bluuebunny/crossref_metadata_2025 huggingface dataset:
Population Tendencies of Pseudomonas cichorii and P. syringae pv. garcae in Young and Mature Coffee Leaves
Authors: Oliveira J.R. , Romeiro R.S. , Muchovej J.J.
Published: May 2008

The population tendencies of Pseudomonas cichorii and P. syringae pv. garcae in young and mature coffee leaves were determined by inoculating streptomycin resistant bacterial cells from 24 h cultures into young and mature coffee leaves. The leaves were then sampled daily for 5 days and the number of bacterial cells per g of leaf tissue was determined. Pseudomonas cichorii increased in mature leaves only while P. syringae pv. garcae increased in young leaves. Symptom development was dependent on the presence of a large number of bacterial cells in the host tissue and coincided with the maximum content of bacterial cells in the leaf.
Comparative Ultrastructural Observations of Plasmalemmasomes in PSTVd‐Infected Healthy and Artificially Stunted Tomato Leaves
Authors: Gruner R. , Santore U. J.
Published: May 2008

Plasmalemmasomes were observed in leaves of healthy, PSTVd (potato spindle tuber vroid) infected and artifically stunted tomato plants. Their shape and distribution could not be clearly related to infection with PSTVd as previously suggested. These membranous proliferations were suggested to represent one of the normal physiological responses of the plants to a multitude of possible exogenous influences.
A Comparative Study of the Effects of Five Chemicals on the Survival of Chlamydospores of Fusarium oxysporum f. sp. narcissi
Authors: Linfield Christine A.
Published: May 2008

Formaldehyde is routinely used in hot water treatment for the control of narcissus basal rot (caused by Fusarium oxysporum f. sp. narcissi) and stem and bulb eelworm (Ditylenchus dipsaci). It does not kill all the thick walled chlamydospores of F. oxysporum. Four chemicals were evaluated for their efficacy against F. oxysporum by comparing them with the standard formaldehyde rate. At rates of 0.25% a.i. or more, a glutaraldehyde formulation (Cidex) killed 100% of spores within 160 min. Peratol, a hydrogen peroxide and peracetic acid containing formulation, gave 100% kill after 80 min at a concentration of 0.5%. A thiabendazole formulation (Storite Clear Liquid) killed all the chlamydospores. Decon 90 failed to control the fungus adequately.

Formaldehyde (as 0.5% commercial formalin) gave good, but not total, control of the fungus but, at higher rates (2.5%), caused flower malformation and corkiness of bulb base plates.

The results suggest that Cidex and Peratol, as they are more effective than formaldehyde in controlling the fungus and less unpleasant to use, may be suitable replacements.
A Pathotype Classification for Mycosphaerella pinodes
Authors: Clulow S. A. , Lewis B. G. , Matthews P.
Published: May 2008

Genetic variation of Mycosphaerella pinodes in the pathogenesis of Pisum sativum is described for the first time. On a particular host line, isolates varied from those producing a few necrotic flecks to those causing large lesions on stems or leaves. Based on reactions of nine differential host lines, 45 isolates from a wide range of geographical locations could be classed, by stem symptoms, into 9 groups or, by leaf symptoms, into 16 groups.
Cellulolytic Actitivity of Penicillium digitatum and P. italicum Related to Fungal Growth and to Pathogenesis in Citrus Fruits
Authors: Barkai‐Golan Rivka , Karadavid Rachel
Published: May 2008

Cultural conditions under which Penicillium digitatum and P. italicum develop were an important factor in determining the extent of their cellulolytic activity. At pH 5.5–7.5 of the culture medium, Cx‐cellulase activity was correlated with mycelial dry weight. However, at pH 4.5 and more so at pH 3.5, activity was markedly reduced while fungal growth was not affected. Cx‐cellulases of both species were not induced by the presence of carboxymethyl cellulose as a carbon source and were defined as constituent enzymes. Cellulase activity of the two Penicillia on different carbon sources was detected prior to the initiation of sporulation. A sporeless mutant of P. digitatum exhibited cellulolytic activity similar to that of the normal strain, suggesting no role for sporulation in the Cx‐cellulase synthesis.

Cx‐cellulase activity in Valencia oranges started during the early stages of pathogenesis, before the appearance of disease symptoms. Correlation between the cellulase activity and the severity of the disease symptoms was apparent during the first three days after inoculation. At the end of the incubation period both fungi almost reached their maximum enzymatic activity, whereas the disease index continued to rise gradually until total fruit rot was achieved. A possible role of Cx‐cellulases of the two Penicillia in the early stages of pathogenesis was suggested.
Flavescence dorée de la Vigne. Présence de MLO et Effets Cytopathogènes Associés, dans le Liber de la Vigne
Authors: Meignoz R. , Boudon‐Padieu E. , Larrue J. , Caudwell A.
Published: May 2008

L'agent pathogène de la Flavescence dorée (FD), difficilement decelable dans les vignes malades prelevees au champ a pu être visualise dans le liber de l'hybride LN33 infecté artificiellement en serre, au stade de jeunes boutures, par la cicadelle vectrice Scaphoideus titanus. Le MLO (mycoplasmalike organism) de la FD induit des effets cytopathologiques importants qui précèdent la mort de nombreuses cellules dans les assises libériennes infectées. La necrose des cellules n'est pas toujours associée a la présence de MLO au moment de l'observation.

Grapevine Flavescence dorée. Presence of MLO and associated cytopathoiogical effects in grapevines

Grapevine Flavescence dorée MLO is difficultly found in tissues of infected grapevines from the field. Numerous MLO cells were found in sieve tubes of grapevine cuttings cv. LN33 which were infected with Scaphoideus titanus from a contamined vineyard, and grown in a greenhouse. Important cytopathoiogical disorders of MLO invaded tissues occurred before the death of numerous phloem cells. Cell necrosis was not always related to presence of MLOs at die moment of observation.

