bluuebunny/crossref_metadata_2025 huggingface dataset:
Mycoplasma‐like Organisms Associated with Proliferation and Big Bud of Solanum lycocarpum St. Hil.
Authors: Chagas C. M. , Oliveira J. M. , Caner J.
Published: May 2008

Mycoplasma‐like organisms (MLOs) were found in sieve tubes of Solanum lycocarpum affected with prolferation and big bud. The MLOs were graft‐transmitted to tomato plants which developed similar symptoms. The association of MLOs with affected but not with symptomless S. lycocarpum and tomato suggests that the abnormality is induced by MLOs. The possible role of S. lycocarpum as a reservoir of a strain of the tomato big bud is discussed.
Zum Einfluß des bakteriellen Phytotoxins Coronatin auf pflanzliche Zellsuspensionskulturen
Authors: Perner Birgit , Schmauder Hans‐Peter
Published: May 2008

Effect of the Bacterial Phytotoxin Coronatine on Plant Cell Cultures

The influence of the bacterial phytotoxin coronatine on cell cultures of Lycopersicon peruvianum and Chenopodium album was studied. It was detectable that the cell culture L. peruvianum more related to the host plant of the phytopathogenic bacteria reacts more sensitive to coronatine. Concentrations of 3.5 ng coronatme/ml culture liquid mduce reductions in growth and the TTC‐activity. In the case of the other used cell culture the critical amount of coronatine was higher than 7 ng/ml culture liquid. In further experiments the concentrations of free amino acids and proteins within the cell were followed. After 6–7 days of culture a slightly recovery of the cultures treated with coronatine was detectable.
Biological Control of Fire Blight of Hawthorn (Crataegus monogyna) with Fluorescent Pseudomonas spp. under Protected Conditions
Authors: Wilson M. , Epton H. A. S. , Sigee D. C.
Published: May 2008

Naturally‐occurring epiphytic fluorescent pseudomonads were isolated and characterized in terms of their potential to control fire blight infection of hawthorn, caused by Erwinia amylovora.

Preliminary testing and selection of antagonists using an immature pear fruit assay gave some inconsistency in the amount of pathogen suppression on the pear tissue and also in the prediction of biocontrol effectiveness on the intact plant.

Selected antagonists provided significant but variable control of fire blight under protected (polythene tunnel and glasshouse) conditions, with isolates HL83 and HL99 giving control of both blossom‐blight and shoot‐blight. In some cases the degree of control was equal to that of chemical treatments, including agrimycin 17 and experimental bactericides, and was achieved without any numerical advantage of applied control agent over pathogen. The timing of pseudomonad application in relation to pathogen inoculation was found to have a significant effect on the level of control of blossom‐blight.
Identification of Rhodococcus fscians (Tilford 1936) Goodfellow 1984
Authors: Hu F.‐P. , Fletcher M. J. , Watson D. R. W. , Clark R. G. , Young J. M.
Published: May 2008

Determinative laboratory tests which distinguish Rhodococcus fasdans from all other coryneform plant pathogenic bacteria were used to compare strains of this species with representative strains of Clavibacter spp. and Curtobacterium spp. The strains were also compared by colony hybridization using genomic DNA from R. fascians as a probe. Only strains of R. fascians authenticated with the determinative tests gave positive reactions to the probe.

The pathogenicity of strains was tested in seedlings of Lathyrus odoratus L. (sweetpea) grown in soil, and asepticaily in agar in tubes. Fasciation was induced in sweetpea by 20 strains of R. fascisms from Begonia sp., Brodiaea laxa, Carica X heilbornii nm. pentagona, C. pubescens, Dahlia sp., Fragaria X ananassa, Lathyrus odoratus, and Verbascum nigrum. Strains of R. fasdans from Chrysanthemum sp., Gladiolus sp., and Justicia brandegeana did not induce fasciation in sweetpea.
Ultrastructural Visualization of Glucide Determinants in Membranes of Mycoplasma‐like Organisms
Authors: Poggi Pollini C. , Giunchedi L.
Published: May 2008

Periodic acid‐thiocarbohydrazide‐silver proteinate (PATAg) reaction for poiysaccharide localization was performed on ultrathin sections of Spurr resin‐embedded tissues of Physostegia virginina and Catharanthus roseusknown to be infected by mycoplasma‐like organisms (MLO). Electron microscopy of PATAg‐treated sections revealed heavy silver deposition on hmiting membranes of all MLO. It was not possible to detect differences m silver deposition within the multi stratified membrane structure because of masking by silver‐grain deposition. Silver deposition was not found in the cytoplasmic region of the MLO. The results indicate the presence of glucide determinants only in the limiting membrane of the MLO. The significance of this finding is discussed.
Effects of Seedbed Management on Blast Development in Susceptible and Partially Resistant Rice Cultivars
Authors: Sah D. N. , Bonman J. M.
Published: May 2008

Four rice cultivars, susceptible or partially resistant to Pyricularia grisea were evaluated for their apparent infection rates (r) and for terminal severity values in seedlings grown in seedbeds. Susceptibility of partially resistant cultivars decreased when seeded in wet seedbed compared to those grown in raised or upland seedbed. The degree of blast reduction due to flooding varied with rice genotype, seeding rate, and environmental conditions. Flooding was effective in managing seedling blast of partially resistant cultivars but not of susceptible cultivar. Use of a lower seed rate in comparison to a higher seed rate also led to reductions in r‐values and terminal disease severities. However, in case of the susceptible cultivar IR50, effect of seed rate was more pronounced, when low amount and short duration of rainfall occurred. Flooding of wet beds with low seed rate further reduced the blast incidence. Results of this study suggest that with appropriate use of water, seed rate, and partial host resistance there are prospects for effective control of leaf blast in the tropics.
Host Effect on Cross Protection Between Two Strains of Tobacco Mosaic Virus
Authors: Rezende J. A. M. , Urban L. , Melgher U. , Sherwood J. L.
Published: May 2008

