bluuebunny/crossref_metadata_2025 huggingface dataset:
Mastigomycotina Developmental Sensitivity to α, β Unsaturated Carbonyl Compounds
Authors: Larsen J. , Lange L. , Olson L. W.
Published: May 2008

Four α, β unsaturated lactones (patulin, penicillic acid, parasorbic acid and tulipalin) and the naphtoquinone plumbagin, all α, β unsaturated carbonyl compounds α, β UCCs), were tested against members of Chytridiomycetes and Oomycetes distributed among the orders: Blastocladiales (Allomyces, 1 isolate), Saprolegniales (Achlya and Dicthyuchus, 1 isolate each), Peronosporales (Pythium, 18 isolates and Phytophthora, 3 isolates). The effect of the α, β UCCs on the development of the various fungi was tested in aqueous solutions. Development of all of the fungi was inhibited by the five α, β UCCs. Patulin and plumbagin were the most effective; the minimal inhibitory concentration (= MIC) was 10 μg/ml and 5 μg/ml, respectively. No variation in the fungi's sensitivity to patulin and plumbagin was observed. There was a large variation in the sensitivity of the fungi to the other three α, β UCCs. Parasorbic acid showed a variation in MIC from < 1 μg/ml to 500 μg/ml depending on the isolate studied. From the fact that all Mastigomycotina developmental stages were inhibited, it appears that the mode of action of α, β UCCs, is in some fundamental process.

Entwicklungsempfindlichkeit in Mastigomycotina gegenüber α, β‐ungesättigten Carbonylverbindungen

Geprüft wurden vier α, β‐ungesättigte Lactone (Patulin, Penicillinsäure, Parasorbinsaure und Tulipalin) und das Naphtoquinon Plumbagin, alle α, β‐ungesättigte Carbonylverbindungen (α, β ‐ UCCs), gegen Vertreter der Chytridiomycetes und Oomycetes der Klassen: Blastocladiales (Allomyces, 1 Isolat), Saprolegniales (Acblya und Dicthyuchus, je 1 Isolat), Peronosporales (Pytbium, 18 Isolate und Pbytopbtbora, 3 Isolate). Der Einfluß der α, β ‐UCCs auf die Entwicklung der verschiedenen Pilze wurde in wäßrigen Losungen untersucht. Die Entwicklung aller Pilze wurde durch die fünf α, β ‐ UCCs gehemmt. Am wirksamsten waren Patulin und Plumbagin; die minimale Hemmkonzentration (= MIC) lag bei 10 μ/ml bzw. 5 μ/ml. Bei der Empfindlichkeit der Pilzarten gegenüber Patulin und Plumbagin wurden keine Schwankungen beobachtet. Es gab jedoch große Schwankungen in der Empfindlichkeit der Pilzarten gegenüber den anderen drei α, β‐UCCs. Bei der Parasorbinsäure z. B. schwankte der MIC von < 1 μg/ml bis 500 /ig/ml in Abhangigkeit von dem untersuchten Isolat. Daß alle Entwicklungsstadien bei der Mastigomycotina gehemmt wurden, deutet darauf hin, daß der Wirkungsmechanismus der α, β‐UCCs in einem grundiegenden Vorgang liegt.
Lipid Composition of Citrus Leaves from Plants Resistant and Susceptible to Citrus Bacterial Canker
Authors: Jiao H. J. , Wang S. Y. , Civerolo E. L.
Published: May 2008

The contents and composition of lipids in citrus leaves in relation to their general resistance to infection by strains of Xanthomonas campestris pv. citri (Xcc) were determined. The composition and contents of total polar lipids and phospholipids and the degree of fatty acid unsaturation were significantly different between resistant and susceptible species. Leaves from resistant plants had less phospholipids, but more free sterols than those from susceptible plants. The predominant fatty acids in the phospholipids were palmitic (16:0), linoleic (18:2) and α‐linolenic acid (18:3). The degree of fatty acid unsaturation was higher in susceptible plants than in resistant plants. Major phospholipids in citrus leaves were phosphatidylchloline (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidylinositol (PI). β‐Sitosterol, campesterol and lanosterol were major sterols in the leaves of citrus plants with resistant species having a higher ratio of free sterols to total phospholipids than susceptible species. Differences in lipid metabolism may contribute to differences in Xcc‐resistance of citrus leaves.
Purification and Identification of a Rhabdovirus from Thunbergia alata
Authors: Dietzgen R. G. , Gowanlock D. H. , Thomas J. E.
Published: May 2008

A subgroup 2 rhabdovirus was isolated in south‐east Queensland from black‐eyed Susan (Thunbergia alata) with symptoms of vein yellowing, vein clearing and leaf distortion. Bacilliform particles accumulated in the perinuclear space of infected plants and measured 69 ± 7 × 161 ± 8 nm in unfixed preparations. The virus was not transmitted mechanically. Purified preparations of the Thunbergia alata rhabdovirus (TaRV) contained four major proteins with molecular weights of 80 kD, 48 kD, 40 kD and 35 kD, similar to those of datura yellow vein virus (DYW), a newly described rhabdovirus from Australia. The 80 kD protein was identified as the viral glycoprotein. In immunoblots, the two largest proteins of TaRV reacted strongly with antiserum to DYW, but were serologically distinct from sonchus yellow net, cereal chlorotic mottle, potato yellow dwarf and lettuce necrotic yellows viruses. TaRV is considered to be a strain of DYW.
Cell Surface Properties of Pseudomonas syringae pv. phaseolicola Wild‐type and hrp Mutants
Authors: Fett WilliamF. , Osman StanleyF. , Dunn MichaelF. , Panopoulos NickolasJ.
Published: May 2008

