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