The expression of cross protection between two strains of tobacco mosaic virus (TMV‐C and TMV‐P) differed in Arabidopsis thaliana cv. Columbia and Nicotiana tabacum cvs Samsun and Xanthi. Protection in A. thaliana cv. Columbia was expressed as a prevention of systemic movement of the challenge strain, regardless of the protecting strain of TMV, Protection in N. tabacum cvs Samsun and Xanthi was expressed as an inhibition of an early event in the infection process. The results presented indicate that the host may influence the mechanism by which cross protection is expressed between the same virus strains.
Selection for Aggressiveness in Erysiphe graminis f. sp. Hordei Towards Partial Resistance in Barley
Authors: Newton A. C.
Published: May 2008

Isolates of powdery mildew were subjected to recurrent selection on partially resistant barley cultivars for 76 inoculation cycles over three years. Previous intermediate tests on up to 32 cycles for adaptation to overcome the host resistance revealed a trend towards adaptation to the cv. 7204 recurrent host in infection frequency data but not towards cv. Golden Promise or 9319, Subsequent cycles demonstrated adaptation to these latter hosts also.
Suppression of Brown Spot Disease of Cultivated Chrysanthemum by Manipulating Phototropic Response of Conidium Germ Tubes of Septoria obesa
Authors: Honda Y. , Kashima T. , Kumagai T.
Published: May 2008

An antagonistic effect between the UV‐blue (shorter than 500 nm) and red (longer than 600 nm) wave regions on the induction of phototropic response in conidium germ tubes has been demonstrated in the fungus Septoria obesa, the causal organism of brown spot disease of cultivated chrysanthemum. Phototropic response of conidium germ tubes was dependent on the ratio of the fluence rates between negative phototropism‐inducing UV‐blue wave region and positive phototropism‐inducing red wave region. Elimination of the UV wave region shorter than 390 nm by an ultraviolet absorbing vinyl film significantly reduced the negative phototropic response of conidium germ tubes and suppressed the invasion of the fungus through the stomata. Thus, a manipulation of the phototropic response of conidium germ tubes by controlling light quality resulted in the suppression of brown spot disease of cultivated chrysanthemum.
Antibacterial and Antifungal Spectra of Antibiotics Produced by Different Strains of Erwinia herbicola (= Pantoea agglomerans)
Authors: El‐Goorani M. A. , Hassanein FerialM. , Shoeib AliaA.
Published: May 2008

Nine antibiotic producer strains of Erwinia herbicola (=Pantoea agglomerans), belonging to different groups, strongly inhibited growth of 21 streptomycin sensitive strains and 6 streptomycin resistant strains of E. amylovora.

The antibacterial spectra of antibiotics produced by the tested strains of E. herbicola were mainly limited to E. amylovora and related tested species. The tested strains of E. amylovora that are resistant to streptomycin did not show cross‐resistance to the different types of antibiotics produced by the tested strains of E. herbicola.

The antibiotics produced by the different tested strains of E. herbicola did not exert any activity on tested fungi with the exception that strains Eh 153 and Eh 351 slightly inhibited the growth of Verticillium dahliae.
Pepper Tree (Schinus terebenthifolius Radii), a New Host Plant for Xanthomonas campestris pv. mangiferaeindicae
Authors: Pruvost O. , Couteau A. , Luisetti J.
Published: May 2008

Apigmented bacterial colonies were obtained in Reunion Island from angular leaf lesions on Pepper tree (Schinus terebenthifoliusRadii), a member ofAnacardiaceae. All isolates were identified asXanthomonas campestris, using physiological and biochemical tests.

These strains were reinoculated to Pepper tree leaves, and Koch postulates were verified. Furthermore, they were inoculated to mango leaves and produced lesions identical to those induced byXanthomonas campestrispv.mangiferaeindicae, the causal agent of bacterial black spot of mangoes. Apigmented and pigmented strains ofX. c.pv.mangiferaeindicaefrom Mango and Ambarella were pathogenic to Pepper tree.

Strains isolated from Pepper tree were compared toX. c.pv.mangiferaeindicae, by means of phenotypic features (utilization of 147 carbon sources) and using a serological assay. A high homology among the strains was observed.

Thus, It is concluded that strains isolated from Pepper tree belong to pv.mangiferaeindicae, and that Pepper tree is a host species forX. c.pv.mangiferaeindicae.
Pre–flowering Low Temperature Predisposition of Sorghum to Sugary Disease (Claviceps africana)
Authors: McLaren N. W. , Wehner F. C.
Published: May 2008

The relationship between pre–flowering climatic conditions and sugary disease incidence m sorghum was quantified over two seasons. In field trials with three male normal genotypes, low night temperatures 3—4 weeks prior to flowering increased susceptibility to the disease. Average night temperatures of <12 °C during the critical period resulted in male–normal genotypes being as susceptible as male–sterile genotypes. Seed set in uninoculated heads under pollination bags was also reduced, suggesting that increased susceptibility was the result of low temperature induced sterility. Genotypes differed in their ability to tolerate pre–flowering cold stress. Greenhouse and growth chamber trials confirmed that cold stress applied 7—8 weeks after planting reduced pollen viability and that this was the primary reason for increased susceptibility to sugary disease.
Observations on the Responses of Lentil Root Cells to Hyphae of Fusarium oxysporum
Authors: Bhalla Munjeet K. , Nozzolillo Constance , Schneider Edward F.
Published: May 2008

