occurred either singly or in geminate arrays. Cytopathological changes in these cells were confined to the nuclei, which were usually larger than normal, with peripheral chromatin and nucleoli. The nuclear envelope of some inclusion–containing nuclei was ruptured, and occasionally a crystal of VLP was found in the cytoplasm of cells in which no intact nuclei were detected. No differences in cytopathology were found between MSV and SSV, or between the two MSV isolates examined.
Studies on Taxonomic Relationships of Mycoplasma–like Organisms by Southern blot Analysis
Authors: Schneider B. , Seemüller E.
Published: May 2008

Chromosomal DNA fragments from the mycoplasma‐like organisms (MLOs) associated with American aster yellows, apple proliferation, clover phyllody, and vaccinium witches' broom were cloned. Several MLO‐specific fragments from each of these four isolates and a sequence from the 16S rRNA gene of an aster yellows MLO were used in Southern blot hybridizations to investigate the taxonomic relationships of 26 pathologically and geographically diverse MLOs. These MLOs were divided into four categories according to the symptoms induced in periwinkle. Genotypically, these isolates represented four groups (16S RFLP groups) of a classification based on restriction fragment length polymorphisms (RFLP) and sequencing data of the 16S rRNA gene. Probes from three isolates of one symptom category hybridized with isolates from all symptom categories. This result indicates that classification of MLOs by symptomatology does often not coincide with genetic relationships. The hybridization results confirmed the findings, of the 16S RFLP classification that most MLOs from herbaceous plants, especially those inducing virescence in periwinkle, are interrelated. These isolates, which were assigned to one 16S RFLP group, could be further differentiated in this study. Itcould be shown that aster yellows, clover phyllody, stolbur, and safflower phyllody and sandal spike are caused by distinct MLOs. The MLOs associated with apple proliferation, vaccinium witches' broom, and witches' broom of lime as well as two isolatesfrom, stone fruits could also be recognized as distinct organisms.
Separation and Degradative Action of Polygalacturonase Isozymes Produced by Colletotrichum musae
Authors: Stanley M. S. , Brown A. E.
Published: May 2008

Polygalacturonase (PG) produced by Colletotrichum musae in liquid culture on banana pectic substances as the sole carbon source resolved into five distinct isozymes, with isoelectric points ranging between pl 4.8‐6.5. All five isozymes were detected in banana tissues rotted by C. musae.

Isozymes PG I (90 kD) and PG II (36 kD) were separated from PG III, IV and V (60‐70 kD) by gel filtration on a Superose 12 column. PG III, IV and V were resolved on a hydrophobic column (Alkyl Superose, HR 5/5) by changing gradients of 0.1 M sodium acetate buffer (pH 5.0). PG II, III, IV and V had endo‐activity and PG I had exoactivity.
Pathogenicity of Race‐1 and Race‐2 Tomato Wilt Isolates of Verticillium dabliae to Four Solanaceous and Two Non‐Solanaceous Hosts
Authors: Mingochi D. S. , Clarkson J. M.
Published: May 2008

The pathogenicity of four race‐1 and three race‐2 tomato with isolates of Verticallium dahliae to tomato, eggplant, tobacco, pepper, French bean and cabbage was investigated. Plants were inoculated without wounding and the symptoms assessed 6, weeks later. Both race‐1 and race‐2 isolates caused foliar symptoms on the race‐1 susceptible tomato cultivar GCR‐26 (Ve/Ve) although these were generally more severe with race‐1. All race‐2 isolates were significantly more pathogenic than race‐1, on the race‐1 resistant tomato cultivar GCR‐218 (ve/ve), although two of the race‐1 isolates caused mild foliar symptoms. None of the race‐2 isolates caused stunting of GCR‐26 whereas they all caused significant stunting of GCR‐218. All isolates reduceddry weight on GCR‐26 whereas only race‐2 affected GCR‐218. All isolates induced significant foliar symptoms, stunting and reduction in dry weight on eggplant. Only one isolates (race‐1) caused foliar symptoms on tobacco but this was not accompanied by areduction in either plant height or dry weight. All isolates were able to cause foliar symptoms on pepper, and two caused moderate to severe symptoms. Four isolates caused a significant reduction in plant height and one of these reduced dry weight. One isolates which caused mild foliar symptoms on papper increased host dry weight. No disease symptoms were observed on the non‐solanaceous host French bean. All isolates were capable of inducing mild foliar symptoms on cabbage but none caused reductions ineither plant height or dry weight. Race‐1 and race‐2 isolates could only be distinguished on the near‐isogenic pair of tomato cultivars. Verticallium was re‐isolated for each fungal isolate/host cultivar combination for tomato, eggplant and tobacco but was sporadic for the other hosts.
Spread of Erwinia chrysanthemi in Kalanchoë blossfeldiana
Authors: Bech K.
Published: May 2008

Meristems were excised from young and 8‐month‐old Kalanchoë blossfeldiana naturally‐infected with Erwinia chrysanthemi (Echr). From heavily infected plants the bacteria were identified in meristems from the very top of the plant as well as from meristems situated lower on the plant. In other naturally‐infected plants Echr was only found at the stem base, depending on how advanced (old) the infection was. Repetition of identification on meristem samples stored in the refrigerator for1 week revealed more positive samples than in the first test. Infection trials showed a quick spread of bacteria from stem base to apex via xylem vessels in some of the inoculated plants. Spread of Echr via capillary mats from inoculated to non‐inoculated Kalanchoë plants were found after 5.5 months growth on the capillary mat. The time lapse before transmission may vary with the seasons of the year.
Changes in Peroxidase Activity in Bean Suspension Cultures after B. cinerea and Elicitor Treatment
Authors: Malolepsza U. , Urbanek H.
Published: May 2008

Treatment of cell suspension cultures of bean (Phaseolus vulgaris) c.v. ‘Gold Saxa’) with Botrytis cinerea resulted in the increase in extra‐ and intracellular peroxidase activity. A similar effect was obtained by treatment of cell suspension cultures with an elicitor active extract from fungal mycelium.