The cell surface hydrophobicity and charge as well as surface polysaccharides of eight independent prototrophic hrp::‐Tn5 mutants (Lindgrenet al., J. Bacteriol. 168, 512–522, 1986) were compared to the wild‐type parent strain NPS3121 of Pseudomonas syringae pv. phaseolicola. No significant differences were found in cell surface charge, but mutant strain NPS4005 exhibited significantly lower cell surface hydrophobicity than the wild‐type and the other mutant strains. The mutant strains all retained the ability to produce the exopolysaccharides (EPS) levan, a neutral fructan, and alginate, an acidic polymer. Relative amounts of EPS produced in vitro was dependent on culture conditions. Lipopolysaccharide (LPS) chemotypes were similar for all nine strains. Chemical as well as 13C‐NMR analyses of the O‐antigens from four wild‐type strains of P. s. pv. phaseolicola representing two physiological races as well as the O‐antigens of two strains of P. s. pv. syringae which belong to the same serogroup as P. s. pv. phaseolicola indicated that all of the O‐antigens were very similar if not identical. LPS of three strains of P. s. pv. phaseolicola produced in vitro or in planta were also compared and no significant differences were detected. The altered phenotype of the Tn5 mutants of P. s. pv. phaseolicola does not appear to be due to changes in the ability to produce exopolysaccharides or to an altered composition of cell surface polysaccharides (LPS and EPS). However, a change in an unidentified cell surface component(s) leading to lowered cell surface hydrophobicity of mutant strain NPS4005 may be important.
Effects of Artichoke Latent Virus Infection on the Production of Artichoke Heads
Authors: Rana G. L. , Elia A. , Nuzzaci M. , Lafortezza R.
Published: May 2008

Virus‐free and artichoke latent virus (ALV) infected plants of ‘Brindisino’ artichoke obtained by in vitro propagation, were studied over a period of three years to evaluate the effect of ALV infection on artichoke field performance and to determine the infection rate of healthy plants.

ALV infection caused qualitative and quantitative changes ‘Brindisino’ artichoke such as leaf and bract discoloration, opening of head apex, delay of first harvest, shortening of head stalk, reduction of head width and a dramatic decrease of yield.

Due to the high infection rate of healthy plants during the trial period, the differences in the production of heads between the two groups of plants decreased in the last year of experiment.
Effect of Post‐infection Application of Fungicides on the Apple Scab Pathogen, Venturia inaequalis (Cke.) Wint.
Authors: Thakur V. S. , Gupta C. K. , Garg I. D.
Published: May 2008

The Ergosterol‐biosynthesis inhibiting (EBI) fungicides had a prolonged inhibitory effect on the growth and sporulation of the fungus, Venturia inaequalis thereby preventing development of typical apple scab symptoms. Atypical lesions in the form of chlorotic or reddish brown flecks had reduced viable sporulation with deleterious effect on subcuticular hyphae when fungicide was applied beyond 144 h but before 170h after inoculation. Myclobutanil (45μg a.i./ml) had the maximum inhibitory effect on sporulation and colony growth while bitertanol (187.50 μg a.i./ml) showed only a temporary inhibition of fungal growth and sporulation. Ultra‐structural studies also exhibited different levels of fungitoxicity by different fungicides when applied 144 h after inoculation.
Tomato Mosaic Virus Infection in a Recirculating Nutrient Solution
Authors: Pares R. D. , Gunn L. V. , Cresswell G. C.
Published: May 2008

We studied the behaviour of tomato mosaic tobamovirus (ToMV) in a recirculating nutrient solution. Particles of tomato mosaic virus were found in the nutrient solution 3 days after leaf inoculation of plants and we demonstrated that the level could increase to a concentration readily detectable by electron microscopy. Virions remained infective in nutrient solution for at least 6 months, could infect bait plants and induced systemic symptoms within 10 days. This is the first report of measurement of infective virions in recirculating nutrient solutions. Hydroponic producers should be aware of the potential for rapid spread of virus diseases in soilless growing systems as one infected plant can serve as a source of inoculum that can ultimately result in an epidemic.
Location of Oospores in Buckwheat Seed and Probable Roles of Oospores and Conidia of Peronospora ducometi in the Disease Cycle on Buchwheat
Authors: Zimmer R. C. , McKeen W. E. , Campbell C. G.
Published: May 2008

Oospores of Peronospora ducometi, the causal agent of downy mildew of buckwheat (Fagopyrum esculentum), were found in the calyx remnant attached to the seed, on the inside of the seedcoat and in the spermoderm layer between the seedcoat and the endosperm. This constitutes a first report documenting the location of oospores in buckwheat seed. Systemic infection of seedlings occurred from oospore‐infested seed. Conidial germination was greater at 14°C than 25°C. Systemic infection also occurred as the result of conidial infection of leaves.

It is proposed that primary infection of buckwheat occurs by the germination of seed‐borne oospores resulting in systemic invasion of the seedling by the germtubes, and followed by conidial formation on the cotyledons. Secondary infection occurs initially from conidia produced on the cotyledons as a result of the systemic infection from seed and subsequently as the result of repeated infections by conidia produced on leaf lesions as the disease progresses up the plant.
Artificial Induction and Evaluation of a Mild Isolate of Tomato Spotted Wilt Virus
Authors: Wang Min , Gonsalves Dennis
Published: May 2008

