The Library
Development of molecular approaches in the study of lettuce downy mildew (Bremia lactucae) population biology
Tools
Xu, Limin, Ph.D. (2011) Development of molecular approaches in the study of lettuce downy mildew (Bremia lactucae) population biology. PhD thesis, University of Warwick.
|
Text
WRAP_THESIS_Xu_2011.pdf - Submitted Version Download (5Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2581485~S1
Abstract
Downy mildew of lettuce caused by Bremia lactucae is a serious disease resulting in
yield loss. The population structure of the pathogen in the UK is poorly understood.
This PhD project concentrated on developing molecular markers to differentiate the
genotypic variation of B. lactucae populations, with the aim of improving methods to
investigate lettuce - Bremia interactions. Thirty-seven B. lactucae isolates (including
single-spore and new field isolates) were collected and characterized for virulence
using the conventional International Bremia Evaluation Board (IBEB) differential set.
Microsatellite markers (SSR, ISSR) were investigated for Bremia race specific
marker development. Three isolates of B. lactucae were characterized by ISSR (inter
simple sequence repeat) primers, although the polymorphic DNA could not be cloned
in this project due to the highly variable results of the ISSR process. Some
microsatellite repeats were found in B. lactucae isolates sequences that amplified by
Plasmopara viticola (grape downy mildew) SSR markers. The development of
Simple Sequence Repeat (SSR) markers from Bremia genomic DNA was not
successful, which might result from the primers used being unsuitable for Bremia
microsatellite enrichment. Bremia specific ITS primers were used for quantitative
PCR. RxLR primers obtained from UC Davis (USA) were tested using the collection
of B. lactucae isolates. RxLR1 primers distinguished between isolates BL801 and
BL806. Eight SNPs were identified in three isolates amplified by RxLR5. No
polymorphism was observed on the gel for the remaining RxLR primers on single
spore races. Unrefined field isolates showed more polymorphisms on the gel than
single spore isolates. The phenotypic differences between these two isolates have
been identified by the IBEB differential set. Microscopy and qPCR quantification
were used to investigate the compatible and incompatible interactions. The results
suggest that BL801 is more virulent than BL806, as more infection structures were
observed in IBEB resistant cultivars. Results of qPCR and spore count/unit weight of
cotyledons showed that BL801 and BL806 were significantly different. The qPCR
quantification results from 4 and 5 dpi were correlated with the spore count/unit
weight of cotyledons. Although further work is required to develop race specific
markers, the methods used in this project demonstrate the potential use of molecular
markers to investigate lettuce - Bremia interactions.
Item Type: | Thesis (PhD) | ||||
---|---|---|---|---|---|
Subjects: | S Agriculture > SB Plant culture | ||||
Library of Congress Subject Headings (LCSH): | Bremia lactucae -- Population, Downy mildew of lettuce -- Transmission | ||||
Official Date: | December 2011 | ||||
Dates: |
|
||||
Institution: | University of Warwick | ||||
Theses Department: | School of Life Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Kennedy, Roy ; Holub, E. B. | ||||
Extent: | xvi, 244 leaves : ill., charts | ||||
Language: | eng |
Request changes or add full text files to a record
Repository staff actions (login required)
View Item |
Downloads
Downloads per month over past year