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  • Articles  (29)
  • Articles: DFG German National Licenses  (29)
  • Blackwell Science
  • 1
    Electronic Resource
    Electronic Resource
    Bounds on the complex conductivity of geophysical mixtures[ Received ] (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Following previous work on bounds for complex dielectrics, bounds on the complex conductivity of a mixture of two isotropic components can be developed which are independent of any special assumption concerning the geometry of the mixture. If certain broad restrictions are assumed, such as isotropy of the mixture, then the bounds can be made more restrictive. These bounds reveal the range of the induced polarization response which can be caused by a mixture of two materials of known complex conductivity. The bounds can also be generalized for spectral responses. The bounds are conservative lithologically in the sense that many of the special models corresponding to boundary responses have lithological counterparts.The chief use for the given bounds is to gain insight into the nature of the induced polarization response. It is also possible to use the bounds to estimate the volume fractions of the components. We illustrate how this is done for the case of a general anisotropic medium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00108.x
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  • 2
    Electronic Resource
    Electronic Resource
    A shear experiment over the Natih field in Oman: pilot seismic and borehole data[ Received ] (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: An experimental multicomponent three-dimensional (3D) seismic survey has been carried out over the Natih field in Oman. This paper describes the small-scale two-dimensional experiment carried out beforehand, and how the results obtained from this pilot were used to assess the feasibility of a nine-component three-dimensional (9C3D) operation as well as to determine the field parameters for the field-scale 3D survey. It also describes the two VSPs and a wireline shear log, acquired in conjunction with the pilot experiment, and the importance of such borehole data for establishing the correct time-to-depth relationship for the seismic data and for providing an independent check on the seismic interpretation. The observation of cusps in the offset VSP indicated the strong anisotropy of the Fiqa shales overlying the Natih reservoir.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00111.x
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  • 3
    Electronic Resource
    Electronic Resource
    Thin-bed AVO effects[ Paper pre] (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Tuning caused by closely spaced impedance boundaries affects seismic amplitudes. At zero-offset the shape of the composite reflected signal approaches the time-derivative of the original pulse as the layer thickness decreases. For layers thinner than half of the tuning thickness, the reflected amplitude is modified by a factor equal to twice the time-thickness of the thin layer. Offset-dependent tuning can be approximated by the time differences between primary reflections. For high-velocity contrasts locally converted waves will also affect the total reflected seismic response. The contribution from intrabed multiples can, in most cases, be ignored. Correction for offset-dependent tuning should be considered before conventional AVO analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00101.x
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  • 4
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    Electronic Resource
    Short note: A simple nomogram for interpretation due to magnetic horizontal cylinders[ Received ] (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The magnetic anomaly ΔF due to a long horizontal cylinder yields three points related to its extrema. A nomogram is presented for the determination of some source parameters of the causative body.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00109.x
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  • 5
    Electronic Resource
    Electronic Resource
    Efficient finite-difference modelling of seismic waves using locally adjustable time steps[ Paper pre] (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Conventional finite-difference modelling algorithms for seismic forward modelling are based on a time-stepping scheme with a constant (global) time step. Large contrasts in the velocity model or in the spatial sampling rate cause oversampling in time for some regions of the model. The use of locally adjustable time steps can save large amounts of computation time for certain modelling configurations.  The computation of spatial derivatives across the transition zone between regions of the model with different temporal sampling requires the definition of the wavefield at corresponding time levels on both sides of the transition zone. This condition can be obtained by extrapolation in time, which is inaccurate, or by multiple time integration in the transition zone. The error in the latter solution is of the same order as the conventional time-stepping scheme because both methods are based on the same iteration formula. The technique of multiple time integration simply requires the use of different sizes of time step. It is applicable only for certain factors of variation of the time step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00110.x
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  • 6
    Electronic Resource
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    Constraining of the zero total surface charge in galvanic modelling (1998)
    Oxford BSL : Blackwell Science
