bluuebunny/crossref_metadata_2025 huggingface dataset:
Diagnosis of Phytophthora infections in raspberry and strawberry plants by ELISA tests
Authors: Olsson C. H. B.
Published: May 2008

Plant diseases caused by Phytophthora spp. may be reproducibly diagnosed by DAS ELISA techniques, but this type of analysis has long been hampered by the presence of phenolic and related compounds in plants to be tested, not least in strawberry and raspberry plants. The compounds will interfere with the ELISA test procedure, leading to high non‐specific optical density readings. To overcome this, a series of experiments was performed. Phenolic and related compounds in the samples were first absorbed to polymers during antigen extraction and thereafter separated by filtration at slow rate. To inhibit non‐specific binding of enzyme‐conjugated antibodies, the plastic wells were preincubated with non‐sensitized wells, equally high background values of optical density were seen under untreated conditions and after the use of polymeric adsorbents. A marked reduction in optical density was, however, seen after blocking with non‐fat dry milk, but the optimal conditions for all concentrations ofantigen were seen first after combined pre‐treatment with polymeric adsorbents and non‐fat dry milk. When the threshold absorbance for positive detection was calculated, the low optical density values from healthy plants, at all antigen concentrations studied, contributed to an excellent discrimination between samples from diseased and healthy plants.
The ice Nucleation Activity of Pseudomonas fluorescens Migula and its Inhibition by Various Chemicals
Authors: Mittelstüdt H.
Published: May 2008

The ice nucleation activity (INA) of three strains of Pseudomonas fluorecens, nos 553, 554 and 606, isolated by the Institute for Pathogen Diagnostics in Ascherleben, Germany, was determined. Under equal growth conditions and at given test temperatures the ice nucleation frequency spectra of the isolates differed slightly. The fraction of cells which acted as ice nuclei increased with falling temperatures. Below −5°C the nucleation frequency rose from 10‐8 to 10‐3. Between, 0 and −10°C only a fraction of approximately 2 to 5 × 10‐3 cells performed ice nucleation activity.

Fifteen newly synthesized chemicals showed no or only a very slight intrinsic INA at −5°C and −7°C. The compounds were used as antinucleators against INA‐exhibiting bacteria.

In INA‐exhibiting suspensions of isolate 553 bacterial ice nuclei were reduced after treatment with the 15 compounds. Dependent on the compounds, a nucleation frequency of −8.32 to −5.10 was detected at −5°C. At −7°C, the frequency amounted to −7.89 to −5.05. As the temperature was lowered to −10°C in bacterial suspensions which were treated with 9 (of the 15) compounds, a remainder of 1.79 to 5.91 × 10‐6 cells retained ice nucleation activity. The most pronounced inhibitory effect was noted for the compounds 1989/6255, 1989/6436 and 1990/6158. In a 10‐fold dilution of isolate 553 the compound 1989/6153 inhibited ice nucleation between 0 and 10°C so strongly that it was about 100 times below the control.

The ‘tube‐freezing’ method showed that on excised corn leaves treated with 1989/6259 and 1990/6155, the bacterial INA decreased while the super‐cooling was more pronounced.

‘Frostgard’, 1986/6205, 1986/6199 and 1989/6259 inhibited most INA‐exhibiting bacteria on corn seedlings. Compared to inoculated plants, a significantly higher percentage of treated plants survived at −2 and −3°C.
The Occurrence of Bacterial Red Streak of Sugarcane Caused by Pseudomonas syringae pv. syringae in Iran
Authors: Rahimian H.
Published: May 2008

A bacterial leaf streak disease characterized by reddish, narrow (1–2 mm wide) streaks of variable size, and occasionally with bleached centers, was found in sugarcane (Saccharum, interspecific hybrid) fields in northern Iran. The incitant bacterium was identified as Pseudomonas syringae pv. syringae (P. s. syringae). The disease is similar in aetiology to the sugarcane ‘red streak’ disease reported recently from Japan. Cultivardependent variations in symptoms were noted., Difference in pathogenicity as well as in electrophoretic profile of cell proteins between strains of P.s. syringae causing red streak in sugarcane and those causing canker on stone fruit trees, were observed.
Light‐Dependent Necrosis Formation by Magnaporthe grisea Toxin(s) in Rice cv. Sekiguchi‐asahi*
Authors: Iedome M. , Arase S. , Honda Y. , Nozu M.
Published: May 2008

The significance of light irradiation in neerosis formation by Magnaporthe grisea toxin(s) on rice cv. Sekiguchi‐asahi was investigated. The effective wave region for light‐dependent neerosis formation was 400 700 nm. An absorption band of the toxin(s) was restricted to the wave region shorter than 400 nm. Both of the phytosynthesis and necrosis formation were inhibited by photosynthetic inhibitors, and the inhibition of both activities was dependent on concentration of the inhibitors. The necrosis formation by the toxin(s) depended on light intensity. The toxin(s) induced the necrosis formation only on the cells with many chloroplasts, and the cells without chloroplasts did not form necrosis even under the light with sufficient intensity. The more the number of chloroplasts decreased, the more the size of necrotic spot decreased on the leaf sheath. From these results we concluded that the photosynthetic activity was involved in the necrosis formation by Magnaporthe grisea toxin(s) in rice cv. Sekiguchi‐asahi.
Pathogenicity of Alternaria alternata and Fusarium moniliforme and Phytotoxicity of AAL‐toxin and Fumonisin B1 on Tomato Cultivars
Authors: Abbas H. K. , Tanaka T. , Duke S. O.
Published: May 2008

