bluuebunny/crossref_metadata_2025 huggingface dataset:
Medium‐ and Light‐dependence of Growth and Conidiomata Production in Phaeocytosporella zeae Pathogenic to Maize
Authors: Lević J. , Petrović T.
Published: May 2008

Culture appearance, mycelium growth and pycnidial conidiomata formation in Phaeocytosporella zeae cultivated on potato dextrose agar (PDA), Leonian agar and carnation leaf agar (CLA) during permanent dark (25 C) or a 12‐h photoperiod (24/18°C) are described. Different media and light conditions significantly affected fungus growth and the occurrence of conidiomata.

Dark conditions favoured more mycelium growth of the fungus than alternating light and dark. Moreover, fungus growth was more rapid on PDA and CLA media than on Leonian agar. Carnation leaf agar and a 12‐h photoperiod provided excellent conditions for the promotion of rapid conidiomata formation in a number of P. zeae isolates.
Genetic Fingerprinting of Pseudomonas syringae Pathovars Using ERIC‐, REP‐, and IS50‐PCR
Authors: Weingart H. , Völksch B.
Published: May 2008

PCR fingerprinting using primers corresponding to repetitive (ERIC and REP) and insertion sequences (IS50) was investigated as a method to distinguish the pathovars of Pseudomonas syringae. After amplification of total DNA with the ERIC‐, REP‐, and IS50‐PCR followed by agarose gel electrophoresis. most of the tested pathovars showed specific patterns of PCR products. The differences between the fingerprints among strains within a pathovar were small, with the exception of pathovars syringae, aptata, and atrofaciens. The fingerprints of the related pathovars savastanoi, phaseolicola, glycinea, morsprunorum, tabaci, lachrymans, and mori generated with the ERIC‐ and REP‐primers were found to be very similar, showing the potential of this technique for taxonomical studies. In contrast, the IS50‐PCR fingerprints of these pathovars were clearly distinguishable. The fingerprint patterns of a strain were highly reproducible with all three tested primer sets, also when whole cells were added to the reaction mixture. Thus, the PCR technique with the ERIC‐, REP‐, and IS50‐primers is a rapid, simple, reproducible, and low cost method to identify and classify strains of the Pseudomonas syringae pathovars.
Rhizoctonia solani Incited Damping‐off in Radish Suppressed by Plasmid and Non‐plasmid Carrying Strains of R. solani that Enhance Host Chitinase Activity
Authors: Tschen J. S.‐M. , Chen C.‐S. , Hsue C.‐C. , Ling Y.‐L. , Cheng Y.‐H.
Published: May 2008

Thirteen Rhizoctonia solani isolates belonging to anastomosis group four were examined. All of the isolates carry plasmids except isolates CHU344 and CHU345. Plasmids were analysed by agarose gel electrophoresis and observed by transmission electron microscope. The plasmid DNA is linear, having a size of 2.6 kbp. The termini of the plasmid have a hairpin structure. The replication of plasmid DNA of R. solani CHU341 (pCHU341) was demonstrated by electron microscopy.

Virulence of the fungi was tested on radish seedlings and expressed according to percentage of radish seedlings that damped‐off. Strains CHU341, CHU344, CHU345, CHU346, CHU347, CHU348, CHU350 and CHU353, suppressed damping‐off of radish seedlings by the virulent isolates, CHU342, CHU349, CHU351 or CHU352 and was expressed according to a suppressiveness index. The chitinase activities of radish seedlings increased from 10 to 20 times after inoculation with suppressive isolates, CHU341, CHU344 and CHU345.

The results indicate that damping‐off of radish seedlings caused by R. solani can be protected by related strains with or without plasmids. The protection of the seedlings may result from the enhancement of chitinase activities induced by the suppressive strains of R. solani.
Natural Infection of Field‐Grown Daikon Radish (Raphanus sativus L.) Crops by Turnip Crinkle Virus in North America
Authors: Reddick B. B. , Putnam M. L. , Habera L. F.
Published: May 2008

In 1993, stunted field‐grown daikon radish plants were found with black lesions on the petioles and leaf blades, and new growth exhibited leaf crinkling and a mosaic pattern on distorted leaves. The plants had hollow roots and seed production was severely reduced. Symptomatic plants contained isometric virions identified as those of turnip crinkle virus (TCV). This is the first report of TCV causing serious economic damage and the first report of natural infection in North America.
Biological Control of Damping‐off of Cucumber caused by Pythium ultimum with a Root‐Colonization‐Deficient strain of Escherichia coli
Authors: Roberts D. P. , Dery P. D. , Hebbar P. K. , Mao W. , Lumsden R. D.
Published: May 2008

Suppression of damping‐off of cucumber and root colonization was compared for strain 501R3 of Enterobacter cloacae and strain S17R1 of Escherichia coli, a rifampicinresistant mutant of E. coli S17‐1. Both strains 501R3 and S17R1 provided effective biocontrol of pre‐emergence and post‐emergence damping‐off of cucumber caused by Pythium ultimum when applied as seed treatments containing approximately 107 cfu per seed. Plant stands from seeds treated with 501R3 or with S17R1 were 93% and 92%, respectively (similar at P ≥ 0.05), when sown in soil‐less mix infested with P. ultimum. The plant stand with the pathogen control was only 30%—significantly less (P ≥ 0.05) than stands from the 501R3 and S17R1 treatments. Cucumber was only briefly susceptible to damping‐off caused by P. ultimum since seeds pregerminated for 29 h or longer before sowing in P. ultimum‐infested soil‐less mix yielded plant stands similar to the healthy control treatment. Plant stands from nonpregerminated seeds were significantly less (P ≥ 0.05) than pregerminated seed treatments. E. coli strain S17R1 was not an effective colonizer of cucumber rhizosphere. When applied as seed treatments containing approximately 104 or 108 cfu per seed, populations of strain S17R1 were significantly smaller (P ≥ 0.05) than with corresponding treatments of strain 501R3 at 24, 48, 72 and 96 h after sowing in soil‐less mix. Populations of strain S17R1 increased only 65‐fold over 96 h when applied at 104 cfu per seed. In contrast, populations of strain 501R3 increased 24000‐fold over the same period when applied at 104 cfu per seed. Populations of strain S17R1 were limited to the upper 1 cm of cucumber root at 7 days and decreased to approximately 101 cfu/g of total root system over 42 days. Strain 501R3 was capable of becoming widely distributed along cucumber roots and was detected at populations of approximately 108 cfu/g of total root system at 42 days. Results from this study indicate that E. coli is capable of suppressing damping‐off of cucumber caused by P. ultimum. In addition, extensive root colonization by E. coli strain S17R1 was not required in this biocontrol interaction because of the brief period of susceptibility of cucumber to this disease.
Bacterial Blister Bark of Apple Trees in Italy
Authors: Scortichini M. , Morone C.
Published: May 2008