A severe isolate (BL) of tomato spotted wilt virus (TSWV) that originated from Hawaii was treated with nitrous acid in an effort to obtain mild mutants. The standardized procedure used in mutation experiments was: extracting infected Gomphrena globosa L. leaf tissue in 0.01 M Na2SO3, 0.125 M sodium acetate and 0.4 M sodium nitrite at pH 5.5 and incubating the extract for 20 min at room temperature. The extract was inoculated to tobacco (Nicotiana tabacum L. cv. Havana 423) and local lesions were subsequently transferred to lettuce (Lactuca sativa L. cv. Minetto). One isolate (R27G) that incited mild symptoms in lettuce was obtained out of 868 local‐lesion‐transfers. Under greenhouse conditions, the isolate induced mild symptoms on tomato (Lycopersicon esculentum Mill.) but was severe on peppers (Capsicum annuum L.). The effect of the R27G isolate on growth of potted tomatoes kept outdoors was variable. In one trial, only 15 % of the fruit had symptoms versus 67 % in another trial. R27G fully protected Datura stramonium L. plants that were challenge inoculated with the severe parent BL isolate. Less effective cross protection was observed against a severe isolate from Oklahoma.
Determination of the Antigenic Protein Size Associated with Faba Bean Phyllody MLO by Using (SDS‐PAGE) Electrophoresis and Immunotransfer
Authors: Saeed Essam , Rage Pierre , Cousin Marie‐Thérégse
Published: May 2008

The antigenic proteins of MLO associated with faba bean phyllody (FBP) occurring in the Sudan were studied by using SDS‐PAGE electrophoresis followed either by silver nitrate staining or by transferring to nitrocellulose membrane probed with specific polyclonal antiserum. No remarkable differences between healthy and FBP infected plants were observed when the gel was colored with silver nitrate. In contrast, after probing the transferred membrane with the specific polyclonal FBP antisera, band formation was only detected with FBP infected plants. These results were treated through an image analyser using a BIOLAB logicial. The analysed proteins measure approximately 18,000 and 36,000 daltons with regard to the protein molecular weight niarkers used (Bio‐Rad). Possibility of the existence of a dimer is discussed. The localization of the bands is the same whatever the origins of FBP: Vicia faba or Crotalaria saltiana. However, the partial purification of the MLO including differential centrifugations followed by precipitation with polyethylene glycol (PEG) and passage through a column of Sepharose 4B were found to be essential for having clear electrophoretic profiles.
The Isolation and Evaluation of Two Naturally Occurring Mild Strains of Vanilla Necrosis Potyvirus for Control by Cross‐Protection
Authors: Liefting Lia , Pearson Michael , Pone Semisi
Published: May 2008

In an attempt to find mild virus strains that would cross‐protect sgainst vanilla necrosis potyvirus (VNPV), Vanilla fragrans plants in Tonga were surveyed for the presence of mild or symptomless potyvirus infections. Potyviruses were detected by indirect ELISA using a commercially available portyvirus group monoclonal anibody. From 28 plants with mild or symptomless infections two portyvirus isolates, designated V1 and V3, included systemic infections in Nicotiana benthamiana following mechanical inoculation. V1, which causes a mild mottle in N. benthamiana, is serologically related to VNPV, while V3 which causes mild vein banding is serologically unrelated to VNPV. Prior inoculation with V1 protected N. benthamiana against the severe mosaic symptoms of VNPV when challenge inoculated after 14 and 21 days, but not after 7 days. When V3 was used as the protecting strain, cross‐protection was observed in some, but not all plants, when chalenged with VNPV after 14 and 21 days.
Temporal and Spatial Development of Papaya Ringspot in Veracruz, Mexico
Authors: Mora‐Aguilera Gustavo , Téliz Daniel , Campbell C. Lee , Avila Catarino
Published: May 2008

The temporal progress and spatial distribution of papaya ringspot virus (PRV) and populations of aphid vectors were monitored in two papaya (Carica papaya) plantations in the state of Veracruz, México. The incidence of PRV had a typical sigmoidal curve and the logistic model was more acceptable for describing the disease progress than the Gompertz model. The rate (rL of increase in disease incidence (0.034 and 0.023/unit/day in Plot A and B, respectively) differed (P = 0.05) between the plots; differences in number of aphids trapped could account for the difference. The initial determination of an apparent regular spatial pattern early in the epidemic, obtained with a quadrat size determined by Greig‐Smith's method (n = 8 plants/quadrat) at 50 % disease incidence, was inconsistent with our biological observations in the field. An arbitrarily selected, square quadrat size (n = 9 plants/quadrat), was more consistent with visual observation for describing the spatial pattern in the field. With 9 plants/quadrat a random pattern was found. Aphid populations had a bimodal distribution at both sites with the highest population peak in December–February and a secondary peak in August–September and change in disease incidence was generally related to the aphid population level in the previous month. None of the five potential aphid vectors (Myzus persicae, Aphis gossypii A. nerii, A. citricola and Macrosiphon euphorbiae) of PRV in Mexico colonized the papaya plants, however, which may explain the absence of clustering of disease.
Comparing the Effects of Rust on Plot Yield, Plant Yield, Yield Components, and Vegetative Parts of Soybean
Authors: Yang X. B. , Dowler W. M. , Tschanz A. T. , Wang T. C.
Published: May 2008

To determine the plant variable for coupling a disease model to a soybean growth model, effects of soybean rust (caused by Phakopsora pachyrhizi) on soybean were quantified at four levels: vegetative parts, yield components, plant yield, and plot yield. Path analysis was conducted to determine the most correlated components to disease in each level. The responses of vegetative parts, such as shoot weight and branches/plant, to disease effects were inconsistent among cultivars. Yield components responded consistently to disease effects among the cultivars, indicated by the high values of correlation coefficients between disease and the components. Path coefficients indicated that reduction of 100‐seed weight was the most important cause of yield loss in this level. No significant within‐plant compensation was detected using path coefficient analysis except for that between pod length to pod width. The most consistent response to disease effect was at population level. Correlation of disease to plant yield was as significant as these to plot yield. Correlations between disease and these plant levels were in the order of plot yield, plant yield, yield components, and vegetative parts. Regression between plot yield and green leaf area duration (GLAD) from flowering to seed full size was highly significant (P < 0,001). This study suggests that green leaf area at population level was the best variable for coupling disease model to crop model.
Infektionsstrukturen von Microdochium bolleyi an Wurzeln und Koleoptilen von Gerste
Authors: Hemens E. , Steiner U. , Schonbeck F.
Published: May 2008