Phytotoxicity of AAL‐toxin and fumonisin B1 to six cultivars of tomato was compared with the pathogenicity of their fungal sources, Alternaria alternata and Fusarium moniliforme, respectively. These include two AAL‐toxin susceptible cultivars with genotypes(asc/asc), three resistant cultivars (Asc/Asc), and a heterozygous cultivar (Asc/asc.) A. alternata spores were pathogenic to the susceptible but not to the resistant cultivars F. moniliforme was not pathogenic to any of the tomatoes. Filtrates of both fungi grown on rice containing their respective toxins caused necrosis within 48 h and eventually mortality on susceptible cultivars but not on the resistant lines. The heterozygous cultivar Asc/asc showed minimal damage and no mortality after 14 days exposure to both filtrates and both toxins. The spores of both fungi had no effect on heterozygous intact plants. Tomato leaf disc bioassays with AAL‐toxin and fumonisin B1 at 1μM caused cellular leakage and reduced chlorophyll content in susceptible cultivars and minimal effects on the heterozygous and resistant varieties.
Studies on the Biological Control of Phytophthora cryptogea Pethybr. et Laff. II. Effectiveness of Trichoderma and Gliocladium spp. in the Control of Phytophthora Foot Rot of Gerbera
Authors: Orlikowski L. B.
Published: May 2008

Bip T containing about 109 spores of Trichoderma viride, applied to peat 10 days before inoculation of substrate with Phytophthora cryptogea, effectively controlled Phytophthora foot rot of gerbera. The biocide in dosage of 300 and 600 g/m3 inhibited the development of the pathogen in substrate. The other potential antagonists T. hamatum and T. viride applied into peat at a dosage of 600 g/m3, decreased Phytophthora foot rot development.
The Biology of Rose Rosette Disease: A Mite‐associated Disease of Uncertain Aetiology
Authors: Epstein A. H. , Hill J. H.
Published: May 2008

Spread of rose rosette disease was best described by a logistic population growth model. In Iowa, peak susceptibility to graft transmission of the disease in the field occurred from May 27 thrrough July 10. Populations of the eriophyid mite vector were low until mid‐July and reached peak levels at the end of August. Host range was limited to multiflora rose and hybrid ornamental roses. No evidence was obtained for seed‐or soil‐transmission of the aetiologic agent and no symptom remission was obtained with either heat therapy or tetracycline treatment. A significant decrease in stored starch corresponded with a major decrease in sucrose and increases in fructose and glucose in infected tissue. Because of its limited host range, the agent may have potential for biocontrol of multiflora rose.
Use of an Immunocapture‐Polymerase Chain Reaction Procedure for the Detection of Grapevine Virus A in Kober Stem Grooving‐Infected Grapevines
Authors: Chevalier S. , Greif C. , Clauzel J.‐M. , Walter B. , Fritsch C.
Published: May 2008

Reliable and highly sensitive detection of grapevine virus A (GVA) in grapevine leaf tissue by reverse transcription‐initiated polymerase chain reaction was achieved after enrichment and partial purification of the virus from grapevine crude sap by an immunocapture (IC) procedure. In comparison with ELISA the gain of sensitivity was estimated up to 1000‐fold in grapevine mature leaf tissue. Using IC‐reverse transcription polymerase chain reaction (IC‐RT‐PCR), GVA could be detected in very young grapevine tissue where the virus titre was largely below the detection limit of ELISA. The comparison of IC‐RT‐PCR and biological indexing results for about 60 grapevine accessions revealed a good correlation between the presence of GVA and the development of Kober stem grooving (KSG) symptoms in the specific indicator rootstock Kober 5BB. Moreover, the elimination of KSG by heat treatment in two Vitis vinifera cultivars, Savagnin rose and Servant, was accompanied by the loss of detection of GVA by PCR, thus providing further argument for the involment of GVA in the aetiology of KSG.
Relationships among Trialeurodes vaporariorum—Transmitted Yellowing Viruses from Europe and North America
Authors: Coffin R. S. , Coutts R. H. A.
Published: May 2008

Beet pseudo‐yellows virus (BPYV), a possible closterovirus first identified in California, has long been thought to cause economically important whitefly‐transmitted diseases worldwide, although serological and molecular evidence for this is lacking. A yellowing virus prevalent in the UK in 1988, originally thought to be identical to BPYV, was shown by a specific reverse transcription polymerase chain reaction (RT‐PCR) test to differ from BPYV and from other whitefly‐transmitted yellowing viruses from France, The Netherlands, Spain and Turkey. Sequence analysis of a putative polymerase gene of the virus showed that it differed from known closterovirus genes, results suggesting that the virus may be an uncharacterized species. Following development of an RT‐PCR test diagnostic for currently prevalent whitefly‐transmitted yellowing viruses, a second virus was shown to be different from that found in 1988 but closely related to BPYV and the other yellowing viruses from Europe. This is the first direct evidence of a relationship between the latter and BPYV.
The Coffea arabica Fungal Pathosystem in New Caledonia: Interactions at Two Different Spatial Scales
Authors: Lamouroux N. , Pellegrin F. , Nandris D. , Kohler F.
Published: May 2008

The simultaneous analysis of epidemiological and environmental variables could contribute to the determination of the main factors which govern the epidemic dynamics of diseases (i.e. rust, anthracnose and Cercospora leaf spot) in Coffea arabica. With this in mind, the condition of previously marked leaves in 29 plots. which were grouped in 11 different sites in New Caledonia. were surveyed monthly. In the same period, the environmental characteristics of the plots (soil type, climate, etc.)were determined.

Statistical analysis of these data revealed significant correlations between pathology and the environment. at the sites’ level (analysis of the mean site values) as well as at the plots' level (analysis of the deviations with the mean site value). The site effects predominated: at those sites in which rust was the major disease, leaf and branch mortality were more pronounced than at sites in which anthracnose or Cercospora leaf spot predominated. Rust was generally associated with soil pH values that were favourable for coffee tree development. with poor soil structure and with large temperature ranges. Within a site. plot exposure to sun and wind could enhance anthracnose and Cercospora leaf spot.

