bluuebunny/crossref_metadata_2025 huggingface dataset:
Natural Infections of Artichoke by Potato Virus X in Tunisia
Authors: Chabbouh N. , Cherif C. , Martelli G. P.
Published: May 2008

Abstract An isolate of potato X potexvirus (PVX) was recovered by mechanical inoculation from diseased Tunisian artichokes. The virus was successfully reinoculated to artochoke seedlings. It was identified on the basis of reactions of herbaceous hosts, particle size and morphology, serology, and cytopathology.
Comparison of Polyclonal Antisera in the Detection of Tomato Spotted Wilt Virus Using the Double Antibody Sandwich and Cocktail ELISA
Authors: Resende R.deO. , Avila A. C.de , Goldbach R. W. , Peters D.
Published: May 2008

Different polyclonal antisera and enzyme‐linked immunosorbent assay (ELISA) procedures have been tested for their potential to detect tomato spotted wilt virus (TSWV). The virus could efficiently be detected in high dilutions of sap from infected plants, and at low concentrations of purified virus and nucleocapsid protein preparations in the cocktail ELISA and the double antibody sandwich ELISA (DAS‐ELISA). Amounts of 1 to 3 ng of virus protein still gave positive readings using purified preparations, while sap could be diluted approximately 100,000 times. Differences in the detection level were observed using nucleocapsid protein antiserum (anti‐N‐serum) and the antiserum against intact virus particles (anti‐TSWV‐serum), but both antisera showed to be powerful sera for the detection of TSWV. Using anti‐N‐serum, TSWV could be detected in highly diluted extracts of different hosts, and also in leaf extracts or intact tissues stored for 30 days under different conditions. These results indicate that the TSWV nucleocapsid protein remains antigenic for long periods.
Cellular Damage to Phytophthora infestans in Tomato Leaves Treated with Oxadixyl: an Ultrastructural Investigation
Authors: Jiang Yong , Grossmann F.
Published: May 2008

Ultrastructural observations showed massive accumulation of electron dense deposits adjacent to plasmalemma and mitochondria and mitochondrial degeneration, which probably leads to cell death, in some hyphae and haustoria of Phytophthora infestans in infected tomato leaves treated with the systemic fungicide oxadixyl (8 μg/ml). However, no changes in the endoplasmic reticulum and number of ribosomes were observed. The cell walls of some hyphae were markedly thickened after oxadixyl treatment. Degenerated haustoria were partly present in intact host cells. Evidently, fungal cell damage by treatment with oxadixyl is not correlated with host cell damage.
Neither Indole Acetic Acid nor Bacteriocin is Apparently Involved in the in vitro Antagonism between the Virulent and the Avirulent Strains of Pseudomonas solanacearum
Authors: Wagih ElsayedE.
Published: May 2008

An avirulent strain of Pseudomonas solanacearum could inhibit the growth of its virulent parent on L‐tryptophan‐containing glycerol nutrient agar (TGNA) medium. It was, also, capable of inhibiting, though to a less degree, Corynebacterium fascians and Pseudomonas marginata, out of five other bacterial species tested. While P. marginata was partially inhibited by the avirulent strain it was totally insensitive to indole‐3‐acetic acid (IAA) up to a concentration of 300 μg/ml. Additionally, Erwinia carotovora var. atroseptica which was totally unaffected by the avirulent strain showed a spectrum of sensitivity to IAA concentrations close to that of the virulent strain. No DNA, RNA, or IAA could ever be detected in the inhibition area and, thus, it is almost certain that the inhibiting agent produced by the avirulent strain is not IAA as was previously speculated. This inhibiting agent was insensitive to autoclaving and to the enzymes, pronase, trypsin, DNAse, and RNAse. P. solanacearum bacteriocin was detected by polyacrylamide gel electrophoresis in the medium near the avirulent growth line and not throughout the inhibition area. This supports the conclusion that bacteriocin alone cannot be held responsible for the inhibition phenomenon observed and leaves the nature of this inhibiting agent unknown.
Suppression by Citrus Exocortis Viroid Infection of the Naturally Occurring Inhibitor of the Conversion of 1‐aminocyclopropane‐1‐carboxylic Acid to Ethylene by Tomato Microsomes
Authors: Bellés J. M. , Conejero V.
Published: May 2008

Citrus exocortis viroid (CEVd) infection of tomato cell cultures suppresses the constitutive inhibitor which blocks the conversion of 1‐aminocyclopropane‐1‐carboxylic acid (ACC) to ethylene by tomato microsomes. The inhibitor is associated to microsomal membranes and is also found in the water soluble fraction co‐isolated from the cells. The inhibitory effect is concentration dependent, heat stable and could be removed from solution by dialysis. Its possible relationship with regulation of the viroid‐induced ethylene production is discussed.
Effect of Sowing Time on the Incidence of Bud Blight in Soybean (Glycine max L. Merr.)
Authors: Almeida ÁLvaroM. R. , Corso Ivan C.
Published: May 2008

The incidence of soybean bud blight in soybeans in Brazil is sporadic in most of the production areas but is endemic in a few others. Tobacco streak virus (TSV), the causal agent, is transmitted by thrips. The vector population starts declining everytime the amount of accumulated rain is over 300 mm. A four year trial (1986—1990) indicated that by delaying the sowing time it was possible to drastically reduce the incidence of the disease, allowing farmers to grow a cash crop. Significant correlations were observed between percentage of infection, number of days with rain, total of accumulated rain and total of thrips surveyed. A multiple linear regression (y = 23.93 + 0.7 × 1—0.06 × 2) that accounted for 80 % of the variation was obtained, considering percentage of infected plants (y), total of thrips (×1) and total of accumulated rain (×2). Results indicated that farmers should sow during the month of December, in areas where the disease is endemic.
Acquired Resistance in Hypersensitive Tobacco Operates by Limiting Cell‐to‐Cell Spread of Virus Infection without Affecting Virus Multiplication
Authors: Pennazio S. , Roggero P.
Published: May 2008

Localized and systemic acquired resistance against tobacco mosaic virus (TMV) or tobacco necrosis virus was induced when local lesions were produced in leaves of Xanthi‐nc tobacco by mechanical inoculation with TMV. Both types of resistance were characterized by reduction in the size of lesions produced by the challenging viruses, whereas accumulation of viral antigen in lesions was slightly increased. These results, confirming previous findings relative to other hypersensitive plant virus combinations, do not support the view that an inhibitor of virus replication operates in the resistant tissues, but indicate that both types of resistance operate only against cell‐to‐cell spread of virus.
Fusarium oxysporum Forms Heterokaryons with Fusarium redolens
Authors: Rataj‐Guranowska M. , Paszewski A. , Walkowiak I.
Published: May 2008

Vegetative compatibility among three isolates of Fusarium oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens from diseased lupins was investigated.