Infection structures of Microdochium bolleyi on barley roots and coleoptiles

Microdochium bolleyi grows within roots and coleoptiles of barley either leading to a damage of the tissue or to a symptomless infection. The present work investigated whether these different types of infection are correlated with different infection structures of the fungus. Two types of hyphae were formed infectmg either the rhizodermis or the epidermis. The fungus spread within the cortex only, not affecting the endodermal cells or the vascular tissue. The extend to which the roots were damaged depended on the infection density. Differences in the structure of hyphae formed in symptomless or necrotic parts of the roots were not observed. In both, roots and coleoptiles, hyphae were detected in dead cells only.
The Activation of Latent Infections of Monilinia fructicola on Apricots by Volatiles from the Ripening Fruit
Authors: Cruickshank R. H. , Wade G. C.
Published: May 2008

Latent infections produced by Monilinia fructicola on green apricot fruit are separated from aqueous contact with live host tissues by hydrophobic suberin. However, they respond to host ripening and become invasive. The time and intensity of production of the volatile compounds acetaldehyde and ethanol during fruit ripening strongly correlated with both the invasive outbreak of mycelium from arrested lesions, and with the stimulation of growth of germ tubes in vitro in the presence of fruit volatiles. Latent infections on green apricots were activated to escape from the lesions in response to exposure to those volatiles in the concentration detected from ripe apricots. However, the tissue of green apricots was stimulated to fresh necrosis and general fruit invasion did not occur.
Random Primer Dependent PCR Differentiates Aggressive from Non‐Aggressive Isolates of the Oilseed Rape Pathogen Phoma lingam (Leptosphaeria maculans)
Authors: Schäfer C. , Wöstemeyer J.
Published: May 2008

A number of isolates of the aggressive an d non‐aggressive pathotype group of the rape seed (Brassica napus) pathogen Phoma lingam (teleomorph: Leptosphaeria maculans) were analyzed by means of a simple, random primer dependent PCR (polymerase chain reaction) approach. Using the four synthetic nona‐ and decamer oligonucleotides 5′‐GGAGCCCAC‐3′, 5″‐ACGGTCTTGG‐3′, 5′GAAACAGCGG‐3′, and 5′‐GGCATCGGCC‐3′ informative bands for both of the pathotype groups could be obtained. These amplified bands were shown to originate not only from repeated but also from single and low copy target sequences. This is the first report on molecular diagnostics of a plant pathogenic fungus, based on random primer dependent PCR. The experimental system is fast and reliable, does not require cloning and sequencing of L. maculans DNA, and works without time‐consuming blotting or hybridization steps.
Development of a Method to Obtain Monospecific Antibodies Directed Against a 31 kD Protein of Pseudomonas syringae pv. syringae
Authors: Niepold F.
Published: May 2008

We describe a simple method of purifying Pseudomonas syringae pv. syringae (P. s. pv. s.) specific polyclonal antibodies which are directed against a cell surface protein sized 31 kD. The actual purification step of the polyclonal antibodies occurs with denatured proteins after an SDS‐PAGE gel electrophoresis and western blotting. Polyclonal antibodies were obtained which recognized a 31 kD protein. On a western blot no cross reaction of the purified polyclonal ‘monospecific 31 kD antibodies’ with other proteins from the same strain was observed. However, a positive “monospecific 31 kD antibody” reaction was only visible when either protein extracts from several selected pathogenic P. s. pv. s. strains from different hosts, or two isolates of Pseudomonas syringae pv. pisi (P. s. pv. p.) were used. An indication that this 31 kD protein is specific to P. s. pv. s. is that no cross reaction was found with protein extracts from the tested pathogenic and non‐pathogenic pseudomonads. However, a differentiation of the tested P. s. pv. s. and P. s. pv. p. isolates was possible when cells were grown above 30 °C. Then protein extracts from P. s. pv. s. revealed the lack of the 31 kD protein but not P. s. pv. p. protein extracts. Polyclonal antibodies raised in rabbits against the 31 kD protein band from the western blot proved to be specific enough to agglutinate whole P. s. pv. s. strain R32 cells or for detecting a single 31 kD protein band on a western blot when whole cell protein extracts of P. s. pv. s. strain R32 were used.
Inhibition of Rust Diseases of Cereals by Metabolic Products of Verticillium chlamydosporium
Authors: Leinhos G. M. E. , Buchenauer H.
Published: May 2008

Verticillium chlamydosporium produced in submers culture several antifungal and/or phytotoxic compounds which were detected in a bioassay by using the pathogen‐host system Puccinia coronata and oat seedlings. The antifungal compounds were also tested against P. recondita on wheat and P. sorghi on corn seedlings. The production of the active metabolic compounds highly depended on the nutrient solution (peptone‐Czapek [PC] and malt extract [ME]) and on the fermentation times. Cell‐free filtrates of PC‐cultures of the fungus were highly phytotoxic; the fungitoxic and phytotoxic compounds were heat‐labile and dialyzable. The ethyl acetate extracts of the PC‐culture filtrates contained only the antifungal active substances. The antifungal compounds in ME‐culture filtrates proved to be heat‐stable, could be dialyzed and extracted with ethyl acetate. Ethyl acetate extracts of PC‐ and ME‐culture filtrates at concentrations of 500 μg/ml reduced rust disease incidence by up to 80 % compared to the control treatment.