Finally, in New Caledonia the three variables soil pH, soil structure and temperature range allow a simple and satisfactory estimation of the epidemiological risks in a given plot.
Rapid Tomato Seedling Assay for Virulent Isolates of Fusarium oxysporum F. sp. Radicis‐lycopersici (FORL), the Tomato Crown and Root Rot Pathogen
Authors: Madhosingh C.
Published: May 2008

A rapid tomato seedling assay was developed for determining the relative wilt capacity of isolates of Fusarium oxysporum f. sp. radicis‐lyco‐persici (FORL), a virulent strain of the tomato pathogen. The procedures for the assay require that 5‐day‐old cv. Bonny Best tomato seedlings be dipped in 30‐day cell‐free concentrated culture filtrates of FORL isolates, which were grown in Czapek‐Dox medium with 2% Bacto‐casamino acids (CDA). The seedlings in the culture filtrates were then incubated at 30 C under artificial light (1200 ftcandles) at 28% relative humidity in a wind stream of 100–150 m min. The relative pathogenicity of the isolates was determined by inoculating the roots of 18‐day‐old seedlings with cultures of FORL isolates. The pattern of cell‐free filtrate wilt among the isolates was the same as that for the disease caused by cultures of the isolates. The seedlings treated with the filtrate from the most virulent isolate (Harrow HRS‐182) wilted in 20 min. The filtrates from less virulent isolates took progressively longer. up to 90 min. to cause comparable wilt. Isolate HRS‐082 was the first isolate also to induce disease in 10‐day‐old seedling assay. Both assays indicate three levels of wilt and disease capacities amongthe isolates examined. The utility of the assay in research and breeding for resistance is discussed.
Altered Expression of Erwinia amylovora HRP Genes in Tobacco Leaves Pretreated with Bacterial Protein‐Lipopolysaccharides
Authors: Minardi P.
Published: May 2008

Infiltration of protein‐lipopolysaccharide complexes (pr LPS) (250 μg/ml) of Pseudomonas syringae pv. aptata into tobacco leaves protected against subsequent elicitation of the hypersensitive response (HR) by Erwinia amylovora. The effect of prLPS on the expression of E. amylovora hrp (hypersensitive response and pathogenicity) gencs was tested in protected tobacco leaves and in a defined medium in which hrp genes were highly expressed. Two,E. amylovora hrp loci transcriptionally fused with the Escherichia coliβ‐glucuronidase (Gus) coding sequence were used as chromosomal reporter genes. The prLPS treatment did not affect hrp gene expression of Hrp‐ mutants both in planta and in vitro, so the effect of prLPS treatment on hrp gene expression of two E. amylovora Hrp+ transformants was assayed during HR development in unprotected tissue and during the same time in prLPS protected tissue. A plasmid containing the same Gus fusions previously located in the chromosome was introduced into a wild‐type strain of E. amylovora. Gus activity was significantly lower in protected tissue. We suggest that HR inhibition by prLPS treatment requires the entire hrp gene cluster in order for the bacteria to send a signal to the plant. which, in turn, inhibits the expression of hrp genes.
Bipolaris multiformis (Jooste) Alcorn Pathogenic on Leaves of Cucumis sativus in Italy
Authors: Vannacci G.
Published: May 2008

A destructive disease was observed in August 1981 in a field of Cucumis sativus cv. Radar. Sincc then sporadic spots on leaves of the same cultivar were recorded in 1985, 1988 and 1993. The causal agent was identified in Bipolaris multiformis (Jooste) Alcorn. The fungus produces frequently irregular (mostly Y‐shaped) conidia in culture but rarely on leaves. The pathogen germinates bipolarly in distilled water at 20–25°C (95 and 90% respectively), and on leaves it produces appressoria;, entry points are either stomata or the intact surface. Pathogenicity tests carried out on various cucurbitaceous plants showed symptom intensity decreasing with the following order: C. sativus cv. Radar and Eeballium elaterium > Brionia cretica subsp. dioica > Cueurbita pepo L. var. pommiformis and C. pepo var. patissonina f. radiata > C. moscata and Sechium edule. The other two tested cultivars of Cucumis sativus (Mezzolungo Marketer and Corto per sottaceti) and C. pepo cv. Verde scuro di Milano showed sterile, very small necrotic dot. Control plants, Citrullus lanatus cv. Sugar baby, Cucumbis melo and Lagenaria siceraria showed no symptoms.
Characterization and Cytopathology of Hibiscus Latent Ringspot Virus Isolated from Kenaf (Hibiscus cannabinus L.) in Italy
Authors: Rubies‐Autonell C. , Turina M.
Published: May 2008

Hibiscus latent ringspot virus (HLRV) was isolated from kenaf plants (Hibiscus cannabinus L.) in Italy. and identified as III. RV by its host range, purification, electron microscopy and serology. Ultrastructural studies showed that infected plants contained membranous cytoplasmic inclusion bodies. characteristic of nepoviruses, and sometimes also crystalline aggregates.
Effect of Temperature and Air Humidity on Multiplication of Xanthomonas campestris pv. undulosa and Symptom Expression in Susceptible and Field‐Tolerant Wheat Genotypes
Authors: Duveiller E. , Maraite H.
Published: May 2008