Flavescence dorée der Rebe. Das Vorhandensein von MLO und die assoziierten cytopathologischen Effekte im Rebenbast

Flavescence dorée MLO der Rebe kann nur mit Schwierigkeiten im Gewebe von infizierten Pflanzen im Feld ermittelt werden. Zahlreiche MLO‐Zellen wurden in Siebelementen von Rebpflan‐zenstecklingen cv. LN33 gefunden, die mit Scaphoideus titanus künstlich im Gewächshaus infiziert wurden. Wichtige cytopathologische Veränderungen des MLO‐infizierten Gewebes wurden vor dem Absterben zahlreicher Phloemzellen beobachtet. Zellnekrosis konnte nicht immer mit dem Vorhan‐densein von MLOs zum Zeitpunkt der Beobachtung verbunden werden.
Demonstration of Mycoplasmas in Prunus Species in Germany
Authors: Lederer W. , Seemüller E.
Published: May 2008

In southwestern Germany, mycoplasmas were detected in peach (Prunus persica), apricot (P. armeniaca), almond (P. amygdalus), Japanese plum (P. salicina) and flowering cherry (P. serrulata). The infected trees showed yellowing and leaf roll symptoms as well as reduced terminal growth, die‐back, and decline. This is the first report on the detection of mycoplasmas in Prunus spp. In Germany.

Nachweis von Mycoplasmen in Prunus‐Arten in Deutschiand

In Südwestdeutschland wurden Mycoplasmen in Pfirsich (Prunus persica), Aprikose (P. armeniaca), Mandel (P. amygdalus), japanischer Pflaume (P. salicina) sowie in der Zierkirsche P. serrulata nachgewiesen. Die befallenen Bäume wiesen als wichtigste Symptome Blattvergilbung, Blattrollen, Kümmerwuchs und Absterbeerscheinungen auf. Dies ist der erste gesicherte Nachweis von Mycoplasmen in Prunus‐Arten in Deutschland.
Comparison of Thermal and Chemical Treatment of Cotton Seed to Control Bacterial Blight (Xanthomonas campestris pv. malvacearum)
Authors: Honervogt B. , Lehmann‐Danzinger H.
Published: May 2008

Xanthomonas campestris pv. malvacearum (X. c. malvacearum) was isolated from cotton seeds from Nicaragua. Thermal treatment with hot water—ranging from 55 °C to 71 °C—for 20 min, was tested on naturally and artificially infected undelinted cotton seed. Germination was reduced only above 67 °C (17 % at 71 °C), but the degree of infection was severely reduced above 55 °C reaching 0 % at 65 °C. Bronopol treatment reduced the amount of infected linted seed from 91 % to 39 % and acid delinting from 17 % to 0.5 %. In contrast to the thermal treatments the chemical treatments eliminated X. c. malvacearum only from the seed surface and not from inside. Chemical treatment may be sufficient for externally infected cotton seed with low infection rate but not under conditions with high infection rates, where seed is also infected internally. Acid delinting could reduce the infection effectively, but not completely. The only possible way to avoid introduction of X. c. malvacearum or new races in already infested areas is thermal treatment of seed and should always be applied for quarantine.

Vergleich von Wärme‐ und chemischen Behandlungen zur Bekämpfung der Eckigen Blattfleckenkrankheit (Xanthomonas campestris pv. malvacearum) an Baumwollsaatgut

Xanthomonas campestris pv. malvacearum (X. c. malvacearum) wurde von Saatgut aus Nicaragua isoliert. Warmwasserbehandlungen zwischen 55 °C und 71 °C für 20 min wurden an natürlich und künstlich infiziertem Saatgut mit Filz (linters) getestet. Die Keimfähigkeit wurde nur bei Temperaturen über 67 °C reduziert (17% bei 71 °C), dagegen verringerte sich der Infektionsgrad erheblich bei Temperaturen von über 55 °C und erreichte 0 % bei 65 °C. Eine Behandlung mit Bronopol verringerte den Befall von 91 % auf 39 %, und eine Schwefelsäurebehandlung von 17 % auf 0.5 %. Im Gegensatz zur Warmwasserbehandlung wurde durch eine chemische Behandlung X. c. malvacearum nur an der Oberfläche, nicht aber im Inneren des Saatgutes abgetötet. Eine chemische Behandlung sollte bei äußerlich infiziertem Saatgut bei geringen Infektionsraten ausreichen, nicht aber bei hohen Raten und intern infiziertem Saatgut. Eine Schwefelsäurebehandlung konnte die Infektion stark reduzieren. Um die Einschleppung von X. c. malvacearum oder neuer Rassen des Erregers zu vermeiden, ist eine Warmwasserbehandlung des Saatguts, insbesondere in der Quarantäne, unumgänglich.
A Strain of Cucumber Green Mottle Mosaic Virus (CGMMV) from Bottlegourd in Saudi Arabia
Authors: Al‐Shahwan Ibrahim M. , Abdalla Omer A.
Published: May 2008

Mosaic symptoms were observed on bottlegourd in the College of Agriculture Research and Experimental Farm at Dirab. The following plant species: Lagenaria siceraria L., Cucumis sativus L., C. melo L., and Citrullus vulgaris L. showed mosaic symptoms when mechanically inoculated with extract from symptomatic bottlegourd. The rest of the inoculated plants did not show any symptoms. Properties of the infective plant extract were as follows: Dilution end point (DEP) was between 10−6–10−7, thermal inactivation point (TIP) was between 90–100 °C, and longevity in vitro was more than 32 days. Electron microscopic examination of negatively stained, partially purified preparations revealed rigid‐rod shaped virus particles measuring 300–325 nm. Positive serological reaction was observed between leaf extract from infected bottlegourd and CGMMV antiserum in immunodiffusion test in agar plates. This report is the first of the presence of CGMMV in this country.