Pairings between five mutants originated from each isolate revealed two compatibility groups. The first VCG comprised race 1 of F. oxysporum f. sp. lupini and one isolate of F. oxysporum var. redolens; the second VCG comprised race 2 of F. oxysporum f. sp. lupini and two isolates of F. oxysporum var. redolens. Heterokaryon formation was observed in many pairings involving mutants of both taxa.

These findings provide evidence of the conspecificity of these two taxa and they support Gordon's classification (1952) according to which F. redolens is actually F. oxysporum.
Recurrent Selection for Adaptation of Erysiphe graminis f. sp. hordei to Partial Resistance and the Effect of Environment on Expression of Partial Resistance of Barley
Authors: Newton A. C. , McGurk Lynne
Published: May 2008

Five isolates of powdery mildew were subjected to recurrent selection on partially resistant barley cultivars and tested at intervals for adaptation to overcome partial resistance. A trend towards adaptation to the recurrent host was observed in infection frequency data, but biomass per colony, measured using sterol cell‐wall determinations and enzyme linked immunosorbent assay, was not greatly affected.

The expression of partial resistance was examined after seedling growth under two different environmental regimes. Significant interactions with both overall resistance expression and latent period were detected using infection frequency data, and the effects were both cultivar and isolate dependent.

Variability between single colony derivatives of an isolate, which had previously shown adaptation to a partially resistant cultivar, was detected in infection frequency data indicating instability and a non‐nuclear component to adaptation.
Transmission Characteristics of the Clover Phyllody Agent by Dodder*
Authors: Carraro L. , Osler R. , Loi N. , Favali M. A.
Published: May 2008

The results obtained in investigations on the biological characteristics of the clover phyllody agent (CPA) in respect to its transmission by the experimental vector Cuscuta campestris Younk, using Catbarantus roseus L. as constant host, are reported.

Transmission efficiency of CPA was comparable whether the “stable bridge” or the “cut strand” of dodder method was adopted. The acquisition and inoculation threshold was between 4 and 6 days. The efficiency of transmission became greater by lengthening the test period up to 15 days. In cuttings of dodder maintained in water after recision, the maximum retention of infectivity, in respect to transmission capacity of CPA, was 28 days. It was proved that CPA invades C. campestris in a persistent manner.

In comparative tests between CPA and APA (apple proliferation agent) it was demonstrated that the former is more efficiently transmitted than the latter. Moreover there is a much higher pathogenic effect of APA than CPA in dodder; in fact C. campestris as well as C. subinclusa Dur. and Hilg. develops poorly and shows deformations when growing on AP infected periwinkles. The basic distinguishable symptoms of the two diseases in C. roseus are: virescence and phyllody for CP; small but never virescent flowers for AP. MLOs have been detected, by electron microscopy, in sieve elements of C. roseus and C. campestris infected by CPA.
Identification of Peanut Green Mosaic Virus Strains in India*
Authors: Naidu R. A. , Sreenivasulu P. , Manohar S. K. , Ramakrishna K. N. , Reddy D. V. R. , Nayudu M. V.
Published: May 2008

During field surveys, three peanut green mosaic virus isolates differing in symptomatology on groundnut and a few other hosts were collected. Ultrathin sections of infected groundnut leaflets showed cytoplasmic inclusions with pin wheels and scrolls. In enzyme‐linked immunosorbent assay they reacted strongly with antisera to peanut green mosaic and soybean mosaic virus antisera, and moderately with adzuki bean mosaic and peanut stripe virus antisera. All isolates also reacted positively with antisera to peanut eye spot, blackeye cowpea mosaic, pea seed‐borne mosaic, potato virus Y and tobacco etch viruses, and did not react with antisera to peanut mottle, bean yellow mosaic, bean common mosaic, clover yellow vein and sugarcane mosaic viruses. SDS‐PAGE analysis of purified virus preparations of the three isolates showed a single polypeptide with mol. wt. of 34,500 daltons. Based on these results, the three isolates are identified as biologically distinct strains of peanut green mosaic virus.
The Effect of Ultraviolet and Solar Radiation and Temperature on Survival of Fungal Propagules
Authors: Rotem J. , Aust H. J.
Published: May 2008

Survival of spores, spore aggregates, sclerotia, and pycnidia of fungi was evaluated after exposure to high temperature in the dark, or exposure to ultraviolet (UV) radiation or sunlight. Under most conditions survival decreased from the most resitant Sclerotium rolfsii to Alternaria macrospora, Mycosphaerella pinodes, Aspergillus niger and Botrytis cinerea, in that order. There was no difference in survival among organisms stored in darkness at 45°C as single spores or aggregated into a mass of spores; or between spores of M. pinodes exposed before and after being released from pycnidia. Exposure to UV reduced survival much more than exposure in darkness. Longevity under UV ranged from more than 7 days for S. rolfsii to approximately 50 min for A. macrospora and 3 min for B. cinerea. Much longer survival occurred for spores of all fungi aggregated together; of spores of M. pinodes irradiated when inside rather than outside pycnidia; and in bigger, darker and older rather than in smaller, paler and younger sclerotia of S. rolfsii. Survival of sclerotia cut into slices and exposed to UV increased with thickness, irrespective of exposure to UV with the outer pigmented or innernonpigmented side. As tested with spore aggregates of A. niger, the rate of survival was linearly proportional to the number of conidia aggregated in each body. Irradiation by sunlight affected survival as described for irradiation by UV. The best protection from the detrimental effects of sun and UV radiation was provided by the infected host tissue.
Variability in the Sensitivity of Rhizoctonia solani Anastomosis Groups to Fungicides
Authors: Kataria HansR. , Verma P. R. , Gisi Ulrich
Published: May 2008