The infection of lentil roots by Fusarium oxysporum Schlecht and the responses of the host cells to invading hyphae were examined by light microscopy. Hyphae from inoculum placed on the zone of cell elongation entered the roots at the juncture of epidermal cells within 8 h after inoculation. Although swollen hyphal apices were observed on the epidermal cells, root penetration occurred without formation of these structures or appressoria. The sheath of material found on the surface of uninoculated roots was absent from inoculated roots penetrated by hyphae. Prior to penetration, the epidermal cells became irregular in shape and their cytoplasm appeared to be plasmolysed or granular. Hyphae were observed in the cortex 10—12 h after inoculation and non–penetrated cortical cells were distinctly lobate. Often these lobed cells had a broad, peripheral band of diffuse cytoplasm. When hyphae were first observed in the cortical cells, the walls were ruptured and only slightly stained or unstained by toluidine blue. The inability of such walls to bind the stain may have been the result of the removal of wall components by fungal enzymes.

Although extensive proliferation of hyphae was evident throughout the cortex after 24 h of incubation, the endodermis and vascular cylinder were free of hyphae for at least 72 h. Hyphae from inoculum placed on the root hairs or the root apex failed to penetrate the roots during the first 24 h of incubation.

The cytological results herein are discussed in relation to the infection of field plantings by this pathogen.
Induction of 6‐Methoxymellein and Resistance to Storage Pathogens in Carrot Slices by UV‐C
Authors: Mercier J. , Arul J. , Ponnampalam R. , Boulet M.
Published: May 2008

Biotic (β‐glucan, fructosan and polygalacturonic acid fragments) and abiotic agents (ultraviolet‐C radiation, gamma radiation and heat) were screened for their potential to elicit the accumulation of the phytoalexin 6‐methoxymellein in carrot slices. Ultraviolet radiation was the only elicitor found effective, with an optimum dose of 2.20 × 105 erg cm−2. At 20 °C, the maximum level was reached in 72 hours and thereafter degradation was apparent. At lower temperatures (1° or 4 °C), 6‐methoxymellein accumulation was slower but reached higher levels which remained stable for up to 35 days after induction. Ultraviolet‐treated slices which were stored at 1° or 4 °C for two weeks to allow 6‐methoxymellein accumulation were significantly more resistant to infection when challenged with Botrytis cinerea or Sclerotinia sclerotiorum. Slices inoculated immediately after ultraviolet treatment did not show any resistance. The data showed that concentrations of 6‐methoxymellein above 30 μg g−1 of tissue were inhibitory to B. cinerea, with maximum inhibition observed around 60 μg g−1. Thus ultraviolet treatment could have potential to enhance the resistance of carrots to storage pathogens.
Properties of Johnsongrass Chlorotic Stripe Mosaic Virus
Authors: Izadpanah K. , Huth W. , Lesemann D. ‐E. , Vetten H. J.
Published: May 2008

Physicochemical, biological, and cytopathological properties of Johnsongrass chlorotic stripe mosaic virus (JCSMV) found in Iran were investigated. Virus particles were polyhedral, showed a knobbed surface structure, were c. 30 nm in diameter and had a buoyant density of 1. 359 g/ml in cesium chloride. Virions contained one major protein with a molecular weight of 41 kd and a single species of ssRNA with a molecular weight of 1. 43 × 106 d. Acid hydrolysis of the virus followed by thin‐layer electrophoresis gave the following molar percentages of the bases: A: 23. 5, G: 27. 5, C: 26 and U: 23. Separation of nucleotides of the viral RNA using alkaline hydrolysis was not successful. Mechanical inoculation of freshly purified virus or isolated RNA failed to infect Johnsongrass or maize plants. The virus was readily detected by ELISA in seeds from infected plants and young seedlings raised from such seeds, but not in later stages of growth. Ultrathin sections of infected cells showed high concentrations of virus particles in the cytoplasm and vacuoles. Virus‐like particles also occurred in the stroma of chloroplasts and mitochondria. Cisternae of endoplasmic reticulum (ER) were often extremely inflated and filled by a fine fibrillar material. Small membrane‐associated vesicles were frequently found in ER elements and occurred also in the permuclear space. Based on particle structure, properties of the nucleic acid, molecular weight of the coat protein and cytopathology, the virus resembles carmoviruses. However, lack of mechanical transmissibility is not known for any virus classified with this group. No serological reaction was detected with a total of 30 antisera to carmoviruses and other isometric viruses.
Histochemistry and Ultrastructure of the Induced Resistance Response of Cucumber Plants to Colletotrichum lagenarium
Authors: Stein Barry D. , Klomparens Karen L. , Hammerschmidt Raymond
Published: May 2008

Lignin is hypothesized to be a factor in the ability of cucurbits to resist fungal infection. To determine if lignin was present around sites of infection, susceptible cucumber plants and cucumber plants with systemic induced resistance were inoculated with Colletotrichum lagenarium, and the ultrastructure of plant and pathogen was examined 24 to 72 hours later. Conidia produced germ tubes with appressoria within 24 hours of inoculation on both control and induced plants. Penetration of plant epidermal cell walls occurred by 48 hours, and papillae formed at the site of penetration. Both elemental bromine and potassium permanganate were used to histochemically stain for lignin. Potassium permanganate, used together with energy dispersive X‐ray microanalysis (EDS), indicated the presence of lignin in papillae and in electron‐dense areas of plant cell walls directly beneath the appressoria. Using EDS, silicon was shown to be localized in the electron‐dense areas of cucumber leaf cells. This is the first report of silicon in induced cucumber plants. There were no qualitative differences between the resistance reactions of induced and control plants.
Natural Occurrence of Seiridium cardinale on Thuja in Germany
Authors: Urbasch I.
Published: May 2008

Seiridium cardinale (Wagener) Sutton & Gibson (syn. Coryneum cardinale Wagener) is the most dangerous parasitic fungus of cypress and other Gupressaceae, already appearing in epidemic proportions, especially in the mediterranean area. Recently (in 1989, 1990 and 1991) this pathogen has been detected in the northern part of Germany (Hamburg and Schleswig‐Holstein) naturally infecting Thuja.