Further studies with extracts of ME‐culture filtrates displayed a distinct protective but no systemic activity. The extract interfered with the development of several infection structures of the rust fungi, mostly with the growth of germ tubes as well as with the formation of the aappressoria and haustorial mother cells. Three rust‐active fractions were obtained by preparative layer chromatography on silica gel. One of these fractions exhibited phytotoxic activity. The most active antifungal fraction is identical with the macrolid antibiotic monorden which caused a desorientated spiral growth in P. coronata germlings on oat leaves.
The Role of Phytophthora cryptogea and Waterlogging in Root Rot Kiwifruit
Authors: Stewart A. , McCarrison A. M.
Published: May 2008

A 48 h or 96 h period of waterlogging induced a partial rotting of the root system of 18 month old potted kiwifruit cuttings. However, root regeneration compensated for the loss of damaged roots and the plants remained healthy. Inoculation with Phytophthora cryptogea under low soil moisture conditions caused a small amount of root rotting (11 %) and regeneration of the roots occurred. Root rot was significantly increased when inoculations were combined with extended periods of waterlogging. Root rot incidence was highest (89 %) in inoculated plants exposed to periods of 96 h waterlogging. Regeneration did not occur with any of these plants and consequently, the shoot systems were severely damaged.
Effects of Commercial Fatty Acids on Cutinase Release by Ascochyta pisi
Authors: Nasraoui B. , Lepoivre P. , Semal J.
Published: May 2008

The effect of a range of commercially available C16 and C18 fatty acids, on the release of cutinase by Ascochyta pisi, was studied. When juniperic acid was used as sole carbon source, cutinase activity was released in the culture medium, and was markedly enhanced by post‐treatment of A. pisi cultures with acetone used as enzyme extractor. Without acetone, less cutinase was naturally released in culture medium containing juniperic acid at 0.5 %, than at 0.0l % or 0.05 %. Upon post‐treatment with acetone, the same level of cutinase was released with all three concentrations, thus suggesting that the enzyme was induced, but not completely released in the presence of 0.5 % juniperic acid. When ricinelaidic or ricinoleic acids were supplemented at 0.5 % to cutin in the culture medium, they strongly inhibited the release of cutinase, even with acetone post‐treatment. Comparable inhibition by ricinoleic acid was also observed when juniperic acid was used as cutinase inducer, thus suggesting that not only the release, but also the production of cutinase were inhibited.
Mycoplasma‐like Organisms in Phloem Elements of Ammobium alatum
Authors: Chang K. F. , Mirza M. , Hwang S. F.
Published: May 2008

Using transmission electron and fluorescent microscopes, Mycoplasma‐like organisms (MLOs) were found in phloem cells of stems and leaves of Ammobium alatum. The diameter of these organisms ranged from 0.12–0.73 μm and averaged 0.4 μm. Symptoms induced by MLOs included chlorosis and reddening of leaves and winged stems, plant stunting and flower phyllody. This is the first report of MLOs associated with disease symptoms in A. alatum.
Isolation and Partial Characterization of a Tenuivirus from Wheat in Iran
Authors: Heydarnejad J. , Izadpanah K.
Published: May 2008

A tenuivirus, tentatively designated Iranian wheat stripe virus (IWSV), was transmitted by the delphacid Unkanodes tanasijevici and induced dwarfing, striping and yellowing symptoms in wheat. It could also infect barley, oat, rice, rye, sorghum and a number of other gramineous species. The virus was purified from wheat by chloroform clarification and differential and density‐gradient centrifugation. It formed several layers in density‐gradient columns. Purified virus preparations had a UV absorption spectrum typical of nucleoproteins and contained flexuous supercoils of 8.7 nm and fine filaments of 4.3 nm width. The antiserum produced against the virus reacted with infected plant sap in agar‐gel diffusion and enzyme‐linked immunosorbent assay (ELISA). The virus could be readily detected in individual viruliferous planthoppers by ELISA. IWSV was serologically related to rice hoja blanca virus but not to maize stripe virus. The relationship of IWSV with other tenuiviruses is discussed.
Growth Characteristics in Cultured Cucumber Tissues Infected with Hop Stunt Viroid
Authors: Takahashi T. , Ghiba K. , Ozaki R. , Sadakata H. , Andoh Y. , Yoshikawa N.
Published: May 2008

Leaf disks from hop stunt viroid (HSVd)‐infected cucumber plants and healthy controls were cultured in vitro under different auxin/cytokinin regimes. Amounts of tissue growth and root formation were consistently reduced as a result of HSVd infection. Histological observations indicated that anomalies in the distribution of peripheral meristems and tracheary elements associated with cambial cells might be involved in the hypoplastic syndrome incited by HSVd.
Fatal Yellowing of Oil Palms: Search for Viroids and Double‐Stranded RNA
Authors: Beuther E. , Wiese U. , Lukáacs N. , van Slobbe W. G. , Riesner D.
Published: May 2008

Fatal yellowing is a serious disease of still unknown origin affecting oil palms in several regions of Central and South America. In this study a search for viroids and viroid‐like RNAs in oil palms was performed using two‐dimensional gel electrophoresis and return gel electrophoresis of nucleic acid extracts. Although RNAs showing viroid‐like gel‐electrophoretic properties were detected, the presence of the known viroids was excluded by hybridization experiments using probes specific for potato spindle tuber viroid (PSTVd), coconut cadang‐cadang viroid (CCCVd), or Coleus blumei viroid 1 (CbVd1). By using double‐stranded RNA (dsRNA) specific monoclonal antibodies, which do not react with viroid RNA, we were able to show that oil palm RNAs, migrating like viroids are double‐stranded RNA species. Since the same dsRNA pattern was found in extracts from diseased as well as from healthy oil palms, the dsRNAs can neither be part of the causative agent of fatal yellowing, nor are they associated with the disease. Their possible origin is discussed. In addition to the standard electrophoretic methods, which have been used for identification of viroids and viroid‐like RNAs, we describe additional control experiments to differentiate unequivocally between circular single stranded and linear dsRNA.
Ultrastructural Histopathology of Infection and Colonization of Maize by Stenocarpella maydis (= Diplodia maydis)
Authors: Bensch M. J. , Van Staden J.
Published: May 2008