Tolclofos‐methyl, iprodione and cyproconazole, among the eleven fungicides tested in vitro, gave consistently strong inhibition against all ten anastomosis groups (AGs) of Rhizoctonia solani. Carboxin, furmecyclox, thiabendazole, fenpropimorph and vinclozolin also inhibited all AGs but with wide variations in toxicity levels (EC90 values). Pencycuron showed strong activity against four AGs but was ineffective against the other six AGs. Generally, R. solani AGs were insensitive to fenarimol and imazalil. Tolclofos‐methyl strongly inhibited 23 AG2‐1 and 20 AG4 rapeseed/canola R. solani isolates from different locations in Saskatchewan, Alberta and Manitoba. The same isolates were also sensitive to iprodione, cyproconazole and carboxin. All AG4 canola isolates were insensitive to pencycuron (EC90 > 500 mg/l) while AG2‐1 isolates showed highly variable levels of sensitivity with EC90s ranging from 0.5 to 220 mg/l. Tolclofos‐methyl, applied to Brassica napus (canola) cv. Westar seed at 1 g a.i./kg, provided 75—100 % control of seedling damping‐off in pots infested with AG2‐1 or AG4 isolates. In parallel experiments, pencycuron (1 g a.i./kg seed) failed to control damping‐off by AG4 canola isolates and gave variable disease control against AG2‐1 isolates.
The Effect of Bacillus subtilis on In Vitro Growth and Pathogenicity of Erwinia amylovora
Authors: El‐Goorani M. A. , Hassanein F. M.
Published: May 2008

Five isolates of Bacillus subtilis were found to be antagonistic to 3 isolates of Erwinia amylovora in vitro on sucrose agar medium. However, B. subtilis or its culture filtrate did not exhibit any activity against E. amylovora in planta tests in the laboratory on immature green pear fruits or in a commercial pear orchard under natural growing conditions.
Fatty Acid Composition of Pseudomonas syringae pv. savastanoi
Authors: Wells J. M. , Casano F. J. , Surico G.
Published: May 2008

Over 85% of total cellular fatty acids of 30 strains of P. syringae pv. savastanoi, grown for one day at 28 °C on King's medium B (KB) agar, were 12:0 (5.0%), 16:0 (27.5%), 16:1 (36.7%) and 18:1 (16.8%). Three hydroxy‐substituted fatty acids comprised 7.2% of the total and 22 other minor components, each occurring at concentrations of less than 1%, comprised an additional 4%. Three percent were unidentified components. Cells grown for 3 and 6 days on KB agar contained lower concentrations of the unsaturated 16:1 (30.4 and 21.1%, respectively), and higher concentrations of branched‐chain and cyclopropane fatty acids than one‐day old cells. No consistent differences in fatty acid composition could be detected between virulent and avirulent strains, nor between pv. savastanoi and other pathovars of P. syringae. However, when cells were grown on a chemically‐defined medium for 6 days, concentrations of 16:0 and a tentatively‐identified 17‐carbon hydroxy fatty acid were higher, and those of 12:0 and 16:1 were lower in strains from Fraxinus than from Olea. P. fluorescens (7 strains) and P. viridiflava (6 strains) could be differentiated from each other but not from P. syringae.
Grassy‐shoot, a New Disease of Lemongrass Caused by Balansia sclerotica (Pat.) Hohnel
Authors: Janardhanan K. K. , Ahmad Absar , Gupta Motilal , Husain Akhtar
Published: May 2008

A new disease of lemongrass (Cymbopogon flexuosus) caused by Balansia sclerotica was observed in India. The systemic infection induced deformed inflorescences and grassy‐shoot symptoms as a result of inhibition of growth of axillary buds and shortening of internodes. A number of ascostromata of the pathogen were produced on inflorescences of infected plants. Microscopic examination of infected host tissue revealed the presence of abundant endophytic mycelia. B. sclerotica was isolated from ascostromata and apical meristems of infected plants and its pathogenicity to lemongrass was experimentally established in three out of eighty‐two seedlings raised from seeds of inoculated plants. This report is one of the rare achievements in establishing the pathogenicity of fungal endophytes experimentally.
Leaf Spot of Alternanthera sessilis and Its Implications for Food Crops
Authors: Oladiran A. O. , Gana R. W.
Published: May 2008

A leaf spot of Alternanthera sessilis caused by Fusarium pallidoroseum (syn. F. semitectum) is described. During pathogenicity tests, the fungus caused leaf spots of Amarantbus sp. Abelmoschus esculentus (okra), Celosia sp. and Sorghum bicolor. It also caused rots of tubers of Dioscorea rotundata, D. alata, Solanum tuberosum, corms of Colocasia esculenta, bulbs of Allium cepa and roots of Daucus carota when wounded. Unwounded tubers, corms, bulbs and roots of these named plants were not infected except roots of Daucus carota which disintegrated between 4 and 6 days after inoculation.
Evaluation of Certain Cowpea Genotypes for Partial Resistance to Powdery Mildew (Erysiphe polygoni)
Authors: Raju S. G. , Anilkumar T. B. , Chandrashekar M.
Published: May 2008

Partial resistance to powdery mildew (Erysiphe polygoni) in twenty one cowpea cultivars was assessed over two to three seasons under field conditions. Mildew incidence was recorded as number of leaflets affected/plant and severity as AUDPC or infection rate using Gompertz transformation. Irrespective of the parameter used to measure mildew resistance or the season, mean response of cvs V‐105, V‐269, V‐276, V‐282 and V‐385 showed clear slow‐mildewing, while RC‐48, S‐488, TVX‐944‐02E, V‐27, V‐36 and V‐118 were rated as susceptible. Mildew resistance in some cultivars was negatively correlated with that for the leaf rust (Uromyces vignae).