The geographical distribution and the progressive spread of S. cardinale is reviewed. Diagnostic features of the fungus, modes of host penetration, principal symptoms of the disease, ways of dispersal and control methods are described.

Possible causal factors for the recently observed occurrence of 5. cardinale in the north of Germany are discussed.
Ultrastructure in Bean Leaves Infiltrated with Bacterial Extracellular Polysaccharides
Authors: Stefani E. , Medeghini Bonatti P.
Published: May 2008

Ultrastructural observations were carried out in bean leaf tissue infiltrated with bacterial extracellular polysaccharides. These investigations revealed changes m the cell fine structure, especially related with chloroplast organization. Up to 24 h after EPS infiltration alterations consisted in irregularly running thylakoids and distortions of stacked regions. Invaginations of the plastid envelope and appearance of cytoplasm pockets inside the stroma were also noted. The most severe alterations, consisting in stroma dilations and envelope infoldings, were noted 24 h after EPS infiltration, parallehng the yellowing of the treated leaf areas; chloroplast shrinkage and collapse of thylakoid system were also sometimes observed. Chloroplast ultrastructure generally recovered 48 h after treatment; at this time local detachment of the plasma membrane and vesicle formation in the periplasmic space were observed, resembling a non specific, locahzed cellular response. The observed, permanent chlorosis and ultrastructural alterations suggest an interference of the EPS in the global metabolism of the bean mesophyll cell.
The Role of Maize in the Epidemiology of Barley Yellow Dwarf Virus in Northeast Spain
Authors: Comas J. , Pons X. , Albajes R. , Plumb R. T.
Published: May 2008

Barley yellow dwarf virus has been detected in maize by indirect enzyme‐linked immunosorbent assay (ELISA) and by immunospecific electron microscopy (ISEM). Samples of maize collected in September 1988, 1989 and 1990 showed that this crop is an important reservoir of BYDV; MAV‐like isolates were the most common although PAV‐like and RPV‐like isolates were also present.

Earlier research in Spain had shown that PAV‐like isolates were predominant. Thus the evidence from this work that MAV was the main isolate, and very widely spread, is important for future research on BYDV epidemiology in Spain.
Triticum durum Desf. a Further Host of Barley Mild Mosaic Virus (BaMMV)
Authors: Proeseler G.
Published: May 2008

After mechanical inoculation by rubbing off with infectious plant sap barley mild mosaic virus (BaMMV) was transmitted to 29 provenances and cultivars of Triticum durum Desf. var. africanum Körn. as well as to the Italian durum wheat cvs ‘Valforte’ and ‘Valnova’. The infected plants reacted partially with distinct mosaic symptoms. BaMMV was detected by ELISA and immunoelectron microscopy.
Transmission Electron Microscopy of Susceptible and Resistant Tomato Leaves Following Infection with Pseudomonas syringae pv. tomato
Authors: Varvaro L. , Fanigliulo R. , Babelegoto N. M.
Published: May 2008

Ultrastructural changes in tomato leaves of susceptible cv. Peto 95 and resistant cv. Ontario 7710 infected with Pseudomonas syringae pv. tomato were followed by transmission electron microscopy. Up to 48 hours from the inoculation host cells of both cultivars looked quite normal and no bacteria were visible in the intercellular spaces; bacterial cells were found only in the substomatal chambers. Afterwards, the leaf cells of cv. Peto 95 began to degenerate and bacteria invaded the intercellular spaces which seemed enlarged. After 15 days the disorganization was complete: tomato cells were plasmolyzed and the intercellular spaces were filled with bacteria. In the leaves of resistant cv. Ontario 7710 no bacteria were observed later than 48 hours and no visible modifications occurred up to 15 days after the inoculation.
Crude Exopolysaccharides (EPS) from Xanthomonas campestris pv. manihotis, Xanthomonas campestris pv. Campestris and Commercial Xanthan Gum as Inducers of Protection in Coffee Plants against Hemileia vastatrix
Authors: Guzzo Sylvia D. , Bach Erna E. , Martins Elzam. F. , Moraes Walkyriab. C.
Published: May 2008

Foliar‐applied exopolysaccharides, obtained from bacterial cells of either Xanthomonas campestris pv. manihotis (EPS‐Xcm) or Xanthomonas campestris pv. campestris (EPS‐Xcc), isolate NRRL B‐1459, were tested for their ability to induce local and systemic protection against coffee leaf rust caused by Hemileia vastatrix. Both preparations of EPS were effective in inducing local and systemic protection when applied 72 h before challenge with the pathogen. Protection was also observed when plants were treated with different concentrations of a commercially available preparation of xanthan gum (CXG).

