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  • 2000-2004  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Plant pathology 51 (2002), S. 0 
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Three soft rot erwinias, Erwinia carotovora ssp. carotovora, E. carotovora ssp. atroseptica and E. chrysanthemi are associated with potatoes causing tuber soft rot and blackleg (stem rot). Latent infection of tubers and stems is widespread. As opportunistic pathogens, the bacteria tend to cause disease when potato resistance is impaired. Pathogenesis or disease development in potato tubers and stems is discussed in terms of the interaction between pathogen, host and environment, microbial competition and recent findings on the molecular basis of pathogenicity. Emphasis is placed on the role of free water and anaerobiosis in weakening tuber resistance and in providing nutrient for erwinias to multiply. Blackleg symptoms are expressed when erwinias predominate in rotting mother tubers, invade the stems and multiply in xylem vessels under favourable weather conditions. Soft rot erwinias tend to out-compete other bacteria in tuber rots because of their ability to produce larger quantities of a wider range of cell wall-degrading enzymes. However, despite extensive studies on their induction, regulation and secretion, little is known about the precise role of the different enzymes in pathogenesis. The putative role of quorum-sensing regulation of these enzymes in disease development is evaluated. The role certain pathogenicity-related characters, including motility, adhesion, siderophores, detoxifying systems and the hrp gene complex, common to most bacteria including symbionts and saprophytes, could play in latent and active infections is also discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-3059
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The relationship between contamination of potato seed tubers with Erwinia carotovora ssp. atroseptica (Eca), blackleg disease development, and the incidence and level of progeny tuber contamination in field grown crops was studied in 1998, 1999 and 2000. Seed tubers were inoculated by vacuum infiltration at three levels (low, intermediate and high) with a streptomycin-resistant marker strain of Eca (SCRI1039Str) and planted in the field. Blackleg disease development was directly related to the level of seed tuber contamination. The higher the level of seed tuber contamination, the earlier in the season blackleg disease appeared and the greater the final level of disease, which continued to rise as the season progressed. High and low levels of seed tuber contamination were related to high and low incidences of progeny tuber contamination, respectively, at all sampling times. However, an intermediate degree of seed tuber contamination tended to be associated with a low level of blackleg disease, a variable incidence of progeny tuber contamination early in the season but a high incidence later in the season. The level of progeny tuber contamination, derived from seed tubers inoculated at the three different levels of Eca, was categorized into four contamination classes (〈 102, 102–103, 103–104 and 〉 104 marker strain colony-forming units/mL peel extract). At the lowest level of seed tuber contamination, progeny tuber contamination tended to be in the two lower categories. However, as seed tuber contamination increased, the proportion of contaminated progeny tubers in the two higher categories also increased. Overall, the results suggest that progeny tuber contamination is related to seed tuber contamination and blackleg disease, and that the threshold level of seed tuber contamination remains an important factor in predicting both blackleg disease and tuber health.
    Type of Medium: Electronic Resource
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