The mode of penetration and colonization of stalk, shank and leaf sheath tissues of maize by Stenocarpella maydis (=Diplodia maydis) was determined by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) observations. Detached plant tissues, inoculated with a conidial suspension and examined by SEM at various intervals, showed that S. maydis conidia germinated on all plant material types after 5 h incubation at 30 °C. After 72 h incubation, appressoria had formed at the hyphal tips. Similar observations were recorded on plants inoculated in the glasshouse except that germination was delayed by 7 days after inoculation. TEM studies showed that penetration was affected by a penetration hypha which resulted in the inter‐ and intracellular colonization of the plant tissues. Colonization was accompanied by degradation of cell walls suggesting that host colonization is facilitated by enzyme activity.
The Role of Polyphenol Oxidase and Peroxidase in Potato Tuber Resistance to Soft Rot Caused by Erwinia carotovora
Authors: ŁOjkowska E. , Hołubowska M.
Published: May 2008

Tubers from somatic hybrids produced by protoplast fusion between Solanum brevidens, a diploid, non‐tuber‐bearing wild species, and a tetraploid S. tuberosum showed resistance to decay caused by soft rot Erwinia. Tubers of the S. tuberosum fusion parent and potato cultivar Russet Burbank are susceptible to bacterial soft rot. Tubers of somatic hybrids indicated higher levels of activities of polyphenol oxidase and peroxidase than tubers of the parental line of S. tuberosum and cultivar Russet Burbank. This is true for intact tubers and also for injured or inoculated tubers.

Polish commercial potato cultivars indicated a higher susceptibility to soft rot than somatic hybrids. However, there were some differences in susceptibility to soft rot between Polish commercial potato cultivars, only slight differences were observed in the activities of the polyphenol oxidase and peroxidase between Polish cultivars. A relation between soft rot resistance and the activity of each enzyme was not found for intact, injured or inoculated tissue of commercial cultivars. On the contrary, the activities of both enzymes were significantly higher in the periderm than in the medullary tissue of somatic hybrids, the parental line and the commercial cultivars.
Isolation and Pathogenicity of Rhizosphere Fungi of Cocoyam in Relation to Cocoyam Root Rot Disease
Authors: Pacumbaba R. P. , Wutoh J. G. , Eyango Sama Anne , Tambong J. T. , Nyochembeng L. M.
Published: May 2008

Cocoyam is the second most important staple crop of Cameroon and root rot is a destructive disease of this plant. Pythium myriotylum (Pm), Fusarium solani (Fs), and Rhizoctonia solani (Rs) were isolated from the rhizosphere of root rot affected cocoyams and from the soil of a cocoyam experimental field plot temporarily devoid of same in Mamu, Cameroon. Pm was isolated from the above soil by the cocoyam leaf disc baits. Fs and Rs were also isolated from the same soils by the water dilution method and from the roots of diseased cocoyams but were always associated with mycelial growth of Pm. Pathogenicity of Pm and in combinations with Fs or Rs or Fs + Rs all developed cocoyam root rot disease (CRRD) symptoms on 3– and 7–month old cocoyam plantlets 2–7 days after inoculation. Symptoms included rotted roots and wilting with general chlorosis of inoculated plantlets. No symptoms of CRRD were noted on cocoyam plantlets inoculated with Fs, Rs, Fs + Rs, and distilled water. Results indicated that CRRD is not caused by several pathogens but only by Pm. Pm isolates from the soils and roots of diseased cocoyams and those maintained in the ROTREP laboratory have significantly bigger diameter of mycelial colony growth in 24 h–period at 31 °C on lima bean sucrose agar, V–8 juice sucrose agar, and potato sucrose agar than on potato dextrose agar and 2 % water agar. The cocoyam plantlets were raised axenically from tissue culture of explants in the laboratory.
The Effect of Glomus mosseae and Enterobacter aerogenes on Apple Seedlings Grown in Apple Replant Disease Soil
Authors: Utkhede R. S. , Li T. S. C. , Smith E. M.
Published: May 2008

Inoculation of apple seedlings with the mycorrhizal fungus Glomus mosseae significantly increased their growth in apple replant disease soil that was neither pasteurized nor fertilized with monoammonium phosphate. The application of Enterobacter aerogenes and peat suppressed the stunting effect observed in apple replant disease soil. These results suggest the potential of using G. mosseae alone or a E.aerogenes and peat combination for the control of apple replant disease.
Purification and Characterization of Indian Cassava Mosaic Virus
Authors: Mathew A. V. , Muniyappa V.
Published: May 2008

The Indian cassava mosaic virus (ICMV) was transmitted by the whitefly Bemisia tabaci and sap inoculation. ICMV was purified from cassava and from systemically infected Nicotiana benthamiana leaves. Geminate particles of 16–18 × 30 nm in size were observed by electron microscopy. The particles contained a single major protein of an estimated molecular weight of 34,000. Specific antiserum trapped geminate particles from the extracts of infected cassava and N. benthamiana plants in ISEM test. The virus was detected in crude extracts of infected cassava, ceara rubber, TV. benthamiana and N. tabacum cv. Jayasri plants by ELISA. ICMV appeared serologically related to the gemini viruses of Acalypha yellow mosaic, bhendi yellow vein mosaic, Croton yellow vein mosaic, Dolichos yellow mosaic, horsegram yellow mosaic, Malvastrum yellow vein mosaic and tobacco leaf curl.
Leaf Spot of Hemp Dogbane Caused by Stagonospora apocyni, and its Phytotoxins
Authors: Venkatasubbaiah P. , Baudoin A. B. A. M. , Chilton W. S.
Published: May 2008