AUDPC was a more robust disease parameter than infection rate and showed a good correlation (r2= 0.79) with incidence.
The Use of Trichoderma koningii in the Control of Web Blight Disease Caused by Rhizoctonia solani in the Foliage of Cowpea (Vigna unguiculata)
Authors: Latunde‐Dada A. O.
Published: May 2008

The foliage of a field‐sown cowpea cultivar (IT82E‐60) was inoculated with an isolate of the aerial ecotype of Rhizoctonia solani and sprayed thereafter, at two frequencies, with a spore suspension of Trichoderma koningii. Although the antagonist restricted the spread of web blight disease the extent of disease reduction and the yield levels were significantly (P 0.05) higher in the plants sprayed twice weekly with T. koningii spore suspension. These levels of disease reduction and yield compared favourably with those obtained from inoculated cowpea plants protected with a fungicide mixture. The significance of these results is discussed in relation to investigations on the application of Trichoderma spp. in the biocontrol of disease of the phylloplane.
The Variability of Pyrenochaeta terrestris Isolates Based on Isozyme Polymorphism, Cultural Characteristics and Virulence on Differential Onion Breeding Lines
Authors: Ferreira J. F. , Bosland P. W. , Williams P. H.
Published: May 2008

Isolates of Pyrenochaeta terrestris from South Africa and the United States of America were evaluated for pathogenicity, isozyme polymorphism and cultural characteristics. Isozyme polymorphism indicated that the isolates of this pathogen, even from the same field, are highly variable. Based on variability in the enzymes: alcohol dehydrogenase, aldolase, malate dehydrogenase and sorbitol dehydrogenase, the isolates could be divided into five electrophoretic types. The virulence of isolates to onion breeding lines resistant, moderately resistant and susceptible to pink root was variable and differentiation depended on the isolate used in the evaluation. The isolates showed extensive variation in both the ability to form setose pycnidia in culture and in the cultural pigmentation.
Identification and Characterization of Tobamoviruses Strains Infecting L‐resistant Genotypes of Peppers in France
Authors: Gebre‐Selassie Kahsay , Marchoux G.
Published: May 2008

Characterization of tobamovirus isolates collected from pepper crops in South East France has revealed the existance of several strains belonging to different viruses of the group. The biological and serological properties of three isolates (Vi76, Adam and Eve), selected as representative strains, have been studied. They have been compared with TMV and ToMV strains already isolated in our region as well as with other reference strains of ToMV‐D and TMV‐U1. They were also compared with other tobamovirus strains P11, P8 and P14, from the Netherlands, and PMMV‐W from Italy also isolated from pepper genotypes possessing the “L” gene for resistance to TMV and ToMV strains.

According to biological and serological reactions, Vi76 is more related to ToMV than to TMV but it is not related to Adam and Eve which are more closely related to PMMV. On the basis of the interaction with the “L” gene for resistance in pepper genotypes we have found that the Adam and P8 strains belong to the P1‐2 pathotype and the Eve and P14 strains to the P1‐2‐3 pathotype and all the 4 strains belong to the PMMV‐W group.

In France, there have been no reports of the isolation of the P11 strain which is distantly related to the Adam strain.
Histochemistry of Tobacco Mesophyll Cell Walls Pretreated with Bacterial Protein‐lipopolysaccharides
Authors: Minardi P.
Published: May 2008

Prevention of hypersensitive confluent‐necrosis in tobacco mesophyll, caused by Pseudomonas syringae pv. aptata, and tolerance towards the incompatible bacterium are induced 48 h after intercellular injection of protein‐lipopolysaccharide complexes. Histochemical analysis and ultrastructural observations were carried out to determine whether there was an association between this tolerance state and cell wall alterations due to callose, lignin and/or suberin deposition either before or after challenge with the incompatible bacterium. No evidence was obtained for such wall alterations.
Isozyme Variation and Genetic Diversity of the European Barley Powdery Mildew Population
Authors: Koch G. , Köhler W.
Published: May 2008

Isozyme and virulence analyses of Erysiphe graminis bordei were performed with samples collected from different sites from nearly all over Europe. Isozymes and unspecific proteins extracted from conidia were separated by starch gel electrophoresis and isoelectric focusing, respectively, and the resulting isozyme banding patterns were compared with the corresponding virulence data.

One isozyme phenotype prevailed in all samples. Only 7.9% of 280 isolates showed divergent banding patterns. Expected frequencies of isolates with divergent banding patterns were calculated for each subsample. In the Italian subsample, isolates with divergent banding patterns were significantly more frequent than expected. At the same time, isolates from Italy had significantly fewer virulence factors than those from N.W. Europe, indicating weaker selection by host resistance genes. It is suggested that isozyme uniformity in the homogeneous north‐western European barley powdery mildew population has arisen from strong selection pressures for specific virulence genes. The direction of this selection, acting upon a mainly asexually reproducing population, has changed over space and time due to the introduction of new resistance genes, forcing local populations through bottlenecks. This may have led to random loss of genetic variation (genetic drift) in the barley powdery mildew gene pool.
Characterization of Deoxyribonucleic Acid of Virulent Bacteriophage and its Infectivity to Host Bacteria, Pseudomonas solanacearum
Authors: Toyoda H. , Kakutani K. , Ikeda S. , Goto S. , Tanaka H. , Ouchi S.
Published: May 2008