At the beginning of spring 1996, raised, brown areas along the bark of trunk and twigs were observed on young apple trees in Piedmont (northern Italy). In many cases the epidermis flaked off. Longitudinal cracks accompanied by necrosis of the tissues beneath the bark were also observed. In one orchard the disease caused the death of 2500 trees. Biochemical, nutritional and pathogenicity tests, as well as the comparison of whole‐cell protein profiles of the isolates with type‐strains, indicated that Pseudomonas syringae pv. syringae was the causal agent of the disease. Bacterial blister bark remains a threat for apple cultivation also in Italy, especially in orchards planted in sandy soils.
Influence of Different Irrigation Regimes on Carpogenic Germination of Sclerotia of Sclevotinia sclerotiorum
Authors: Twengström E. , Köpmans E. , Sigvald R. , Svensson C.
Published: May 2008

The effects of irrigation level, irrigation interval, length of irrigation break and of soil type on apothecial production, apothecial survival and sclerotial survival of Sclerotinia sclerotiorum were studied in field experiments in 1991 and 1992. The experimental area was sown with spring rapeseed and naturally produced sclerotia were placed 1 cm deep in the soil. Apothecia production started after 25‐30 days of continuous soil moisture and was strongly influenced by the irrigation regime. Apothecia development was delayed if an irrigation break occurred before the start of apothecia production. The delay was approximately of the same length as the irrigation break. A high irrigation level caused more abundant apothecia production in the sand than in the loam, while at a low irrigation level, more apothecia were produced in the loam than in the sand. The maximum lifespan of apothecia was 33 days which was measured in the sand irrigated at 5 mm/day. The length of the moist period needed for carpogenic germination and the influence of dry periods are shown in this study and can be used when predicting the start of apothecia development. It is also shown that both soil type, amount of irrigation or rainfall and its distribution must be considered when estimating the number of apothecia and apothecia longevity.

Einfluß verschiedener Bewässerungssysteme auf die karpogenc Keimung von Sklerotien des Pilzes Sclerotinia sclerotiorum

In den Jahren 1991 und 1992 wurde in Feldversuchen geprüft. welchen Einfluß das Ausmaß einer Bewässerung, die Dauer der Bewässerung. die Dauer einer Unterbrechung der Bewässerung und der Bodentyp auf die Bildung und das Überleben der Apothezien sowie das Überleben der Sklerotien von Sclerotinia sclerotiorum ausübten. Die Versuchsfläche wurde mit Sommerraps eingesät, und natürlich gebildete Sklerotien wurden 1 cm tief in den Boden gelegt. Die Apothezienbildung begann. nachdem der Boden für 25 bis 30 Tage kontinuierlich feuchtgehalten worden war, und wurde stark vom Bewässerungssystem beeinflußt. Wurde die Bewässerung vor Beginn der Apothezienbildung unterbrochen. Verzögerte sich die Apothezienentwicklung. Die Dauer der Verzögerung entsprach der Dauer der Unterbrechung der Bewässerung annähernd. Bei starker Bewässerung wurden auf Sand mehr Apothezien gebildet als auf Lehm, bei schwacher Bewässerung wurden auf Lehm mehr Apothezien gebildet als auf Sand. Die maximale Lebensdauer der Apothezien betrug 33 Tage und wurde auf Sand festgestellt, der mit 5 mm/Tag bewässert worden war. Die Dauer der für eine karpogene Keimung nötigen Feuchtig‐keitsperiode und der Einfluß von Trockenphasen werden in dieser Arbeit dargelegt und können verwendet werden. um den Beginn der Apothezienentwicklung zu prognostizieren. Ferner wird gezeigt, daß sowohl der Bodentyp als auch das Ausmaß der Bewässerung bzw. die Regeninenge und deren Verteilung in Betracht gezogen werden müssen, wenn die Zahl der Apothezien und ihre Lebensdauer geschützt werden sollen.
Inheritance of Virulence of Venturia inaequalis Toward Mains×domestica Cultivars
Authors: Sierotzki H. , Gessler C.
Published: May 2008

The resistances of the three apple cultivars ‘Boskoop’, ‘Spartan’, and ‘Golden Delicious’ were differential to the isolates Bo‐7 and Sp‐7 of Venturia inaequalis. Isolate Bo‐7 was virulent towards ‘Boskoop’ and ‘Golden Delicious’ not to ‘Spartan’, and Sp‐7 was only virulent toward ‘Spartan’, suggesting that a gene‐for‐gene relationship is working in this pathosystem. The two isolates were hybridized in order to determine the genetic basis of virulence. All theoretically possible phenotypes were found in 33 ascospore progenies from two selected strains carrying virulence towards ‘Boskoop’ and ‘Spartan’, with 14 progenies virulent towards ‘Boskoop’. 9 virulent to ‘Spartan’. and 15 virulent to ‘Golden Delicious’. Seven progeny were avirulent to all three cultivars, which is in agreement with the theoretical number of isolates with three avirulences. The segregation of virulence and avirulence among the progeny towards ‘Boskoop’. ‘Spartan’, and ‘Golden Delicious’ fit best to the hypothesis that one gene is responsible for virulence to ‘Boskoop’ and ‘Golden Delicious’ and that two genes are responsible for virulence towards ‘Spartan’, assuming that each gene segregated independently from the other genes. The two genes for virulence to ‘Spartan’ were complementary and were inherited independently. Virulence of V. inaequalis is governed by few heritable genes for each cultivar. Combinations of virulences are observed, indicating that the building‐up of complex races is possible.