Multiplication of Xanthomonas campestris pv. undulosa in the leaf tissues of susceptible and field‐tolerant wheat genotypes was determined at the secdling stage, under different incubation conditions of temperature and air humidity. Dry air conditions did not hamper the multiplication of the population trend. Symptoms were not observed at 15°C. The occurrence of lesions coincided with populations of baeteria that had reached an estimated threshold of 108 colony forming units/leaf. Differences in populations between genotypes Alondra and Pavon were only noticeable at 25°C and dry air conditions, without correlation to differences in symptom expression. Considering these two genotypes, resistance to bacterial leaf streak did not seem to operate at the seedling stage when plants were inoeulated by infiltration. In both genotypes, lesions did not extend significantly. An aetive mechanism stopping bacterial growth which is apparently temperature‐dependent or a saturation of the, target sites was possibly involved, as shown in the different experiments by the fit‐curves calculated for Alondra and Pavon. This study provided information on the role of climatic factors in relation to epidemics. Temperature appeared to have a major effect on the disease and results confirmed that the risk of bacterial leaf streak prevails in warmer non‐traditional wheat growing areas. Several types of resistance are likely to exist in the X. e. pv. undulosa/wheat system.
Spontaneous Genetic Variation for Leaf Rust Reaction in Sinvalocho MA Wheat
Authors: Sacco F. , Favret E. A. , Suarez E. Y. , Solari R. M. , Saione H. A.
Published: May 2008

Spontaneous off‐type plants for leaf rust reaction to Argentine races 66 and 77 of Puccinia recondita tritici were found at rates of 3.4 per 1000 and 0.44 per 1000, respectively, in the progeny of self‐pollinated (bagged) spikes of Sinvalocho, MA wheat. Leaf rust reaction changes were associated to aneuploidy in most cases. The variation to race 66 was associated to monosomy of chromosome 6B or probably deletions on chromosome arm 6BL. Some off‐type plants however showed, in subsequent generations. changes for reaction to race 77 or simultaneous changes to races 66 and 77 as well as changes in leucine aminopeptidase isozyme expression, which cannot be explained on grounds of allelic dosage. The origin of these genetic and chromosomal changesis not clear in some cases, however, a common origin could be suggested by the presence of transposonlike elements.
A Method for the Quantitative Assessment of Wound‐induced Chitinase Activity in Potato Tubers
Authors: Appel M. , De Ries G. F. W. , Hofmeyr J.‐H. S. , Bellstedt D. U.
Published: May 2008

A method for the quantitative assessment of chitinase activity was developed. Dilution series of crude potato tuber chitinase extracts were assayed with a colorimetric microtitre plate assay. using CM‐chitin‐RBV as enzyme substrate. Linearity between absorbance values mea‐sured (540 nm) and enzyme concentration was found to be limited to the low concentration range. where depletion of the substrate was no longer limiting. As as absorbance of 0.1 always fell within the concentration range for which absorbance‐concentration linearity was valid. one unit of enzyme activity was defined as the amount of enzyme needed to yield and A of 0.1. A more reliable method for the assessment of chitinase activity was established by basing the difinition of enzyme, activity on a concentration rather than on as absorbance value. as was done previously. Using this method, differences in the rate of chitinase induction upon wounding were demonstrated for six commercial potato cultivars.
Oxidative Protective Mechanisms and Resistance to the Dicarboximide Fungicide, Iprodione, in Alternaria alternata
Authors: Steel C. C. , Nair N. G.
Published: May 2008

The free radical scavengers α‐tocopherol and butylated hydroxytoluene, but not ascorbate, diminished the growth‐inhibiting effects of the dicarboximide fungicide, iprodione in Alternaria alternata. Growth of A. alternata in the presence of iprodione increased the activities of superoxide dismutase and glutathione reductase while catalase was unaffected. Four iprodione sensitive and four iprodione resistant isolates of A. alternata were compared for activity of free radical enzymes. The isolates of A. alternata resistant to iprodione had more catalase activity than those which were sensitive, but did not differ in superoxide dismutase of glutathione reductase, activities. 3‐Amino‐1.24.‐triazole, a specific inhibitor of catalas, reduced the ability of DAR 69775, a dicarboximide resistant isolate of A. alternata. to grow in the presence of iprodione. In A. alternata dicarboximide resistance appeats to be at least partially mediated by enhanced activitiesof, catalase.
Characteristics of Serially Produced Zoospore Suspensions of Polymyxa betae for Transmission of Beet Necrotic Yellow Vein Virus
Authors: Dirven J. A. A. M. , Peters D.
Published: May 2008

Zoospore suspensions of Polymyxa betae were analysed for their potential as inocula to infect sugar beet plants with beet necrotic yellow vein furovirus. The infectivity could be maintained when zoospore suspensions were serially transferred. When zoospore‐producing seedlings were individually transferred some of these seedlings lost their infectivity after several passages. Infectivity was first detected in suspensions within I day after inoculation of the plant by zoospores. The suspensions remained infectious for at least 10 h after removal of the plants producing viruliferous zoospores. Both the number of test plants infected and the concentration of virus that developed were greater at 25 C than at 20 C.
Susceptibility of Barley Cultivars and Lines to Fusarium Infection and Mycotoxin Accumulation in Kernels
Authors: Perkowski J. , Kiecana I. , Chelkowski J.
Published: May 2008

Heads of 12 barley genotypes (8 cultivars and 4 lines) were inoculated with conidial suspension of the following single isolates: F. culmorum no. 3, F. graminearum no. 122 and F. sporotrichioides no. ATCC 62 360. The number of kernels per head. 1000 Kernel weight and yield have been calculated for each genotype. Seed samples collected at harvest were analysed for each genotype. Seed samples collected at harvest were analysed for several trichothecene mycotoxins and zearalenone.The mycotoxin concentrations (mg/kg) in barley kernels inoculated with F. graminearum were as follows. deoxynivalenol (DON) 0.1 to 5.4 (av. 2.3). 3‐acetyldeoxy‐nivalenol (3‐AcDON) 0.0–0.2 (av. 0.1), 15‐acetyldeoxynivalenol (15‐AcDON) 0.0–0.7 (av.0.2), nivalenol (NIV) 0.0–0.8 (av. 0.3). zearalenone (ZEA) 0.0–0.1 (av. 0.0); F. culmorum: DON 0.6 to 12.0 (av. 5.3), 3‐AcDON 0.1 to 1.0 (av. 0.6). 15‐AcDON nd. NIV 0.1–0.7 (av. 0.3). ZEA 0.1–0.5 (av. 0.2). F. sporotrichioides T‐2 toxin 2.4–13.9 (av. 6.0), HT‐2‐toxin 0.1–0.8 (av.0.3) and neosolaniol 0.2–1.5 (av.0.7).
Different Assessment Techniques of Leaf Blotch (Rhynchosporium secalis (Oud.) J. Davis) in Winter Barley after Artificial Inoculation
Authors: Foroughi‐Wehr B. , Lind V. , Zöchner S. , Rabenstein F.
Published: May 2008