Virulent bacteriophage PK‐101 was isolated from soil infested with strain K‐101 of Pseudomonas solanacearum and nucleic acid was prepared from the phages. Some chemical properties of phage nucleic acid and its infectivities to various strains of P. solanacearum were examined in the present study. By digestion with restriction endonucleases, phage nucleic acid was shown to be linear duplex DNA approximately 35 kb long. Restriction fragment length polymorphism was observed when electrophoresis patterns of enzyme‐digested PK‐101 DNA were compared with those of DNA prepared from different phage isolates. Transfection of host strains by PK‐101 DNA was carried out, and it was infectious not only to host strain K‐101, but also to other strains which were resistant to phage particles. Transfection efficiency was considerably enhanced by directly introducing phage DNA into bacterial cells by means of an electroporation. The electroporation technique was also effective to transform P. solanacearum with large‐size plasmid DNA.
Differentiation of the Soft‐Rotting Erwinias (the Carotovora Group) by Fatty Acid Composition
Authors: Wells J. M. , Moline H. E.
Published: May 2008

About 90 % of total cellular fatty acids in E. carotovora, grown on KB medium for 1 day at 28°C, were the saturated, even‐carbon straight chains 12 : 0 (5.9%), 14 : 0 (1.7%) and 16 : 0 (30.1 %), and the unsaturated 16 : 1 (36.6%) and 18 : 1 (15.0%) fatty acids. Other components were the hydroxy‐substituted 3‐OH 14 : 0 (5.3%) and 21 minor fatty acids each occurring less than 0.1 % of the total — 14 of them reported herein for the first time in Erwinia. The ratio of 16 : 1/18 : 1 in KB‐grown cells was as useful in differentiating subspecies of E. carotovora as previously reported by other workers for TSA‐grown cells. A comparison of fatty acid profiles of E. carotovora on 4 different media, KB, TSA, NA and PDA, indicated that on KB there was the greatest proportion of Class A and C fatty acids, and the highest number of detectable components. Significant differences were noted in the 5 major fatty acids and in cyclic fatty acids among the 4 species of the carotovora group –E. carotovora, E. chrysanthemi, E. rhapontici and E. cypripedii. These differences could be expressed as algorithms that, when used in sequential dichotomous steps, could differentiate the 4 species.
Effects of Infection Density on the Size of Barley and Wheat Leaf Rust Colonies before and on the Size of Uredia after the Start of Sporulation
Authors: Baart P. G. J. , Parlevliet J. E. , Limburg H.
Published: May 2008

Three barley genotypes were exposed to four different inoculum densities of barley leaf rust, Puccinia hordei. Colony area well before first sporulation and uredia size well after the start of sporulation were measured. In a second series two barley and two wheat cultivars were exposed to four different inoculum densities of barley and wheat leaf rust (P. recondita f. sp. tritici), respectively.

Before the sporulation is initiated the colony size was independent of the uredia density. This was valid for densities ranging from approximately 7 to over 200 uredia per cm2 leaf area. After the sporulation had started the uredia size was strongly dependent on the uredia density. The size of the uredia was approximately halved when the uredia density increased from about 10 to about 150 per cm2. The urediospore production per uredium decreased much stronger with increased uredia density.
Amylase Activity May Play a Role in the ‘Pathosmosis’ Thought to Develop in the Areas of Virus Localization in Plants
Authors: Wagih E. E.
Published: May 2008

Tobacco necrosis virus causes both qualitative and quantitative differences in the total soluble protein fraction and amylase isozymes of cucumber (Cucumis sativus L. cv. Beit Alpha MR) cotyledons. A constitutive amylase isozyme with an Rf value of 1.0 on 10 % polyacrylamide gel is detected in both healthy and TNV‐infected tissue. In addition, a major (Rf 0.70) band of amylase activity was located in virus‐infected but not in healthy, abraded tissue. It is proposed that the previously observed osmotic stress conditions prevailing in areas of virus localization (Pathosmosis) is likely to be due to the induced amylase activity with subsequent local accumulation of free sugars. The results presented in this paper may elucidate the biological function of the major component of the γ fraction, a stress‐related protein known to be induced in cucumber cotyledonary leaves following exposure to biotic or abiotic agents.

Amylaseaktivität könnte eine Rolle bei der “Pathosmosis” spielen, von der man glaubt, sich in Bereichen der Viruslokalisierung in Pflanzen zu entwickeln

Tobacco necrosis vims (TNV) verursacht sowohl qualitative wie auch quantitative Unterschiede in der gesamt löslichen Proteinfraktion und Amylase‐Isoenzymen von Gurke (Cucumis sativus L., Sorte Beit Alpha MR)‐Kotyledonen. Ein konstitutives Amylase‐Isoenzym, mit einem Rf‐Wert von 1,0 bei 10%igem Polyacrykmidgel, wurde bei gesunden und TNV‐infiziertem Gewebe beobachtet. Außerdem wurde eine Hauptzone von Amylaseaktivität (Rf 0,70) bei infiziertem, aber nicht bei gesundem, abgeriebenem Gewebe ermittelt. Es wird behauptet, daß die durch osmotischen Streß verursachten Bedingungen im Berdch der Viruslokalisierung (Pathosmosis) wahrscheiniich durch die induzieite Amylaseaktivität, die wiederum zu einer lokalen Ansammlung von freien Zuckem führt, verursacht werden. Die in dieser Arbeit dargesteliten Ergebnisse könnten die biologische Funktion der Hauptkomponente der γ‐Fraktion, ein streßgebundenes Protein, erklären, welches bekannt ist, daß es in Gurkenkotyledonen nach einer Aussetzung zu biotischen oder abiotischen Agenzien induziert wird.
Pectolytic Enzymes from Interactions between Pseudomonas syringae pv. Phaseolicoia and French Bean (Phaseolus vulgaris)
Authors: Longland Annette C. , Slusarenko A. J. , Friend J.
Published: May 2008

Pectolytic enzymes were extracted from both compatible and incompatible interactions between Pseudomonas syringae pv. phaseolicola and French bean. Much lower levels of activity were obtained from control, buffer‐inoculated leaves.