Stagonospora apocyni causes a leaf spot disease on hemp dogbane (Apocynum cannabinum L.). The fungus produced phytotoxins citrinin, mellein, tyrosol and α–acetylorcinol in liquid culture. All toxins caused necrosis when placed on leaves of hemp dogbane, and eight other weed species. All four toxins were non–specific phytotoxins. Citrinin showed antimicrobial properties against some bacteria and fungi.
Blossom–end Rot of Pears: Systemic Infection of Flowers and Immature Fruit by Botrytis cinerea1
Authors: de Kock Selma L. , Holz G.
Published: May 2008

A histological study was made of the systemic growth of Botrytis cinerea from styles, stamens and sepals to the flower receptacle and mesocarp of immature pear fruit. In most styles, hyphal growth ceased in the upper portion at the onset of stylar senescence, which occurred at about 1 wk after full bloom. Hyphae never passed through styles into the carpel. Unlike the styles, hyphae in filaments grew without restriction and progressed within 4 days, via vascular tissue, through sepals into tissues of the upper end of the flower receptacle, or of the mesocarp adjoining the sepals, without causing symptoms. Filaments remained green to partly green until harvest. B. cinerea entered filaments and spread into the receptacle or mesocarp at any time between blossoming and harvest and then became latent in these tissues. Filaments were, however, more susceptible at the flowering stage. After 2 months floral tubes were closed, and the stamens protected from infection. Careful inspection of ripe, cold–stored fruit showed that decay invariably spreads from mesocarp tissue adjoining the sepals, outward along the vascular bundles, but not from secondary inoculum in the floral tube. The behaviour of the pathogen suggests that control of blossom–end rot could be achieved if pears are sprayed with fungicide at 75—100% petal fall (when most stamens are exposed) and a month later (before floral tubes started to close).
Interactions Between Race 2 of Fusarium oxysporum f. sp. Lycopersici and Near‐Isogenic Resistant and Susceptible Lines of Intact Plants or Callus of Tomato 58731 F71 137
Authors: Kroon B. A. M. , Elgersma D. M.
Published: May 2008

The interaction between Fusarium oxysporum f. sp. lycopersici race 2 and near‐isogenic resistant and susceptible tomato lines of the cultivar Moneymaker and callus cultures derived from these lines was studied. Resistance was expressed in callus tissue for a short period, during 4 days after inoculation. This was shown by a delay in fungal growth on callus tissue derived from resistant plants. Accumulation of the phytoalexin rishitin was similar in callus tissue and whole plants. Tomato plants resistant to race 2 did not accumulate more rishitin than susceptible plants during the first 4 days after inoculation, in contrast to plants resistant to race 1 and inoculated with race 1. The different response of tomato plants and calli towards race 1 and 2 of F. oxysporum f. sp. lycopersici suggests that the mechanism of resistance controlled by the 1–1 and the 1–2 gene is different. Callus tissue might be useful to study these differences in resistance.
About Changes in the Chromatin Structure after Resistance Induction in Hordeum vulgare L.
Authors: Kraska T. , Schönbeck F.
Published: May 2008

The application of the three resistance inducers Trigonelline (N‐Methyl‐nicotinic acid), Isonicotinic acid methyl ester and the culture filtrate of Bacillus subtilis (B 50) to barley resulted in a reduction of infection with powdery mildew up to 65 %. When the isolated high molecular‐weight DNA was hydrolized to single bases the genomic DNA methylation of induced resistant plants was reduced between 3.1 % and 4.8 % compared to the control. On the basis of the given results the hypothesis that inducers could change the DNA structure is discussed considering further information from literature about gene regulation.
Studies of Polyclonal Antibodies for the Detection of MLOs Associated with Faba Bean (Vicia faba L.) Using Different ELISA Methods and Dot‐blot
Authors: Saeed Essam M. , Roux Jacqueline , Cousin Marie‐Thérèse
Published: May 2008

Polyclonal antibodies were raised in rabbits against MLO associated with faba bean (Vicia. faba L.) phyllody which exists in the Sudan. Two indirect ELISA methods were able to detect the MLO antigens. In the former, the whole antigen was directly coated onto plates, while in the second, only the F(ab')2, fragments of the IgG were used to coat the ELISA plates. Higher detectable efficiency was obtained when the F(ab')2 method was used. Moreover the obtainable antiserum was found to exhibit a high degree of specificity through which the MLO associated with faba bean phyllody in the Sudan, are serologically differentiated from other isolates of MLO existing in the Sudan as well as European MLO isolates maintained at Versailles, and Spiroplasma citri, causal agent of Citrus Stubborn Disease. The positive reactions obtained with this antiserum against MLO phyllody naturally existing in the Sudan on Crotalaria saltiana and some Catharanthus roseus demonstrate that these plants are potential reservoirs of the disease in the Sudan. The same antiserum was used in order to distinguish healthy and diseased plant preparations using the membrane ELISA method (dot‐blot).
Occurrence of Mosaic Mottle, a Viroid Disease of Pigeonpea (Cajanus cajan) in India
Authors: Bhattiprolu S. L.
Published: May 2008

During investigations of viroid diseases of food crops in Delhi, India, an infectious low‐molecular‐weight RNA (Mr 1.3 × 105) was isolated from pigeonpea (Cajanus cajan) plants showing mosaic mottling and reduced size of leaves, stunting and no flowering. This RNA infected mechanically inoculated C. cajan, Chenopodium amaranticolor, Nicotiana glutinosa, and N. clevelandii. The causal agent, for which the name pigeonpea mosaic mottle viroid (PMMVd) is proposed, differed from N. glutinosa stunt viroid (NgSVd), the only viroid reported to infect legumes, in size and symptom expression on the original host species.
Cytopathology of Lettuce Mosaic Virus‐infected Lettuce Seeds and Seedlings
Authors: Hunter D. G. , Bowyer J. W.
Published: May 2008

