The genetic and molecular basis of plant disease resistance
Four sections
A specialized topic?
Why do organisms have sex?
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“It takes all the running you can do, to keep in the same place.”
“ Sex is about disease. It is used to combat the threat from parasites. Organisms need sex to keep their genes one step ahead of their parasites. Men are not redundant after all”
Disease resistance is also important for mate choice.
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Females sniffing the T-shirts recently worn by males favored the scent of those whose immune response genes were different from their own
Constant selection for disease resistance has likely been a profound factor in the evolution of most metazoans.
Disease results in losses of about 20% per year on a global basis
May be involved in speciation
Economic Impact of Host Plant Resistance
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Most plants are resistant to most diseases. Resistance is the rule and susceptibility is the exception.
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aka: Vertical; Qualitative; Inoculum-reducing; Major-effect; Hypersensitive; Monogenic; ‘R’ gene. Complete Race-specific Single gene “Vertical” Gene-for-gene
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aka: Horizontal; Rate-reducing; Minor-effect; General; Polygenic; Additive; Incomplete, Partial Race-nonspecific Multi-genic
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Implies, interaction (direct of otherwise) of dominant Resistance and Avirulence gene products leads to resistance.
Gene-for-gene interactions were identified in many different interactions with many different types of pathogens
Pathogen is ‘trying to lose’ Avr genes.
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A rapid, localized host cell death that occurs at the site of pathogen penetration, associated with qualitative resistance.
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Detection
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Often associated with hypersensitive response (HR)
Confirms our understanding of Gene-for-Gene
Pierre de Wit
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Identified specific elicitors associated with R-gene-mediated defense response.