    Geophysical prospecting 46 (1998), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: The galvanic problem is frequently solved by a Fredholm integral equation of the second kind based on a single layer source formulation. At higher conductivity contrasts between the model and its surroundings the homogeneous part of the integral equation approaches an eigenvalue equation. With infinite contrast the solution of this limiting integral equation is non-unique, but in the subspace of zero total charge the solution is unique. This mathematical property of the integral equation is reflected in its numerical solution with the result that large numerical errors may appear and convergence of the solution becomes very slow. Errors are, for the most part, related to the computed excess charge generated in the numerical solution. The effect is studied by comparing the results computed from the solution of the integral equation alone with those computed from a particular solution where the requirement of zero total charge is used as a constraint. The model examples clearly show that the use of the constraint condition significantly improves the accuracy of the results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2478.1998.00112.x
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  • 7
    Electronic Resource
    Electronic Resource
    Albugo candida staghead formation in Brassica juncea in relation to plant age, inoculation sites, and incubation conditions (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Maximum staghead formation was obtained in 26-day-old (growth stage [GS] 3.1) Brassica juncea plants by inoculating differentiating flower buds with a zoospore suspension of Albugo candida race 2 V; exposing apical meristem tissues by opening the flower buds with forceps proved more conducive to staghead formation. Inoculation of 35- and 45-day-old plants (GSs 4.1 and 5.0, respectively) produced fewer hypertrophies, mainly in isolated flowers. Inoculation of 7- and 13-day-old plants (GSs 1.0 and 2.1, respectively) did not produce any hypertrophied flowers, but did result in the production of hypertrophied branches at the first node on the main stem. In general, hypertrophies were initiated more readily under greenhouse conditions than in the growth chamber. Other Brassica hosts inoculated with A. candida race 2 V or 7 V at GS 31 showed similar rankings for staghead formation and leaf infection. The technique should prove useful in screening breeding lines for disease resistance, particularly staghead formation, the most damaging phase as far as yield loss is concerned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-6.x
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  • 8
    Electronic Resource
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    The role of alternative hosts of Polymyxa betae in transmission of beet necrotic yellow vein virus (BNYVV) in England (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The host range of beet necrotic yellow vein virus (BNYVV) and Polymyxa betae was determined by growing plants in naturally infested soils from rhizomania outbreaks in England. Apart from Beta vulgaris, plant species infected by BNYVV were included in the families Chenopodiaceae (Atriplex patula, Chenopodium bonus-henricus, C. hybridum, C. polyspermum and Spinacia oleracea), Amaranthaceae (Amaranthus retroflexus) and Caryophyllaceae (Silene alba, S. vulgaris, S. noctiflora and Stellaria graminea). Only P. betae isolates from B. vulgaris, C. polyspermum and S. oleracea were found to be able to transmit BNYVV back to sugar beet. When a range of weed plants from infected fields were tested, none were found to be infected by BNYVV. Therefore, it seems likely that the weed hosts play only a minor role in the spread of rhizomania disease compared to that of sugar beet, other Beta vulgaris crop types or spinach.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-182.x
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  • 9
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    Assessment of Phaeotheca dimorphospora for biological control of the Dutch elm disease pathogens, Ophiostoma ulmi and O. novo-ulmi (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The antagonistic fungus Phaeotheca dimorphospora was tested as a biocontrol agent against the Dutch elm disease pathogens, Ophiostoma ulmi and O. novo-ulmi, on Ulmus americana seedlings in the glasshouse. Curative inoculation of seedlings with P. dimorphospora had no significant effect on disease development. Conditioning inoculation of seedlings with the antagonist protected them against O. ulmi but not against the more aggressive O. novo-ulmi. In seedlings challenged with both the antagonist and either one of the pathogens, P. dimorphospora only spread locally around the inoculation point; however, the pathogens spread systemically throughout the whole plant. O. novo-ulmi survived in the region colonized by P. dimorphospora, whereas O. ulmi did not.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-161.x
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  • 10
    Electronic Resource