It was shown by means of electrofocusing that the infection‐ or elicitor‐related increase in total intracellular peroxidase activity was associated with the increase in the activity of a specific isozyme with an isoelectric point of 4.8. This anionic peroxidase did not differ in substrate specificity to guaiacol, syringaldazine and chlorogenic acid.
Virus Content and Virulence of Polymyxa betae Keskin Isolates Obtained from Different Regions in Europe
Authors: Kastirr U. , Pfeilstetter E. , Burgermeister W.
Published: May 2008

Polymyxa betae isolates were obtained by means of bait plants from a large number of soil samples collected in eastern Germany. Additional P. betae isolates were received from several institutions in western Germany and abroad. Isolates were grown on sugarbeet seedlings and tested for the presence of beet necrotic yellow vein virus (BNYVV) and beet soilborne virus (BSBV). BNYVV was only present in isolates from western Germany and abroad but absent in all isolates from eastern Germany., In contrast, BSBV was detected in more uniform geographic distribution in 14 out of 33 P. betae isolates tested. The virulence of P. betae isolates was estimated on the basis of the extent of resting spore formation in the root system of sugarbeet seedlings. Differences in virulence were found among virus‐free as well as virus‐carrying P. betae isolates. The mean value of virulence ratings was distinctly lower with BNYVV‐carrying isolates and slightly lower with BSBV‐carrying isolates as compared to virus‐free isolates.
Restriction Fragment Length Polymorphisms Within the Apple Proliferation Mycoplasmalike Organism
Authors: Kison H. , Schneider B. , Seemüller E.
Published: May 2008

Genetic homogeneity of the mycoplasmalike organisms (MLOs) associated with apple proliferation (AP) disease was examined by comparing samples collected in south‐western Germany, France, Italy, and Romania by Southern blot analysis. The material examined consisted of two periwinkle‐maintained strains of the AP‐MLO, samples from witches' brooms of 48 symptomatic trees, and root samples from 14 latently infected trees. Six cloned chromosomal DNA fragments of one of the periwinkle‐maintained strains were used as probes. These probes, which were specific for the AP‐MLO and other European fruit MLOs, hybridized with DNA of all samples which indicates that the MLO5 examined were closely related with one another. However, restriction fragment length polymorphism was common bands. Therefore, the AP agent can be regarded as a taxonomic entity. The variability among the isolates seems not to due to their geographical origin but might be related to pathological traits.
Adenosine/Adenine‐Containing Nucleotides in the Leaves and Roots of Young Barley Plants after Infection of the Primary Leaf by Erysiphe graminis
Authors: Schmidt G. , Boyle C. , Aust H. J. , Wagner K. G.
Published: May 2008

The levels of adenosine, the adenine nucleotides AMP, ADP, ATP, as well as NAD, NADP, protein and chlorophyll were determined in young barley plants of which the primary leaves were infected by Erysiphe graminis DC. f. sp. hordei MARCHAL. The largest changes of these metabolite levels, compared to the non‐infected control, occurred in the infected leaf and to a lesser degree also in the roots and in healthy younger leaves. The increase in the levels of most metabolites in the primary leaf revealed the sink property of this infected tissue and possible stress or defence reactions of the host, whereas the reductions in the roots showed the impaired supply of this natural sink organ due to the infection. Changes in the healthy leaves were most pronounced in the tertiary leaf and may reflect metabolic stimulation in that healthy organ. The changes of the adenosine pool, a precursor of the adenine nucleotides, were discussed in terms of translocation and its possible role as a precursor for fungal purine nucleotide synthesis.
Sources of Resistance to Common Bunt (Tilletia foetida and T. caries) in Durum Wheat
Authors: Mamluk O. F. , Nachit M. M.
Published: May 2008

Screening of durum wheat germplasm for resistance to common bunt (Tilletia foetida and T. caries) resulted in the identification of 26 resistant genotypes. The screening was made using nine common bunt isolates from the West Asia and North Africa (WANA) region. In one isolate the two pathogens were represented in ratio of 1:1, whereas eight isolates contained only T. foetida. The correlation, principal components and clustering analyses grouped the genotypes into three clusters., Cluster one comparised genotypes close to Senatore (S.) Cappelli and Haurani, the latter is a landrace from Syria. Cluster three comprised advanced genotypes containing resistance genes from Mindum, a Turkish landrace. Results indicated that donor sources of resistance appear to be related to the three major sources mentioned. Cultivar S. Cappelli is considered resistant since it has been grown by farmers on a large scale for many years and remained resistant to common bunt throughout 7 years of testing. This resistance is assumed to be of a durable type. The isolates were also grouped into three clusters representing different ecological areas and the wheat types from which the isolates originated. We infer that the different clusters reflect the presence of three pathotype groups of the pathogens.
Evaluation of Some Fungi and Bacteria for Potential Control of Safflower Rust
Authors: Tosi L. , Zazzerini A.
Published: May 2008

Some fungal and bacterial isolates applied as soil and seed treatments in greenhouse trials gave a good protection against Puccinia carthami Cda. on safflower, significantly reducing the infection from rust‐infested seeds.