Temperature and pH optima were similar for enzyme extracted from both inoculated and control leaves. Temperature and pH profiles were similar for enzymes from compatible and incompatible interactions, but different from those of the controls.

Enzyme activity in inoculated leaves did not increase until 20 h after inoculation, but then increased rapidly over the succeeding 2–3 days. Activity from control leaves had increased marginally by 48 h after inoculation, but then decreased to about 50 % of the original level.

Enzymes from incompatible and compatible interactions both had pi values of 7.7. Substrate degradation studies and analysis of reaction products indicated that the enzymes were endopolygalacturonases. HPLC indicated that the enzyme from the compatible interaction had a relative molecular mass of approximately 44,000. When injected into leaves the partially purified enzyme was a potent elicitor of phytoalexin accumulation.

Pektolytische Enzyme aus der Wechselwirkung zwischen Pseudomonas syringae pv. phaseolicola und der Gartenbohne (Phaseolus vulgaris)

Pektolytische Enzyme wurden sowohl aus verträglichen als auch aus nicht verträglichen Wechselwirkungen zwischen Pseudomonas syringae pv. phaseolicola und der Gartenbohne extrahiert. Viel niedrigere Aktivitatsgrade wurdcn aus den mit Puffern inokulierten Kontrollblättem ermittelt.

Temperatur‐ und pH‐Optima waren für die Enzyme aus inokuUerten bzw. nicht inokulierten Blänem ähnlich. Temperatur‐ und pH‐Profile der Enzyme aus verträglichen und nicht verträglichen Wechselwirkungen waren ähnlich, aber unterschieden sich von denen der KontroUe.

Die Enzymaktivität in inokulierten Blättem stieg erst 20 h nach der Inokulation an, eine weitere, schneile Steigerung folgte jedoch über die nächsten 2–3 Tage. Bei der KontroUe konnte eine minimale Steigerung 48 h nach der Pufferinokulation ermittek werden, fiel dann aber zuriick auf ca. 50 % des Ausgangswertes.

Die Enzyme aus verträglichen und nicht verträglichen Wechselwirkungen hatten pl‐Werte von 7,7. Substratabbaustudien sowie eine Analyse der Reaktionsprodukte zeigten, daß es sich um EndoPolygalacturonase‐Enzyme handelt. HPLC‐Untersuchungen zeigten, daß das aus den verträglichen Wechselwirkungen stammende Enzym eine relative Molekularmasse von ca. 44 000 besaß. Nach einer Spritzung in Blättern fungierte das zum Teil aufgereinigte Enzym als ein starker Elicitor der Phytoalexinakkumulation.
Bioassay of Toxins as a Diagnostic Method for Pseudomonas syringae Pathovars
Authors: Wei Y. D. , Mortensen C. N.
Published: May 2008

Six pathovars of Pseudomonas syringae were tested for bioassay of toxins. P. syringae pv. syringae and pv. maculicola showed an inhibitory effect on the growth of Escherichia coli in mineral medium. The inhibition for P. syringae pv. syringae was reversed by L‐arginine, not by L‐glutamine and L‐citrulline. It appears that the biochemical target of the toxin(s) from P. syringae pv. syringae is involved in the metabolism of citrulline to arginine in the urea cycle. Under the experimental conditions, the toxin activity was not detected with the isolate of P. syringae pv. phaseolicola in vitro, but the isolate retained it's pathogenicity in a susceptible variety of bean.

Bioassay von Toxinen als Methode zur Diagnostizierung von Pseudomonas syrrngae‐Pathovaren

Die Toxinaktivität von sechs Pathovaren von Pseudomonas syringae wurde in einem Biotest geprüft. P. syringae pv. syringae und pv. maculicola zeigten eine hemmende Wirkung auf das Wachstum von Escherichia coli in Mineralmedium. Die Hemmung von P. syringae pv. syringae wurde durch L‐Arginin aufgehoben, jedoch nicht durch L‐Glutamin und L‐Citrullin. Es scheint, daß die biochemische Erkennungsstelle (Target) des Toxins von P. syringae pv. syringae in Verbindung steht mit dem Metabolismus von Citrullin zu Arginin im Harnstoffzyklus. Unter den Versuchsbedingungen konnte in vitro keine Toxizität bei P. syringae pv. phaseolicola gefunden werden, jedoch behielt das Isolat seine Pathogenität gegenüber einer empfindlichen Bohnenart.
Artenspektrum der Aphidenvektoren des clover yellow vein potyvirus (Kleegelbadrigkeits‐Virus)
Authors: Karl E. , Schmidt H. E. , Giersemehl I.
Published: May 2008

Range of aphid vector species of the clover yellow vein potyvirus

A Central European isolate of the clover yellow vein potyvirus (CYVV) from Trifolium repens L. was tested for its transmissibility by 20 aphid species using Vicia faba L. as virus source and test plant species. All tested aphid species were able to transmit this isolate. Depending on the aphid species, the proportion of infected test plants ranged between 35 and 82.5 per cent. As new vectors of CYVV 17 aphid species were ascertained. The following species could be of special epidemiological importance for the spread of CYVV: Acyrthosiphon pisum (Harr.), Aphis fabae Scop., Aphis nasturtii Kalt., Brevicoryne brassicae (L.), Macrosiphum euphorbiae (Thom.), Metopolophium dirhodum (Walk.), Myzus persicae (Sulz.), and Rhopalosiphum padi (L.).