Ein Isolat des cucumber green mottle mosaic virus (CGMMV) aus dem Flaschenkürbis in Saudi‐Arabien

Mosaiksymptome wurden an Flaschenkürbis bei dem College of Agriculture Research and Experimental Farm in Dirab, Saudi‐Arabien, beobachtet. Nach einer mechanischen Inokulation mit dem Extrakt aus befallenen Flaschenkürbispflanzen zeigten die folgenden Pflanzenarten Mosaiksymptome: Lagenaria siceraria L., Cucumis sativus L., C. melo L. und Citrullus vulgaris L. Andere Pflanzenarten, die gleichzeitig inokuliert worden waren, zeigten keine Symptome. Der infektiöse Pflanzenextrakt hatte folgende Eigenschaften: der Verdünnungsendpunkt (DEP) lag zwischen 10−6 und 10−7, der thermale Inaktivierungspunkt lag zwischen 90–100 °C, und die Langlebigkeit in vitro betrug mehr als 32 Tage. Elektronenmikroskopische Untersuchungen von negativ gefärbten, partiell gereinigten Präparaten offenbarten stabile, stabähnliche Viruspartikeln, die eine Größe von 300–325 nm hatten. Immunodiffusionstests in Agarplatten zeigten eine positive serologische Reaktion zwischen dem Blattextrakt von infizierten Flaschenkürbispflanzen und dem CGMMV‐Antiserum. Über das Vorhandensein vom CGMMV in Saudi‐Arabien wird hier zum ersten Mal berichtet.
Furcraea Necrotic Streak Virus: An Apparent New Member of the Dianthovirus Group
Authors: Morales F. , Castaño M. , Calvert L. , Arroyave J. A.
Published: May 2008

The causal virus of the ‘macana’ or necrotic streak disease of fique (Furcraea spp.), the most important fiber crop in Colombia, South America, was further characterized in this study. The virus has isometric particles ca. 34 nm in diameter, with an A 260/280 ratio of 1.64, a single protein species of mol.wt. 40,000, and two single stranded RNA molecules of approximately 4,000 and 1,600 bases. The virus was observed in the cytoplasm of infected leaf and root cells as mature virions, sometimes associated with electron‐dense, tubular inclusions. Immunoenzymatic assays of different fique plant organs demonstrated that the virus is consistently detected only in the roots. The fique virus was serologically related to red clover necrotic mosaic virus (RCNMV) and hybridized with RCNMV RNA1 and RNA2 cDNA clones. We propose the name furcraea necrotic streak virus (FNSV) for this new member of the dianthovirus group.

Furcraea necrotic streak virus: Anscheinend ein neues Mitglied der Dianthovirus‐Gruppe

In dieser Arbeit wurde das Erregervirus der “macana‐” oder necrotic streak‐Krankheit von Furcraea spp., der wichtigsten Faserkultur in Columbien, Süd‐Amerika, näher charakterisiert. Das Virus besteht aus isometrischen Partikeln ca. 34 nm im Durchmesser, mit einem A 260/280‐Verhältnis von 1,64, einer einzelnen Proteinspezie mit einem Molekulargewicht von 40 000 und zwei einzelkettigen RNS‐Fäden aus ca. 4 000 und 1 600 Basen. Das Virus wurde in Cytoplasmen infizierter Blattund Wurzelzellen als reife Virionen beobachtet, die gelegentlich mit elektronengesättigten, rohrförmigen Einschlüssen assoziiert waren. Immunoenzymatische Assays unterschiedlicher Furcraea‐Pflanzentile zeigten, daß das Virus nur in den Wurzeln konsequent zu beobachten war. Das Furcraea‐Vims war serologisch mit dem red clover necrotic mosaic virus (RCNMV) verwandt und konnte mit RCNMV RNS1 und RNS2 cDNS‐Klonen kreuzen. Der Name furcraca necrotic streak virus (FNSV) wird für dieses neue Mitglied der Dianthovirus‐Gmppe vorgeschlagen.
Electron Microscopy Studies of a Xylem‐Limited Bacterium in Sweet Orange Affected with Citrus Variegated Chlorosis Disease in Brazil
Authors: Chagas Cesar M. , Rossetti Victoria , Beretta Maria J. G.
Published: May 2008

Citrus variegated chlorosis (CVC), a serious disease affecting sweet orange (Citrus sinensis Osb.) groves in São Paulo and Minas Gerais States, Brazil, was first observed in 1987 and found to be associated with a Gram‐negative, xylem‐limited bacterium (GVG‐B). Electron microscopic studies revealed that the bacterium may appear in situ evenly distributed in the lumen of the tracheary elements and, occasionally, embedded in a lucent matrix adhering to the inner surface of the cell wall elements. GVG‐B measured 1–3.5 μm × 0.3–0.5 μ m and appeared to be at different developmental stages; fibril‐like structures were seen attached to bacteria. GVG‐B rippled wall showed a periodical or annulated structural arrangement with thickness from 25–35 nm in the furrows and 45–55 nm in the ridges. The wall consisted of 3 layers, i.e., an outer, an inner (each comprised of 3‐layered unit membrane structure) and a middle peptidoglycan layer. DNA‐like threads and ribosome‐like granules were present in the cytoplasm. GVG‐B is structurally and morphologically similar to Xylella fastidiosa of which it could be a citrus strain or a strain from other hosts adapted to citrus.

Elektronenmikroskopische Untersuchungen eines im Xylem‐limitierten Bakteriums bei Süßorangen in Brasilien, die mit citrus variegated chlorosis disease infiziert sind