Trichoderma viride and T. harzianum added alone and in combination as air‐dried inoculum to the soil were the most effective fungal isolates. However T. viride at two higher rates reduced the rate of emergence of safflower seedlings.

Among bacteria, Bacillus subtilis, B. cereus, isolates of Pseudomonas fluorescens and B. thuringiensis reduced rust infection when added both as soil drench and as seed treatment.

Good results in the biocontrol of P. carthami were also obtained with some combination antagonist treatments such as T. viride + B. cereus, T. viride + P. fluorescens (16), T. viride + T. harzianum + B. cereus and T. viride +, T. harzianum + P. fluorescens (16).

Fungal isolates added as soil treatment increased seedling length, whereas no similar effects were observed when these isolates were applied as seed treatment.
Rapid Differentiation of Soybean Mosaic Virus Isolates by Antigenic Signature Analysis
Authors: Hill J. H. , Benner H. I. , Van Deusen R. A.
Published: May 2008

Antigenic differences among 14 soybean mosaic virus (SMV) isolates were shown by signature analysis employing a panel of nine well‐characterized monoclonal antibodies. Sets of binding curves were generated by reacting aliquots of serial dilutions of leaf extracts from soybean plants infected with each strain of SMV simultaneously with each antibody in the panel. An iterative alignment procedure allowed comparison of binding profiles from different assays in which the starting concentrations of SMV antigen were unknown. Desiccation of infected soybean leaf tissue altered antigenic signatures by inducing changes in reactivity of epitopes recognized by certain antibodies. The method was useful for the elucidation of subtle antigenic differences amongSMV strains. The procedure requires a minimum amount of tissue processing, the analysis is rapid and sensitive, and it requires neither purification nor knowledge of concentration of virus in ground leaf tissue from infected plants.
Differential Interaction Between PAV‐like Isolates of Barley Yellow Dwarf Virus and Barley (Hordeum vulgare L.) genotypes
Authors: Chalhoub B. A. , Sarrafi A. , Beuve M. A. , Lapierre H. D.
Published: May 2008

Four PAV‐like isolates of barley yellow dwarf virus (BYDV) were identified as causing very severe (RG), severe (2t), moderately severe (3b) and mild symptoms (13t) in barley (Hordeum vulgare) cultivar Plaisant in a growth chamber at 25 days after inoculation. These isolates had different effects on a range of barley genotypes. Cultivar Vixen, which contains the Yd2 resistance gene, and 80‐81 BQCB10 were not affected by any isolate. Five other genotypes were significantly affected by at, least one of the isolates. Line Ea52 (which is a mutant of the Japanese cultivar Chikurine Ibaraki) was more susceptible to BYDV‐PAV than Chikurin Ibaraki 1.

No serological differences were detected between the four isolates using monoclonal or polyclonal antibodies. Virus antigen concentration, estimated by enzyme‐linked immunosorbent assay (ELISA), was correlated with the decrease in the shoot fresh weight for all isolates and all genotypes except for Vixen and 80‐81BQCB10.

In field tests, the severity of symptoms induced by the BYDV‐PAV isolates was in accordance with that estimated in the growth chamber. However isolate 2t was more severe on cultivar Vixen and overcame the partial resistance of Chikurin Ibaraki 1 to the three other isolates.

The results show that virus antigen concentration not only contributes to characterizing the resistance levels of barley genotypes but also the severity of BYDV‐PAV isolates.
The Grouping of Strains of Pseudomonas syringae subsp. savastanoi by DNA Restriction Fingerprinting
Authors: Mugnai L. , Giovannetti L. , Ventura S. , Surico G.
Published: May 2008

A selected group of strains of Pseudomonas syringae subsp. savastanoi from olive, oleander and ash were compared with pathogenicity tests and with DNA restriction fingerprinting using sodium dodecyl sulphate‐polyacrylamide gel electrophoresis (SDS‐PAGE) and silver staining. The strains from each host were distinguishable by their pathogenicity to the same host and to the other two plant species. A division into the same groups was obtained with unweighted pair‐group method with averages (UPGMA) clustering of the data from genomic fingerprinting, even though high overall similarity between the strains also indicated that they formed a single, well characterized taxon. It seems clear that the subspecies savastanoi of P. syringae comprises at least 3 groups of strains that differ in their precise host range, in the nature of the symptoms induced on the individual hosts, and in their genomic profile.
Interaction of Partially Purified Phytotoxins from Phytophthora cactorum on Apple Cell Plasma Membrane
Authors: Mezzetti B. , Capasso R. , Evidente A. , Hammerschlag F. A. , Zimmerman R. H. , Cristinzio G. , Rosati P.
Published: May 2008

The ‘crude’ filtrate (CF) of Phytophthora cactorum containing phytotoxin(s), having some properties similar to the toxins isolated from other Phytophthora species, was processed by three steps (acetone precipitation, dialysis and gel filtration chromatography). The CF fractions corresponding to the progressive steps of purification were tested for phytotoxicity on tomato sedlings and for activity on cell trans‐membrane electrical potential (Em) of susceptible and resistant apple root stocks (Malus domestica).