Ein mitteleuropäisches Isolat des Kleegelbadrigkeits‐Virus (clover yellow vein potyvirus, CYVV) von Trifolium repens L. wurde auf seine Übertragbarkeit durch 20 Aphidenarten untersucht. Als Virusquelle und Testpflanze diente Vicia faba L. Alle geprüften Aphidenarten waren zur Übertragung dieses Isolates befähigt. Der Anteil infizierter Testpflanzen lag je nach Blattlausart zwischen 35 und 82,5 %. Als neue Vektoren für das CYVV konnten 17 Aphidenarten ermittelt werden. Es wird eingeschätzt, daß insbesondere die folgenden Arten für die Ausbreitung des CYVV epidemiologische Bedeutung haben können: Acyrthosiphon pisum (Harr.), Aphis fabae Scop., Aphis nasturtii Kalt., Brevicoryne brassicae (L.), Macrosiphum euphorbiae (Thom.), Metopolophium dirhodum (Walk.), Myzus persicae (Sulz.) und Rhopalosiphum padi (L.).
Wirkung der pflanzengesundheitsfördernden Rhizobakterien Agrobacterium radiobacter und Bacillus sphaerkus auf den Globodera pallida‐Befall der Kartoffel und das Pflanzenwachstum
Authors: Racke J. , Sikora R. A.
Published: May 2008

Influence of the plant health‐promoting rhizobacteria Agrobacterium radiobacter and Bacillus sphaericus on Globodera pallida root infection of potato and subsequent plant growth

The plant health‐promoting rhizobacteria (PHPR) Agrobacterium radiobacter and Bacillus sphaericus as well as a blend of both bacteria were tested under greenhouse and field conditions for their ability to reduce Globodera pallida root infection on the potato cultivar ‘Hansa’. In greenhouse tests the PHPR, sprayed individually, caused a significant reduction (p = 1 %) of approximately 41 % in nematode penetration whereas the blend had no effect on the infection process. Under field conditions the blend caused a significant (p = 1 %) 31 % and the treatment with B. sphaericus alone a significant (p = 1 %) 29 % reduction in penetration. Nematode reproduction was reduced significant by (p = 1 %) 51 % following application of B. sphaericus. The reduction in final cyst number detected in the field trials in the PHPR treatments was not statistically significant. Increased root growth was not observed in either the greenhouse or the field trials. However, tuber yield increased by 18 % and 22 % in the field trials when the tubers were treated with A. radiobacter or the blend, respectively. There was a significant increase (p = 5 %) of 38 % in the number of tubers per plant in the treatment with the blend.

Die pflanzengesundheitsfördernden Rhizobakterien (PGFR) Agrobacterium radiobacter und Bacillus sphaericus sowie deren Mischungen wurden unter Gewächshaus‐ und Feldbedingungen in ihrer Wirkung auf den Globodera pallida‐Befall der Kartoffelsorte Hansa untersucht. Die Einzelbehandlungen der PGFR bewirkten im Gewächshaus eine signifikante (p = 1%) ca. 41%ige Reduktion der Nematodeneindringung, während die Mischung beider Stämme keinen Einfluß zeigte. Im Freiland hemmte dagegen die Mischungsvariante den Befall signifikant (p = 1 %) um 31% und B. sphaericus signifikant (p = 1 %) um 29%. Die Nematodenvermehrung wurde im Gewächshaus durch B. sphaericus signifikant (p = 1 %) um ca. 51 % gemindert. Im Feld ermittelte Reduktionen der Zystenvermehrung nach Behandlung mit PGFR waren statistisch nicht abzusichern. Einflüsse der Bakterien auf das Wurzelwachstum konnten weder im Gewächshaus noch im Freiland festgestellt werden. Der im Freiland ermittelte Knollenertrag war durch A. radiobacter um ca. 18 % und durch die Mischung der Stämme um ca. 22 % erhöht. Die Anzahl der gebildeten Knollen pro Staude war an den mit beiden Bakterien inokulierten Pflanzen signifikant (p = 5 %) um 38 % höher.
Cytopathological, Negative Staining and Serological Electron Microscopy of a Clostero‐like Virus Associated with Pear Vein Yellows Disease
Authors: Giunchedi L. , Pollini C. Poggi
Published: May 2008

Ultrastructural and immunocytochemical studies were made on thin sections of Nicotiana occidentalis leaves systemically infected with a clostero‐like virus associated with pear vein yellows. The virus particles were also studied in negative stain and by the decoration technique.

Virus‐like particles were seen only in mesophyll parenchyma cells, usually arranged in long bundles. An antiserum to apple stem pitting virus gave positive gold labelling of the virion aggregates. Labelling intensity was higher using IgG‐gold than with protein A‐gold. Osmium tetroxide postfixation did not adversely affect the labelling. Virus particle morphology in negative stain resembled that of closteroviruses, although the cytopathic effects in many respects did not resemble those caused by closteroviruses; the cytoplasmic vesicles characteristic of closterovirus infections were not observed.

Zytopathologische negative Färbung und serologische Elektronenmikroskopie eines clostero‐ähnlichen Virus, assoziiert mit der pear vein yellow Krankheit

Ultrastrukturelle‐ und immunozytochemische Untersuchungen wurden an dünnen Schnitten von Nicotiana ocddentalis‐Blättern, die systemisch mit einem clostero‐ähnlichen Virus, assoziiert mit pear vein yellows, infiziert waren, durchgeführt. Die Viruspartikeln wurden auch bei der Negativfarbung und der Dekorations‐Technik untersucht.

Virus‐ähnliche Partikeln wurden nur in Mesophyllparenchymzellen beobachtet, normalerweise in langen Bündeln orientiert. Ein gegen das apple stem pitting virus entwickeltes Antiserum verursachte eine positive Gold‐Markierung der Virionaggregate. Die Intensität der Markierung war mit IgG‐jGold höher als mit Protein‐A‐Gold. Eine Nachfixienmg mit Osmiumtetroxid beeinfiußte die Markierung nicht. Die Viruspartikelmorphologie in der Negativ‐Farbung war die der Closteroviren ähnlich, obwohl die zytopathologischen Einflüsse in vielen Hinsichten den durch Glosteroviren verursachten Einflüsse nicht ähnlich waren. Die zytoplasmatischen Vesikel, die bei Glosterovirusinfektionen charakteristisch sind, wurden nicht beobachtet.
Mode of Action of α, β Unsaturated Carbonyl Compounds
Authors: Larsen J. , Olson L. W.
Published: May 2008