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    Genetic analysis of partial resistance to bacterial leaf streak (Xanthomonas campestris pv. cerealis) in wheat (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Genetic variability of partial resistance to bacterial leaf streak was investigated in hexaploid winter wheat (Triticum aestivum.), using 16 parental genotypes and 48 pure lines (F10) derived from a composite cross programme. Two experiments were undertaken in a controlled growth chamber. Seeds of all genotypes were grown under controlled conditions using a randomized block design with three replications. Each replication consisted of a row of 20 seedlings of each parent and pure line. An Iranian strain of bacterial leaf streak was used for the inoculation of 12-day-old seedlings. In a third experiment, eight genotypes from parents and F10 pure lines representing a large variability for partial resistance were inoculated with four other Iranian strains of bacterial leaf streak. A large genetic variability was observed amongst the 64 genotypes for partial resistance to the disease. Partial resistance heritability estimates were rather high (70%), indicating that the resistance factors may be transmitted by crossing. Amongst all genotypes investigated, ‘DC2-30-N2’ and ‘IBPT-66’ displayed the highest partial resistance to the disease. Significant correlations between strains in the third experiment show that a genotype resistant or susceptible to one strain will have similar reactions with other strains. No significant genetic gain was observed for partial resistance in the best pure line of the 48 lines studied, when compared with the best parental line. Increasing the number of pure lines is likely to result in the identification of genotypes that might prove to be more resistant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-166.x
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  • 11
    Electronic Resource
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    Long-term maintenance of nonculturable apple-proliferation phytoplasmas in their micropropagated natural host plant (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Phytoplasmas associated with apple proliferation (AP) disease of apple trees have been maintained in their micropropagated natural host plant Malus pumila since 1985. Different isolates of these nonculturable plant pathogens could thus be studied in vitro. Amplification of a pathogen-specific DNA fragment by polymerase chain reaction (PCR) confirmed the presence of AP phytoplasmas in the diseased plants even after 10 years of in-vitro propagation. Restriction fragment length polymorphism analysis of the amplified chromosomal DNA fragments revealed no genetic difference between the AP phytoplasma isolates. Growth parameters, symptom expression and phytoplasma concentration were examined to compare the in-vitro behaviour of four different AP phytoplasma isolates and to compare different subculture conditions. A comparison of these data obtained after 2 or 8 years of micropropagation revealed no essential differences. Eight years after culture initiation, diseased shoots still exhibited typical symptoms like witches’ broom, small leaves with large stipules and stunted growth. The use of phytoplasma-diseased micropropagated plants to establish a ‘type culture collection’ of these otherwise nonculturable plant pathogens is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-171.x
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  • 12
    Electronic Resource
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    Vegetative compatibility of Fusarium oxysporum from sweet basil in Israel (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fusarium wilt and crown rot of sweet basil, caused by Fusarium oxysporum f.sp. basilici (F.o.ba.), is widespread in Israel. Affected plants show a variety of symptoms, including vascular wilt as well as crown rot, and masses of macroconidia on stem surfaces. We used vegetative compatibility to determine whether F.o.ba. isolates associated with various symptoms and sources are genetically related. All 119 isolates previously described as F.o.ba., and 42 additional F. oxysporum isolates which had not been tested for pathogenicity, belonged to a single vegetative compatibility group (VCG). The various symptoms are therefore induced by a single pathogenic form which appears to be a specific clone of F. oxysporum. The isolates of F.o.ba. from Israel were vegetatively compatible with eight isolates of F.o.ba. from Italy and the USA, but not with nonpathogenic isolates of F. oxysporum from basil, or with F.o. lycopersici or F.o. radicis-lycopersici from tomato. We conclude that the population of F.o.ba. in Israel belongs to the common VCG of this pathogen described in the USA, and which includes American and Italian isolates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-177.x
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  • 13
    Electronic Resource
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    Resistance mechanisms of Cucumis melo var. agrestis against Trialeurodes vaporariorum and their use to control a closterovirus that causes a yellowing disease of melon (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: One of the yellowing diseases that affects melon (Cucumis melo) crops cultivated under plastic greenhouses in southern Europe is caused by a closterovirus transmitted by the greenhouse whitefly Trialeurodes vaporariorum. A Cucumis melo var. agrestis accession shows a certain level of resistance to that virus. Under free-choice conditions, the reproduction of T. vaporariorum on this accession was significantly lower than on the susceptible control accession C. melo cv. ‘Bola de Oro’, and this suggests that T. vaporariorum prefers to colonize other accessions before C. melo var. agrestis. Under no-choice conditions, we observed that T. vaporariorum reproduction on C. melo var. agrestis was less than on the susceptible controls. The results showed the participation of both antixenosis and antibiosis resistance mechanisms against T. vaporariorum in C. melo var. agrestis. It is difficult to cultivate melon completely free from T. vaporariorum and yellowing disease. However, success in breeding commercial melon cultivars which incorporate the antixenosis and antibiosis found in C. melo var. agrestis together with biological or chemical insect control, or a combination of these, would reduce the insect population and, therefore, the melon-yellowing disease would occur later and in less severe form.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-169.x
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  • 14