The fractions (F4), obtained from chromatography on Sephadex G50 fine and eluted in the zone corresponding to a molecular weight of 15 ± 2kD, induced a specific alteration on susceptible apple cell membranes. These metabolites, even though incompletely purified, are able to induce a high and specific activity on susceptible apple cell Em only, not on resistant ones. As a consequence, they may be of potential use in screening for insensitive cells.
Effect of Herbicides on the Toxicity of Fungicides Against Rhizoctonia solani Causing Damping‐off of Cotton
Authors: Omaima A. Awadalla , Ilham M. El‐Refaie
Published: May 2008

The effect of two herbicides (paraquat and simazine on the antifungal activity of two fungicides (captan and mounsrin) against Rhizoctonia solani was studied. when the herbicides paraquat and simazine were applied to soil they altered the effectiveness of both fungicides in controlling R. solani, thus causing damping‐off of cotton. Both herbicides increased the toxicity of both fungicides against mycelial growth of the fungus. In pot tests, seeds or soil treated with captan or mounsrin, gave better control of R. solani damping‐off disease when the soil was treated with paraquat or simazine compared to untreated soil. Captan was, however, found to be more effective in controlling the disease than mounsrin.
Antagonistic Activity in Fusarium acuminatum
Authors: Logrieco A. , Mule G. , Bottalico A.
Published: May 2008

Ten of 19 (53%) tested isolates of Fusarium acuminatum, from different geographical origins and sources, showed in vitro antagonistic activity (inhibition at distance) to mycelial growth of F. moniliforme. Moreover, when F. acuminatum ITEM‐728 was tested against 25 different fungal species, an initial inhibition at a distance was observed which was followed by the spread of the F. acuminatum mycelium over the opposite fungal colony to various degrees. Most of the F. acuminatum isolates which showed antagonistic activity proved to be enniatin B (EB) producers, and some of them also formed moniliformin (MF). The toxic activity of the methanol extract of F. acuminatum ITEM‐728 towards some test microorganisms was closely related to the EB concentration. In particular, Bacillus subtilis proved to be a very sensitive test microorganism.
Production, Characterization, and Use of Monoclonal Antibodies Against Acremonium coenophialum
Authors: Scott S. W.
Published: May 2008

Monoclonal antibodies were produced using intact mycelium of the fungus Acremonium coenopbialum as the immunogen. During the initial stages of characterization, the antibodies were found to react to A. coenophialum, A. loliae, Epichloe typhina, and also to cross‐react with some other fungi normally associated with tall fescue. Careful selection of the ELISA system in which the antibodies were used eliminated reactions to all but the two Acremonium spp. and E. typhina. Asa result it was possible to detect Acremonium spp. (presumably A. coenophialum) sensitively and unambiguously in leaf tissue of tall fescue.
Water Stress in Leaves of Pbaseolus vulgaris Infected with Xanthomonas campestris pv. phaseoli
Authors: Goodwin P. H. , Sopher C. R.
Published: May 2008

Infection of bean leaves (Phaseolus vulgaris) by Xanthomonas campestris pv. phaseoli in the field frequently resulted in the appearance of isolated flaccid areas in green leaf tissue adjacent to necrotic and chlorotic lesions. The flaccid leaf areas had significantly higher stomatal resistances compared to nearby turgid areas on the same leaf, and the turgid areas had stomatal resistances that were the same or only moderately elevated compared to those of healthy leaves. The flaccid tissues also had significantly lower relative water contents than turgid tissues on the same leaf demonstrating that pathogeninduced water stress was localized. The levels of free proline, another indicator of water stress, were directly correlated (r2= 0.556) with disease severity. The change in free proline content implied that water stress increased in direct proportion with the amount of tissue infected. Water stress may be due to the disruption of xylem elements by the invasion of X. c. phaseoli from nearby lesions. One result of xylem invasion could have been severe water deficits which were sufficient to cause stomatal closure and leaf flaccidity; however, this effect was highly localized and the remainder of the diseased leaf was either significantly less water stressed or not affected.
Effects of Temperature and Leaf Weness on the Latent Period of Rbynchosporium Secalis (Leaf Blotch) on Leaves of Winter Barley
Authors: Davis Helena , Fitt B. D. L.
Published: May 2008

Effects of temperature and leaf wetness on the latent period of Rhynchosporium secaits (leaf blotch) on winter barley were examined in controlled environment experiments. At 100% relative humidity (continuous leaf wetness) the mean length of the latent period was c.24 days at 5°C, c. 19 days at 10°C, c. 16 days at l5°C and c. 13 days at 20°C. The mean number of days between the appearance of the first and the last lesions was c. 13 days at 5°C, c. 6 days at 10°C, c. 5 days at 15°C and c. 3 days at 20°C. A negative curvilinear regression of latent period on temperature accounted for 99% of the variance. The mean area of lesions per leaf was 38 mm2 at 5°C, 46 mm2 at 10°C, 24 mm2 at 15°C and 24 mm2 at 20°C. At 10°C, after a 48 h wet infection period, the interruption of leaf wetness for 5 or more days at any time during the next 15 days of the latent period did not decrease subsequent lesion area. However, absence of leaf wetness after these 15 days, at the onset of sporuiation, did decrease the area of lesions which developed.
Multiplication of Xanthomonas campestris pv. Phaseoli and Intercellular Enzyme Activities in Resistant and Susceptible Beans
Authors: Goodwin P. H. , Sopher C. R. , Michaels T. E.
Published: May 2008