Systemic protection was induced by EPS‐Xcm, EPS‐Xcc and CXG even after the removal of the treated leaves immediately before the challenge. Local protection lasted at least 5 weeks, when EPS‐Xcm was applied at the concentration of 100 μg equivalents of glucose/ml. Fluorescent microscopic studies of pathogen development in protected and control leaves indicated that neither the germination, appressoria formation nor the number of infection sites were affected by treatment with EPS‐Xcm.
A New Virus Isolated from an Ash Tree with Die‐Back
Authors: Bertioli D. J. , Hayle A. , Cooper J. I.
Published: May 2008

A virus isolated from an ash tree with die‐back has icosahedral virions c. 28 nm in diameter which contain a polyadenlyated and infectious bipartite single stranded RNA genome. The RNAs have M. Wts of c. 2.4 and 2.6 × 106. The virus was transmitted in 5/48 seed from infected Chenopodium quinoa. Serological tests failed to detect any relationships with 10 viruses. cDNA to the viral RNA was cloned. The sequences of the 5′ and 3′ ends of two clones were determined. One of these clones represents the 3′‐terminus of one of the viral genomic fragments. A search of nucleic acid sequence databases showed some similarity of the 3′‐terminal sequence of the virus to the 3′‐terminal sequence of cowpea mosaic virus. The virus is possibly a previously undescribed nepovirus or comovirus.
Production of a Host‐Specific Toxin by Germinating Spores of Alternaria tenuissima Causing Leaf Spot of Pigeon Pea
Authors: Nutsugah S. K. , Kohmoto K. , Otani H. , Kodoma M. , Sunkeswari R. R.
Published: May 2008

Production of a host‐specific toxin by Alternaria tenuissima, the cause of pigeon pea leaf spot, was investigated in spore‐germination fluids (SGF). The SGF selectively induced necrosis on pigeon pea leaves in a deteched leaf assay. Necrotic lesions were observed when a toxin from SGF was applied onto detached young leaves of the pigeon pea cultivar Bahar at concentration as low as 5 ng/ml. The resistant line Tanzania and nonhosts tolerated at least 20,000 times higher concentration of the toxin. The differential activity of the toxin on hosts and nonhosts of the fungus, as well as on susceptible and resistant cultivars or lines, suggested host‐specific property of the toxin. At a concentration of 10 ng/ml, the toxin induced susceptibility of pigeon pea leaves to a non‐pathogenic isolate of Alternaria alternata. The toxin possibly plays a role as a disease determinant of A. tenuissima, because the toxin was released from germinating spores as early as 3 h of incubation andthe, amount detected within 9 h was about 6 times of the concentration required for necrotic toxicity.
Differentiation of Erwinia Species in the “Amylovorap” Group by Class Analysis of Cellular Fatty Acids
Authors: Wells J. M. , Zwet T.van der , Hale C. N.
Published: May 2008

Cellular fatty acids of Erwinia species in the Amylovora group (E. amylovora, E. nigrifluens, E. quercina, E. rubrifaciens, E. salicis and E. tracheiphila), grown on King's medium B agar for 1,3, and 6 days at 28°C, were analyzed by gas‐liquid chromatography, grouped by chemical class, and compared in order to differentiate the species. For the group in general, the average percentage in 1‐day‐old cells ranged 36.4–41.5% for the saturated straight‐chain even‐carbon fatty acids, (Class A), 0.3–0.7% for saturated straight‐chain odd‐carbons (Class B), 43.4–53.3% for unsaturated acids (Class C), 4.5–7.1% for hydroxy‐substituted acids (Class D), 0.2–2.0% for branched‐chain acids (Class E), and 0–7.5% for cyclopropane fatty acids (Class F). Species could be differentiated in 4 sequential steps based on: 1) percentage of the 12:0 fatty acid (E. amylovora >3.6%, E. quercina (1%);2) sum of Classes E + F (E. tracheiphila (0.3%);3) ratio Class A/(E + F) (E. salicis <8); and percentage of 18:1 (E. rubrifaciens >14%, E. nigrifluens < 14%). Physiological age significantly affected relative percentages of Classes B, C and F in E. amylovora and E. salicis; of Classes A, C and F in E. quercina; of Class A in E. tracheiphila; and of Class C in E. nigrifluens.
Production of Zoospores, Mode of Infection, and Inoculum Potential of Pythium myriotylum Propagules on Cocoyam
Authors: Pacumbaba R. P. , Wutoh J. G. , Muyali Mary B. Meboka , Tambong J. T.
Published: May 2008

Zoospores of Pythium myriotylum were consistently produced from sporangia of detached mycelia in vitro in deionized water at pH 7.0 with 0.001 M sucrose in 24 h of continuous fluorescent light at 31°C. The oblong‐to‐pea shaped zoospores measured from 2.5–7.5 μm in diameter and remained motile for more than 48 h. The lengths of flagella were 1–1.5 times the diameter of the zoospores. Contaminated cultures of P. myriotylum were revived to pure isolates by the use of zoospores. The penetration of P. myriotylum propagules took from 6 to 7 h following contact of the inoculum with the roots, and the invasion was inter‐ and intracellular. At the minimum concentrations of 200 zoospores/ml or 180 mycelial strands/ml, P. myriotylum caused symptoms of CRRD within 3 to 6 days after inoculation of the roots of cocoyam plantlets, results indicating that the pathogen is very destructive in cocoyam.
Development of Powdery Mildew Fungi on Leaves Submerged Under Water
Authors: Sivapalan A.
Published: May 2008

Effects of submerging inoculated leaves under water on the development of Erysiphe graminis f. sp. hordei on barley, E. pisi f. sp. pisi on pea and Sphaerotheca pannosa on rose were investigated. Submerging leaves immediately after inoculation removed 27–40% of conidia from leaves. Additionally, conidia either failed to germinate or germinated abnormally resulting in reduced elongating secondary hyphae (ESH) production. Submerging leaves 24 h after inoculation had, little effect on the numbers of ESH. Conidiophore production from mycelia occurred under water, although mildew growth was slower. Sporulating colonies treated with water produced conidia which had the ability to produce ESH. Experiments with E. aquilegiae on Aquilegia vulgaris, E. depressa on Arctium lappa, E. verbasci on Verbascum thapsus and Microsphaera alphitoides on Quercus rober suggest that the wettability of leaves and the presence of trichomes on leaf, surfaces play an important role in determining germination behaviour and subsequent ESH production on leaves.
Antagonistic Activity of Five Myrothecium Species Against Fungi and Bacteria in Vitro
Authors: Gülay Turhan , Grossmann F.
Published: May 2008