Citrus variegated chlorosis (CVC), eine bedeutende Citruskrankheit bei Süßorangen (Citrus sinensis Osb.) in Plantagen in den brasilianischen Staaten Sao Paulo und Minas Gerais, wurde zum ersten Mai 1987 beobachtet, auch wurde ein Zusanimenhang mit einem Gram‐negativen, im Xylemlimitierten Bakterium (CVC‐B) festgestellt. Elektronenmikroskopische Untersuchungen haben gezeigt, daß das Bakterium in situ gleichmäßig im Lumen der Leitelemente verteilt sein kann, und auch manchmal in einer klaren, an der inneren Oberfläche der Zellwandelemente anhaftenden Matrix eingebettet. CVC‐B maß 1–3,5 μm × 0,3–0,5 μm und schien in unterschiedlichen Entwicklungsstadien zu sein; fibrilähnliche Strukturen waren mit den Bakterien verbunden. CVC‐B hat eine gekräuselte Wand, die eine regelmäßge oder geringelte strukturelle Anordnung zeigte. Die Wandstarke betrug 25–35 nm in den Rillen und 45–55 nm bei den Kämmen. Die Wand bestand aus 3 Schichten, d. h. einer aufieren, einer inneren (jede bestehend aus einer 3‐schichtigen Membranstruktur) und einer mittleren Peptidoglycanschicht. Im Cytoplasma befanden sich DNS‐ãhnliche Fäden und Ribosom‐ähnliche Körnchen. CVC‐B ist von der Struktur und der Morphologie mit Xyelella fastidiosaähnlich und könnte ein Stamm für Zitrusarten sein oder ist ein von einem anderen Wirt adaptierter Stamm von X. fastidiosa.
Accumulation of a Complex of Pigments in Sorghum Mesocotyls in Response to Wounding
Authors: Lopez A. M. Q. , Pascholati S. F.
Published: May 2008

Sorghum mesocotyls upon mechanical injury with an abrasive (carborundum) or inoculation with the fungi Helminthosporium carbonum (non‐pathogen) or Colletotrichum graminicola (pathogen) accumulate a methanol‐soluble pigment complex with an absorption maximum around 480–490 nm. Spectral and thin‐layer chromatographic analyses showed that the complexes which accumulated either in response to wounding or inoculation are similar. Thus, it is suggested that the accumulation of the pigmented phytoalexins in sorghum mesocotyls is a non‐specific response of the tissues towards mechanical injury or fungal infection.
Identification of a Cross Between Two Compatible Isolates of Magnaporthe grisea (Hebert) Barr and Genetic Analysis of Avirulence/Virulence of Rice
Authors: Silué Drissa , Notteghem Jean Loup
Published: May 2008

A cross was successful between two field isolates of Magnaporthe grisea Guy 11 and CD 128, both pathogenic to rice. One ascospore isolated in this cross could be backcrossed to the most fertile parental isolate Guy 11. Backcrosses to CD 128 were not compatible. All progenies were inoculated to seven rice varieties in order to analyze the genetic basis of avirulence. Avirulence to Kusabue was found to be controlled by one gene. Two other controls of avirulence to rice were shown: a) two independent genes involved in avirulence to Pi‐n°4, both required by the isolates for virulence expression, b) two independent genes, each one leading to virulence on the rice varieties K 1 and Aichi asahi. Implications of these results to Flor's gene‐for‐gene hypothesis are discussed.
Effekt und Risiko des Knöllchentests auf Braunfäuleresistenz bei Kartoffelsämlingen im System der Auslese in der Phytophthora‐Resistenzzüchtung
Authors: Darsow U.
Published: May 2008

The effects and risks involved with the small tuber assay in plant breeding programmes with potato seedlings for resistance to Phytophthora infestans

In an assay which involved 838 potato seedlings, the relative resistance to leaf‐Phytophthora (KRG) was tested at the 4–6 leaf growth stage, and the relative tuber resistance to infection was determined on small pot‐grown tubers (BK) and, in the following 2 years, in slices from field‐grown potatoes (Bs). The small tuber assay is described and its value as a measure of disease resistance, compared with the potato slice assay, discussed. Among 357 leaf‐Phytophthora susceptible clones (KRG≤ 5) were 10 clones with a good to very good tuber resistance. 18 of 204 leaf‐Phytophthora highly resistant idiotypes were extremely susceptible to tuber rot. After discarding those seedlings which showed KRG‐values ≤ 5 and BX‐values ≤ 5, 208 of the remaining 241 (= 86 %) tuber rot resistance carrying seedlings were selected. 14 % of the clones which showed adequate resistance in the potato slice assay were falsely discarded according to the small tuber assay. 80 clones remained as ballast in the field trials (BK≤ 5, Bs≤ 6.4), 160 (33 % of the idiotypes tested) had been correctly eliminated. The work‐intensive small tuber assay presents a possibility by which breeding material can already be reduced in the seedling stage. In this respect there must be a pronounced genetic differentiation present in the potato population and the selection procedure carried out must not be too harsh.
The Establishment and Structure of Latent Infections with Monilinia fructicola on Apricots
Authors: Wade G. C. , Cruickshank R. H.
Published: May 2008

Latent infections of apricot fruit with Monilinia fructicola were initiated by inoculation at shuck fall and 43 and 63 days after shuck fall. The fungus entered via the stomata and penetrated a guard cell through the thin walled region at the stomatal pore. The fruit tissue responded by death of cells around the point of infection, suberization of walls of surrounding living cells and accumulation o phenolic compounds in cells up to 20 distant. Periderm developed around lesions formed at shuck fall but was absent from those formed 65 days later. When the fruit ripened, approximately 100 days after shuck fall, viable hyphae in latent infections escaped from the lesions by growing out between the cuticle and epidermis or just below the epidermal cells. Outbreak was more efficient from later inoculations and only a small proportion of latents initiated at shuck fall became invasive.
Studies on Antagonistic Effects of Trichoderma Isolates Against Phytophthora cactorum
Authors: Lederer W. , Lorenz K.‐H. , Seemüller E.
Published: May 2008

Bioassays were used to demonstrate the antibiotic effect of Trichoderma isolates on P. cactorum. When both fungi were grown on benomyl‐containing PDA medium, the mycelial growth of Trichoderma was suppressed. However, the production of antibiotics by this fungus remained active, leading to inhibition of the mycelial growth of P. cactorum. The antibiotic effect of Trichoderma on zoospores and cysts was tested on a PDA substrate precultured with Trichoderma on cellophane sheets. On the substrate of some Trichoderma isolates, lysis of zoospores, formation of extracellular vesicles, and hypertrophy of the water expulsion vesicle did occur, both resulting in the death of the zoospores. Conidial suspensions of Trichoderma isolates also induced zoospore lysis. It is presumed that membrane‐active peptide antibiotics (peptaibols) are involved in zoospore lysis. The peptaibol paracelsin caused lysins of zoospores at a concentration of 2.5 × 10−4 M. The effect on cysts depended on the Trichoderma isolate tested and the age of Trichoderma preculture. Old cultures (after beginning of sporulation) affected cysts more severely than young cultures (before sporulation) which usually were not lethal to the cysts but induced preferably microsporangium formation, inhibition of cyst germination, and retardation of germ tube growth.
Production of Fumonisins by Fusarium moniliforme Cultures Isolated from Jimsonweed in Mississippi
Authors: Abbas HamedK. , Vesonder R. F. , Boyette C. D. , Hoagland R. E. , Krick T.
Published: May 2008