In order to assess resistance to common bean blight, populations of two isolates of Xanthomonas campestris pv. phaseoli were monitored in leaves of two Phaseolus vulgaris breeding lines, BLT87‐2 (susceptible) and OAC88‐1 (partially resistant) and a resistant tepary bean accession, P. acutifolius P. I. 440795. The breeding line OAC88‐1 possesses resistance to common bacterial blight which was incorporated from P. acutifolius by an interspecific cross. In susceptible, leaves, bacterial populations increased to 108 CFU/g leaf at 3 wk after inoculation whereas, in resistant leaves, bacterial populations declined to 101 ‐ 103 CFU/g leaf. In partially resistant leaves the population first declined similar to that in resistant P. acutifolius but later increased, and typical bacterial blight symptoms appeared. Cellulase, protease and amylase activities were monitored in culture and intercellular leaf spaces. Only cellulase activity was, clearly related to bacterial growth in the susceptible host; other enzyme activities were variable in their relationship to host resistance and bacterial growth. Differences between strains in cellulase activity inside partially resistant leaves corresponded to their ability to secrete cellulase in culture. Measuring cellulase activity in intercellular wash fluids may be a simple and sensitive method for determining X. c. phaseoli populations in leaves.
The Genetic Relationship Between Mycoplasma‐like Organisms Causing Diseases in the Sudan and Different Continents Revealed by Polymerase Chain Reaction (PCR) Amplification of the 16S rRNA Gene Followed by Restriction Fragment Length Polymorphism Analysis
Authors: Saeed E. M. , Cousin M. T.
Published: May 2008

The genetic relationship between faba bean (Vicia faba L.) phyllody and other mycoplasma‐like organism (MLO) diseases has been studied by amplification of the conserved region of the 16S rRNA gene followed by restriction fragment length polymorphism (RFLP) analysis using Alu I restriction endonuclease. The restriction patterns produced by faba bean phyllody MLO were smilar to that of Crotalaria saltiana phyllody MLO which persists throughout the year in the Sudan. These, and serological results clearly confirmed that C. saltiana is a reservoir of faba bean phyllody MLO in the Sudan. Moreover, restriction patterns have also shown that MLOs of other diseases have the same RFLP fragment pattern as faba bean phyllody MLO, including C. juncea witches'broom (Thailand) and tomato big‐bud (Australia), which differs from the other selected MLO diseases (Gladiolus aster yellow, clover phyllody and yellow decline of lavender, aqll from France).

Fragment patterns also revealed the existence of genetically diverse MLO strains in the Sudan. Faba bean phyllody may be placed in group III including WX, apricot chlorotic leaf roll, golden flaveswcence dorée of grapevine, plum leptonecrosis of Prunus salciana, peachy yellow leaf roll, sunnhemp phyllody from Thailand, and blueberry witches' broom.
Effect of Pyroquilon, an Inhibitor of Melanin Synthesis, on Sporulation and Secondary Infection of Magnaporthe grisea
Authors: Uehara T. , Arase S. , Honda Y. , Nozu M. , Tswimoto K.
Published: May 2008

The effect of pyroquilon. an inhibitor of meianin synthesis. on the sporulation and secondary infection of Magnaporthe grisea spores was investigated. Spore formation of M. grisea was significantly inhibited on the pyroquilon‐containing medium. but mycelial growth was not impaired. Moreover, although the colour of the spore suspension obtained from control medium without pyroquilon was black, the suspension prepared from spores which had grown on the pyroquilon‐containing medium was red‐brown. The cell walls of the spores consisted of two layers. the outer of which was highly electron‐dense and saw‐like in cross section, regardless of treatment. Both the outer and the inner layers of the cell walls of spores which had grown on pyroquilon‐containing medium were thin compared with those of control spores. When M. grisea spores which had formed on the pyroquilon‐containing medium were inoculated onto rice leaf sheaths, red brown appressoria were formed. Compared with the control, appressorial penetration and hyphal growth in the host cells were inhibited. The inhibitory effect pyroquilon exerted upon the infection behavior of M. grisea spores was dependent on the dose of the chemical.
Apple Proliferation Epidemics Detected in Scab‐Resistant Apple Trees
Authors: Loi N. , Carraro L. , Musetti R. , Firrao G. , Osler R.
Published: May 2008

In the Friuli‐Venezia Giulia, a region of Italy, where serious epidemics of apple proliferation (AP) are known to occur, varieties resistant to scab (Venturia inaequalis (Cke.) Wint.) are increasingly being used in new orchards. The most important cvs are Florina. Prima and Priscilla. These varieties were cultivated according to organic farming regimes with no insecticides used. The results obtained in two orchards during a 7‐year period of investigation indicated that the three varieties resistant to scab are highly susceptible to AP. Florina was most susceptible (high infection rate) to AP while Priscilla was most sensitive (severely affected). The identification of the disease was based on symptom expression, DAPI (4–6‐diamidino‐2‐phenylindole) fluorescence technique, electron microscopy observations and by polymerase chain reaction (PCR). Neither complete spontaneous recovery nor death of AP‐infected plants was noticed. The pattern of natural diffusion of AP does not seem to be uniform, the affected trees may be in line or grouped in certain spots of the orchards. This may indicate the activity of a not very mobile vector. It can be concluded that planting of Florina, Prima and Priscilla should be discouraged in areas where AP is a problem, particularly when organic farming regimes are being applied.
Infection Studies of Cicer arietinum (L.) with GUS‐(E. coli β‐glucuronidase) Transformed Ascochyta rabiei Strains
Authors: Köhler G. , Linkert C. , Barz W.
Published: May 2008

Ascochyta rubiei (Pass) Labr. was transformed with the GUS‐(β‐glucuronidase) reporter gene of E. coli. Integration of vector‐DNA into the A. rabiei genome was documented by Southern analysis.

