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  • 1
    Electronic Resource
    Electronic Resource
    Production of conidia by Peronosclerospora sorghi on sorghum crops in Zimbabwe (1998)
    Oxford, U.K. and Cambridge, USA : Blackwell Publishers
    Plant pathology 47 (1998), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Factors affecting the production of conidia of Peronosclerospora sorghi, causing sorghum downy mildew (SDM), were investigated during 1993 and 1994 in Zimbabwe. In the field conidia were detected on nights when the minimum temperature was in the range 10–19°C. On 73% of nights when conidia were detected rain had fallen within the previous 72 h and on 64% of nights wind speed was 〈 2.0 m s−1. The time period over which conidia were detected was 2–9 h. Using incubated leaf material, conidia were produced in the temperature range 10–26°C. Local lesions and systemically infected leaf material produced 2.4–5.7 × 103 conidia per cm2. Under controlled conditions conidia were released from conidiophores for 2.5 h after maturation and were shown to be well adapted to wind dispersal, having a settling velocity of 1.5 × 10−4 m s−1. Conditions that are suitable for conidia production occur in Zimbabwe and other semi-arid regions of southern Africa during the cropping season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1998.00235.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sclerotial formation and strand growth of Phymatotrichopsis omnivora in minirhizotrons planted with cotton at different soil water potentials (1998)
    Oxford, U.K. and Cambridge, USA : Blackwell Publishers
    Plant pathology 47 (1998), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In situ strand growth and sclerotium formation of Phymatotrichopsis omnivora were observed in minirhizotrons using a microvideo camera. Strand growth was greater in soils subject to decreasing levels of soil matric potential (high water stress) compared with a continuously wet treatment. Intermediate levels of water stress (−0.5 to −0.9 MPa) resulted in less strand growth than either the dry or wet treatments. In all treatments strand growth increased to a maximum within 10 days of inoculum placement in soil but then declined to approach an apparent steady-state value. The effects of soil matric potential on sclerotium formation were apparent when barley seeds were sown in the experimental units 3 weeks after the experiment had begun, permitting differential water cycling patterns to be obtained. Sclerotia were recovered in larger numbers from experimental units in which high water potentials (〉 −0.2 MPa) occurred 2 weeks prior to and following the death of host plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1998.00241.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Charcoal rot (Macrophomina phaseolina) resistance and the effects of water stress on disease development in sorghum (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant pathology 44 (1995), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In three field experiments, plants subjected to post-flowering water stress and inoculated with Macrophomina phaseolina had greater development of charcoal rot symptoms than did inoculated plants not subjected to water stress. Two sorghum genotypes (B35-6 and SC265-14E) were found to be consistently more resistant to M. phaseolina, an assessment that was facilitated by the use of appropriate soil moisture conditions at the time of greatest plant susceptibility to charcoal rot.In addition, an isolate of M. phaseolina originally isolated from a sorghum genotype with resistance to charcoal rot caused greater symptom development than did two other isolates originally obtained from sorghum genotypes susceptible to charcoal rot.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3059.1995.tb02729.x
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of wind on the dispersal of oospores of Peronosclerospora sorghi from sorghum (1997)
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 46 (1997), S. 0 
    Details
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The effect of wind on the dispersal of oospores of Peronosclerospora sorghi, cause of sorghum downy mildew (SDM) is described. The oospores are produced within the leaves of aging, systemically infected sorghum plants. These leaves typically undergo shredding, releasing oospores into the air. Oospores are produced in large numbers (6.1 × 103 cm−2 of systemically infected leaf) and an estimate of the settling velocity of single oospores (0.0437 m s−1) of P. sorghi indicated their suitability for wind dispersal. In wind tunnel studies wind speeds as low as 2 m s−1 dispersed up to 665 oospores per m3 air from a group of leaves previously exposed to wind and displaying symptoms of leaf shredding. The number of oospores dispersed increased exponentially with increasing wind speed. At 6 m s−1, up to 12 890 oospores per m3 air were dispersed. Gusts increased oospore dispersal. A constant wind speed of 3 m s−1 dispersed a mean of 416 oospores per m3. When gusts were applied the mean was 15 592 oospores per m3. In field experiments in Zimbabwe, oospores were sampled downwind from infected plants in the field and at a height of 3.8 m above ground level immediately downwind of an infected crop. These data indicate that wind could play a major role in the dispersal of oospores from infected plants in areas where SDM infects sorghum, perhaps dispersing oospores over long distances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3059.1997.d01-31.x
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  • 5
    Electronic Resource
    Electronic Resource
    Pathology and control of soil-borne fungal pathogens of potato (1996)
    Springer
    Potato research 39 (1996), S. 437-469 
    Details
    ISSN: 1871-4528
    Keywords: Verticillium dahliae ; Rhizoctonia solani ; Spongospora subterranea ; tuber-borne diseases ; intraspecific variation ; detection ; integrated control ; research needs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Several soil-borne fungal pathogens continue to cause problems in potato production worldwide. The reasons for these problems are illustrated by reference to the pathogensVerticillium dahliae, Rhizoctonia solani, Spongospora subterranea and a group normally considered to be tuber-borne, includingColletotrichum coccodes, Helminthosporium solani andFusarium species. Generally, the long-term persistence of survival structures, the difficulties in reducing inoculum and lack of good sources of resistance hinder attempts to improve control of soil-borne fungal pathogens. Post-harvest fungicide treatment of seed or ware potatoes does not entirely alleviate storage problems. In the foreseeable future there is no alternative to the use of integrated measures from the time of planting seed to movement from storage. Key research areas that arise as a means of better controlling most of these pathogens are: the role of intraspecific variation in pathogenesis and ecology, problems of detecting and quantifying inoculum, and the need for improved methods for biological control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02357949
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Space-time statistics for environmental and agricultural related phenomena (1998)
    Springer
    Environmental and ecological statistics 5 (1998), S. 155-172 
    Details
    ISSN: 1573-3009
    Keywords: space-time variograms ; anisotropy ; space-time kriging ; root-rot ; optimal sampling ; simulated annealing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper presents an overview of space-time statistical procedures to analyse agricultural and environmental related phenomena. It starts with an application on root-rot development in cotton. Dependence modelling in space and time is done with the space-time variogram. Various kriging interpolators are presented for making predictions in space and time. Simulated annealing is used to design an optimal monitoring network for estimation of space-time variograms. In the application no clear indication was found for anisotropy, although strong evidence exists that the disease not only proceeds within rows but also jumps between rows. The optimal sampling scheme showed a spatial clustering of observations at the first and the last monitoring day and less observations at intermediate times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009614821618
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    Paper (German National Licenses)
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