Vererbung der Virulenz gegenüber Apfelsorten in Venturia inaequalis

Die Isolate Bo‐7 und Sp‐7 von Venturia inaequalis sind dilferentiell zu den Apefelsorten ‘Boskoop’. ‘Spartan’ und ‘Golden Delicious’. Das Isolat Bo‐7 ist virulent auf ‘Boskoop’ und ‘Golden Delicious’ und Sp‐7 ist nur virulent auf’ Spartan’. Die Nachkommenschaft von 33 Isolaten spalteten in alle theoretisch möglichen Phänotypen auf: 14 Nachkommen sind virulent auf ‘Boskoop’, 9 auf ‘Spartan’ und 15 auf ‘Golden Delicious’. Sieben Nachkommen sind avirulent auf alien drei Sorten, was mit dem errechneten Wert übereinstimmt. Die Segregationsdaten für Virulenz und Avirulenz gegenüber den drei Sorten zeigen. Daß die Virulenz gegenüber ‘Boskoop’ und ‘Golden Delicious’ von einem Gen und die Virulenz gegenüber ‘Spartan’ von zwei Genen bestimmt wird. Die Gene werden unabhängig voneinander vererbt. Die beiden Gene für die Virulenz gegenüber ‘Spartan’ sind komplementär und unabhängig vererbt. Virulenzkombinationen wurden beobachlet, was auf die Möglichkeit der Entstehung von kimplexen Rassen schliessen lässt.
Genetic Analysis of a Cross of Two Venturia inaequalis Strains that Differ in Virulence
Authors: Sierotzki H. , Gessler C.
Published: May 2008

A genetic map of the fungus Venturiainaequalis based on the Bo‐7 × Sp‐7 cross linking 30 RAPD‐PCR markers to the ITS‐region, the mating‐type locus and the virulence/avirulence to the apple cultivar ‘Boskoop’ was constructed. The map covers 270 cM and is divided into six linkage groups. The mating‐type locus is flanked by two RAPD‐PCR markers in 28.9 and 18.9 cM distance. The ITS‐region is located on one chromosome, spans a length of 7.16 cM and is linked to a RAPD‐PCR marker at 15.7 cM distance. The virulence/avirulence to ‘Boskoop’ is linked to a RAPD‐PCR marker at 19.5 cM. Virulence to ‘Golden Delicious’ is unlinked. The relative positioning (linked or unlinked) of virulence/avirulence genes is important for the adaptation of V. inaequalis strains to new introduced host resistances or lo new combinations of host resistances genes.

Genetische Analyse einer kreuzung zwtier Venturia inaequalis Stämme mit unterschiedlicher Virulenz

Durch die Kopplung von 30 RAPD‐PCR Markern, der ITS‐Region, dem ‘Mating’‐Typ und der Virulenz gegenüber ‘Boskoop’ wurde eine genetische Karte von Venturia inaequalis basierend auf der Kreuzung Bo‐7 × Sp‐7 erstellt. Die Karte ist 270 cM lang und in sechs Gruppen unterteilt. Der ‘Mating’‐Typ Locus ist von zwei RAPD‐PCR Markern eingeschlossen in 28.9 und 18.9cM Entfernung. Die ITS‐Region und mit ihr die r‐DNS ist auf einem Chromosom lokalisiert und ist 7.16 cM lang. Die ITS‐Region ist in 15.7 cM Entfernung zu einem Marker gekoppelt. Die Virulenz gegenüber ‘Boskoop’ ist in 19.5 cM zu einem Marker gekoppelt.
Critical review of Identification Techniques for Armillaria spp. and Heterobasidion annosum Root and Butt Rot Diseases
Authors: Schulze S. , Bahnweg G.
Published: May 2008

The need for a rapid and definite diagnosis of the Armillaria spp. and Heterohasidion annosum root and butt rot diseases as well as general requirements expected of a test to detect the pathogens are reviewed. As a spin‐off from more fundamental molecular biological research there has been a remarkable increase in new methods for diagnosis (i.e. detection and identification) in recent years. These new methods all have in comtnon that they use strtjctural elements of the target organisms such as proteins, polysaccharides, glycoproteins, nucleic acids, etc. for the construction of antibodies, probes and primers for detection, or to produce electrophoretic patterns to be used for classification and identification. This paper presents a short review of principles, advantages, disadvantages and some perspectives of the new methods developed for Armillaria spp. and H. annosum diagnosis compared with conventional ones, such as interfertility testing or visual inspection of the pathogens in situ and in vitro in pure culture. It will be noted that the specificity and reproducibility of the new techniques, which are closely linked with potential experimental error, lead to principal pitfalls which should be kept in mind when conclusions are drawn on data generated by them.

