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Developing research tools to investigate the biology and epidemiology of Pythium violae causing cavity spot on carrot to enable disease management
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Hales, Kathryn Rebecca (2018) Developing research tools to investigate the biology and epidemiology of Pythium violae causing cavity spot on carrot to enable disease management. PhD thesis, University of Warwick.
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WRAP_Theses_Hales_2018.pdf - Submitted Version - Requires a PDF viewer. Download (35Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b3420602~S15
Abstract
Cavity spot is a major disease of carrots worldwide, resulting in high-value losses each year in Britain. Cavity spot is caused by the oomycete Pythium, which attacks the mature carrot root causing sunken, elliptical lesions making the crop unmarketable. Disease management is challenging due to variable fungicide efficacy and difficulty implementing long rotations. New control approaches have been hampered by a lack of fundamental knowledge concerning Pythium violae epidemiology, basic tools for research including diagnostics, and no reproducible inoculation procedure. The work in this thesis aimed to address this problem by building greater understanding of Pythium biology/genetics, and developing molecular detection tools and artificial inoculation methods.
To determine the Pythium species associated with cavity spot, 150 isolates were collected from diseased carrots. Following DNA extraction and sequencing, the main species associated with cavity spot disease in the UK was P. violae. Further characterisation with housekeeping genes separated Pythium isolates into multiple clades within species. Pathogenicity experiments using representative isolates of P. violae, P. sulcatum and P. intermedium from different clades identified a range of virulence within and between species.
A reproducible source of P. violae oospore inoculum was developed and used to inoculate carrot seedlings, and pot/field-grown carrots. This resulted in abnormal carrot growth and development of typical cavity spot lesions. Results were variable in seedling and pot experiments, but commercially significant cavity spot was achieved for two consecutive years in the field.
An oospore capture method and qPCR assay were developed to improve capture, detection and quantification of P. violae in soil. The oospore capture was successful in detecting P. violae oospores from sand/oat samples. The qPCR assay was highly sensitive and specific to P. violae. Capture and detection from soil proved challenging with highly variable results. A commercial field site was monitored to establish P. violae dynamics, but results were inconsistent.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QK Botany S Agriculture > SB Plant culture |
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Library of Congress Subject Headings (LCSH): | Carrots -- Diseases and pests, Pythium, Pythium -- Genetics | ||||
Official Date: | September 2018 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Clarkson, John | ||||
Sponsors: | Great Britain. Agriculture and Horticulture Development Board | ||||
Format of File: | |||||
Extent: | xvi, 192 pages : illustrations, charts | ||||
Language: | eng |
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