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    Aetiology and biological control of Fusarium wilt of pinks (Dianthus caryophyllus) using Trichoderma aureoviride (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fusarium oxysporum f.sp. dianthi (F.o.d.) was the species isolated most frequently from wilted glasshouse-grown pinks in south-west England, whereas F. avenaceum was less prevalent and F. culmorum was not found. Although infections by F. avenaceum, via the roots or through a cut-stem wound, caused symptoms identical to those characterizing mild infections due to F.o.d., the former was always pathogenically weak relative to the latter. Of several organisms screened for potential antagonistic capacity towards F.o.d., using an in-vitro dual culture plate technique, Trichoderma aureoviride, isolated as an endophyte from healthy pinks, proved most effective. Elevated temperatures substantially reduced the antagonistic capacity of micro-organisms in both in-vitro and in-vivo screens, except in the case of T. aureoviride where maximum antagonism occurred at 28°C, which was near the optimum for wilt disease in pinks. The tolerance shown by T. aureoviride to a wide range of pesticides used in commercial production of pinks under cover indicated its potential in a proposed integrated disease control programme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-162.x
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  • 15
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    Development of empirical forecasting models for rice blast based on weather factors (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Regression equations used as empirical models to predict rice blast caused by Pyricularia grisea on cv. Jinheung at Icheon, South Korea, and on cvs. IR50 and C22 at Cavinti, Philippines, were generated, using weather factors identified by the WINDOW PANE program to be highly correlated with disease. Consecutive days with RH≥80% (CDRH80), number of days with RH≥80% (NDRH80), consecutive days with precipitation, and number of days with precipitation ≥ 84 mm day−1 were important variables predicting blast at Icheon. Total precipitation, precipitation frequency, mean maximum and minimum temperatures, number of days with wind speed above 3.5 m s−1, CDRH80, and NDRH80 were important predictors of blast at Cavinti. The Allen’s predicted error sum of squares (PRESS) criterion and a cross-validation procedure were used to evaluate the models using data that were not included in model development. Validation test showed that all models developed for the two sites, except the models predicting maximum lesion number and panicle blast incidence at Icheon, and panicle blast severity on IR50 at Cavinti, predicted blast reasonably well based on low PRESS values and close to zero average prediction errors. These models can be applied in actual rice production systems, but future validation is needed to further improve their predictive ability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-168.x
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  • 16
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    Prevalence of Plasmodiophora brassicae in a spring oilseed rape growing area in central Sweden and factors influencing soil infestation levels (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: During 1986–87 the presence of clubroot in soils sampled from 190 fields was assessed using a bioassay method, based on baiting the soils with Brassica campestris spp. pekinesis cv. Granaat. Clubroot was detected in 148 (72%) of the fields investigated and, on average, 49.2% of the plants were infected according to the bioassay. Subsequent testing of fields in 1990 and 1992 (54 and 81 fields, respectively) where no further Brassica crops had been grown indicated a significant decrease in the degree of infestation to 7.1% in 1992. Clay soils showed, on average, the highest degree of infestation, and high infestation was recorded for a wide range of pH values (5.2–6.6). The highest degree of infestation was recorded on fields where oilseeds were grown five times during the period 1965–85. The results presented show that, in a field with 100% infestation, the level of infestation declined to below the detection level after a period of 17.3 years. The half-life of the spore inoculum was determined to be 3.6 years. During the sensitivity testing of different Brassica species and cultivars, it was found that Chinese cabbage showed a low percentage of infestation in two soils, whilst some oilseed rape and spring oilseed turnip rape cultivars showed high degrees of infestation in these soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-173.x
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  • 17
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    Resistance to Sphaerotheca pannosa in roses induced by 2,6-dichloroisonicotinic acid (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The susceptible rose cv. Madelon and the partially resistant cv. Sonia both responded with reduced development of rose powdery mildew when they were treated with the synthetic inducer 2,6-dichloroisonicotinic acid (INA). The EC50 for number of colonies cm−2 was approximately 0.4 mg L−1 in both cultivars when treated 4 days prior to inoculation. However, conspicuous differences were observed with respect to number of spores per cm2. For sporulation, the EC50 was 0.37 mg L−1 in cv. Madelon and only 0.08 mg L−1 in cv. Sonia. A comparison with the pathosystems cucumber/Sphaerotheca fuliginea and red cabbage/Peronospora parasitica is made and the importance of the observed phenomenon for the selection of parents in a breeding programme for (partial) resistance is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-180.x
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  • 18