Even though PCR‐based methods become increasingly more widespread it is likely that most diagnostic methods will continue to be used or co‐exist in some form in the future.
Black Spot of Globe Artichoke: a Calcium‐deficiency Disorder
Authors: Morzadec J. M. , Hourmant A. , Corre J. , Romancer M. Le , Cottignies A. , Migliori A.
Published: May 2008

Experiments were performed with field‐grown artichoke (Cynara scolymus L.) cv. Capitan to determine whether the black spot disorder was associated with calcium deficiency in receptacles. Ageing of the plants and size of heads contributed to lower Ca levels of receptacles. Receptacles with lower amounts of Ca were more affected by the disorder. Globe artichoke infection by artichoke latent virus (ALV) and/or broad bean wilt virus strain french artichoke (BBWV‐FA) resulted in decreases in both the relative water content (RWC) of leaves and the Ca content of receptacles, and in increased black spot incidence. In addition, a wind‐screen and an anti‐trans‐pirant spray (composed of a wax emulsion and a spreader/sticker surfactant) increased the RWC of leaves and bracts and the Ca content of receptacles, and also significantly reduced the incidence of necrosed buds.

These data support the view that Ca deficiency is involved in the occurrence of black spot disorder.
Studies on Fusarium‐Gladiolus Interactions
Authors: Straathof TH. P. , Roebroeck E. J. A. , Löffler H. J. M.
Published: May 2008

Using standardized conditions, 65 genotypes of Gladiolus were screened for Fusarium resistance. High levels were found in ‘large‐flowered” types, Primulinus hybrids, G. callianthus, G. garnierii, and G. dalenii. Some accessions of G. dalenii exhibited no disease symptoms when inoculated with two standard test isolates. No resistance was found in ‘small‐flowered’ types. To estimate race‐specifity of the resistance, eight highly resistant Gladiolus genotypes were tested in an in vitro test against 43 isolates of F. oxysporum f.sp. gladioli. Two isolates were able to partially infect the G. dalenii accessions and this was confirmed using whole plants. Implications for resistance breeding are discussed.
Preservation of Purified Peanut Stripe and Turnip Mosaic Potyviruses by Freezing and Freeze‐drying
Authors: Fukumoto F. , Tochihara H.
Published: May 2008

During storage at ‐ 20 °C of purified preparations of peanut stripe and turnip mosaic potyviruses, infectivity of intact particles and RNA extracted from preserved preparations decreased. This decrease can be attributed to several factors such as virus aggregation and alterations of the nucleic acids and coat proteins. However, the addition to the preparations of 0.5% peptone or 1% sucrose permitted a high level of infectivity to be retained for extended periods. Freeze‐drying led to aggregation of the particles and in a marked decrease of infectivity. Virus aggregatioti and RNA degradation were suppressed by the addition of protectants such as 0.5% lysine. Results suggest that other potyviruses may be well preserved under similar conditions.
Use of Heteroduplex Mobility Analysis (HMA) for Differentiating Phytoplasma Isolates Causing Witches’ Broom Disease on Populus nigra cv Italica and Stolbur or Big Bud Symptoms on Tomato
Authors: Cousin M‐T. , Roux J. , Boudon‐Padieu E. , Berges R. , Seemuller E. , Hiruki C.
Published: May 2008

Heteroduplex mobility analysis (HMA) was performed to distinguish French and German isolates of phytoplasmas from Populus nigra cv Italica witches broom. The French isolate was similar to the phytoplasma responsible for the European aster yellows while the German isolate was different but closely related to it. When phytoplasmas inducing similar “stolbur” symptoms in tomato were compared to HMA, a high degree of genetic differences was observed among the reference stolbur C (StC) isolate, the European aster yellows and the other phytoplasmas inducing stolbur or big bud symptoms in tomato. Pseudo‐stolbur B and D from Brazil were differentiated from the reference St C using this method.
PCR‐Based Detection of Artificial Latent Infections of Geranium by Xanthomonas campestris pv. pelargonii
Authors: Sulzlnski M. A. , Schlagnhaufer B. , Moorman G.W. , Romaine C.P.
Published: May 2008

A procedure entailing biological enrichment and PCR amplification was developed to detect small populations of Xanthomonas campestris pv. pelargonii (X.c, pv. pelargonii) in tissues of geranium. Known numbers of colony forming units (CFU) of X.c. pv. pelargonii were introduced into ‘Red Elite’ geraniums through wounding of petioles and stems. Immediately after inoculation, sections of the petioles and stems were harvested and incubated for 24 or 48 h in nutrient broth (biological enrichment). After enrichment, bacterial cells were collected by centrifugation, followed by rapid extraction of total nucleic acid from the cells with GeneReleaser™, PCR amplification of DNA with pathovar‐specific primers, and ethidium bromide‐stained agarose gel electrophoretic analysis of the PCR products. After 48 h biological enrichment, it was possible to detect as few as 1 CFU of Xc. pv. pelargonii in stems and petioles collected immediately after inoculation, with the detection limit ranging between 1 and 120 CFU during multiple experiments. It also was possible to detect systemic movement of the bacterium in intact plants sampled 24 h after inoculation with a minimal inoculum (4 CFU). This procedure may have application in geranium certification programs concerned with the detection of latent infections associated with low levels of X.c.pv. pelargonii.
The Use of Detached Seedling Leaves of Triticum aestivum to Study Pathogenicity in Puccinia recondita f. sp. tritici
Authors: Felsenstein F. G. , Park R. F. , Zeller F. J.
Published: May 2008