Antagonistic activity of 69 Myrothecium isolates belonging to M. carmichaelü, M. cinctum, M. roridum, M. tongaense and M. verrucaria against six soil‐borne plant pathogenic fungi was investigated by using the streak method. Results clearly showed that M. carmichaelü is a strong antibiont having a very high degree of antifungal efficacy. M. cinctum and M. tongaense isolates were found to have an antagonistic activity either through antibiosis or mycoparasitism or both against the test fungi. M. roridum and M. verrucaria isolates also possessed both kinds of activities. After this first screening (of all Myrothecium isolates), one isolate from each species exhibiting the highest degree of antagonistic activity was selected for further studies. Inhibitory effects of culture filtrates of these representative isolates on the mycelial growth of the test fungi were investigated by incorporating them into PDA at a dilution of 1:8. M. carmichaelü was the most and M. cinctum the least effective species under assay. Moreover, culture filtrates and mycelium extracts of the selected isolates were found to have both antifungal and antibacterial properties using the agar‐well method. Among the test fungi, Sclerotinia sclerotiorum proved to be generally the most, and Pythium debaryanum the least sensitive to the antibiotic effects. M. cinctum showed the widest antibacterial spectrum inhibiting five bacterial species except for Pseudomonas syringae Pv. Phaseolicola. Additionally, the observations using light and scanning electron microscopy clearly demonstrated that all of the five Myrothecium species were able to parasitize all of the tested fungi.
Tolerance in Isolates of Colletotrichum coffeanum to Prochloraz‐Mn in Kenya
Authors: Agnes W. Mwang'ombe
Published: May 2008

Coffee berry disease, caused by Colletotrichum coffeanum is a serious disease of Coffea arabica in Kenya. Control of this disease is achieved mainly through the use of fungicides which currently include chlorothalonil and prochloraz‐Mn (Octave). Fungicide resistance in C. coffeanum to benzimidazoles has been well documented. Isolates of C. coffeanum highly sensitive to prochloraz‐Mn have been shown to acquire tolerance to high levels of prochloraz‐Mn in culture. These isolates were able to grow and sporulate in malt extract agar (MEA) amended with 250 μg ml‐1 prochloraz‐Mn. The prochloraz‐Mn tolerant isolates of C. coffeanum showed low level of tolerance to benomyl. The benomyl tolerant isolates of C. coffeanum equally showed low level of tolerance to prochloraz‐Mn. The prochloraz‐Mn and benomyl tolerant and sensitive isolates were found to be highly pathogenic and induced sporulating lesions on seedlings and berries of coffee cv. SL 28 whichis, very susceptible to C. coffeanum. Mixed inoculation tests using prochloraz‐Mn and benomyl tolerant isolates and prochloraz‐Mn tolerant and sensitive isolates of C. coffeanum showed that the prochloraz‐Mn tolerant isolate was competitive.
Towards an Understanding of the Expression of Stem Rust Resistance Gene Sr5
Authors: Lennox C. L. , Rijkenberg F. H. J.
Published: May 2008

In an attempt to determine the timing and expression of stem rust resistance gene Sr5, infection structure development of Puccinia graminis f. sp. tritici race 2SA2 in a resistant line (ISr5 Ra) and a susceptible line (ISr8 Ra) was compared quantitatively using a fluorescence microscopy technique. The results indicated that there were no significant differences in numbers of pre‐primary haustorium infection structures observed in the two near‐isogenic lines at 48 hours post inoculation, however the resistant line housed fewer colonies with higher numbers of secondary haustorial mother cells. It was concluded that Sr5 is expressed once primary haustorium formation has been initiated, and results in a limitation of the number of secondary haustorial mother cells.
Designation of Pathotypes of Plant Pathogens
Authors: Limpert Eckhard , Müller Kaspar
Published: May 2008

For evaluation and communication of data on populations of plant pathogens a sensible code to name pathotypes can be extremely helpful. Starting from a coding system proposed by Habgood in 1970, a system, called “coded triplets” is developed which has the same advantages but is easier to understand and to use. This is especially useful as, in the meantime, pathotypes did become increasingly complex due to the increased number of genes conferring race specific resistance in the host. An important advantage of the coded triplets is that codes change only at one digit if, for example, a new differentia) is added or if the pathotype changes from avirulence to virulence or vice versa on a single differential. In this way evoluationary patterns and changes in the pathogen population can be visualized easily. The system is used to describe complex data on haplotypes of the barley mildew pathogen, but it is suited equally well for designation of pathotypes of other pathogens. Some basic principles of coded triplets are similar to octal notation, described by Gilmour in 1973, which has, however, not become widely known. Reasons for this are discussed. – There is a fourth system belonging to the same group of mathematical, condensing codes. As there is reason to believe that the evolution of condensing codes is drawing to an end, the systems are compared extensively, and the benefits of a generally accepted designation are outlined.
The Level of Abutilon Mosaic Geminivirus in Leaf Discs and Wound Callus
Authors: Song J.‐Y. , Jeske H.
Published: May 2008