Seven winter barley cultivars expressing different field resistance against leaf blotch (Rhynchosporium secalis) and 60 doubled haploid (DH) lines descending from and F1 hybrid resistant x susceptible were used to develop a test for the quantitative determination of disease severity. Differences in the level of resistance could be measured very precisely after artificial infection of seedlings at the 4‐leaf‐stage and subseqent incubation at 7 C. The protein of six isolates was usedf, or antiserum production which was subsequently supplied for serological testing (Enzyme‐Linked‐Immunosorbent‐Assay) of infected leaves. The results of visible scoring of the seedlings was significantly correlated with measuring with the ELISA reader. The, results of the seedling test also corresponded to field scores after natural infection.
Effects of Induced Resistance on Disease Severity/Yield Relations in Mildewed Barley
Authors: Kehlenbeck H. , Schönbeck F.
Published: May 2008

Field experiments showed that the treatment of winter barley with microbial metabolites produced by a Bacillus subtilis strain led to increased yields in spite of a remaining mildew infection. Disease severity/yield relations obtained on a single tiller basis for either mildew infection at EC 75 or area under disease progress curve (AUDPC) were negatively correlated for untreated plants (R2= 89%, 94%) while this relation did not exist for inducer‐treated ones (R2= 10%, 13%). Despite an increasing infection density. yields of main tillers of inducertreated plants were not decreased. On the other hand area under green leaf area curve (AUGLAC) showed a higher correlation with grain yield (R2= 89%) of inducer‐treated plants. Possible explanations for the mitigated damaging effect of powdery mildew were expected in carbohydrate metabolism. especially carbohydrate formation and translocation. Assimilation rates of flag leaves of inducer‐treated barley with similar infection densities to those of untreated plants were increased over a prolonged period and even exceeded those of non infected ones. In inducer‐treated plants the export of 14CO2 from flag leaves into ears remained unimpaired by mildew infection and the allocation of assimilates to grains was highest at late stages of grain filling. Obviously plants were stimulated by inducer treatments to compensate for the damaging effect of powdery mildew and to tolerate mildew infection without yield loss.
Chrysanthemum Stem Necrosis Caused by a Possible Novel Tospovirus
Authors: Duarte L. M. L. , Rivas E. B. , Alexandre M. A. V. , De ÁVila A. C. , Nagata T. , Chagas C. M.
Published: May 2008

Necrotic lesions surrounded by yellow areas on leaves followed by stem necrosis were observed on chrysanthemum plants cultivated in Atibaia, Sào Paulo State, Brazil. The host range, in vitro properties and particle morphology of the causal virus were typical of a Tospovirus. Serological studies demonstrated that the virus differed from tomato spotted wilt. tomato chlorotic spot, groundnut ringspot and inpatiens necrotic spot Tospoviruses. The virus isolate is thus possibly a representativeof a new serogroup of a new virus.
Use of Cross‐Reactive Antibodies to Detect Members of the Potyviridae
Authors: Richter J. , Rabenstein F. , Proll E. , Vetten H. J.
Published: May 2008

In attempts to use cross‐reacting antibodies for the broad‐spectrum detection of potyviruses two broad‐spectrum immunoreagents, the monoclonal antibody P‐3‐3H8 and antiserum Tu MV‐314 raised against an isolate of peanut stripe virus and turnip mosaic virus, respectively, were examined for their ability to detect members of the Potyviridae in a simple indirect plate‐trapped antigen (PTA) ELISA. Both immuno‐reagents reacted strongly not only with isolate of 50 different virus species of the genus Potyvirus but also with several isolates of ryegrass mosaic virus, the type member of the genus Rymovirus A few members of the genus Potyvirus as well as agropyton mosaic and hordeum mosaic viruses, two other species of the genus, Rymovirus did not react with P‐3‐3H8 but only with TuMV‐314 which showed the highest degree of cross‐reactivity. In no case were positive reactions obtained with members of the genera Bymovirus and Ipomovirus. These two immunoreagents which appear to be directed to conserved epitopes gave good results when they were employed for detecting potyviruses in field samples from ornamental (Liliales) and leguminous plants. The potential and limitations of cross‐reactive antibodies for the routine detection of potyviruses are discussed.
VerticilliumWilt of Pepper (Capsicum annuum) in Morocco
Authors: Douira A. , Ben Kirane R. , Ouazzani Touhami A. , Okeke B. , Elhaloui N. E.
Published: May 2008

Pepper crops in Morocco formerly thought to be free from attack byVerticilliumwere found to be susceptible to this pathogen.Verticilliumwilt of pepper was observed in plots where the crop was cultivated in rotation with tomatoes. Strains ofVerticilliumisolated from pepper possessed different morphological and pathogenic characteristics.
Fusarium moniliforme Sheldon — Pathogenicity to Wheat Seedlings and Ability to Produce Fumonisins
Authors: Chelkowski J. , Visconti A. , Dokko B. , Wiśniewska H.
Published: May 2008