A method is described for establishing isolates of Puccinia recondita f. sp. tritici (causal agent of brown rust of wheat) on detached seedling leaf segments. The method was used to compare the responses of leaf segments and intact seedling leaves for 28 differential genotypes inoculated with eight rust isolates. Leaf segments were incubated at two post‐inoculation temperatures (17 and 23C) and intact seedlings at 20–25 C. Reliable determinations of isolate pathogenicity was obtained using detached leaf segments of wheats with genes Lr l. Lr2a, Lr3a, Lr3bg., Lr3ka, Lr9, Lr15, Lrl9. Lr20, Lr24, Lr25. Lr26, Lr28, and Lr30 at both post‐inoculation temperatures, and for wheats with genes Lr2b. Lr2c, Lrl7, Lr23, Lr27 + Lr31 and LrH, at 23°C. Differences between leaf segments and intact leaves for the remaining eight differentials were attributed to inconsistent or poor expression of genes in detached leaf segments. By repeating tests with detached leaf segments, it was possible to establish the pathogenicities of the isolates on all of these differentials except those carrying Lr13, Lr14a, Lr16 and Lr18. Potential uses and limitations of the technique in studies of Puccinia recondita f. sp. tritici are discussed.
The Interaction of Humidity and Resistance Elicitors on Expression of Polygenic Resistance of Barley to Mildew
Authors: Newton A. C. , Dashwood E. P.
Published: May 2008

Elicitor‐active glucan was applied to leaves of genotypes of barley expressing different levels of resistance to powdery mildew (Erysiphe graminis f. sp. hordei)which was assessed by measuring mildew colonies per leaf or speed of papilla induction response to mildew challenge. The influence of humidity was also assessed by treating leaves with glucan, inoculating with mildew and immediately sealing the leaves in Perspex containers in an apparatus which enabled temperature, air speed and humidity to be controlled accurately. In water‐treated controls low humidity alone reduced colonies per leaf, and at 60% r.h. genotype 7204 showed significantly less effect of humidity compared with other genotypes, although at 40% it responded as other genotypes. At low humidity glucan stimulated resistance for genotypes Proctor and 7204 but not for Golden Promise or 9855; the effect of humidity or elicitor alone was only significant on genotype 7204, Chitin also proved an effective elicitor, but at high and not at low humidity. Time of pre‐treatment before mildew challenge, leaf stage, type of elicitor, concentration of elicitor, post‐inoculation light regime, mildew isolate and barley genotype all had major influences on papilla response. Other factors were less important. Based on papilla formation, the barley cultivar Proctor was most and Golden Promise the least responsive to glucan as an elicitor. The potential for exploiting the genetic basis of inducible resistance is discussed.
Surface‐related Changes of Fusing Phytophthora Zoospores
Authors: Ersek T. , English J. T.
Published: May 2008

Zoospores of Phytophthora spp. were fused and then regenerated using a technique previously described. At various points in the fusion and regeneration processes, components of spore surfaces were immunolabelled with specific monoclonal antibodies. Changes in the antigenic properties of spore surfaces during these events were monitored by fluorescence microscopy. Additional, surface‐related processes of the phenomena were monitored by electron microscopy, in the presence of lithium ions and polyethylene glycol, zoospores aggregated into clumps and began to fuse. During this time, zoospores retained their reniform shape and antibodies reacted only with plasma membrane‐bound antigenic components that are characteristic of the zoosporic state. Immuno‐labelling of cell wall occurred only after the fusion solution was replaced with a regeneration solution. As expected, the fusion and the asynchronous regeneration process resulted in the formation of enlarged cells with enlarged or multiple nuclei.
Pathogenicity, Non‐Host Hypersensitivity and Host Defence Non‐Permissibility Regulatory Gene hrpX is Highly Conserved in Xanthomonas Pathovars
Authors: Oku T. , Wakasaki Y. , Adachi N. , Kado C. I. , Tsuchiya K. , Hibi T.
Published: May 2008

Xanthomonas campestris pv. campestris and X. oryzae pv, oryzae contain the 1428 base pair hrpX gene whose product is involved in the regulation oi hrp genes required for pathogericity, non‐host hypersensitivity and non‐permissibility of compatible host defence responses. Previous Southern blot hybridization studies have suggested that hrpX is conserved in several X. campestris pathovars and X. oryzae. strains. We have confirmed and extended these findings using hrpX gene amplification by polymerase chain reaction, coupled with Southern blot hybridization analyses. Sixteen distinct pathovars of X. campestris and 12 strains of X. oryzae pv, oryzae were shown to contain homologs of hrpX which were not apparent in heterologous bacteria such as Agrobacterium tumefaciens, A. rhizogenes, Erwinia carolovora ssp. carotovora, Pseudomonas syringae pv, glycinea. P. syringae pv, labaci, and Escherichia coli. The hrpX gene is therefore highly conserved among Xanthomonas species and its gene product strongly resembles positive regulatory proteins of the AraC protein family,
A UK Isolate of Impatiens Necrotic Spot Virus From Glasshouse‐grown Cineraria
Authors: Weekes R. J. , Barker I. , Spence N. J. , O'Neill T. , Wood K. R.
Published: May 2008

A tospovirus was detected by ELISA in a Cineraria sample from a commercial protected crop in the UK. Its seroiogical properties indicated it to be Impatiens necrotic spot virus (INSV), results confirmed by RT‐PCR tests and nucleotide sequence data on the nucleoprotein‐encoding region of the genome. This is the first report of the presence of INSV in a protected crop grown in the UK.
Changes in Photosynthetic Electron Transport in Potato Cultivars with Different Field Resistance after Infection with Phytophthora infestans
Authors: Schnabel G. , Strittmatter G. , NOGA G.
Published: May 2008

The estimation of field resistance of potato cultivars to Phytophthora infestans are usually carried out in expensive and time consuming field experiments over several years. Therefore, a procedure is required for the fast and objective determination of qualitative and quantitative field resistance of new cultivars. This study correlated level of field resistance to P. infestans in leaf discs or leaflets of various potato cultivars to characteristic changes of Chlorophyll‐a fluorescence (CF) parameters Fm (maximal fluorescence) and Fv (maximal variable fluorescence). Two different inocula, both containing virulence genes 1‐11 were tested. The results were achieved when leaf discs from greenhouse or field plants were each inoculated with a P. infestans spore suspension and incubated for 24 h. In field measurements, comparable results were obtained 48 h after inoculation. The estimation of field resistance by measuring specific CF parameters could be an economical and rapid procedure to reduce or substitute visual lesion assessment for determining cultivar field resistance.
Induction of Systemic Resistance in Pea to Pea Powdery Mildew by Exogenous Application of Salicylic Acid
Authors: Frfy S. , Carver T. L. W.
Published: May 2008

