05_EmilyBoys_RRES_UKBRC_May08

Resistance to Pyrenopeziza brassicae (light leaf
spot) in a mapping population of Brassica napus
Emily Boys, Rothamsted Research
Supervisors:
Bruce Fitt, Rothamsted Research
Jon West, Rothamsted Research
Graham King, Rothamsted Research
Peter Werner, KWS UK Ltd.
Paul Dyer, University of Nottingham
Project aims
•
Mapping the major gene(s) for resistance against P. brassicae that are
segregating in the N26 doubled haploid population
– Identified a number of microsatellites (SSRs) linking to the resistance phenotype
– Relationship of markers to established linkage groups not yet clear
B. rapa x B. oleracea var. atlantica
Synthetic amphidiploid x B. napus cv. Cobra
Mapped PBR1 (A1) & PBR2 (C6) in DH population
Imola (resistant) x 218-11 (susceptible)
B. napus cv. Imola
Bradburne et al. (1999)
N26 DH population
Project aims
•
•
To map the major resistance gene(s) against P. brassicae that are
segregating in the N26 doubled haploid population
To investigate the phenotype/mechanism of this resistance
Susceptible
B. rapa x B. oleracea var. atlantica
Synthetic amphidiploid x B. napus cv. Cobra
“Resistant”
Mapped PBR1 (A1) & PBR2 (C6) in DH population
Imola (resistant) x 218-11 (susceptible)
B. napus cv. Imola
Bradburne et al. (1999)
N26 DH population
Investigating the resistant phenotype
Apex (susceptible)
Extensive subcuticular hyphal growth on
leaf vein, with branching and growth out
from vein onto rest of leaf
9dpi
Imola (“resistant”)
Cell collapse (“black flecking”) and
hyphal growth on leaf vein; less growth
away from vein
SEMs produced with Jean Devonshire,
Rothamsted Centre for Bioimaging
Investigating the resistant phenotype
Apex (susceptible)
Intact leaf vein cells, with subcuticular
hyphal growth
9dpi
Imola (“resistant”)
Cell collapse (“black flecking”) and
subcuticular hyphal growth on leaf vein
SEMs produced with Jean Devonshire,
Rothamsted Centre for Bioimaging
Investigating the resistant phenotype
Apex (susceptible)
Subcuticular hyphal growth on leaf vein
13dpi
Imola (“resistant”)
Subcuticular hyphal growth on leaf vein
SEMs produced with Jean Devonshire,
Rothamsted Centre for Bioimaging
Investigating the resistant phenotype
Apex (susceptible)
Asexual sporulation on leaf vein
20dpi
Imola (“resistant”)
Cell collapse (“black flecking”) away from
leaf vein
SEMs produced with Jean Devonshire,
Rothamsted Centre for Bioimaging
Investigating the resistant phenotype
Apex (susceptible)
Asexual sporulation on leaf vein
20dpi
Imola (“resistant”)
Cell collapse (“black flecking”) away from
leaf vein
SEMs produced with Jean Devonshire,
Rothamsted Centre for Bioimaging
Pathogen hyphae grow
in sub-cuticular space
9
Ascospores germinate and
directly penetrate cuticle
Air-borne ascospores
initiate epidemic
but slowed and
cell collapse
Asexual sporulation
produces conidia
8
Symptomless
Phase
Asexual
Reproduction
Sexual
Reproduction
Secondary
Cycles
9
in artificially
inoculated
conditions
Apothecia develop
on infected debris
8
Infection of leaves,
stems, meristems & pods