All 17 examined Polish isolates of Fusarium moniliforme Sheldon [syn. F. verticillioides (Sacc.) Nirenberg], originating from wheat, maize and barley kernels, exhibited pathogenicity to wheat seedlings of the cultivar ‘Almari’ (5 isolates‐very strong, 3 strong, 3 medium, 5 weak and only one very weak). The same isolates were able to produce the mycotoxins fumonisins on rice under laboratory conditions. Fumonisin B1 (FB1) was detected in concentrations ranging from 1.3 to 2240mg/kg and fumonisin B2(FB2) from 0.7 to 600 mg/kg. The yield of the fumonisins produced in vitro was not related to the pathogenicity of individual isolates.
A Set of Differentials to Characterize Populations of Pyrenophora teres Drechs. for International Use
Authors: Afanasenko O. S. , Hartleb* H. , Guseva N. N. , Minarikova V. , Janosheva M.
Published: May 2008

From 1989 to 1992 populations of Pyrenophora teres from Russia. Germany. Czech Republic and Slovakia were studied to determine their structure. and to develop a barley differential set for potential international use. The infection responses were scored on a 5‐point reaction scale using detached leaf pieces incubated on filter paper saturated with a aquaeos benzimidazole solution. A set of 12 differentials. incorporated under 4 digits using the octal nomenclature, was identified and is presented.
An Assay Based on the Polymerase Chain Reaction for the Detection of N‐ and L‐types of Pseudocercosporella herpotrichoides in Wheat
Authors: Gac M. L. , Montfort F. , Cavelier N.
Published: May 2008

A polymerase chain reaction (PCR) test combined with restriction enzyme digestion of an amplified ribosomal DNA fragment is currently available for the identification of N‐ and L‐type isolates of Pseudocercosporella herpotrichoides from purified fungal DNA. This study shows that both types of the fungus can be differentiated in the plant using the PCR assay and that the test is extremely sensitive. The PCR assay is used to compare the development of one isolate of each the N‐ and L‐type in wheat under glasshouse conditions. The results indicate that for an identical infection date, the N‐type tends to penetrate the tissues faster than the L‐type.
Differential Accumulation of Phytoalexins in Leaves of Susceptible and Resistant Genotypes of Groundnut (Arachis hypogaea L.) Inoculated with Puccinia arachidis Speg.
Authors: Sankara P. , SubbaRao P. V. , Strange R. N.
Published: May 2008

The accumulation of phytoalexins in a rust‐susceptible (KH 241‐D) and a rust‐resistant (PI 259747) genotype of groundnut 2,6, 15 and 25 days after inoculation with the rust pathogen, Puccinia arachidis Speg. was investigated. Within 2 days of inoculation of the resistant genotype, total phytoalexins reached 35 μg/g fresh weight, remained close to this level for a further 13 days but reached 104μg/g at 25 days after inoculation. In contrast, the susceptible genotype accumulated only 4μg/g fresh weight 2 days after inoculation and this increased gradually to 13, 23 and 52 μg/g fresh weight at 6, 15 and 25 days, respectively. Extracts from uninoculated leaves of both genotypes showed the presence of an antifungal compound which appeared as a diffuse spot in the Thin Layer Chromatography (TLC) bioassay, but this was essentially absent in inoculated leaves and did not correspond to any peak detected on High Performance Liquid Chromatography (HPLC). Compounds with UV spectra corresponding to isoflavanones were the major component of the phytoalexin response whereas other phytoalexins, formononetin, daidzein, and medicarpin comprised a minor component. A further compound with a retention time of 23.0 min on HPLC and a λ max of 280 nm only accumulated in inoculated leaves of the resistant genotype.
Virulence Patterns of Uromyces appendiculatus from Different Geographical Areas and Implications for Finding Durable Resistance to Rust of Common Bean
Authors: Mmbaga M. T. , Steadman J. R. , Eskridge K. M.
Published: May 2008

Single‐uredinium cultures of Uromyces appendiculatus (Pers) Unger from Honduras, Dominican Republic, Puerto Rico, Tanzania and USA were evaluated for virulence on 19 standard bean (Phaseolus vulgaris) rust differential lines/cuitivars that had been previously selected on the basis of resistance to bean rust. A disease rating scale, based on uredinium diameter, was used to study pathogenic variability of the bean rust fungus. Virulence of the cultures was measured by the vector of disease score (mds) on all 19 differentials and the nearest centroid sorting algorithm was used to cluster the cultures according to virulence similarity. A total of 373 different virulence patterns was identified from more than 2000 cultures and were grouped into four virulence clusters. None of the cultures produced a susceptible reaction on all the differentials. Cultures that produced uredinia > 0.5 mm in diameter in 15 differentials were considered to have high virulence. About 59, 15, 20, 5 and 0%, respectively, of the Honduran, Dominican, Puerto Rican, USA and Tanzanian cultures were highly virulent. The lines/cultivars Ecuador 299, Mexico 235, 51051, NEP‐2, Mexico 309, California Small White 643, A × S 37, and Aurora had a high degree of resistance to most cultures and can be used as sources of broad resistance. Virulence patterns of the differentials indicated redundancy in some host parasite interactions and the need to modify the composition of the differential lines/cultivars.
Occurrence of Cucumber Mosaic Cucumovirus with Satellite RNA in Lethal Necrosis Affected Tomatoes in Croatia
Authors: ŠKoric D. , Krajacic M. , Barbarossa L. , Cillo F. , Grieco F. , ŠAric A. , Gallitelli D.
Published: May 2008

In the last few years, tomato crops of Southern coastal Croatia have been repetitively stricken by a devastating necrotic tomato disease on such a scale that it endangered tomato production in the area. Cucumber mosaic cucumovirus (CMV) was found in symptomatic plants by serology. Low‐molecular weight RNA bands were detected in total nucleic acid extracts from naturally infected tomato fruits. The satellite nature of this RNA was proven by molecular hybridization with a digoxigenine‐labelled satellite RNA probe. Molecular and biological characterization of the satRNA proved to be involved in codetermination of the lethal necrosis disease. This is the first report of CMV strain containing a satRNA in Croatia.
Comparison of Methods for Detection of Erwinia carotovora ssp. atroseptica in Progeny Tubers Derived from Inoculated Tubers of Solanum tuberosum L.
Authors: Fraaije B. A. , Birnbaum Y. , VanDen Bulk R. W.
Published: May 2008