The toxicity of the α, β unsaturated carbonyl compounds (α, β UCCs) (patulin, penicillic acid, parasorbic acid, tulipalin and plumbagin) towards Pythium sp. group F (Van Der Plaat‐Niterinks 1981) was neutralized by the addition of an excess of cysteine. This suggests that the mode of action of these compounds could be due to a binding of the α, βi UCCs to sulphydryl groups in enzymes or other macromolecules. Alcohol dehydrogenase (ADH), an enzyme with a sulphydryl group at the active site, was assayed spectrophotometrically and all the α, β UCCs inhibited ADH.
Symptom Severity, Yield, Seed Mottling and Seed Transmission of Soybean Mosaic Virus in Susceptible and Resistant Soybean: The Influence of Infection Stage and Growth Temperature
Authors: Tu J. C.
Published: May 2008

The effect of soybean mosaic virus (SMV) infection on symptom severity, yield, seed mottling and seed transmission in soybean in relation to the growth stage at infection and subsequent temperature was investigated using a susceptible (Harosoy), a moderately resistant (Evans) and a highly resistant (Merit) cultivar. Disease symptoms were more severe with early infection. A greater reduction in plant growth and seed yield, and higher percentages of mottled seeds and seed transmission of SMV also occurred with early infection. Virus titer was higher in younger plants than in older ones and also higher in plants infected at the ealier stage than at the later stage of growth. Merit (a highly resistant cultivar previously reported to be immune to seed mottling) inoculated at the early stage of plant growth resulted in infection and production of some mottled seeds.

Temperature affected all parameters investigated. The effect of temperature was greater in the susceptible cultivar than in the resistant one. The optimal temperature for symptom severity, yield, seed mottling and seed transmission was 20 °C. Virus titer was highest at 30 °C in all three cultivars. Maturity of susceptible cultivar was delayed by infection.
Some Characteristics of Potyvirus Isolates from Vanilla tahitensis in French Polynesia and the Cook Islands
Authors: Wang Y.‐Y. , Pearson M. N.
Published: May 2008

Further characterization of vanilla mosaic potyvirus (VaMV) confirmed that it is quite distinct from vanilla necrosis potyvirus (VNV). In immuno‐blot ELISA, a polyclonal antiserum to vanilla mosaic virus from Vanilla tahitensis in French Polynesia did not react with vanilla necrosis potyvirus infected V. fragrans from Tonga. However, samples of V. tahitensis with leaf distortion and mosaic from the Cook Islands reacted strongly with the VaMV antiserum. Host range studies involving 20 plant species failed to find a host for VaMV outside the genus Vanilla, confirming that VaMV has a much more restricted host range than VNV. The mean particle length of VaMV from purified preparations was 763 nm (Std. Dev. 48) and SDS‐polyacrylamide electrophoresis indicates a single coat polypeptide of Mr 34 × lO3.
Use of Oospore Formulations of Pythium oligandrum for Biological Control of Pythium Damping‐off in Cress
Authors: McQuilken M. P. , Whipps J. M. , Cooke R. C.
Published: May 2008

Abstrac

Oospore preparations of Pythium oligandrum produced by liquid and solid‐substrate fermentations were evaluated for biocontrol activity against Pythium damping‐off in cress in artificially infested sand and naturally infested soil. Oospore biomass preparations from liquid fermentation of six isolates of P. oligandrum were equally effective in reducing damping‐off in sand when tested as seed‐coatings, whereas this type of preparation of a single isolate formulated as a kaolin dust, on Perlite and as alginate pellets incorporated into sand gave little or no control. None of the formulations containing oospores produced by solid‐substrate fermentation incorporated into sand had any effect. In soil, a formulation containing oospores produced in a barley‐Perlite solid‐substrate fermentation and all oospore‐biomass formulations which were prepared increased seedling survival, but none of these were as effective as a propamocarb HCl drench.
Endogenous Elicitor Present in Barley Seeds
Authors: Hiramoto T. , Tobimatsu R. , Shiraishi T. , Yamada T. , Ichinose Y. , Oku H.
Published: May 2008

Endogenous elicitor(s) present in barley seeds induce the accumulation of antifungal substances effective against powdery mildew fungi. Antifungal substances induced by the treatment with barley seeds extract coincides with the one induced by the inoculation with compatible or incompatible races of powdery mildew fungi on thin‐layer chromatography analysis. The resistance induced by the treatment with barley seeds extract correlates to the accumulation of the antifungal substances in barley leaves. Furthermore, the activity of phenylalanine ammonia‐lyase was also induced by the treatment with barley seeds extract.
Protective Effect of Homologues of Host‐Specific AF‐Toxin I Produced by Alternaria alternata Strawberry Pathotype on Strawberry Cells
Authors: Lee S.‐S. , Tsuge T. , Doke N. , Nakatsuka S. , Nishimura S.
Published: May 2008

The protective effect of homologues of host‐specific AF‐toxin I from Alternaria alternata strawberry pathotype on susceptible strawberry cells was quantitatively examined by using the cultured cells. Among three AF‐toxin molecules, AF‐toxin II did not exhibit toxicity to strawberry cells, although AF‐toxin I and III were highly toxic to the cells. AF‐toxin II protected strawberry cells from AF‐toxin I action. The protection was remarkable when the cultured cells were exposed to excess amounts of AF‐toxin II both prior to and simultaneously with AF‐toxin I addition. The simultaneous treatment, however, was most effective at preventing AF‐toxin I action: it gave complete protection at a 50 : 1 (toxin II : toxin I) ratio on a molar basis. The epoxy‐decatrienoic acid moiety of the AF‐toxins also prevented the cell death caused by AF‐toxin I, but was less effective than AF‐toxin II. Protection was apparent when the cultured cells were exposed to AF‐toxin II for 3 h, rinsed to remove free AF‐toxin II and then exposed to AF‐toxin I. These results suggest that the toxoids of AF‐toxin I, such as AF‐toxin II and the decatrienoic acid, act as competitive inhibitors of AF‐toxin I.