The level of Abutilon mosaic geminivirus in leaf discs, wound callus and suspension culture was monitored by hybridization. Over 25 days the amount of AbMV DNA decreased in the leaf discs kept under various experimental conditions including different temperatures, light regimes and hormone concentrations. In primary callus or in suspension culture no viral DNA was detectable. When leaf discs were kept in liquid medium instead of on agar plates a shift from viral single‐stranded DNA to replicative double‐stranded DNA was observed when phytohormones were supplied. It is discussed here why under these conditions, rapidly dividing tissues seem to be virus‐free.
Mycoplasma–like Organisms Associated with a Grapevine Yellows Disease Occurring in Italy
Authors: Credi R.
Published: May 2008

Transmission electron microscopy of tissues from Vitis vinifera L. plants, naturally infected with a yellows disease similar to flavescence dorée (FD), revealed the presence of pleomorphic mycoplasmalike organisms (MLOs). These occurred in varying concentrations in mature sieve tube elements of leaf veins. Generally the concentration was very low, although large populations of MLOs were found colonizing almost the entire lumen of two cells. The micro–organisms varied considerably in size, shape and electron opacity. Spherical, oval and filamentous forms were recognized. The bodies showed the typical ultrastructural details of other known plant pathogenic MLOs. They were bounded by a smooth trilaminar membrane and contained ribosome–likegranules and DNA–like strands.
A Novel Method for In Situ Hybridization in Fungal Cells based on Pricking Micro–injection of Photobiotin Labelled Probes
Authors: Matsuda Y. , Toyoda H. , Morita M. , Ikeda S. , Tamai T. , Nishiguchi T. , Ouchi S.
Published: May 2008

A novel method, a combination of a micro–injection and in situ hybridization cytochemistry, was developed for the examination of gene expression in Erysiphe graminis f. sp. hordei. In view of its high cellular content, hence high probability of hybridization with corresponding probes, cytoplasmic rRNA was chosen as the target and hybridized with a micro–injected photobiotin–labelled nucleic acid probe. The rDNA sequence was isolated from a genomic library of the fungus by the, use of cDNA derived from 28S RNA of Fusarium oxysporum f. sp. lycopersici, and the complementry RNA strand was synthesized in vitro for a probe. Since neither intact nor fixed conidial cells took up FITC–labelled albumin, the photo, biotin–conjugated RNA probe was introduced into cytoplasm of conidiospores by a pricking method. Positive hybridization was visualized by the colour–generating reaction catalyzed by biotinylated enzyme (alkaline phosphatase) which was first bound to the hybridized photobiotinlabelled probe. Specific hybridization was detected in cytoplasm of more than 80% of pricked conidiospores. A similar result was obtained when a probe was introduced into appressoria and haustoria formed on/in barley coleoptile epidermal cells. Hybridization was also observed in these structures when a double–stranded rDNA probe was introduced by pricking.
Differential Patterns of Bacteriolytic Activities in Potato in Comparison to Bacteriophage T4 and Hen Egg White Lysozymes
Authors: Düring K.
Published: May 2008

A comparison of the enzymatic activities of endogenous potato bacteriolytic enzymes with bacteriophage T4 and hen egg white lysozyme has been performed. Using Erwinia carotovora atroseptica and Pseudomonas solanacearum as substrates in, comparison to Micrococcus lysodeikticus a differential pattern of bacteriolytic activities could be detected. The expression pattern of endogenous potato lysozymes suggests that their functional activity against phytopathogenic bacteria in planta is unlikely. Antibacterial activities in transformed, T4 lysozyme expressing and non–transformed potato plants are evaluated.
Molecular Cloning, Detection of Chromosomal DNA of the Mycoplasmalike Organism (MLO) Associated with Faba Bean (Vicia faba L.) Phyllody by Southern Blot Hybridization and the Polymerase Chain Reaction (PCR)
Authors: Saeed E. , Seemüller E. , Schneider B. , Saillard C. , Blanchard B. , Bertheau Y. , Cousin M. T.
Published: May 2008

DNA from faba bean (Vicia faba L.) phyllody‐diseased periwinle plants was separated from host plant DNA by bisbenzimid‐CsCl buoyant‐density gradient centrifugation. The mycoplasmalike organism (MLO) DNA was used for the construction of DNA probes. Two probes, 1.45 and 1.35 kbp, were selected and used for the detection of MLO DNA associated with faba pean (FBP) and for assessing the genetic relatedness of FBP‐MLO with other mollicutes. The 1.45 kbp DNA probe hybridized with all MLO strains and, with Spiroplasma citri. The 1.35 kbp DNA probe specifically detected the MLO associated with FBP.

Moreover, a specific primer pair (E1 and E2) selected from the partially sequenced 1.35 kbp probe allowed amplification of the 1.35 kbp fragment. DNA amplification was obtained also with Crotaltiana saltiana phyllody (Sudan), C. juncea, witches' broom (Thailand), and tomato big‐bud (Australia), but no amplification was obtained in the cases of the healthy control, C. roseus phyllody (isolate n0) from Sudan, clover phyllody, Gladiolus aster yellow and yellow decline of lavender from France. The very strong signal observed in the case of FBP and C. saltiana phyllody agrees with previous results indicating that FBP and C. saltiana phyllody are caused by an identical MLO, and hence, C. saltiana acts as a reservoir of FBP‐MLO in the Sudan. The weak signal obtained in the case of C. juncea witches' broom and tomáto big‐bud indicates partial nucleotide homology. The major interest of this primer pair is the low quantity (as little as 100 pg) of the total DNA of diseased plant required for the detection of the FBP disease and the possibility of detecting genetic relatedness with other MLOs.
Association of the Decline of Nashi Pears with an MLO
Authors: Pollini C. Poggi , Giunchedi L. , Seemüller E. , Lorenz K.‐H.
Published: May 2008