The ultrastructure of lettuce mosaic potyvirus (LMV)‐infected lettuce seeds and seedlings was studied by transmission electron microscopy. Conventional thin‐section electron microscopy and immunogold cytochemistry were both successfully employed to study the location of LMV in embryonic and non‐embryonic seed parts. LMV particle aggregates and cytoplasmic “pinwheel” inclusions characteristic of potyviruses were observed throughout the embryonic tissues (radicle, hypocotyl and cotyledon) of infected lettuce seeds and seedlings, and also in the non‐embryonic endosperm layer. LMV particles, but not inclusions, were also located in the non‐embryonic pericarp layer.
Cucumber Vein Yellowing Virus; Host Range and Virus Vector Relationships
Authors: Mansour A. , Al‐Musa A.
Published: May 2008

Cucumber vein yellowing virus (CVYV) is transmitted by Bemisia tabaci, it has a narrow host range restricted to some cucurbitaceous plants including Cucumis sativus, C. melo, C. melo var. flexousus, Cucurbita pepo, C. foesti, Citrullus vulgaris, C. colocynthis and Lagenaria siceraria.

Although a single whitefly can transmit the disease, the efficiency of transmission was low. At least 15–20 insects per plant were required to cause an infection of 55 % of inoculated plants. The minimum acquisition and inoculation feeding periods were 30 and 15 min, respectively.

The latent period in the vector is about 75 min and the whitefly was infectious for not more than 5 h.
Serological Specificity of the Lipopolysaccharides, the Major Antigens of Pseudomonas syringae
Authors: Guillorit Christians , Samson Regine
Published: May 2008

The nature of major antigens of Pseudomonas syringae was studied on one strain of four pathovars (pvs aptata, mors‐prunorum, phaseolicola and tabaci) belonging to four separate serogroups. Bacterial antigens were prepared by 4 procedures: extraction by phenol‐water (PW), by citrate‐NaCl (CN), by trichloracetic acid (TCA), and precipitation of a glycoproteic extracellular complex (GP). 3‐Deoxy‐2‐octulosonic acid (KDO) revelation in all the extracts showed that the four procedures led to antigens containing similar amounts of lipopolysaccharide (LPS). Twenty polyclonal antisera were raised in rabbits against whole bacteria and the different extracts. Serological reactions were tested by gel double diffusion (DD) and indirect immunofluorescent staining (IF).

The anti‐whole cell sera were shown to contain mostly anti‐LPS antibodies. For each pathovar, whole bacteria used as antigens in DD gave precipitation bands identical to the bands given by the LPS extracts (PW, CN or TCA), identical to the heated bacteria (HB), and identical to LPS sidechain preparations. The GP extract itself was shown to be rich in LPS. To serotype P. syringae, it is advised to raise antisera against either whole bacteria or GP extracts; whereas the reacting antigens for DD would be heated bacteria.
Etiology of a Root Rot Disease Complex of Alstroemeria in Alberta, Canada
Authors: Chang K. F. , Mirza M. , Hwang S. F.
Published: May 2008

Fusarium oxysporum, Pythiu‐m ultimum, and Rhizoctonia solani were isolated from the basal stems of diseased alstroemeria showing symptoms of dark brown stripes along leaf margins, leaf chlorosis, plant wilting, browning or rotting of basal stem, rhizome, and storage and fibrous roots. The pathogen isolated most frequently was Fusarium spp. (40.5 % of plants examined). Pythium spp. and R. solani were isolated less frequently (5.5 % and 6.8 % of plants examined, respectively). F. oxysporum caused the highest mortality in alstroemeria when rhizomes were grown in unsterilized soil‐less mix medium. This is the first report in North America of a root‐rot disease complex affecting alstroemeria.
Chalara elegal‐Infected Tobacco Roots: Ultrastructural Observations on in vitro Host‐Fungus Relationships
Authors: Tahiri‐Alaoui A. , Gianinazzi S. , Dumas‐Gaudot E.
Published: May 2008

Evidence, based on ultrastructural observations of stages involved in root infection oi Nicotiana tabacum cv. Xanthi n.c. in vitro by the black root rot fungus Chalara elegans, indicates that host cells from various layers react differently when challenged by the pathogenic fungus. All the host responses observed were associated with host cell wall modifications. Host reaction to fungal invasion occurring in the epidermal cells was limited to a disorganization of the cytoplasm. In the hypodermal cell layer, fibrillar cell wall outgrowths and wall thickenings were the earliest and the most obvious host reactions. In parenchymal cells, the host reacted by depositing papilla‐like wall appositions directly adjacent to the infecting hyphae; with secondary infection of these cells, a densely staining material was laid down, mainly around the distal region of the infecting hyphae. In all these tissues, infection also led to disorganization of the host cytoplasm. Colonization of the endodermis did not lead to any rapid lethal modifications in either the host or the fungus, and a biotrophic‐like state seemed to occur at this stage of the infection. No hyphal infection occurred in the central cylinder.
Strains of Peanut Stripe Potyvirus Rapidly Identified by Profiling Peptides of the Virion Proteins
Authors: Kittipakorn Kruapan , McKern Neil M. , Gibbs Adrian J. , Shukla Dharma D.
Published: May 2008

Virion proteins of five potyvirus isolates from groundnut in Thailand which induce a range of symptoms were compared with those from the type strains of peanut stripe potyvirus (PStV) and peanut mottle potyvirus (PeMoV). Profiles obtained by high performance liquid chromatography (HPLC) of tryptic peptide digests of the virion proteins of all five Thai isolates and PStV were very similar, whereas that of PeMoV was quite different. The results indicate that the Thai isolates are strains of PStV, and reaffirm the value of HPLC peptide profiling for rapidly identifying potyviruses.