Eight Fusarium spp. were isolated from greenhouse‐grown jimsonweed (Datura stramonium L.) in Mississippi in 1990. Four isolates of Fusarium moniliforme were obtained and when grown on autoclaved rice, produced 115 to 3,200 mg/kg fumonisin B1, (FB1). Other fumonisin‐related compounds, such as FB2, FB3 and FB4 were also produced at levels of 240, 210 and 160 mg/kg, respectively. F. semitectum (1 isolates) was negative for production of fumonisin and other phyto‐toxins. F. oxysporutn (1 isolate) produced only 3.5 g/kg moniliformin. This is the first report of production of fumonisins by F. moniliforme isolated from weeds such as jimsonweed.
Use of Trichoderma harzianum and Gliocladium vitens for the Biological Control of Post‐emergence Damping‐off and Root Rot of Cucumbers Caused by Pythium ultimum
Authors: Wolffhechel H. , Funck Jensen D.
Published: May 2008

The antagonist strains Gliocladium virens G2 and Trichoderma harzianum T3 originally isolated from Pythium suppressive peat, and two benomyl‐resistant strains of T. harzianum, T12B and T95, were evaluated as biological control agents of damping‐off and root rot of cucumbers in sphagnum peat caused by Pythium ultimum. All strains were equally effective when applied as 1 % peat‐bran preparations, whereas the effectiveness of disease control was reduced at higher concentrations of the antagonists. The two wild‐type strains were also found to be effective when applied as conidial suspensions, and in this case no reduction in disease control was seen at higher concentrations. G. virens G2 and T. harzianum T12B showed antibiotic activity against P. ultimum in in vitro tests; however there were no signs of mycoparasitism of P. ultimum by any of the antagonist strains.
Hyperparasitic Attack of Trichothecium roseum on Conidia of Pestalotiopsis funerea
Authors: Urbasch Irene
Published: May 2008

Trichothecium roseum (Tr) has been shown to be a highly effective hyperparasite on conidia of Pestalotiopsis funerea (Pf) in vivo and in vitro.

The stages of this spore parasitism are:

positive tropism of Tr towards Pf conidia, contact between Tr and Pf, formation of simple or lobed appressoria of Tr on the host conidial surface, penetration of the attacked host cells from the base of the appressoria, development of host‐internal, mostly branching parasitic hyphae by Tr, desintegration, lysis and death of the parasitized host cells, exit of Tr from the destroyed host cells and its intensive sporulation over Pf remnants.

Pf did not show any defence reactions against the attack by Tr.

In addition to the antagonistic activities of Tr against Pf reported previously, which are due to extracellular toxins released by Tr, direct hyperparasitism is a second mechanism of antagonism, which contributes to the successful competitive ability of Tr in this fungal interaction.
Chitinase Activity in Stylosanthes guianensis Systemically Protected Against Colletotricbum gloeosporioides
Authors: Brown AverilE. , Davis RobertD.
Published: May 2008

Three‐ and four‐fold increases in chitinase activity were detected in the youngest, fully expanded leaf (L1) of Stylosanthes guianensis cv. Endeavour following inoculation of the second youngest, fully expanded leaf (L2) with virulent Type B and Type A isolates of Colletotrichum gloeosporioides compared with chitinase activity in L1 leaves of uninoculated plants. Only small increases in β‐1,3‐glucanase were detected in L1 leaves of systemically protected plants. Chitinase activity was maximal in leaf L1 36 to 48 h after inoculation of leaf L2, and this was coincident with the onset of resistance to anthracnose in L1 leaves. Chitinase activity also increased in L1 leaves inoculated with a weakly pathogenic isolate of C. gloeosporioides. Resistance developed in these L1 leaves to subsequent infection by a virulent isolate of the pathogen approximately 36 h after protective‐inoculation with the weakly pathogenic isolate.

Two chitinase isozymes, with molecular weights of 65,000 daltons (pI 3.1) and 54,000 daltons (pI 4.0), were separated from extracts of C. gloeosporioides‐challenged S. guianensis cv. Endeavour leaves. S. guianensis chitinase caused death of C. gloeosporioides hyphae, particularly in the presence of β‐1,3‐glucanase. Mycelial viability declined as activity of chitinase was increased in mixtures containing a fixed activity of β‐l,3‐glucanase.
Time and Site of Inoculation of Maize for Optimum Infection of Ears by Stenocarpella maydis
Authors: Bensch M. J. , van Staden J. , Rijkenberg F. H. J.
Published: May 2008

The optimum inoculation position on the maize plant, and optimum time of inoculation with Stenocarpella maydis for artificial induction of ear rot were determined in field trials. The placement of a conidial suspension on the shank at silking resulted in the highest incidence of S. maydis ear rot.
A Histological Evaluation of Induced Resistance to Phytophthora infestans (Mont.) de Bary in Potato Leaves
Authors: Strömberg Anita , Brishammar Sture
Published: May 2008

Systemically induced resistance against Phytophthora infestans in the potato cultivar ‘Bintje’ was studied histologically at the light microscopy level on the leaf surface, in the epidermis and in the mesophyll of challenged potato leaves. Systemic disease resistance was induced by a local pre‐infection with the same fungus. On the leaf surface of induced plants, the germination of cysts was enhanced. In the epidermis of induced plants, papilla deposition increased and penetration decreased, whereas in the mesophyll of induced plants the spread of hyphae was reduced. It is suggested that the reduction of disease severity in induced plants is the result of the combined action of several successive defence reactions.
Occurrence and Pathogenicity of Fusarium Species in Banana Fruits
Authors: Jiménez M. , Logrieco A. , Bottalico A.
Published: May 2008