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    The influence of inoculum concentration, relative humidity, and temperature on infection of greenhouse tomatoes by Botrytis cinerea (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Botrytis cinerea causes serious crop losses in greenhouse tomato crops through infection of flowers and stem wounds. Experiments were carried out to determine the effects of inoculum concentration, relative humidity (RH), and temperature at these two infection sites. Infection of permanent flower parts increased as a function of inoculum concentration and both length of exposure to high RH (approximately 100% for 0–36 h) and specified continuous RH (56–100%). A low level of infection was still evident under continuous 56% RH. Interruption of periods of high RH with breaks of low RH did not reduce infection. Infection of stem wounds was less dependent on inoculum concentration or RH. Factorial combinations of inoculum concentration, RH, and temperature produced significant interactions. Higher temperature increased infection of flowers but reduced infection of stem wounds. The main implications for control in commercial crops are as follows. Lowering the aerial spore concentration by maintaining the disease at a low level will reduce flower infection. Lowering RH will reduce but not eliminate flower infection but will have only a small effect on stem infection. Raising the temperature (from 15 to 25°C) will reduce stem infection, and whilst flower infection increases, this is counteracted by increased flower production and a decrease in the proportion of infections reaching the peduncle and stem.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-163.x
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  • 19
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    Pathogenic specialization in Melampsora epitea var. epitea on Salix (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Eighteen isolates of the rust fungus Melampsora from different locations in England were tested for pathogenicity to a large range of willow clones (Salix spp.) in experiments involving inoculation of leaf discs. Seventeen of the isolates were of leaf-infecting M. epitea var. epitea, 16 of which represented forms which alternated on Larix and one of which alternated on Ribes. The remaining isolate was of uncertain identity. Two experiments were carried out. In the first experiment, 24 willow clones consisting of 20 Salix species and interspecific hybrids were inoculated with eight isolates from clones of S. viminalis. In the other experiment, 77 clones from 57 species or hybrids were inoculated with 10 isolates from several Salix spp. The M. epitea var. epitea isolates from S. viminalis clones were all similarly pathogenic, whilst most of the other isolates expressed distinct host specificity. Eight distinct pathotypes were recognized within M. epitea var. epitea. All except one of these alternated on Larix and could be assigned to three formae speciales which had been reported previously in Europe: four pathotypes to f.sp. larici-epitea typica, two to f.sp. larici-retusae, and one to f.sp. larici-daphnoides. The Ribes-alternating pathotype of M. epitea var.epitea infected only S. purpurea. Nine differential willow hosts are proposed as reference clones to distinguish between the larch-alternating pathotypes, the Ribes-alternating rust and the ‘stem-infecting’ form. The extent of pathogenic variation encountered amongst sexually reproducing rusts suggests that more pathotypes probably exist and will arise in future in response to selection given by long-term clonal willow plantings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-174.x
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  • 20
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    Elimination of ornithogalum mosaic virus from chincherinchee (Ornithogalum thyrsoides) by meristem tip culture, and field trials of reinfection (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Meristem domes excised from plantlets of Ornithogalum thyrsoides infected with ornithogalum mosaic virus (OrMV) in Kenya were cultured on basic Murashige and Skoog medium without added growth hormones. Of the resulting plantlets 30% were virus-free as determined by symptom appearance, mechanical inoculation to virus-free O. thyrsoides, electron microscopy and serological tests. When healthy plants were placed within a field of diseased O. thyrsoides, 35% became re-infected within 4 months and 100% infection was reached within 8 months. However, healthy plants placed in isolation, about 2 km downwind of infected commercial plantings, remained healthy over the 12-month test period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-181.x
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  • 21
    Electronic Resource
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    Bioassays of glucosinolate-derived isothiocyanates against postharvest pear pathogens (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The present study assayed the effect of six isothiocyanates (ITCs), produced by the enzymatic hydrolysis of glucosinolates, on fungal pathogens of pear. Sample pear fruits were artificially inoculated through induced wounds with conidial suspensions of Botrytis cinereaRhizopus stoloniferMonilinia laxaMucor piriformis or Penicillium expansum and were then treated with ITCs. Of the six ITCs tested, the ITC from glucoraphenin showed the highest effectiveness after 6 days at 20°C, against M. laxaB. cinerea and M. piriformis. The effectiveness of the ITC from glucoraphenin against M. laxa was assayed in two further trials to test the effect of ITC concentration on different concentrations of inoculum and to determine the duration of the curative effect of this ITC. ITC concentration directly affected fungus control capacity. The highest ITC concentration (3.6 mg mL−1) afforded pathogen control at the highest level of pathogen concentration (106 conidia mL−1) after 6 days at 20°C. Its curative effect was evident up to 40 h after inoculation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-5.x