Mycoplasma‐like organisms (MLOs) were constantly detected by the DAPI technique and by restriction fragment length polymorphism (RFLP) analysis of PCR‐amplified DNA in trees of Pyrus pyrifolia cvs Hosui and Kosui grafted on P. communis, seedlings rootstock with symptoms similar to the slow form of pear decline. These symptoms included upward curling of the leaves along the midrib. Leaves were abnormally thick and later turned reddish while major veins became swollen and brown. Trees with symptoms were usually 4–5 years old and were growing in the major pear areas of central Italy. The incidence of affected trees was particularly high in one orchard adjacent to a pear orchard strongly affected with the slow form of pear decline. In this case the distribution pattern of affected Nashi trees suggests that the causal agent was introduced from the adjacent pear orchard by an aerial vector. Although oriental pears are well‐known hosts of the pear‐decline agent when used as rootstocks of French cultivars, this is the first report of pear decline in P. pyrifolia varieties.
Pseudomonas syringae pv. helianthi (Kawamura 1934) Dye, Wilkie et Young 1978, a Pathogen of Sunflower (Helianthus annuus L.)
Authors: Arsenijević M. , Vennete R. J. , Maširević S.
Published: May 2008

Among the bacterial strains isolated from diseased sunflower leaves, eight were studied in some detail. A fluorescent pseudomonad isolated from necrotic tissues and its reisolates belong to group Ia of phytopathogenic pseudomonads which includes Pseudomonas syringae bacterium. A study of host range indicated that the pathogen infects only sunflower but not the other plant species. Based on the pathogenicity study and biochemical and physiological tests, it was concluded that the pathogen belongs to the bacterium Pseudomonas syringae pv. helianthi.
Isolation and Characterization of Viruses Present in Four Clones of Garlic (Allium sativum) in Venezuela
Authors: Marys E. , Carballo O. , Izaguirre‐Mayoral M. L.
Published: May 2008

Isolation and characterization of viruses infecting garlic in Venezuela indicate the presence of onion yellow dwarf virus [OYDV] in most field‐grown plants of the clones Criollo venezolano, Morado peruano and Blanco, while 14% of the Criollo venezolano plants showed co‐infection of leek yellow stripe virus [LYSV] and OYDV. In leaf tissues OYDV showed an average concentration of 165 μg/g fresh wt., the value being similar among clones. In Criollo venezolano plants co‐infected by LYSV and OYDV the concentration of the former was three fold lower than that of OYDV. Serological tests on leaf extracts of garlic plants indicated the absence of the garlic yellow streak virus [GYSV], shallot latent virus [SLV] and garlic latent virus [GLV] in the clones Criollo venezolano, Morado peruano and Blanco. GLV was found to infect plants of the clone Gigante. Physicochemical analysis of purified GLV strongly supports the inclusion of this virus as a definitive member of the carlavirus group.
The Role of Toxin(s) Produced by Germinating Spores of Pyricularia oryzae in Pathogenesis
Authors: Fujita K. , Arase* S. , Hiratsuka H. , Honda Y. , Nozu M.
Published: May 2008

Pyricularia oryzae produced toxin(s) during spore germination which induced susceptibility to infection by non‐pathogenic Alternaria alternata of rice leaves. The induced susceptibility was independent of the compatibility between the races of blast fungi used for obtaining the toxin(s) and the rice cultivars used for bioassay. Susceptibility was also induced in other susceptible species (e.g. barley, Italian ryegrass, perennial ryegrass and wheat), results suggesting that the toxin(s), are host‐selective and determine the host specificity at plant species level.
Morphological Variation in Spores of Pyricularia oryzae Cavara
Authors: Arase* S. , Katano Y. , Li X. , Honda Y. , Nozu M.
Published: May 2008

Two mutant isolates of Pyricularia oryzae formed abnormal, longer, cylindrical spores with more septa than those of normal, obpyriform spores of wild isolates. These isolates also produced normal spores, although their number was less than that of the abnormal spores. When normal and abnormal spores were single‐spore‐isolated from the lesions caused by the mutant isolates and inoculated to an agar medium, each colony produced both types of spores, regardless of the type of single spores usedfor inoculation.
Inoculum Sources for the Spread of Leaf Scald Disease of Sugarcane Caused by Xanthomonas albilineans in Guadeloupe
Authors: Klett P. , Rott P.
Published: May 2008

Leaf scald of sugarcane, caused by Xanthomonas albilineans, is thought to be spread mainly in infected cuttings and transmitted on infested cutting implements. Several observations made in Guadeloupe indicated that other means of spreading also occur. The dispersal of the pathogen outside sugarcane was investigated with plants inoculated by an antibiotic‐resistant marked strain of X. albilineans and with plants naturally infested with wild strains of the pathogen. The bacteria were isolated in water droplets (rain or dew) on the surface of sugarcane leaves at dawn. It was also detected on the surface of dry leaves during the day by leaf imprinting onto a selective culture medium. The bacteria were much more frequently isolated from the surface of symptomatic leaves than from symptomless ones. Aerial dispersal of X. albilineans was investigated by placing Petri dishes containing selective culture medium between sugarcane plants but without direct contact with the leaves. The pathogen was isolated in four out of 270 dishes which were randomly set 3‐14 h in a diseased field. These results indicated that the pathogen exuded from the leaves and then was spread by aerial means (rain, insects,…) or by leaf contact. The bacteria were also found in roots and rhizospheric soil of infested sugarcane stools suggesting that X. albilineans could be transmitted by root to root contact or by the soil. Finally, isolations of the pathogen in sugarcane inflorescences were positive. So, fuzz transmission may also occur.