Dr. Paul Hand
•  A publicly available F8 mapping population
and genetic linkage map
•  A 96 accession lettuce diversity set
•  A lettuce TILLING population
•  Putative sources of resistance to Nasonovia ribisnigri
•  Genetic analysis of post harvest discolouration
•  Genetic analysis of nitrate accumulation in lettuce
Saladin x Iceberg recombinant inbred population
For trait analysis &
genetic mapping
>300 F6 lines
125 Most Informative Lines
F7 genetic map
F8 Seed available
•  Map length 1040 cM covering all 9 lettuce
chromosomes.
•  Anchored to integrated lettuce map (Truco et al.
2007)
•  425 polymorphic markers mapped
•  Up to 500 additional markers to be mapped
Capturing natural variation
Type
Bu/erhead
Cos
Wild
Crisp
Cu=ng
La@n
Batavian
Stem
Iceberg
Leaf
Oilseed
Stalk
No.
25
17
17
10
10
7
4
2
1
1
1
1
Comment
(L.
serriola
&
L.
virosa)
(Saladin)
(Waldermann's
Dark
Green)
(Balady)
(L.
sa:va)
All but 8 lines produced seed – biennial or re-sown
Founder plant DNA stored
Introducing variation through chemical mutation
M1
M2
From: Henikoff, S. & Comai, L. (2003) Ann. Rev. Plant Biol. 54: 375-401
Introducing variation through chemical mutation
M1
M2
From: Henikoff, S. & Comai, L. (2003) Ann. Rev. Plant Biol. 54: 375-401
Introducing variation through chemical mutation
M1
M2
From: Henikoff, S. & Comai, L. (2003) Ann. Rev. Plant Biol. 54: 375-401
Introducing variation through chemical mutation
M1
M2
From: Henikoff, S. & Comai, L. (2003) Ann. Rev. Plant Biol. 54: 375-401
•  M3 seed of 3240 lines available
•  M2 DNA arrayed in 96 well format
•  DNA mutation load assessment by
BBSRC RevGenUK @ John Innes Centre
•  Resistance already deployed BUT
•  New resistance-breaking biotype of
N. ribisnigri
•  Screening of lettuce diversity set of
96 lines
•  Testing began December 2010
•  Several N. ribisnigri clones in culture
including host-plant-resistancebreaking aphids collected in UK
•  Assay undertaken with clone
that dies on cultivars resistant to
N. ribisnigri
•  5 new-born aphids per plant
•  Confined to plant with bread
bags
•  Kept for 3 weeks at 20°C
•  Aphids counted
•  Ranged from 1 to 508 aphids per
plant (winged and wingless)
•  Consistency within lines
•  Low aphid numbers on Iceberg mapping parent
•  Further replication underway to confirm differences
between lines
•  Could go on to test host-plant-resistance-breaking
aphids
•  Trait analysis showed discolouration linked
to several map regions
•  Discolouration gene candidates identified
from phenylpropanoid pathway
•  Direct mapping of 3 candidate gene
markers
•  Comparative mapping of a further 20
•  Several candidates map to discolouration
regions
Can nitrate levels be reduced through breeding?
Mapping lines grown in hydroponics and soil
•  Previous work identified 13 genetic links to
nitrate accumulation
•  Combined trait analysis across seasons
and growth conditions
•  3 clusters on genetic map
•  Targets for further mapping
•  Require better genetic markers for
candidate genes
•  Add markers to genetic map (approx. 500)
•  Collect seed of final Diversity Set lines
•  Measure TILLING mutation load: make DNA
available
•  Complete N. ribisnigri screen
•  Confirm candidate genes mapping to
discolouration loci
•  Map gene markers for Nitrate content
•  Incorporate high-density markers/genomic
sequence
Warwick
U.C. Davis
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Dave Pink
Rosemary Collier
Ian Burns
Laura Atkinson
James Lynn
Howard Hilton
Neale Grant
Sandy McClement
Helen Mayne
Steve Jackson
Aaron Abbott
James Durnford
Jon Horridge
Richard Michelmore
Leah McHale
Oswaldo Ochoa
Maria-Jose Truco
Rijk Zwaan
•  Johan Schut
•  Wendy Deijkers
•  Bass Brussaard
BBSRC RevGen
•  Fran Robson