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  • 22
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    Association of Pythium coloratum and Pythium sulcatum with cavity spot disease of carrots in Western Australia (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: All 170 Pythium isolates from carrot cavity spot lesions from a field in Western Australia were found to belong to either P. coloratum or P. sulcatum. All isolates of P. coloratum produced large, brownish-black, water-soaked and depressed lesions on mature carrots inoculated with agar plugs colonized by the pathogen. In comparison, only a few isolates of P. sulcatum produced lesions and these were small. In glasshouse trials, P. coloratum produced substantial and numerous lesions at an inoculum density of 0.5% (weight of millet seed-based inoculum/weight of soil), whilst P. sulcatum produced few and small lesions at inoculum densities of 0.8 and 1% and none at 0.5%. This is the first record of P. coloratum as a causal agent of cavity spot of carrots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-8.x
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  • 23
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    PCR-based detection of Colletotrichum acutatum on strawberry (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: An oligonucleotide primer (CaInt 2) was synthesized from the variable internal transcribed spacer (ITS) 1 region of ribosomal DNA (rDNA) from Colletotrichum acutatum. PCR with primers CaInt2 and ITS4 (from a conserved sequence of the rDNA) amplified a 490 bp fragment from several isolates of C. acutatum but not from other members of the genus Colletotrichum. Amplification of this fragment was achieved from 100 fg of fungal DNA. These primers amplified a fragment of the same size from DNA extracted from strawberry tissues infected by C. acutatum. Southern hybridization analysis confirmed the 490 bp fragment from C. acutatum DNA and infected strawberry to be identical. The species-specific primer (CaInt2) developed in this work could be used for the accurate identification of C. acutatum and its detection on other host plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-3.x
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  • 24
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    Effect of split applications of fenpropimorph-containing fungicides on sensitivity of Erysiphe graminis f.sp. tritici (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A field trial was conducted in the south of the Netherlands over a period of 3 years (1992–94) in order to test the effect of fenpropimorph-containing fungicides on the sensitivity of Erysiphe graminis f.sp. tritici to fenpropimorph. In general, use of split applications resulted in a better protection against wheat powdery mildew than use of normal applications. This is ascribed to a better timing of the split applications. The sensitivity to fenpropimorph of the mildew population in plots treated with normal applications of both fungicides did not change during the growing seasons of the years investigated. In contrast, the sensitivity of the mildew population from plots treated with split applications of Corbel became significantly lower. A significantly lower sensitivity was also found in the mildew population from plots treated with split applications of Tilt Top in 1993 and 1994. These results indicate that split applications can increase the rate at which E. graminis f.sp. tritici can become less sensitive to fenpropimorph. Because maintenance of sensitivity of the pathogen population is valued highly, the split application strategy of fenpropimorph-containing fungicides is not recommended for wheat powdery mildew control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-7.x
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  • 25
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    Effects of Ascochyta blight caused by Mycosphaerella pinodes on the translocation of carbohydrates and nitrogenous compounds from the leaf and hull to the seed of dried-pea (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of Ascochyta blight (caused by Mycosphaerella pinodes) on changes in dry weight and in water, carbohydrate, nitrogen and free amino acid contents were studied in the leaf, the hull and the seeds on the second fructifer node of pea (Pisum sativum). Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia at the beginning of seed filling, with uninoculated plants as controls. Disease induced a premature water loss of hulls and leaves, accelerated seed desiccation and reduced seed weight. Biochemical analyses revealed a decline in the carbohydrate content and a lower nitrogen remobilization in diseased leaves and hulls. Thus, Ascochyta blight alters carbohydrate metabolism, protein remobilization and free amino acid translocation from these organs. Disease also reduced carbohydrate and nitrogen content in seeds and, in case of high disease severity, the carbohydrate/nitrogen ratio in the seeds was also affected (seed protein concentration increased and starch concentration decreased).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-170.x
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  • 26