Exogenous application of salicylic acid (SA) solutions to pea leaves induced systemic resistance to Erysiphe pisi. reducing by 20–30% the percentages of fungal germlings that successfully infected untreated leaves of SA‐treated plants. SA concentrations of 1.5 and 15 mM were similarly effective, but 0.15 mM had no detectable effect. While 15 mM SA solutions were phytotoxic. 1.5 mM solutions caused no apparent damage indicating that resistance induction was not due to tissue damage. The induced resistance persisted for at least 13 days after treatment, but excision of treated leaves 1 day after SA application prevented full induction of systemic resistance, and the resistance was not expressed if untreated leaves were inoculated fewer than 3 days after SA application. The effect of SA was transmitted to leaves at nodes both above and below treated leaves. Chemical induction of systemic resistance may provide an additional means for controlling pea diseases.
Differential Reaction of Barley Genotypes to Rhynchosporium secalis
Authors: Cselenyi L. , Friedt W.
Published: May 2008

Spring barley cultivars currently grown in Germany are all more or less susceptible to Rhynchosporium secalis (Oudem.) J.J. Davis, but there are obvious differences in the degree of susceptibility under field conditions. Small genotypic differences may be caused by both genetic and environmental effects, respectively. To minimize the influence of environmental variation on disease expression, several inoculation methods were developed in the present study. In two experiments the effectiveness of the inoculation by spraying of single spore isolates was tested in the glasshouse and in the field, respectively. High infection levels were achieved in the glasshouse. Despite the infection of barley in the field, disease expression levels remained low due to unfavourable conditions. Another experiment showed the usefulness of infected straw applied in the autumn only for testing the seedling infection type of spring barley cultivars against R, secalis. Seedling assay scores and field infection levels were closely related (r = 0.796, P < 0.01; r = 0.911, P < 0.001). Therefore, both the spray infection technique in the glasshouse and the inoculation technique using infected straw in the field appear to be suitable to detect genetic differences in resistance/susceptibility of spring barley cultivars against leaf blotch.
Variation in Metabolite Production by Septoria nodorum Isolates Adapted to Wheat or to Barley
Authors: Bousquet J. F. , Kollmann A.
Published: May 2008

The production of secondary metabolites by S. nodorum strains was examined in relation to their adaptation to wheat or to barley. Eleven strains of each type previously characterized were tested for the production in culture of (‐)‐(3R)‐mellein (ochracin), (3R)‐O‐metbylmellein; (‐)‐(3R,4R)‐4‐hydroxyniellein, (‐)‐(3R,4S)‐4‐hydro‐xymellein, mycophenolic acid, septorine, N‐methoxy‐septorine, N‐methoxyseptorinol, and a new compound (=UN).

Mellein was produced by every strain. Both 4‐hydro‐xymellein isomers were yielded by all wheat‐adapted strains and six barley‐adapted strains. Most of the strains produced mycophenolic acid. On the other hand the pigmentation of culture filtrates of wheat‐adapted strains was pale‐yellow whereas the pigmentation of barley‐adapted strains was grey‐blue. The productions of O‐methylmellein, septorine, N‐metboxyseptorine and N‐methoxyseptorinol were typical for wheat‐adapted strains. The detection of UN was restricted to the filtrates of barley‐adapted strains. If the pigmentation of filtrates and the production of septorines, UN and O‐methyl‐mellein are considered the strains fell into two groups. This classification is related to the host adaptation except for one barley‐adapted strain that showed characteristics of wheat‐adapted strains and one wheat‐adapted strain which did not produce septorines.
Biological Activities of Analogues of Ser‐Val‐Gly‐Glu (AS‐I), a Toxin Pathogenic to Sunflower
Authors: Liakopoulou‐Kyriakides M. , Metaxas A. , Sarigiannis Y. , Magafa V. , Stavropolulos G. , Laidou I. , Thanassoulopoulos C. C.
Published: May 2008

The tetrapeptides Ser‐Val‐Glu‐Gly, Hse‐Val‐Gly‐Glu, Thr‐Val‐Gly‐Glu, Val‐Ser‐Gly‐Glu and Ser‐Val‐Glu‐Gly, analogues of the AS‐1 toxin which is pathogenic to sunflower, were examined for biological activity on sunflower and eight other plant species. These peptides were synthesized in solution or on a solid phase. Of the species studied by leaf inoculation, sunflower and zucchini were the most susceptible and cotton the most resistant to ail of the toxins tested. The effect of Ser‐Val‐Glu‐Gly was similar to that reported for AS‐I, whereas the tetrapeptide Thr‐Val‐Gly‐Glu was the most toxic.
The Occurrence and Pathogenicity of Cylindrocarpon, Cylindrocladium and Fusarium on Calluna vulgaris and Erica spp. in England and Scotland
Authors: Litterick A. M. , Mcquilken M. P.
Published: May 2008

