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  • 1
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Phytopathology 32 (1994), S. 523-544 
    ISSN: 0066-4286
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 53 (2004), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Four foliar and two stem-base pathogens were inoculated onto wheat plants grown in different substrates in pot experiments. Soils from four different UK locations were each treated in three ways: (i) straw incorporated in the field at 10 t ha−1 several months previously; (ii) silicon fertilization at 100 mg L−1 during the experiment; and (iii) no amendments. A sand and vermiculite mix was used with and without silicon amendment. The silicon treatment increased plant silica concentrations in all experiments, but incorporating straw was not associated with raised plant silica concentrations. Blumeria graminis and Puccinia recondita were inoculated by shaking infected plants over the test plants, followed by suitable humid periods. The silicon treatment reduced powdery mildew (B. graminis) substantially in sand and vermiculite and in two of the soils, but there were no effects on the slight infection by brown rust (P. recondita). Phaeosphaeria nodorum and Mycosphaerella graminicola were inoculated as conidial suspensions. Leaf spot caused by P. nodorum was reduced in silicon-amended sand and vermiculite; soil was not tested. Symptoms of septoria leaf blotch caused by M. graminicola were reduced by silicon amendment in a severely infected sand and vermiculite experiment but not in soil or a slightly infected sand and vermiculite experiment. Oculimacula yallundae (eyespot) and Fusarium culmorum (brown foot rot) were inoculated as agar plugs on the stem base. Severity of O. yallundae was reduced by silicon amendment of two of the soils but not sand and vermiculite; brown foot rot symptoms caused by F. culmorum were unaffected by silicon amendment. The straw treatment reduced severity of powdery mildew but did not detectably affect the other pathogens. Both straw and silicon treatments appeared to increase plant resistance to all diseases only under high disease pressure.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 50 (2001), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Over 3 years, five crops of winter wheat with different fertilization or pesticide treatments were grown in replicated plots in which straw, cattle manure or nothing was incorporated into the soil. It was previously shown that severities of several foliar diseases were reduced by the treatment with straw. Treatments with straw slightly increased leaf microbial numbers at growth stage (GS) 10, and significantly but slightly decreased numbers at GS 60 and 70, when averaged over all crops. There was no evidence of differences in potential for biological control between plots, because no differences were demonstrated between treatments in the proportion of phylloplane residents able to produce chitinase, siderophores or antibiotics. There was no link between soil and leaf nitrogen and microbial populations or soil amendment. The two youngest leaves of straw-treated plants remained green longer than leaves from untreated or manure-treated plants. Microbial numbers differed between crops, but within crops were more stable on leaves and ears than in soil. Soil populations were larger before the crops were sown. Bacteria predominated over fungi in all habitats throughout the growing season. The ratio of Gram-negative to Gram-positive bacteria recovered was similar on leaves and in soil, but not on ears. Soil and leaf microbes utilized similar carbon sources. More leaf epiphytes than soil microbes produced siderophores. The majority of identified organisms belonged to only a few species. Chromogenic organisms were more abundant on aerial surfaces. A fungicide, chlorothalonil, was applied in one crop; it reduced the microbial population but did not alter its composition (without affecting the reduction in disease due to straw). It is postulated that straw acts in the field by altering plant physiology and thus altering both microbial colonization and disease.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, U.K. and Cambridge, USA : Blackwell Science Ltd
    Plant pathology 46 (1997), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Change in sensitivity of populations of Septoria tritici resulting from single sprays of the sterol demethylation-inhibiting fungicide flutriafol was measured. Field trials were conducted over 3 years at two sites separated by about 15 km, on cvs Mercia and Riband at each site, in plots at least 10 × 12 m. Treatments included the full recommended rate and a reduced dose of flutriafol and a mixture of flutriafol with chlorothalanil. Sprays were applied at GS37; samples were taken just before spraying and as soon as lesions appeared on leaf 2, which had had no visible disease at the time of spraying. Epidemiological evidence suggests that sprays acted both curatively and as protectants. Significant shifts in sensitivity occurred after spraying in both water-sprayed and fungicide-sprayed plots; all plots became less sensitive. Disease severity after spraying clearly decreased with increasing fungicide concentration and with the use of a mixture of flutriafol and chorothalanil. However, after correction for the shifts in the water-sprayed plots, no dose produced a significant change in population sensitivity level, although sample sizes were large. There was no trend in sensitivity in the population over the 3 years of the experiment.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effects of temperature on the development of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape were investigated in controlled-environment experiments. The proportion of conidia which germinated on leaves, the growth rate of germ tubes, the severity of light leaf spot and the production of conidia increased with increasing temperature from 5 to 15 C. The time to 50% germination of conidia and the incubation and latent periods of light leaf spot lesions decreased when temperature increased from 5 to 15°C. At 20°C, however, light leaf spot severity and production of conidia were less and the incubation and latent periods were longer than at 15 C. There were differences between P brassicae isolates and oilseed rape cultivars in the severity of light leaf spot, the production of conidia and the length of the incubation period but not in the length of the latent period. The responses to temperature for lesion severity and incubation and latent periods appeared to be approximately linear over the temperature range 5-15°C and could be quantified using linear regression analysis.