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    The effectiveness of postharvest hot water dipping on the control of grey and black moulds in sweet red pepper (Capsicum annuum) (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effectiveness of hot water dipping on the control of grey mould, caused by Botrytis cinerea, and black mould, caused by Alternaria alternata on sweet red pepper quality was investigated. Dipping naturally infected or artificially inoculated fruit at 508C for 3 min completely inhibited, or significantly reduced, decay development caused by B. cinerea and A. alternata, respectively. Heat damage was observed on fruit dipped for 5 min at 50°C, or at 55°C for 1 min or longer. Damage appeared as cracks and pitting on the fruit surface. Spore germination and germ tube elongation in vitro was inversely related to the duration of exposure or to the range of temperature used. The ET50 for spore germination for B. cinerea was 3.2, 1.5 and 0.8 min, and for A. alternata 8.8, 4.2 and 1.4 min, at 45, 50 and 55°C, respectively. The ET50 for germ tube elongation for Botrytis was 2.6, 0.9 and 0.5 min, and for Alternaria, 7.2, 2.5 and 1.6 min, at 45, 50 and 55°C. The mode of action of hot water dips on decay of pepper appears to be by direct interaction with the fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-175.x
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  • 27
    Electronic Resource
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    A possible role of sexuality in the population structure of Diaporthe adunca, a pathogen of Plantago lanceolata (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In this study, the population structure of the fungal pathogen Diaporthe adunca on its perennial wild host plant Plantago lanceolata was analysed, together with the occurrence of the sexual stage of the fungus. The fungus overwinters on scapes infected in the previous year. In spring, it sporulates asexually on these scapes leading to primary infection sources for an epidemic. From mid-June onwards, after asexual reproduction has ceased, the sexual stage is formed on the same overwintered scapes. In one location where the sexual stage was prominent, a more diverse fungal population structure was found than in another location where the sexual stage was less frequent and where one clone (with a low female fertility) dominated the same area during three consecutive years. A trade-off was found between the sexual and asexual reproduction. Female sterile isolates, which have lost the ability to produce the sexual stage, may invest all available nutrients in the scape for asexual reproduction and, therefore, might be selected for under relatively stable regimes. In unstable situations, where there is a lower probability of host plant survival, selection may favour sexual reproduction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-178.x
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  • 28
    Electronic Resource
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    Pathogen behaviour and plant cell reactions in interactions between Alternaria species and leaves of host and nonhost plants (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The growth behaviour of several Alternaria species on leaf discs of host and nonhost plants was examined by u.v. microscopy. Specific patterns of development were found for the pathogens. Differences in development which correlated to host specificity, or which differentiated specialized pathogens from weak or opportunistic pathogens, were obvious only after attempted penetration. Thus, little variation was observed amongst different plants for individual Alternaria species in the rate of germination, in the extent of germ-tube growth or in the frequency of appressorium production. However, plant responses to attempted penetration, which included the formation of callose-containing papillae, callose deposition in the walls of attacked cells and their neighbours and cell necrosis, varied with specific pathogen–plant interactions. Callose deposition occurred at sites of both successful and unsuccessful penetrations and may, therefore, not be a determining factor in the plant–pathogen interactions examined. A biplot technique is used to illustrate the different degrees of host specificity apparent at pre- and post-penetration stages of fungal development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-4.x
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  • 29
    Electronic Resource
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    Resistance to bacterial wilt in tomato as discerned by spread of Pseudomonas (Burholderia) solanacearum in the stem tissues (1996)
    Oxford, U.K. and Cambridge, USA : Blackwell Science
    Plant pathology 45 (1996), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Different criteria were compared for assessing bacterial wilt resistance in 13 tomato genotypes varying in disease susceptibility. Wilt severity and bacterial invasiveness at collar and midstem were compared in the field under cooler (March to May, 20–28°C) and warmer months (June to August, 23–29°C), which were unfavourable and favourable to wilt symptom expression, respectively. A model was proposed for determining resistance regardless of climatic conditions prevalent during field experimentation. This model was based on an estimate of bacterial invasiveness termed the colonization index. Using a qualitative imprint method we confirmed that the more resistant the genotype, the lower the bacterial colonization of the stem. The colonization index accounted both for wilted plants and for infected asymptomatic plants in which Pseudomonas solanacearum populations failed to produce wilt. The colonization index at midstem was the more useful indicator of resistance under favourable conditions. When environmental conditions were unfavourable to wilt, colonization index at collar level discerned resistant genotypes more clearly. The results formed the basis for a model for predicting the degree and stability of resistance in tomato.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1996.d01-9.x
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