Cylindrocarpon, Cylindrocladium and Fusarium spp. were often isolated from the woody roots, stem‐base and lower foliage of diseased container‐grown Calluna vulgaris and Erica spp. plants collected from English and Scottish nurseries. The highest isolation frequencies were obtained for Cylindrocarpon destructans, Cylindrocladium scoparium, Cylindrocladium ilicicola. Fusarium tricinctum, Fusarium avenaceum and Fusarium sporotrichioides. Isolations of these fungi were made more frequently from diseased plants that were at least 1‐year‐old. The percentage incidence of Cylindrocarpon, Cylindrocladium and Fusarium spp. did not differ between Scottish and English nurseries. Cylindrocarpon destructans. Cylindrocladium ilicicola and C. scoparium were more pathogenic to rooted C. vulgaris cuttings than F. tricinctum. F. avenaceum or F. sporotrichioides in laboratory and glasshouse tests. The high isolation frequency of Cylindrocarpon. Cylindrocladium and Fusarium spp., and their pathogenicity in tests, suggests that these fungi are involved in root, stem‐base and lower foliage diseases in crops of C. vulgaris and Erica spp. The importance of these findings for the integrated control of diseases on ericaceous plant nurseries is discussed.
Preliminary Evidence for Phytoalexin Production by Eucalyptus urophylla Leaves as a Response to Inoculation with the Incompatible Pathogen Acidovorax avenae pv. avenae
Authors: Romeiro R. S. , Lima V. B.
Published: May 2008

Leaves of eucalyptus (Eucalyptus urophylla) were infiltrated with a cell suspension of the incompatible pathogen Acidovorax avenae pv. avenae and showed a typical hypersensitive response within 24h. Necrotic leaf areas were excised, vacuum infiltrated with 40% ethanol and left under continuous agitation at room temperature for 24h. The diffusate was concentrated, partitioned with ethyl‐acetate, concentrated to dryness and resuspended in a small volume of methanol. The biological activity of extracts was evaluated by an agar diffusion method against noncompatible bacteria (A. avenae pv. avenae and Xanthomonas axonopodis pv. manihotis) and fungi (Penicillium sp. and Aspergillus sp.). Inhibition haloes, when present, were always larger in extracts from leaves infiltrated with the incompatible bacterium than the water control. Thin layer chromatography resolution of crude extracts from leaves infiltrated with both incompatible pathogen cell suspension and water, followed by bioautography with Thieleviopsis paradoxa, consistently rendered, in both situations, a large, diffuse inhibition halo near the origin, assumed to be due to preformed antimicrobial substances. However, extracts from leaves infiltrated with the living cells of the incompatible pathogen gave rise to a smaller, second inhibition halo, near the front, that was interpreted as being one or several phytoalexins.
Induced Resistance Against Plasmopara helianthi in Sunflower Plants by DL‐β‐Amino‐n‐butyric acid
Authors: Tosi L. , Luigetti R. , Zazzerini A.
Published: May 2008

Sunflower plants treated with the nonprotein amitio add, DL‐β‐attiino‐n‐butyric acid (BABA) were protected against infection with Plasmopara helianthi. Soil drenches at the highest rates (150‐250 mg/kg soil), applied one day before the inoculation induced high levels of protection (80‐83%) against the disease and more than 90% control was observed when BABA was applied at 300 mg/kg soil. However, at this concentration phytotoxic symptoms were observed. This compound also provided a curative activity when applied one day post‐inoculation. BABA had no antifungal activity in vitro against P. helianthi. The effect of BABA on zoosporangia germination was evaluated by treating pre‐germinated seeds with the compound solution and the zoosporangia suspension for 3 h. Then, seeds were sown and the percentages of infected plants were determined. The other two aminobutyric acid isomers (a and g) were ineffective against downy mildew. The mechanisms by which DL‐β‐amino‐n‐butyric acid protect sunflowers against downy mildew awaits more detailed elucidation.
Echinochloa Hoja Blanca and Rice Hoja Blanca ViriKies Occupy Distinct Ecological Niches
Authors: Madriz J. A. , DE Miranda J. R. , Cabezas E. , Oliva M. , Hernandez M. , Espinoza A. M.
Published: May 2008

This study provides both direct and indirect evidence that, in Costa Rica, rice hoja blanca virus and Echinochloa hoja blanca virus occupy distinct ecological niches, implying that their molecular differences are the result of evolutionary divergence rather than variation within a single virus population. For this reason they should be considered separate virus species, rather than strains of a single species.
Biological and Serological Variability of Zucchini Yellow Mosaic Virus in Sudan
Authors: Mahgoub H. A. , Desbiez C. , Wipf‐Scheibel C. , Dafalla G. , Lecoq H.
Published: May 2008

Zucchini yellow mosaic potyvirus (ZYMV) is prevalent in different cucurbit growing agro‐ecosystems in Sudan. A study of the biological and serological variability of isolates originating from different regions was conducted to better understand ZYMV epidemiology and to develop adapted and durable control strategies. Variability was detected among isolates regarding symptomatology, host range and virulence towards the Zym resistance gene in melon (Cucumis melo L.) PI 414723. Serological variability was also revealed using a set of seven differential monoclonal antibodies (mAbs) raised against a French isolate (ZYMV‐E9). Six serotypes were differentiated, but a majority of isolates (88%) reacted with all the mAbs as did the reference strains from Italy and France. All isolates from Sudan were equally well controlled by the resistance genes described in squash (Cucurhita moschata (Duchesne) Duchesne ex Poir. cvs. Menina and Nigeria) and in cucumber (Cucumis sativus L. cv. TMG), or by cross protection with the mild ZYMV‐WK strain. All isolates were transmitted in a nonpersistent manner by Aphis gossypii Glover and Myzus persicae Sulzer.
Development of Early Infection Structures of Puccinia recondita f. sp. tritici in Non‐host Cereal Species
Authors: Hu G. G. , Rukenberg F. H. J.
Published: May 2008