Several techniques for detection of Erwinia carotovora ssp. atroseptica (Eca) on potato tubers were used to study the transmission of Eca from inoculated mother tubers into progeny tubers for 12 different potato cultivars. The sensitivity of the polymerase chain reaction (PCR) for a direct detection of Eca in crude peel extracts was only 107‐108 cells/ml, due to inhibition of PCR amplification by potato tuber‐derived compounds. With dilution plating and ELLSA, 105 and 107 cells/ml were detected, respectively, Immunofluorescence cell staining (IF), with a detection threshold of 104‐105 cells/ml, was shown to be most sensitive for direct detection, and transmission of Eca was found for six potato cultivars, whereas with the other techniques tested no transmission was found. After 48 h enrichment of peel extract in polypectate medium at 20 C, IF and PCR detected an initial inoculum concentration of 10 Eca cells/ml, whereas 102, 104 and 104 cells/ml were detected in dilution plating, ELISA and conductimetry, respectively. With dilution plating, PCR and IF, performed after enrichment, transmission of Eca was found for, respectively, four, six and seven out of 12 potato cultivars tested. No transmission was found using ELISA and conductimetry, due to their lower sensitivity, Erwinia carotovora ssp, carotovora (Ecc) was only detected in the progeny tubers of control plants. No relation was found between the transmission of Eca to progeny tubers and blackleg incidence in the field.
Chlorosis of Sequentially Older Leaves of Poa pratensis Induced by Biologically Active Products of Bipolaris sorokiniana
Authors: Hodges C. F. , Campbell D. A.
Published: May 2008

Research was initiated to develop a rapid assay for determining the ability of biologically active products of Bipolaris sorokiniana to induced chlorosis in intact (not detached) leaf blades of Poa pratensis, and to determine if the active products interact with leaf senescence. The presence of membrane disrupting substances in the extract was confirmed by the leakage of betacyanin from red beet root cells. The non‐diluted extract induced severe leaf chlorosis in leaves of all ages. At dilutions of 10−1 and 10−2 the youngest leaf blade remained visibly green, and the second leaf blade showed mild chlorosis. The third and fourth (oldest) leaf blades showed severe chlorosis in response to the 10−1 dilution, and chlorosis occurred on about one‐half the length of the leaf blades in response to the 10−2 dilution. Chlorosis of treated leaf blades developed slowly and toward the tip end of the leaf. Severely chlorotic leaves often developed necrotic flecks and/or necrotic midvein streaks. It was concluded that the extract from B. sorokiniana induces chlorosis, interacts with leaf senescence, and contains substances active in pathogenesis.
An RT‐PCR Test for the Detection of Tomato Spotted Wilt Tospovirus Incorporating Immunocapture and Colorimetric Estimation
Authors: Weekes R. , Wood K. R. , Barker J.
Published: May 2008

A reverse transcription‐polymerase chain reaction (RT‐PCR)‐based assay for the detection of tomato spotted wilt virus (TSWV) has been modified and improved by the use of immunocapture of virus by solid phase adsorbed antibodies and colorimetric detection of nested PCR products, into which digoxigenin has been incorporated, by an ELOSA (enzyme‐linked oligonucleotidesorbent assay)‐like assay. The use of the colorimetric assay for the detection of tospoviruses by using ‘universal’ primers in the RT‐PCR stage is also described.
Western Blots Reveal that Grapevine Viruses A and B are Serologically Related
Authors: Goszczynski D. E. , Kasdore G. G. F. , Pietersen G.
Published: May 2008

Isolates of grapevine virus B (GVB) and grapevine virus A (GVA) were obtained by mechanical transmission from grapevines to Nicotiana benthamiana. Western blot studies of these isolates using various antisera to GVB and GVA showed that they are serologically related.
Biological Control of Take‐all of Wheat in the Pacific Northwest of the USA Using Hypovirulent Gaeumannomyces graminis var. tritici and Fluorescent Pseudomonads
Authors: Duffy B. K. , Weller D. M.
Published: May 2008

Hypovirulent Gaeumannomyces graminis var. tritici strain L108hv, five strains of Pseudomonas spp., and a mixture of four of these bacterial strains were used individually and in combination for the suppression of takeall of wheat. In the growth chamber, L108hv and all five individual bacterial strains provided a significant reduction in take‐all severity compared with an untreated control. Combination of L108hv and the bacteria did not significantly enhance the suppressiveness of either agent. In the field at Pullman, WA, 108hv significantly reduced crown root infection of winter wheat but not seminal root infection, while the reverse was true for a mixture of bacterial strains suggesting these agents may be more effective at different stages in disease development. In a second field trial at Pullman, yield of spring wheat was increased by 20.8%. In contrast, in two field trials at Mt. Vernon, WA, L108hv had no effect on take‐all of spring wheat. We conclude that specific biocontrol agents may be better suited for certain environments and that biocontrol treatments should be customized for the target site.
Biological Characterization of an Italian Isolate of Barley Yellow Dwarf Luteovirus from Barley
Authors: Guglielmone L. , Caciagli P.
Published: May 2008

