Download - 2014 bgri dracatos rev
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Australian Cereal Rust Control Program
Non-Host Resistance,
Near-Host Resistance, or Just Resistance?
Dr Peter Dracatos
Plant Breeding Institute Cobbitty Australia
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Concepts of Non-Host Resistance and Near Host Resistance
• Most plants are resistant to most pathogens
• Rusts are highly specialised • Non-Host resistance:
– i.e. Puccinia graminis f. sp. tritici (Pgt) on rice and dicot plants
• Near-host resistance – Some genotypes of closely related
cereals to the host are susceptible • Barley to P. graminis f. sp.
avenae (Pga) and P. striiformis f. sp. tritici (Pst)
• Wheat to P. graminis f. sp. secali (Pgs)
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• Watson and Sanghi (1968) showed that resistance in wheat to Pgs was simply inherited (e.g. Yalta = 1 gene, Morocco = 2 genes, Mentana = 4 genes) • Martens in 1983 showed that 1 gene shared between 3 barley lines provided resistance to Pga and this was different to that for Pgt • Niks and Boyd Near-host resistance in barley to different rusts and powdery mildew • Ayliffe (CSIRO) – why is rice immune to rust (Non-Host Resistance)?
– Simple inheritance of resistance to Pga and Pst in Brachypodium
Background
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Applications in Plant Breeding • Potentially a large reservoir of resistance • Important rust resistance genes sourced from closely
related species – Wheat Stem Rust: Secale cereale, Thinopyrum ponticum, Triticum spp – Barley Leaf Rust: Hordeum bulbosum
• Could we clone these genes and swap them between cereal species that are not inter-crossable? – Cassettes of multiple genes from different species
• Implications for durability and gene stewardship • Understand more about P. graminis – cereal
pathosystem – What cereal species play a role in epidemiology
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Outline of Presentation • Mendelian inheritance – Near–Host resistance • Pathotype-specific vs non-specific resistance • Near-host resistance
– Large variation and overlap in varieties
• Specific examples – Resistance in barley to:
• P. graminis formae speciales • Pst
– Resistance in oats: • Pgt
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10a
Pgt
‘Yerong’ Barley
‘Franklin’ Barley
‘Swan’ Oat
‘Morocco’ Wheat
Host specificity of Pgt vs Pga
Pga
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Resistance in Barley to formae speciales of Pg
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Resistance to Pga in Barley • 35 DH populations assessed for resistance to Pga
– Mostly R x R crosses
• Susceptible varieties of barley – High infection types (IT) noted in 12 populations – Suitable for intercrossing
• Segregation in many cases to more than one resistance gene
• Numerous phenotypic variation for resistance – ITs similar to host-pathogen interactions – Complete immunity – Incomplete susceptibility
• Mesothetic ITs
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Resistance in Yerong x Franklin to Pga
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Genetic Analysis in Yerong x Franklin
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Rpg5 Resistance in Barley to Pgt, Pga and Pgs
• Q21861 carries Rpg1 and rpg4/Rpg5 • Bruggeman et al.
– rpg4/Rpg5 - resistance to Pgt including Ug99 – Rpg5 – resistance to Pgs
• F8 RIL population Q21861 x F line – F line - mesothetic susceptibility to Pga and Pgt – Screened with Pga and Pgt – Fixed for Rpg1 – 1:1 segregation for Pgt and Pga – Marker analysis demonstrates effectiveness of Rpg5 against
multiple f. spp. of P. graminis
• Such genes may be particularly important for transfer into target cereal species
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Resistance in Oats to Pgt
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“Near-host” resistance eat stem rust on oats
TTKST Ug99 +Sr24
TRTTF-virulence to Sr13 and Sr9e
Wheat
Hexaploid oats
Diversity of Resistance to Pgt in oats
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Diverse International Oat Screening
• 600 internationally diverse oat lines inoculated with: • P. graminis f. sp. tritici
• Range of infection types • ;;nnn, ;n, ;;, ;cn, 22+ • 95 lines - showed ITs >0; Pgt
• Selected lines above plus lines from diverse origin giving immune ITs (0;) will be used for Association mapping analysis
14
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Resistance to Puccinia striiformis f. sp. tritici (Pst) in Barley
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Plant Genotype
P. striiformis f. sp. tritici
Ps f. sp. pseudohordei
1979 pt 2002 pt Barley Finniss ;c 0; 23c
Maritime 2c/2cn ;c 3
Fong Tien 22+ 3 3
Commander 0; ; 0;
Hindmarsh 0; 0; 0;
Wheat Morocco 3+ 3+ ;/1p 3+
Chinese 166 ; 0; 33+
Different ITs in Barley to Pst
• Susceptibility in barley • Pst • P. striiformis f. sp.
pseudohordei
• Variation of resistance in barley between:
• P. striiformis pathotypes
• P. striiformis f. sp.
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5X
5X Commander M2.7 resistant sib 7dpi
Commander M2.7 susceptible 7dpi Chlorosis but no pustules
5X
Putative Resistance Gene
Knockouts
5X • Finnis and Commander M3 progeny
tested candidates • 6 Finnis families • 2 Commander families
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Fong Tien Hindmarsh
Hindmarsh*Fong BC1 F2 # 3 #3
Hindmarsh*Fong BC1 F2 # 3 14dpi
3: 1 ratio indicating single gene from Hindmarsh Mapping and mutagenesis in progress
Resistance to Pst in Barley
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Summary – Near-Host resistance • Barley suitable for genetic analysis of resistance to
different Puccinia species • Resistance is Resistance!
– Necrosis, chlorosis, flecking, reduced sporulation • Large variability of ITs and mechanisms of
resistance • R genes confer resistance to different formae speciales • Pre-haustorial • Pathotype specific- formae speciales specific
• Future work • Fine-map and cloning of resistance genes and transfer to
target cereals
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Acknowledgements University of Sydney
• Dr Davinder Singh • Professor Robert Park
CSIRO Canberra • Shidah Mojerlou • Dr Wolfgang Spielmeyer • Dr Michael Ayliffe
Canada Agriculture • Dr Tom Fetch
The Sainsbury Laboratory • Dr Brande Wulffe • Dr Matthew Moscou