The development of infection structures, derived from urediospores of Puccinia recondita f.sp. trilici in nearisogenic lines of susceptible and resistant wheat, and in non‐hosts (viz. maize, oat, sorghum and barley), was examined by fluorescence microscopy and scanning electron microscopy (SEM). The infection structure formation on and in five cereal species follows a similar pattern. In sorghum, fungal development is arrested at the stage of substomatal vesicle formation, while, in maize, most fungal structures collapse during the stage of primary hypha development. By contrast, in wheat, barley and oat, the fungus forms many branched infection hyphae and haustorial mother cells.
Sequence of a Plastocyanin cDNA From Wheat and the Use of the Gene Product to Determine Serologically Tissue Degradation after Infection with Pseudocercosporella herpotrichoidesa
Authors: Coff C. , Poupard P. , Xiao Qiu , Graner A. , Lind V.
Published: May 2008

Pseudocercosporella herpotrkhoides, the causal agent of the eyespot disease of wheat, induces lesions at the stetn bases, in degraded tissue a specific protein (Pc) cannot more be detected whereas it is abundantly produced in the green tissue showing no disease symptotns. In plant satnples including the stem bases, the amount of protein Pc is therefore correlated with the degree of tissue degradation. A serological test (ELiSA) was developed for the quantitative determination of the protein. ELISA readings can be used as estimates of disease severity.

By sequence analysis, Pc was identified as plastocyanin. Based on the nucleic acid sequence, wheat pre‐plastocyanin consists of a transit peptide of 61 amino acids and a tnature peptide of 97 residues. Comparison of the nucleotide sequences of plastocyanin of wheat and barley showed homology of 93.7%.
Conidium Germination and Appressorium Penetration of Colletotrichum gloeosporioides on Stylosanthes guianensis
Authors: Munaut F. , Maraite H.
Published: May 2008

Pre‐penetration and early penetration phases of two pathogenic strains of Colletotrichum gloeosporioides (HM 502, HM 514) from Zaire were investigated quantitatively on four Stylosanthes guianensis genotypes (cv. Schofield, cv. Graham, ClAT 184 and CIAT 10136) of various levels of susceptibility.

The results demonstrated control of the rates and type of conidial germination by the fungus, influenced to a lesser extent by the host genotype. Cell reactions were visible as papillae and cytoplasmic aggregations closely associated with the penetration peg. No fungal growth was observed when deposits of papillae occurred under appressoria‐forming infection pegs, whereas the effect of the cytoplasmic aggregations varied according to the host genotype. In the interactions with strain HM 502, the highest rates of plant reaction were recorded on the resistant CIAT 184 genotype, while the highest level of penetration without reaction was observed on the most susceptible cv. Schofield. Cytoplasmic aggregations were also observed under a few ungerminated appressoria on this genotype. Differences were thus detected in the rates and types of conidial germination, in the rates and types of cell reactions under appressoria and in the appressorial penetration rates without cell reactions. However, these differences did not completely explain the range of macroscopic symptoms observed on the various genotypes.
Detection of Tobacco Mosaic Virus Movement Protein in Association with Tobacco Nuclei Isolated from Intact and Detached Leaves
Authors: Susi P.
Published: May 2008

The movement protein (MP) of tobacco mosaic virus was observed to cofractionate with nuclei from intact and detached tobacco (Nicotiana tahacum cv. Xanthi‐nn) leaves. When purified nuclei were treated with proteinase K, MP disappeared indicating that MP is localized close to but not inside nuclei. Moreover, the amount of MP was showti to increase greatly in nuclei isolated from detached leaves, thus facilitating the detection of MP. Accumulation close to nuclei was strongest early in infection, results indicating that it may be an early step in the pathway of MP from cell cytoplasm to plasmodesmata. Other TMV‐specific proteins were not detected in the nuclei fraction.
UP‐PCR Genotyping and rDNA Analysis of Ascochyta pisi Lib
Authors: Lübeck P. S. , Alekhina I. A. , Lubeck M. , Bulat S. A.
Published: May 2008

Isolates of Ascochyta pisi, previously identified as separate pathotypes, were genotyped by rDNA‐RFLP and UP‐PCR using 8 UP‐primers and 2 arbitrary primers individually or in pair‐wise combinations. The appearance of polymorphic UP‐PCR products for all studied isolates facilitated their differentiation. The markers were suitable in identifying isolates, and may be useful for developing isolate‐ or pathotype‐specific PCR‐based diagnostic assays. In studying genetic relatedness by UP‐PCR among A. pisi isolates, two distinct clusters were revealed. rDNA analysis of the isolates based on endo‐ntjclease digestion of amplified ITSl and 1TS2‐25S nuclear rDNA regions did not separate the isolates, whereas the variabihty of the isolates using UP‐PCR was more than 40%.
Transformation of Erwinia carotovora ssp. atroseptica with the Green Fluorescent Protein Gene from Aequorea victoria
Authors: Pesnyakevich A. G. , Lyon G. D.
Published: May 2008

Erwinia carotovora ssp. atroseptica has been transfortned with the green fluorescent protein (GFP) gene from Aequorea victoria. Transformants had very high levels of GFP expression but some plasmid instability was apparent when bacteria were not grown on atnpicillin. Confocal microscopy showed variation between cells in the level of expression of GFP. Transfonnants retained their pathogenicity on potatoes, rotting tubers and causing typical blackleg symptoms when inoculated into stems, but the level of fluorescence was not suitable for observing bacterial movement. In contrast, E. coli producing GFP could be used to follow bacterial movement within vascular tissue of potato leaves.
Single Spore Infections with Sunflower Downy Mildew
Authors: Spring O. , Rozynek B. , Zipper R.
Published: May 2008

A technique was developed to select vital zoospores of Plasmopara haistedii after zoosporogenesis for the infection of sunflower leaf disks. Successful infections were performed with samples containing several zoospores originated from a single sporangium as well as with samples containing only one single zoospore. Infections were indicated by spontaneous sporulation at the surface of inoculated sunflower leaf discs and were secured by transfer to whole seedlings. Using this method it was possible to generate unithallic infections and genetically homogenous strains of sunflower downy mildew.