An isolate of BYDV (BYDV‐OC), from barley in Northwest Italy with typical symptoms of yellowing and dwarfing, was transmitted by Rhopalosiphum padi, Sitobion fragariae. S. avenae, Metopolophium festucae, R. maidis and M. dirhodum, but not by Myzus persicae or Schizaphis graminum. It reacted in DAS‐ELISA with monoclonal and polyclonal antisera to PAV, but not with antibodies to MAV, RPV and RMV. A polyclonal antiserum prepared to BYDV‐OC did not react with MAV‐like, RPV‐like, or RMV‐like isolates of BYDV in ELISA or in Western blots. The concentration of BYDVOC in Avena byzantina plants decreased from weeks 1 to 10 after inoculation, but the total virus content per plant increased up to weeks 7 to 8, following the increase of plant weight.
Legume Hosts of Macrophomina phaseolina in Kenya and Effect of Crop Species on Soil Inoculum Levels
Authors: Songa W. , Hillocks R. J.
Published: May 2008

Studies were conducted in eastern Kenya to determine the common legume crop and weed hosts of Macrophomina phaseolina (Tassi) Goid., the inciter of charcoal rot disease. The effect of maize, sorghum, bean, and cowpea on the soil inoculum level was also investigated after field inoculation. All the legume crops and weeds tested were found to be infected by the pathogen after artificial inoculation. Common bean, soybean, cowpea were the most susceptible while pigeonpea, green gram, and hyacinth bean were moderately susceptible. Groundnut, chickpea. Cassia spp. and Crotalaria spp. were least susceptible after artificial inoculation, Monocropping of sorghum, maize, cowpea and common bean for three consecutive crop seasons increased M. Phaseolina soil inoculum in ascending order.
The Involvement of Fusaric Acid in the Bulb‐rot of Gladiolus
Authors: Remotti P. C. , Löffler H. J. M.
Published: May 2008

Tissue cultures of Gladiolus have been used successfully to determine host specific properties of fusaric acid, a phytotoxin produced by Fusarium oxysporum f. sp. gladioli (Mas.) Sny. et Hn. Ten Gladiolus genotypes, including three wild South African species, varying in resistance to Fusarium‐rot. were differentiated based on the expressed insensitivity to fusaric acid. Shoots and callus cultures were challenged in vitro with various concentrations of fusaric acid. The ion‐release caused by the toxin was measured with callus and intact cormels. In all above mentioned bioassays resistant and susceptible genotypes could be generally discriminated. However, only two of the developed bioassays, the shoot assay and the ion‐release with intact cormels, gave significantly coinciding results with the Fusarium‐resistance assessed in a greenhouse experiment. When using callus tissue in the assays, the obtained answer correlated less with the Fusarium‐resistance. It is concluded that a part of the Fusarium‐resistance is based on fusaric acid insensitivity.
Local and Systemic Induction of β‐1,3‐Glucanase and Chitinase in Coffee Leaves Protected Against Hemileia vastatrix by Bacillus thuringiensis
Authors: Guzzo S. D. , Martins E. M. F.
Published: May 2008

β‐1,3‐glucanase and chitinase activities were induced locally and systemically 4–25 and 11–25 days, respectively, after spraying the surface of the third pair of coffee leaves from the apex of 8‐month‐old plants with a 50 mg/ml aqueous suspension of Bacillus thuringiensis in a commercial formulation (Thuricide HP‐Sandoz). The treatment also induced local and systemic resistance against Hemileia vastatrix after the application of the inducer. Within 14–18 days of application of the Thuricide inducer, the β‐1,3‐glucanase activity in the locally and systemically‐protected unchallenged leaves reached maximum levels of 226% and 279% higher levels respectively, than in control plants. The chitinase activity reached maximum levels of 224% and 181% respectively, within 18–21 days after treatment with the inducer. Two β‐1,3‐glucanase bands were detected by native PAGE electrophoresis in extracts from locally‐and systemicallyprotected unchallenged coffee leaves.
Purification of the Phytoplasma Associated with China‐tree (Melia azedarach L.) Decline and the Production of a Polyclonal Antiserum for its Detection
Authors: Gomez G. G. , Conci L. R. , Ducasse D. A. , Nome S. F.
Published: May 2008

China‐tree or paraiso (Melia azedarach) decline, caused by a phytoplasma, is a disease in Argentina for which hitherto no diagnostic reagents were available. The production of a polyclonal antiserum using a purification protocol involving a double Percoll gradient is reported. The antiserum was used successfully in immuno‐dot blot assay to discriminate between infected and healthy plants. It also recognized, although less reliably, other phytoplasmas present in garlic (Allium sativum), peach (Prunus persica) and tona (Tona cilliata). Organisms that by their size and morphology resembled phytoplasmas were detected by immuno‐electron microscopy and immunogold labelling. The ability of the antiserum to discriminate between healthy and infected plants was confirmed by PCR amplification of fragments only from infected plants.
Moniliformin Accumulation and other Effects of Fusarium avenaceum (Fr.) Sacc. on Kernels of Winter Wheat Cultivars
Authors: Golrnski P. , Kosteckt M. , Lasocka I. , Wisniewska H. , Chelkowski J. , Kaczmarek Z.
Published: May 2008

Accumulation of the mycotoxin moniliformin (MON) and other effects on kernels were examined in 13 Polish winter wheat cultivars inoculated with F. avenaceum (Fr.) Sacc. isolate ATCC 64451. Kernels from inoculated ears were divided into three fractions: Fusarium damaged kernels (FDK), kernels with black point symptoms (BPK) and healthy looking kernels (HLK). The average moniliformin content (mg/kg) was highest in chaff (11.69), lower in infested kernels (FDK + BPK) (2.70) and lowest in HLK (1.16). The mean level (mg/kg) of moniliformin in kernels (total sample) ranged from 0.78 in cv. Liwilla to 3.84 in cv. Gama. Moniliformin levels in chaff were correlated (r= 0.5322) with the average metabolite concentration (mg/kg) in kernels, and ranged from 4.97 in chaff of cv. Roma to 22.9 of cv. Alba. The moniliformin concentration in kernels (total sample) was highly correlated with the level of the metabolite in diseased kernels. This is the first report of the relationship of black point symptoms with F. avenaceum colonization of kernels and moniliformin accumulation.