Topic 1: How do pathogen/pest populations respond to deployment of host resistance?

Topic 1: How do pathogen/pest populations respond to deployment of host resistance?

Natural, co-evolving systems (vs. artificial, agricultural/horticultural systems)

Evolution of R genes in local populations: transient polymorphism model of co-evolving host-pathogen system (Holub et al)

In contrast: the “trench warfare” model of natural (co-evolutionary) systems:

Natural system 1: Puccinia coronata on Avena sterilis (wild oat) in Israel, a stable coevolving pathosystem in the center of origin

Natural system 2: Melampsora lini on Linum marginale (wild flax) in southeastern Australia

L. marginale frequently composed of many different host resistance phenotypes distributed unevenly through the deme

Why don’t virulent M. lini strains dominate and wipe out susceptible host populations?

Natural system 3: powdery mildew (Podosphaera plantaginis) on Plantago lanceolata (ribwort) on a Finnish island

Natural system 4: long-mouthed weevil and Japanese camellia in Japan (obligate parasite – trying to lay eggs in seeds)

Pericarp thickness is a heritable quantitative trait

Fitness is positively correlated with pericarp thickness

Geographic mosaic theory of co-evolution (John Thompson, UC Santa Cruz)

Geographic mosaic theory of co-evolution

Predictions of geographic mosaic theory of co-evolution

More on evolution of resistance and virulence in natural systems:

Some conclusions from natural systems

Natural plant systems