To verify that the transformation process had not adversely affected biochemical traits potentially important for fungal pathogenicity. i.e. hydrolytic exoenzymes. the extent of solanapyrone‐toxin production and phytoalexin degradation were measured, Significant differences between the transformants and the wildtype were not observed. Transformants also showed the same degree of virulence as the wildtype A. rabiei strain.

Histological studies with the GUS‐transformed genotypes were performed and the time course of infection was monitored by light microscopy. A. rabiei penetrates its host directly through the cuticle and penetration through hydathodes has also been found. After penetration. A. rabiei spreads mainly in the apoplast. When growing through leaflets towards petioles, the fungus could mainly be found in the apoplast and in the cells of phloem, but rarely in xylem. The infection process leads to a total collapse of plant tissue with extensive formation of pycnidia near the vascular tissue.
Barley Yellow Dwarf Virus Strain Incidence in Small Grain Cereals in Northeast Spain
Authors: Comas J. , Pons X. , Albajes R. , Plumb R. T.
Published: May 2008

Barley yellow dwarf virus (BYDV) was detected in forage cereals and small grain cereals by indirect enzyme‐linked immunosorbent assay. Samples of forage cereals collected in the winters of 1987/1988, 1988/1989 and 1989/1990 showed that this crop is a reservoir of BYDV during the end of summer and autumn. PAV‐like and MAV‐like isolates, in single or mixed infection, were the most common. The proportion of isolates in the infected samples was relatively stable, Samples of winter cereals collected in the springs of 1988, 1989 and 1990 showed that PAV‐ and MAV‐like isolates were widespread. The proportion of samples infected with PAV‐like isolates was much more variable than that of MAV‐like isolates. The incidence of PAV‐like isolates in winter cereals is more dependent on the population of Rhopalosiphum padi during the winter and early spring, than is the incidence of MAV‐like isolates on Sitobion avenae density. In northeast Spain (Lleida basin) forage cereals are a constant source of PAV‐ and MAV‐ like isolates from which BYDV inoculum is introduced into winter cereals.
Detection by RT‐PCR of Cymbidium Mosaic Virus in Orchids
Authors: Hyun Ryu Ki , Yoon K. E. , Park Won Mok
Published: May 2008

The cymbidium mosaic potexvirus (CyMV) coat‐protein gene was selected for the design of oligonucleotide primers. Reverse transcription‐polymerase chain reaction (RT‐PCR) was performed with 20‐mer CyMV coat‐protein‐specific primers to amplify a 692 base‐pair fragment from crude nucleic acid extracts of virus‐infected orchid‐leaf tissue. The lowest concentration of template viral RNA required to detect the virus was 10 fg. No PCR products were obtained when odontoglossum ringspot virus (ORSV) RNA orextracts of healthy Cymbidium sp. were used as templates in RT‐PCR using the same primers. A 2μl aliquot of crude nucleic‐acid extracts from 0.1 g of the CyMV‐infected leaf tissue was sufficient to yield a diagnostic PCR product.
Structures of Lipopolysaccharide Side‐chains of NCPPB 871, the Neopathotype Strain of Pseudomonas syringae pv. aptata, Strain 299A of pv. pisi and NCPPB 52, the Neopathotype Strain of pv. phaseolicola, in Relation to O‐serogroup
Authors: Spitali M. , Rees N. , Wait R. , Smith A. R. W.
Published: May 2008

The side‐chains of lipopolysaccharides from Pseudomonas syringae pvs. aptata, pisi and phaseolicola contain D‐rhamnose. Using 1H‐and 13C‐nuclear magnetic resonance spectroscopy and methylation analysis, the side‐chains of NCPPB 871, the neopathotype strain of pv. aptata, and strain 299A of pv. pisi race 1 were found to be of identical structure:

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Side‐chains from NCPPB 52, the neopathotype strain of pv. phaseolicola, were based on the same backbone structure, but were substituted to the extent of approximately 67% with branch D‐fucose residues:

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Side‐chain structures are correlated with a previously proposed serouping system.
Structures of Lipopolysaccharide Side‐chains of NCPPB 2995, the Neopathotype Strain of Pseudomonas syringae pv. mors‐prunorum and Three Other Strains, in Relation to O‐serogroup
Authors: Spitali M. , Patel M. , Smith A. R. W.
Published: May 2008

Side‐chains from the lipopolysaccharides (LPSs) of three virulent isolates of Pseudomonas syringae pv. mors‐prunorum all contained D‐rhamnose. Using Smith degradation, 1H‐ and 13C‐nuclear magnetic resonance spectroscopy, methylation analysis, and GC‐MS, the side‐chain of strain CFBP 2115 was shown to consist of the repeat sequence:

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NCPPB 2995, the neopathotype strain of P. syringae pv. mors‐prunorum, contained an identical side‐chain, which co‐purified with a glycogen‐like polymer composed of terminal, 1,4,6‐ and 1,4‐linked D‐glucose residues in the ratio 1:1:2.25. The side‐chain of P. syringae pv. mors‐prunorum strain NCPPB 2422 bore the same backbone structure as CFBP 2115, but was substituted by up to 80% with branch D‐fucofuranose residues:

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From the pattern of hydrolysis by phage A7 rhamnanase, the tetra and trisaccharide repeat sequences appeared to be irregularly interspersed. The side‐chain from LPS of P. syringae pv. syringae strain C414 was of similar structure, but was only 35% fucosylated. Sidechain structures are correlated with a previously proposed serogrouping system.
Complementary DNA Hybridization Analysis of Double‐stranded RNAs Associated with Cucumber Mosaic Virus‐As Strain
Authors: Hyun Ki , Park Won Mok
Published: May 2008

Virus‐specific double‐stranded (ds) RNAs were isolated from leaves of Nicotiana tabacum cv. Xanthi‐nc infected with the As or Y strains of cucumber mosaic virus (CMV). These dsRNAs on agarose gels produced 5 bands corresponding, respectively to three genomic RNAs (dsRNAI, −2, −3), the subgenomic mRNA for coat protein (dsRNA4). and satellite dsRNA (dsRNA5) with estimated molecular weights of respectively, 2.5, 2.4, 1.45, 0.69 and 0.28 × 103 kD. In northern‐blot analysis, a 1 kbp complementary DNA (cDNA) to CMV‐As RNA4 hybridized strongly with dsRNA3 and dsRNA4 extracted from CMV‐As infected tobacco, but did not hybridize with dsRNAI, dsRNA2, or satellite dsRNA (dsRNA5). In slot‐blot analysis, the cDNA hybridized strongly with virus‐,specific dsRNAs isolated from CMV infected plants, but not with dsRNAs of TMV‐Korean common, potato virus Y‐VN, or total RNA of healthy tobacco plants.
Epidemiological Aspects of Uromyces appendiculatus on Dry Bean (Phaseolus vulgaris) After Treatment with Bacillus subtilis
Authors: Mizubuti E. S. G. , Maffia L. A. , Muchovei J. J. , Romeiro R. S. , Batista U. G.
Published: May 2008

The number of pustules per leaf area, the average diameters of pustules and average spore production and spore viability were determined on fully expanded primary leaves of dry bean (Phaseolus vulgaris) which had been treated with a suspension of 106 cells of Bacillus subtilis. either as culture broth or as lyophilized broth, 24, 48, 72, 96 or 120 h before inoculation with urediniospores of Uromyces appendiculatus. Urediniospores were collected from treated plants, inoculated to new plants and the number of pustules per leaf area determined. The number of pustules per leaf, spore production per leaf area and the viability of spores were all significantly reduced by previous application of either liquid cultures or lyophilized broth, with greater reductions occurring at shorter intervals before inoculation with U. appendiculatus. There was no effect of treatment on the diameter of pustules. This reduction of disease severity could be of significance in the production of grown beans.
Spatial Dependence in Anthracnose Development in Mixtures of Stylosanthes scabra
Authors: Chakraborty S. , Pettitt A. N. , Choy S. Low , Boland R. M.
Published: May 2008

Development of anthracnose caused by Cotletotrichum gloeosporioides in mixtures of the tropical pasture legume Stylosanthes was studied in 3 successive years. The performance of three accessions of Stylosanthes sp., 36260, QiaO42 and 55860 and cv. Seca were evaluated by growing these in three different mixtures with other susceptible or resistant components. Small test plots of these mixtures were established within large grazed background paddocks which were sown to a pure stand of S. scabra cv. Seca or a mixture of six S. scabra genotypes, including ‘Seca’, This simulated the widely used practice of oversowing existing pastures with improved cultivars. In all 3 years, 36260, Q10042, 55860 and ‘Seca’ developed more disease when grown in a mixture with the susceptible ‘Fitzroy’. A hexagonal lattice design was used in the test plots to study the influence of nearest neighbours on the partially resistant 55860. At a plant level, the area under the disease‐progress curve, averaged over the six neighbours, NADPC, was used as a covariate to approximate the influence of inoculitm pressure in th e neighbourhood. The partial regression coefficient for this covariate wa s significant (P < 0.05) for mixture with ‘Fitzroy’ in 1989 and 1990, for mixture with the highly resistant 93116 in 1989, and for mixture with the moderately resistant ‘Verano’ in 1990. The NADPC was further subdivided into three components to separate inoculum pressure due to the component unique to a mixture, the resistant component ‘Seca’ and th e three moderately resistant components 36260, 55860 and Q10042. This showed that the NADPC effect was largely due to inoculum pressure from the moderately resistant components. The study demonstrates the lack of any significant protection of susceptible components from resistant components in the immediate neighbourhood. The practical implication of this finding is that only resistant components should be used when oversowing Stylosanthes pastures.
Characterization of the N Gene of a Groundnut Ringspot Virus (GRSV) Isolate from Argentina
Authors: Dewey R. A. , Semorile L. , Grau O. , De Avila A. C. , Kitajima E. W.
Published: May 2008

