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The genetics of host and non-host resistance to
Septoria Tritici BlotchHarriet R. Benbow
Professor Fiona M. Doohan
@HarriRB
Septoria tritici blotch
• Zymoseptoria tritici
• Hemibiotrophic
• ~70% European Fungicide use
• Emergence of resistant strains
Ponomarenko A., S.B. Goodwin, and G.H.J. Kema. 2011. Septoria tritici blotch (STB) of wheat. Plant Health Instructor.DOI:10.1094/PHI-I-2011-0407-01
Plant immunity – the zigzag model• Described by Jones and Dangl (2006)
Host resistance/gene-for-geneNon-host
Host Non-Host
Host Non-Host
PTI
ETI
Host vs Non-host
• Brachypodium• Incompatible host
• Tool to study non-host resistance
• Wheat• True host
• Novel/species-specific defence pathways (orphans)
Comparative time-course transcriptomics
Host vs Non-host
• Brachypodium• Incompatible host
• Tool to study non-host resistance
• Wheat• True host
• Novel/species-specific defence pathways (orphans)
Comparative time-course transcriptomics
• Recombinant Inbred population• Doubled Haploid population
• Panel of elites
Time-course transcriptomics
Tran
scri
pto
mic
s
Brachypodium RILs
Wheat
Doubled Haploid
Elite panel
TILLING
Time-courseBulked Segregant analysis
Exome Capture
Time-course transcriptomics
Tran
scri
pto
mic
s
Brachypodium RILs
Wheat
Doubled Haploid
Elite panel
6 hours 24 hours 2 days 4 days 5 days 6 days 7 days 8 days 9 days 10 days 11 days 12 days
Gene validation at all time-points
Wheat
• Doubled Haploid Population Bulked segregant analysis
Population developed by Limagrain
Segregating for STB resistance (3 x phenotype screens)
Hypothesis:Population is segregating for STB resistanceAims:Identify the genes responsible
Ciarán Brennan (PhD Student, UCD)
Wheat
• Phenotype Screens
Elite panel – Bulked segregant analysisScreened a panel of 37 modern varieties – Dr. Gerard Hehir (Teagasc)
Brachypodium distachyonPreviously shown to be an incompatible host
Screened a population of RILs segregating for STB response
Host or non-host?• Between some genotypes and conditions, the fungus will complete its lifecycle
Aisling Reilly – PhD student, UCD/Teagasc
Some evidence of pycnidia formation in stomatal cavities in Brachypodium
TILLING~700 lines of the T. aestivum cv. Cadenza TILLING population screened for flag leaf STB response (Thalia Christodoulou)
Cadenza
Resistant1
Resistant2
Susceptible1
Susceptible2Photo:ThaliaChristodoulouPhoto:ThaliaChristodoulou
Two resistant lines showing a dominant phenotype• Candidate gene list from both lines• Backcrossing is underway
Future candidates?
• Special focus on ‘orphans’• OG discovery pipeline is being developed (Sobia Ajaz – Marie Curie ESR - UCD)
VIGS for Orphans• Septoria responsive orphan gene
• Up-regulated in a resistant cultivar at 4, 8 and 12 DPI
• Virus-induced gene silencing caused a breakdown of resistance
VIGS EV
Ciarán Brennan
University College Dublin
• Ciarán Brennan
• Thalia Christodoulou
• Aisling Reilly
• Dr Anna Tiley
• Sobia Ajaz
• Prof. Fiona Doohan
• The Doohan Crops Lab
Teagasc
• Dr Gerard Hehir
• Dr Ewen Mullins
The John Innes Centre
• Dr Cristobal Uauy
Limagrain
• Dr Simon Berry
Univeristy of Minnesota
• Assistant Prof. David Garvin