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Broadening and improving the Turnip yellows virus resistance base in oilseed rape (Brassica napus) (BITYR)
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Greer, Shannon Faye (2020) Broadening and improving the Turnip yellows virus resistance base in oilseed rape (Brassica napus) (BITYR). PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b3736640
Abstract
The aphid-transmitted Turnip yellows virus (TuYV) and the soil-borne fungus Verticillium longisporum are important, yield-robbing pathogens of oilseed rape. Both pathogens are poorly controlled by chemical treatments, either due to their inefficacy and/or bans on their usage, consequently host-resistance has become a necessary method for their control. Oilseed rape (Brassica napus) is an amphidiploid (genome AACC) resulting from interspecific hybridisations between Brassica rapa (genome AA) and Brassica oleracea (genome CC).
Currently the only characterised sources of host-resistance to TuYV are in the resynthesised B. napus line ‘R54’ and variety ‘Yudal’, which in previous studies, were mapped to single dominant QTLs on B. rapa chr. A04. The ‘R54’ TuYV resistance has been introgressed into commercial varieties of oilseed rape and was fine mapped in this study in the oilseed rape variety Amalie. Polymorphic markers, which positioned on chr. A04, were identified and used to fine map TuYV resistance in a segregating backcross (BC1) population, produced by crossing Amalie to the susceptible B. napus line ‘R7011-AB’. TuYV resistance was mapped to a region on B. rapa chr. A04 where a homoeologous recombination or gene conversion event had occurred between the Brassica A and C genomes within a putative DHAR2 gene.
Unpublished studies have suggested that B. napus lines possessing the TuYV resistance introgression from Amalie are also tolerant to V. longisporum. In this study, a V. longisporum inoculation assay to B. napus was developed by testing the pathogenicities of five V. longisporum isolates and the effect of inoculation method and concentration on disease severity. Following successful development of a V. longisporum inoculation assay, glasshouse experiments confirmed previous findings and showed that Amalie was tolerant to V. longisporum and this tolerance was not dependent on activation of its TuYV resistance following challenge with the virus.
To broaden the TuYV resistance base in oilseed rape, resistance in the B. napus progenitor species were characterised. The TuYV-resistant B. rapa line ‘ABA15005’ and B. oleracea line ‘JWBo12’ were crossed to susceptible lines to produce segregating BC1 populations for QTL analysis. QTL interval mapping and modelling of a BC1 population segregating for the ABA15005 resistance, identified dominant, putative and novel TuYV resistance QTLs on chr. A07 and A09. TuYV resistance in JWBo12 was also shown to be dominantly inherited and a segregating BC1 population was produced for future QTL mapping. The identification of TuYV resistance-linked molecular markers will help accelerate the introgression of these resistances into commercial oilseed rape types by marker-assisted selection. The TuYV-resistant ABA15005 and JWBo12 were also crossed to produce resynthesised B. napus plants, which were subsequently phenotyped and shown to possess TuYV resistance that was similar in strength to the parental resistances and the ‘R54’ resistance in Amalie.
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): | Turnip yellow mosaic virus, Verticillium wilt diseases, Rape (Plant) -- Diseases and pests, Rape (Plant) -- Disease and pest resistance | ||||
Official Date: | January 2020 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Walsh, John A. ; Barker, Guy C. ; Gegas, Vasilis | ||||
Sponsors: | Biotechnology and Biological Sciences Research Council (Great Britain) ; Limagrain UK Limited | ||||
Format of File: | |||||
Extent: | xxi, 265 leaves : illustrations | ||||
Language: | eng |
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