This paper describes the characterization of a Tospotirus isolate (M316) from Mendoza, Argentina. The N gene was cloned and sequenced. The sequence obtained was compared with the N gene sequences of other tospoviruses. The percentages of the nucleotide homology and amino acid similarity showed that this isolate may be considered a member of the species groundnut ringspot virus (GRSV). The conclusion drawn from the molecular studies was confirmed by DAS‐ELISA and western blotting. This is thefirst report of GRSV in Argentina, previously described for a South African (SA‐05) and Brazilian (BR‐08) isolates.
Resistance Induced in Potato Tubers by Treatment with Acetylsalicylic Acid to Soft Rot Produced by Erwinia carotovora subsp. carotovora
Authors: López‐López M. J. , Liébana E. , Marcilla P. , Beltrá R.
Published: May 2008

Acetylsalicylic acid (aspirin) at concentrations of 0.0125, 0.025, 0.03, 0.04 and 0.05% (w/v) pH 7 does not inhibit bacterial growth of Erwinia carotovora subsp. carotovora‐225 (Ecc‐225); without pH adjustment at concentrations of 0.025 and 0.03%, little inhibition of bacterial growth was observed. However, above 0.04% inhibition was total.

When studying the action of acetylsalicylic acid in the soft rot induced by Ecc‐225 on tubers stored at 4 C, we observed that treatments with this compound at concentrations of 0.0125, 0.025 and 0.05% in water adjusted to pH 7, were able to produce a considerable reduction of the soft rot; the possibility of a causal relationship between acetylsalicylic acid treatments of potato tubers and inhibition of soft rot has been established.
Morphology of Phytophthora cinnamomi Isolates from Avocado Orchards in the Coastal Area of Southern Spain
Authors: López‐Herrera C. J. , Pérez‐Jiménez R. M.
Published: May 2008

The morphological characters of 35 isolates of P. cinnamomi collected over a 6‐year period from infected roots of avocado trees from eight different orchards in different parts of Andalusia. southern Spain, were studied.

The fact that no fusion organs were found in the single cultures revealed their heterothallic nature. The great similarity and small variation of characters of these Spanish A2 isolates, the hot dry climate, and the fact that the dry cultivated previous crops were olive, grapevine, and almond, are not susceptible to natural infection by P. cinnamomi, suggest that the fungus was not indigenous in this area and was probably introduced on apparently healthy material from California or Mexico.
Quantification of Leptosphaeria maculans Growth in Cotyledons of Brassica napus Using ELISA
Authors: Balesdent M.‐H. , Desthieux I. , Gall C. , Robin P. , Rouxel T.
Published: May 2008

The result of the Leptosphaeria maculans/Brassica napus interaction is usually assessed by symptom scoring following a cotyledon‐inoculation test. However, an early evaluation of the interaction, and reliable quantitaive data of fungal growth inside plant tissues are needed to supplement the visual assessment of the symptoms. For this purpose, we developed a quantitatve double antibody sandwich enzyme‐linked immunosorbent assay (DAS‐ELISA) using rabbit polyclonal antisera directed against soluble mycelial proteins. The specificity of the serum was first assessed by immunoblotting following isoelectric focusing of soluble proteins (Western blot) and by DAS‐ELISA. Except for Alternaria brassicae, no cross‐reactions were observed with my celial extracts of saprophytes or pathogens of B. napus following DAS‐ELISA. Although Tox+ and Tox0 isolates of L. maculans were unequivocally discriminated by Western blot, they were quantitatively indistinguishable following ELISA, thus enabling us to analyse a wide range of L. maculans isolates in planta. The detection limit of the assay was less than 10 ng of fungal proteins per ml of plant extract. For a given isolate, time‐course studies showed that fungal growth in cotyledons was correlated with symptom scoring. In the case of hypersensitive response, only 34% of the plants were ELISA‐positive, and these plants never contained more than 10 ng of fungal protein per cotyledon. In contrast, in the cases, of susceptibility, 100% of the plants were ELISA‐positive and fungal protein content was higher than 10 μg per cotyledon. Moreover, significant differences in ability to colonize the tissues were observed among Tox+ isolates. Finally, using the ELISA quantification, intermediate symptoms could be differentiated as lateresistance responses or susceptibility.
Compartment Analysis of Disease Progression in Time. I. Unrestricted Disease Increase
Authors: Analysis S.
Published: May 2008

Disease progression in time through presporulating (latent), sporulating (infectious) and postporulating (removal) stages has been modelled as a three‐compartment system in the case where no upper bound for total disease increase is considered. Deterministic compartment analysis has been performed based on Jeger's linked differential equations. Some important, well‐established epidemilogical principles and concepts have been ‘rediscovered’, clarified or redefined. A new variable, defined as total inoculum reservoir of the host, is suggested as an additional epidemiological concept. Three rate parameters with phytopathological meaning were included in the system: R the constant intrinsic infection rate comparable to the Vanderplankian R,c, h pathogen's ‘hatching rate’, related to the mean latent period p and g the intrinsic removal rate related to the infectious period i. Another parameter λ1 is empirical and comparable to the logarithmic, infection rate, sensu Vanderplank if time becomes very large. In the compartment system iR= 0 is a threshold condition for total disease to increase over initial disease level and iR= 1 is a threshold condition for an ‘explosive’ total disease increase that may induce a large epidemic rather than a threshold for total disease to start or to exist. When iR < 1, the total disease level approaches α asymptotically, a finite value, while when iR > 1, the total disease, increase is explosive; only where λ1=√dh does this increase follows the exponential law at larger t, otherwise the exponential law with the same rate parameter λ1 underestimates or overstimates the amount of total disease at any time t. Some further implications are discussed and compared with those derived from the Vanderplankian system of epidemiological analysis.