Banana fruits were studied over a six‐month period in order to determine the incidence of species of the Fusarium genus and assess their potential pathogenicity. The 72 samples studied were commercially available in Italy and Spain, where they were brought from Panama, Ecuador and Canary Islands. Among the species detected in the fruits, Fusarium semitectum var. majus Wollenw. was predominant, followed by F. moniliforme Sheld., F. solani (Mart.) Appel & WoUenw., F. oxysporum Schlecht., F. proliferatum (Matsushima) Nirenberg, F. graminearum Schw., F. camptoceras WoUenw. &C Reinking, F. subglutinans (WoUenw. & Reinking) Nelson et al., F. dimerum Penzig in Sacc, F. acuminatum EU. & Ev., and F. equiseti (Corda) Sacc. Fusarium proliferatum had never been reported to occur as contaminating fungi in banana fruits to date. Fusarium subglutinans, F. acuminatum and F. graminearum were found to be the most markedly pathogenic of all. The lack of noticeable differences in relation to the incidence of the different species isolated from the samples indicates that the mycoflora found is typical of this fruit and does not depend on its origin.
Evaluation of Biological and Chemical Treatments for Control of Crown Gall on Young Apple Trees in the Kootenay Valley of British Columbia
Authors: Utkhede R. S. , Smith E. M.
Published: May 2008

Field trials at Creston in 1988, 1989, and 1990 on silty loam soil naturally infested with Agrobacterium tumefaciens showed that Agrobacterium radiobacter strain K84 did not control crown gall on young Antonovka apple trees when apphed as a root‐dip treatment. Copper oxychloride applied as a root‐dip treatment at 2.5 and 5.0 g ai/1 and sewage sludge applied at 260 g per tree as broadcast were effective in reducing crown gall infection but these treatments were toxic to young apple trees in 1989. Lower rates of copper oxychloride, 0.3, 0.6 and 0.9 g ai/1, and sewage sludge at 130 g per tree, did not control crown gall in the 1990 field trial. The biological treatment with the strain AB8 of Bacillus subtilis applied as a root‐dip effectively controlled crown gall and was not phytotoxic to young Antonovka apple trees. These results suggest that strain AB8 of B. subtilis has the potential to control crown gall on young apple trees under field conditions.
Effect of Thermal and Cycloheximide Pre‐treatments on Light‐Dependent Necrosis Formation to Rice Leaves byPyricularia oryzae Toxin(s)*
Authors: Arase S. , Nozu M. , Iedome M. , Honda Y. , Yamaji Y.
Published: May 2008

Effects of thermal and cycloheximide pre‐treatments on light dependent‐necrosis formation by Pyricularia oryzae toxin(s) on cv. Sekiguchi‐asahi were investigated. Thermal treatments of rice leaves at 55 °C for 10 and 15 sec significantly suppressed leaf necrosis formation. Such heat‐induced insensitivity of rice leaves to toxin(s) was greater at a thermal treatment of 55 °C for 15 sec than that of 55 °C for 10 sec. Cycloheximide pre‐treatment also suppressed leaf necrosis formation under light.
Induction of Systemic Resistance to Tobacco Powdery Mildew by Tobacco Mosaic Virus, Tobacco Necrosis Virus or Ethephon
Authors: Marte M. , Buonaurio R. , Della Torre G.
Published: May 2008

Local infections of either TMV or TNV in tobacco plants cv. Havana 425 (hypersensitive to TMV) proved effective in inducing systemic resistance to subsequent inoculation with the powdery mildew fungus Erysiphe cichoracearum DC. The proportion of leaf surface invaded by this pathogen and the amount of conidia it produced were both significantly lower in virus inoculated plants than in non‐inoculated controls. However, the decrease in sporulation rate was less regularly observed than the reduction in leaf area infected. TMV was more effective than TNV in protecting tobacco plants from powdery mildew. E. cichoracearum is thus added to the list of challenge pathogens to which TMV or TNV are known to induce resistance in the host plants.

Necrotic lesions caused to the leaves by local treatment with Ethephon (an ethylene‐releasing compound) also conferred to tobacco some degree of systemic resistance to the same fungal pathogen, more frequently visible as a reduction of leaf area invaded. The protection due to the Ethephon lesions was in present experiments less marked than that of TMV. No effects against subsequent powdery mildew infection were obtained when point freeze necrotic lesions were provoked on the plants.
Detection of Mycoplasma‐like Organisms in Infected Potato by Electron Microscopy
Authors: Açlikgöz Serap
Published: May 2008

By using electron microscopy pleomorphic mycoplasma‐like bodies were observed only in the phloem cells of the field infected potato plants showing purple top roll symptoms. The bodies surrounded by unit membranes were 50–300 nm in diameter.
Identification of some Bacteria from Paddy Antagonistic to Several Rice Fungal Pathogens
Authors: Rosales A. M. , Vantomme R. , Swings J. , De Ley J. , Mew T. W.
Published: May 2008

The effect of 23 bacterial strains from ricefields in the tropics on rice seed germination and on radicle and hypocotyl development of four rice cultivars was determined. There was a varietal difference in response to seed bacterization with the different bacterial strains. Germination of cv. IR58 increased from 78 to 93 %, that of cv. IR64, from 89 to 97 %. Less effects on germination of cvs IR42 and IR36 were observed. All strains inhibited the mycelial growth of Rhizoctonia solani in vitro. The three strains, identified as Bacillus subtilis, inhibited the mycelial growth of eight fungal pathogens whereas the other strains were pathogen‐specific. Seed bacterization with these bacterial strains provided a sheath blight protection of 4. 5 to 73 % in the glasshouse trial. These 23 bacterial strains were identified by phenotypic tests using the API systems, morphological and biochemical features, and by comparison of electrophoretic patterns after sodium dodecyl sulphate polyacrylamide gel electrophoresis. Bacterial strains were identified (number of strains in brackets) as: Bacillus subtilis (3), Bacillus laterosporus (1), Bacillus pumilus (1), Pseudomonas aeruginosa (7), Pseudomonas belonging to section 1 (5), Erwina herbicola‐like (1), and Serratia marcescens (1). The features of the other four strains were similar to Serratia except for the DNAase and lipase activities.
Comparative Cytology of Rice Tungro Viruses in Selected Rice Cultivars
Authors: Cruz F. C. Sta. , Koganezawa H. , Hibino H.
Published: May 2008