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 43 (1994), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Two models of plant disease in crops regulated by a virus disease or by a hyperparasite are introduced. If the host crop is annually harvested or dies back, the pathogen population at the end of each year may fluctuate indefinitely and irregularly in a way which depends very precisely and for ever on the initial populations. This means that even in an environment which is identical every year, the pathogen populations in each year vary enormously and erratically. However, the combinations of pathogen and virus incidence or hyperparasite infection that can occur exhibit very well defined patterns, even if parameters in the model exhibit substantial random annual variation. It is important that pathologists should be aware that population fluctuations may not be caused by environmental fluctuations and may be, in principle, unpredictable by a deterministic model.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 43 (1994), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The sensitivity of Septoria tritici to the sterol biosynthesis inhibiting fungicide flutriafol was assessed using a quick and objective technique based on light absorbance to measure fungal growth. Microtitre plates were inoculated with suspensions of pycnidiospores taken directly from single pycnidia on leaves, after which glucose peptone broth containing different fungicide concentrations was added. After 10 days’ incubation in the dark at 17°C, growth was measured using a spectrophotometer at 405 nm. A dose-response curve fitted to the absorbance data was used to estimate the fungicide concentration reducing absorbance by one half (EC50). The method was precise, quick, reproducible and objective, with substantial advantages over conventional techniques.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 42 (1993), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Epidemics of disease caused by Septoria tritici were studied in detail in 11 crops of winter wheat cv. Longbow over 4 years. Serious damage to the uppermost two leaf layers was caused by splash-borne infection from lower in the crop early in the life of the leaves, followed by one or rarely two cycles of multiplication within a leaf layer. Infection conditions rarely limited damage, even in a dry year; the timing and, to a lesser extent, amount of initial inoculum movement to an upper leaf layer was of greater importance. Timing of initial infection was determined by when rain splash occurred in relation to emergence of a leaf layer. Occurrence of infections soon after a leaf layer started to emerge allowed more time for multiplication of disease within that layer. These infections tended to be more severe because the leaves were closer to inoculum sources within the crop. Slight differences in phenology between locations explain why initially random disease distributions sometimes become aggregated. Early-sown crops are at greater risk because they mature more slowly, allowing more disease multiplication and better transfer between leaf layers.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 38 (1989), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The pattern and extent of primary infection by Septoria tritici were compared over a period of 3 years in winter wheat grown at sites with differing histories and from seed stocks obtained in different countries, in the open, under airtight cover and in sterilized soil. Only the airtight cover altered the number of lesions found, substantially reducing it. Lesions were evenly distributed. Lesions were found throughout the autumn and occasionally in the winter and spring on wheat seedlings exposed in trays to the open air for periods of 1 week, then given good conditions for infection to occur. This was true even at a site 0.4 km distant from wheat residues. The results show that the main source of primary infection of winter wheat in these experiments was evenly dispersed and airborne. It probably consisted mainly of ascospores of Mycosphaerella graminicola.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 38 (1989), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A simple model of the evolution of polygenically controlled fungicide resistance is presented. The basic model contains four parameters, all of which are experimentally measurable. The first, β, describes how much a given change in fungicide sensitivity alters the fitness of a clone of the organism in the presence of fungicide. The second, γ, describes the strength of stabilizing selection, which tends to restore sensitivity to an optimal value. The third, σ2, specifies the variance in fungicide sensitivity existing among genotypes in the population. The fourth parameter is the heritability, h2. of fungicide sensitivity; it applies only to pathogens reproducing sexually. The model suggests that changes in sensitivity of populations to fungicide will only be weakly dependent on the concentration applied, but will be mainly controlled by the slope of the graph for fungicide sensitivity against fitness in the presence of fungicide. Unless stabilizing selection is very strong, it will only slightly modify the rate at which sensitivity changes. Loss of resistance in the absence of the fungicide will be, at most, half as fast as its initial gain. If the heritability, h2, is close to 1, annual sexual reproduction will scarcely affect the conclusions drawn above; if h2, is small, long-term changes will be substantially slowed down and a cycle in population fungicide sensitivity may occur within each year. In suitable fungi, limits could be placed on the strength of stabilizing selection by looking for changes in variance in fungicide sensitivity between clones before and after sexual reproduction. Data to test the model are sparse, but do not contradict it.
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