Asare-Bediako, Elvis (2011) Brassicaceae : Turnip yellows virus interactions. PhD thesis, University of Warwick.

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Abstract

Turnip yellows virus (TuYV) is the most common and important virus infecting
oilseed rape (Brassica napus) in the UK. It causes reductions in growth and seed
yield in oilseed rape. Between 2007 and 2010, the prevalence of TuYV in oilseed
rape crops in Lincolnshire, Warwickshire and Yorkshire was determined; incidences
of infection ranged from 0 and 100%. The highest levels of infection were detected
in Lincolnshire and the lowest in Yorkshire. Highest incidences were recorded
during 2009-10 and the lowest in 2008-9. Incidences of TuYV were closely related
to the flight activities Myzus persicae vector. Most fields showed slightly aggregated
pattern of infection during autumn but spring sampling revealed more random
patterns. Phylogenetic analysis of both nucleotide and amino acid sequences of the
P0 and P3 genes of TuYY revealed three and two genetic groups of TuYV
respectively, infecting oilseed rape in Lincolnshire, Warwickshire and Yorkshire.
The P0 gene was more variable than the P3 gene and both were under purifying
selection. TuYV populations in the three regions were highly structured with limited
gene flow between them. Analysis of molecular variance (AMOVA) indicated 96-
97% of the observed variation was due to the variation between isolates within
fields. Three RT-PCR assays were developed to differentiate the three genotypes.
They successfully detected and discriminated isolates of the two major genotypes
from oilseed rape in Lincolnshire. Twenty seven accessions of a B. napus Diversity
Fixed Foundation Set (DFFS) screened for resistance against TuYV infections varied
in their susceptibility to the virus. An accession Yudal had partial resistance to some
but not all the isolates of the two major genetic groups tested. TuYV caused yield
losses of up to 44.7% in a glasshouse experiment. A major QTL for the partial TuYV
resistance was detected on chromosome C4 (N14), explaining up to 50.5% of the
observed resistance.

Item Type:	Thesis or Dissertation (PhD)
Subjects:	Q Science > QR Microbiology > QR355 Virology S Agriculture > SB Plant culture
Library of Congress Subject Headings (LCSH):	Rape (Plant) -- Viruses -- Genetics
Official Date:	September 2011
Dates:	Date Event September 2011 Submitted
Institution:	University of Warwick
Theses Department:	School of Life Sciences
Thesis Type:	PhD
Publication Status:	Unpublished
Supervisor(s)/Advisor:	Walsh, John
Sponsors:	Ghana ; University of Cape Coast
Extent:	xvii, 253 leaves : ill., charts
Language:	eng
URI:	http://wrap.warwick.ac.uk/id/eprint/44041

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