Ultrastructural studies were made using plants of five selected rice cultivars infected with rice tungro viruses. In all cultivars, rice tungro bacilliform virus (RTBV) was found in both xylem and phloem, while rice tungro spherical virus (RTSV) was observed only in the phloem. In tolerant cultivars Balimau Putih and Utri Merah, plants infected with RTBV and RTSV or RTBV alone, had fewer cells containing tungro viruses than plants of the sensitive cultivar Taichung Native 1. In RTBV‐sensitive cultivars FK 135 and ASD 8 infected with both viruses or RTBV alone, electron‐dense cytoplasm was observed in most cells of the phloem. Abundant phloem necrosis was also observed in FK 135. These observations were correlated with the reaction of each rice cultivar to tungro infection.
Mycoparasitism of Alternaria alternata by an Additional Eight Fungi Indicating the Existence of Further Unknown Candidates for Biological Control*
Authors: Turhan Gülay
Published: May 2008

In studies using light and scanning electron microscopy it was clearly demonstrated that Nectria inventa, Gliocladium roseum, G. ca.tenula.tum, Clonostacbys sp., Sesquidllium sp., Verticillium nigrescens, Dicyma olivacea, Stachybotrys elegans, Myrothecium carmichaelii, M. cinctum, M. roridum, M. tongaense, M. verrucaria and Coniothyrium sporulosum are able to parasitize Alternaria alternata. With the exception of N. inventa and the five Myrothecium spp., none of the other fungi has been previously reported to be mycoparasitic on Alternaria. Moreover, there is no current information about the mycoparasitic and antibiotic activity of the genera Clonostacbys and Sesquici‐lium.

The mode of parasitism was nearly the same in all of the mycoparasites. In many cases, penetration was achieved directly by the hyphal tips without the formation of appressorium like structures (ALS) and there was no evidence that the formation of ALS was a prerequisite for penetration. Dependant on the severity of infection, a gradual shrinkage, distortion and an eventual collapse of the parasitized conidia were observed. A bursting and total collapse of the spores without any penetration was detected by the antibiotic producing mycoparasites such as G. roseum, G. CAtenulatum, Clonostacbys sp., Sesquicillium sp., D. olivacea and the five Myrothecium species.

In consideration of their activity, all of the tested antagonists would appear to be candidates for in vivo investigations to check their suitability as biocontrol agents.
A Carlavirus and a Rhabdovirus Infecting Lonicera X brownii cv. Dropmore Scarlet in Western Canada
Authors: Weintraub M.
Published: May 2008

Chlorotic and necrotic spots, yellow mottle, and vein banding leaf symptoms were seen on two honeysuckle vines in the Botanical Garden, University of British Columbia. Electron microscopic examination showed the presence of rhabdovirus and carlavirus particles. This is the first report of a rhabdovirus in honeysuckle. The carlavirus may be honeysuckle latent virus, although it was transmitted to only three of its nine reported herbaceous hosts, and it was not transmitted by the reported aphid vector, Hydaphis foeniculi. Both types of virus particles were seen in mesophyll, phloem parenchyma and companion cells of honeysuckle. The rhabdovirus was not transmitted to any other host and, in honeysuckle, was found only in the Spring. As its concentration declined, the number of carlavirus particles increased.
The Interaction of Either an Effective or a Defeated Major Gene with Non‐specific Resistance on Mildew Infection (Erysiphe graminis f. sp. hordei) and Yield in Mixtures of Barley
Authors: Newton A. C. , Thomas W. T. B.
Published: May 2008

Three‐component mixtures of two barley cultivars expressing partial resistance to mildew (Erysiphe graminis f. sp.hordei) with the third component either expressing complete resistance or a defeated major gene gave more yield than the mean of their components in monoculture in a series of field trials. However, there was no reduction in mildew infection in the mixtures and even a significant increase in one trial. The potential for using partially resistant cultivars in mixtures is discussed.
Life Cycle of Mycosphaerella brassicicola (Duby) Lindau and Ascospore Production in vitro
Authors: Götz M. , Zornbach W. , Boyle C.
Published: May 2008

The germ‐hyphae of the M. brassicicola ascospores penetrated the host leaves (white cabbage) 10 days after inoculation during the summer at 17 °C. The penetration occurred without exception by way of the stomata. Following a period of intercellular growth which lasted up to 15 days, brownish discolourations of the host cell walls and the destruction of mesophyll cells were observed. At this stage of infection, fruit‐body primordia developed from hyaline, thick‐walled, granulated mycelium, which blackend after conglomeration due to melanine deposits. The further ascocarp development was ascolocular.

Ascospore production of M. brassicicola was increased in vitro by variation of the incubation temperatures, medium‐pH and irradiation. The highest sporulation rate was obtained in cultures on vegetable juice medium adjusted to pH 6, incubated at 17 °C and subjected immediately after onset of growth to 4 h UVA radiation. The percentage of germinated ascospores (70 %) corresponded to that of the dark incubated controls. Fructification and infectivity were subject to seasonal fluctuations under growth chamber conditions.
Differentiation of Erwinia Species in the “Herbicola” Group by Class Analysis of Cellular Fatty Acids
Authors: Wells J. M. , van der Zwet T. , Butterfield J. E.
Published: May 2008

Profiles of cellular fatty acids of Erwinia herbicola, E. ananas, E. stewartü and E. uredovora, comprising the Herbicola group in the genus Erwinia, contained 7 major components accounting for 90–95% of total fatty acids, and,30 minor components, each less than 1% of the total. The major components and their average percentage ranges in cells on King's medium B at 28°C for 1 days were: 12:0 (3.5–4.5%), 14:0 (3.6–4.3%), 16:0 (28.1–35.7%), 16:1 (17.5–24.2%), 18:1 (13.9–31.9%), 3‐OH 14:0 (4.6–7.2%) and cyclopropane 17:0 (trace levels in E. stewartii, 5.0–6.7% in other species). Fatty acid composition changed as a function of physiological age of the cells. The regression coefficient (b) as a function of age for percentage of saturated even‐ and oddcarbon, straight‐chain fatty acids (Classes A and B) was either negative or not significant for E. ananas and positive for the other species. A series of dichotomous steps was constructed based on fatty acid algorithms to differentiate all four species.
Characteristics of a Pythium arrhenomanes with High Frequency in Barley Soils
Authors: Olsson S. , Kadir S.
Published: May 2008

Soils from two long‐term crop rotation experiments were examined for incidence of root pathogens with a test tube method, where a great number (hundreds) of small portions (15–68g) of soil were biotested. There was a 4–5 times higher frequency of a root‐infecting Pythium sp. In barley monoculture soil when compared to crop rotation soil, where winter turnip rape was the preceding crop. In pathogenicity tests the isolated pathogen caused severe root rot on barley, wheat and rye, but did not affect growth of oats, maize, peas and winter rape. In all essential morphological characters it resembles P. arrhenomanes and we classify it as belonging to this species.
The Characterization of a Strain of Zucchini Yellow Fleck Virus Found in Southeastern France
Authors: Gilbert‐Albertini F. , Lecoq H.
Published: May 2008

A virus was isolated from squirting cucumber (Ecballium elaterium L.) collected in France (Alpes de Haute Provence). After mechanical inoculation, eight species belonging to the Cucurbitaceae were found susceptible to this virus with systemic symptoms of mosaic, chlorotic spots, and fruit deformations. The French ZYFV (ZYFV‐Fr) isolate differed from the type strain in its ability to infect some differential host plants. Elongated flexuous particles with a modal length of 752 nm were observed by electron microscopy in leaf extracts. Cytoplasmic inclusions similar to those associated with infections by members of the potyvirus group were observed by light microscopy. The virus was found by SDS‐immunodiffusion and DAS‐ELISA to be serologically related but distinct from the type strain of zucchini yellow fleck virus from Italy (ZYFV‐lt). ZYFV has not yet been found in cultivated cucurbit plants in France; this virus appears to be restricted to squirting cucumbers in a few localities. The distribution of ZYFV in France is discussed.
Evaluation of Pathogenicity and of Cultural and Biochemical Tests for Identification of Pseudomonas syringae Pathovars syringae, morsprunorum and persicae from Fruit Trees
Authors: Burkowicz A. , Rudolph K.
Published: May 2008

Comparative studies were based on 216 isolates of the Pseudomonas syringae pathovars syringae, morsprunorum and persicae, mainly originating from fruit trees in several European countries, but also from USA, USSR, South Africa, New Zealand and Turkey. All the identified morsprunorum isolates were obtained from stonefruit trees, which were also a source of some syringae isolates.

Fluorescent strains HR negative on tobacco leaves were regarded as saprophytic pseudomonads. Nearly all the HR positive but none of the HR negative isolates caused lesions on sweet cherry shoots and fruitlets. The largest lesions on sweet cherry shoots were caused by the morsprunorum isolates. Syringae strains always caused lesions on pear fruitlets, whereas the morsprunorum strains never did so. Some degree of specialization within the pathovar syringae seemed to exist.

Cultural and biochemical tests well suited to differentiate the three pathovars were as follows: colour after growth in sucrose nutrient broth, liquefaction of gelatin, activity of β‐glucosidase (arbutin) and tyrosinase, use of L‐leucine, L(+)tartrate and DL‐lactate as sole carbon source, fluorescent pigment production, crystaline inclusions in the nutrient agar medium, and growth rate in 0.2% yeast extract nutrient broth. Tests for longevity on nutrient agar with 5% sucrose turned out to be fairly unreliable. A tube assay gave the most consistent results when studying utilization of organic substrates. The capability for gelatin liquefaction correlated with virulence, and mucoid isolates showed a tendency for higher aggressiveness than rough colony variants.

Page of protein extracts obtained from freeze‐pressed bacterial cells revealed that the pathovars syringae and morsprunorum could be differentiated due to specific isoenzyme patterns for esterases and acid phosphatases.

It was concluded that several pathogenicity, cultural and biochemical tests allowed an unequivocal differentiation of the Pseudomonas syringae pvs. syringae and morsprunorum. Some of the discriminating biochemical characters may, play a role during pathogenesis.
The Mode of Inhibition of TMV‐ and PVX‐Induced RNA‐Dependent RNA Polymerases by some Antiphytoviral Drugs
Authors: Schulze S. , Kluge S.
Published: May 2008

Six nucleobase and nucleoside analogues (6‐aminouracil [6‐AU], 6‐aminothymin [6‐AT], 6‐fluorothymin [6‐FT], 2,4‐dioxohexahydro‐1,3,5‐triazine [DHT], 9‐(2,3‐dihydroxypropyl) adenine [DHPA] and 1‐β‐D‐ribofuranosyl‐1,2,4‐triazol‐3‐carboxamid [ribavirin]) with potential antiphytoviral activity were tested in an in vitro replication system for their effect on tobacco mosaic virus (TMV)‐and potato virus X(PVX)‐induced RNA dependent RNA polymerase. 6‐AU, 6‐AT, 6‐FT, and DHPA inhibited both polymerases which may be a target of these compounds. A Putative noncompetitive mode of inhibition is discussed. Whereas ribavirin did not affect the in vitr RNA synthesis in the established systems, the uracil‐derivative DHT inhibited only the PVX‐specific enzyme.